Topics

Transmitter gain calibration


Robert W5AJ
 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ


Ray Maxfield
 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 


Colin Smithers
 

How are you measuring power output?

I have set up three K3s now and have found the following:

- my measurement of power was all over the place until I calibrated my power meters with against a professional one - HP438: my Bird was 20% out, slug cal was off with a very noisy cal pot. All my various power meters of various ages were out to some degree. Better agreement now.

- Out of the box the K3s are set to deliver higher power than indicated, around 10-15%.

- power can be set right at  half power or full power (i.e. 5/50, or 10/100) but not both as the power measurement is not quite linear

- Low voltage limits power output, and dodgy power cables/ connectors can achieve this

Don’t know if this helps

73, Colin G4CWH


On 6 Jun 2020, at 02:36, Robert W5AJ via groups.io <woodr90@...> wrote:


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ


Bob McGraw - K4TAX
 

Since most power meters we use are voltage sensing devices.   Therefore the accuracy of the dummy load will affect the indication of the meter.   A dummy load that is simply marked "50 ohms" may or may not be truly 50 ohms.   I find them to vary as much as 10% or more.  This will likewise affect the power meter indication as they are usually calibrated for 50 ohms.   Please check all dummy loads with an ohm meter and then with an antenna bridge at the frequency one intends to use the load.   Just because it says "50 Ohms" on the label is no assurance it is still 50 ohms.

While a dummy load that measures +/- 10% or more of 50 ohms,  is still good to dissipate heat from RF, it may not be good enough for accurate power measurements.   Also, I am always concerned about "used" E-Bay or hamfest Bird slugs.   I find that a given slug will likely show different values when used in different meters.  Ideally, one should use only 1 meter and make sure the slug is calibrated for that meter.  

73
Bob, K4TAX


mikerodgerske5gbc
 

Here we go again with those fet's. 

Mike R

7!
Absolutely Awesome 

On Jun 6, 2020, at 9:24 AM, Bob McGraw - K4TAX <rmcgraw@...> wrote:

Since most power meters we use are voltage sensing devices.   Therefore the accuracy of the dummy load will affect the indication of the meter.   A dummy load that is simply marked "50 ohms" may or may not be truly 50 ohms.   I find them to vary as much as 10% or more.  This will likewise affect the power meter indication as they are usually calibrated for 50 ohms.   Please check all dummy loads with an ohm meter and then with an antenna bridge at the frequency one intends to use the load.   Just because it says "50 Ohms" on the label is no assurance it is still 50 ohms.

While a dummy load that measures +/- 10% or more of 50 ohms,  is still good to dissipate heat from RF, it may not be good enough for accurate power measurements.   Also, I am always concerned about "used" E-Bay or hamfest Bird slugs.   I find that a given slug will likely show different values when used in different meters.  Ideally, one should use only 1 meter and make sure the slug is calibrated for that meter.  

73
Bob, K4TAX


Gerard
 

If I remember, you take out the 100W module to access them, i replaced one before.  Gerard EI5KF


On Sat 6 Jun 2020, 05:05 Ray Maxfield, <wa6vab@...> wrote:

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 


Ray Maxfield
 

To tell you the Truth I don t Remember.

But…. I think I just turned the K3 upside-down and

Un-solder the fet….

I used a Solder-Sucker to get the solder from around the Leads.

If you are concerned about Static-ESD… Take a clip- lead and connect it to

Each lead as you Un-solder them. Verify you Soldering Tip is Grounded

Use your Ohm meter…..  Hope that Helps   Ray WA6VAB  K3

 

From: Gerard
Sent: Saturday, June 6, 2020 11:19 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

If I remember, you take out the 100W module to access them, i replaced one before.  Gerard EI5KF

 

On Sat 6 Jun 2020, 05:05 Ray Maxfield, <wa6vab@...> wrote:

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 


Robert W5AJ
 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 


Ray Maxfield
 

Hi Robert………… Thanks for the Feed Back.

This seems to be a Somewhat of a failure in the K3.

The Sticky Pad, is suppose to help transfer Heat from the Fet to the Bottom Cover.

They Work, but are NOT as Good a the Old Original Thermal Compound.

I went to the Computer Parts store and purchase a small syringe of Thermal compound

And applied some to Each Tab of the Fets, and re-assemblied the bottom cover.

Making Sure to get the Star Lockwashers on each…. Tighten with a Hefty Fist.

I would order 2 Each, One to keep as a Spare! 

 

Oh Yes, we use to call the thermal compound, FBI Finger print ink !

It will get on Everything if your not Careful.

 

Great Job…. So far.

When you get the Fet installed, Run the Gain Caliberation Test,

So the radio will Reset to the Correct Power output…..

Use dummy Load if at all possible.   ……….. VAB 

   

 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Sunday, June 7, 2020 8:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 


David Cutter
 

I would caution against the Hefty Fist technique.  This can distort the tab and/or the panel it is attached to so that part of the tab is no longer in contact.  I recall a torque setting for optimum contact pressure and it's not very much.  Even for very large devices (as big as your hand) it's only 5Nm from memory. 

Have a read through this document, it recommends around 0,8Nm for T0-220 

https://www.infineon.com/dgdl/Infineon-AN2013_12_Screw_Tightening_Torque-AN-v1.0-en.pdf?fileId=db3a3043429a38690142a3a1f142107f


David G3UNA/G6CP



On 08 June 2020 at 05:57 Ray Maxfield <wa6vab@...> wrote:

Hi Robert………… Thanks for the Feed Back. 

This seems to be a Somewhat of a failure in the K3.

The Sticky Pad, is suppose to help transfer Heat from the Fet to the Bottom Cover.

They Work, but are NOT as Good a the Old Original Thermal Compound.

I went to the Computer Parts store and purchase a small syringe of Thermal compound

And applied some to Each Tab of the Fets, and re-assemblied the bottom cover.

Making Sure to get the Star Lockwashers on each…. Tighten with a Hefty Fist.

I would order 2 Each, One to keep as a Spare! 

 

Oh Yes, we use to call the thermal compound, FBI Finger print ink !

It will get on Everything if your not Careful.

 

Great Job…. So far.

When you get the Fet installed, Run the Gain Caliberation Test,

So the radio will Reset to the Correct Power output…..

Use dummy Load if at all possible.   ……….. VAB 

   

 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Sunday, June 7, 2020 8:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 

 


 


 


Ray Maxfield
 

around 0,8Nm for T0-220 …….   Let me see What range my torque wrench is Calibrated in.

I will check the Flatness of the Devices, and if needed.. File it Flat( or Lap the surface) and use Thermal compound.

Non Flat devices have been around for Years.   They were Found in Motorola Power devices

In the 70’s, I was repairing RF Amplifiers Then. ……

Ray  WA6VAB. 

 

From: CUTTER DAVID
Sent: Monday, June 8, 2020 2:11 AM
To: Elecraft-K3@groups.io; Ray Maxfield
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

I would caution against the Hefty Fist technique.  This can distort the tab and/or the panel it is attached to so that part of the tab is no longer in contact.  I recall a torque setting for optimum contact pressure and it's not very much.  Even for very large devices (as big as your hand) it's only 5Nm from memory. 

Have a read through this document, it recommends around 0,8Nm for T0-220 

https://www.infineon.com/dgdl/Infineon-AN2013_12_Screw_Tightening_Torque-AN-v1.0-en.pdf?fileId=db3a3043429a38690142a3a1f142107f

 

David G3UNA/G6CP

 

 

On 08 June 2020 at 05:57 Ray Maxfield <wa6vab@...> wrote:

Hi Robert………… Thanks for the Feed Back. 

This seems to be a Somewhat of a failure in the K3.

The Sticky Pad, is suppose to help transfer Heat from the Fet to the Bottom Cover.

They Work, but are NOT as Good a the Old Original Thermal Compound.

I went to the Computer Parts store and purchase a small syringe of Thermal compound

And applied some to Each Tab of the Fets, and re-assemblied the bottom cover.

Making Sure to get the Star Lockwashers on each…. Tighten with a Hefty Fist.

I would order 2 Each, One to keep as a Spare! 

 

Oh Yes, we use to call the thermal compound, FBI Finger print ink !

It will get on Everything if your not Careful.

 

Great Job…. So far.

When you get the Fet installed, Run the Gain Caliberation Test,

So the radio will Reset to the Correct Power output…..

Use dummy Load if at all possible.   ……….. VAB 

   

 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Sunday, June 7, 2020 8:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 

 


 


 

 


David Cutter
 

It's a lot easier to achieve correct and even pressure using a spring clip that presses on the body of the device, rather than one end.  Several shapes available.  I can understand the desire to use a screw that you tighten to the limit of the thread.  It's the same syndrome as turning off a tap with all your strength: it's simply unnecessary and can lead to premature failure. Sorry for the drift.

David G3UNA/G6CP

On 08 June 2020 at 15:12 Ray Maxfield <wa6vab@...> wrote:

around 0,8Nm for T0-220 …….   Let me see What range my torque wrench is Calibrated in.

I will check the Flatness of the Devices, and if needed.. File it Flat( or Lap the surface) and use Thermal compound.

Non Flat devices have been around for Years.   They were Found in Motorola Power devices

In the 70’s, I was repairing RF Amplifiers Then. ……

Ray  WA6VAB. 

 

From: CUTTER DAVID
Sent: Monday, June 8, 2020 2:11 AM
To: Elecraft-K3@groups.io; Ray Maxfield
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

I would caution against the Hefty Fist technique.  This can distort the tab and/or the panel it is attached to so that part of the tab is no longer in contact.  I recall a torque setting for optimum contact pressure and it's not very much.  Even for very large devices (as big as your hand) it's only 5Nm from memory. 

Have a read through this document, it recommends around 0,8Nm for T0-220 

https://www.infineon.com/dgdl/Infineon-AN2013_12_Screw_Tightening_Torque-AN-v1.0-en.pdf?fileId=db3a3043429a38690142a3a1f142107f

 

David G3UNA/G6CP

 

 

On 08 June 2020 at 05:57 Ray Maxfield <wa6vab@...> wrote:

Hi Robert………… Thanks for the Feed Back. 

This seems to be a Somewhat of a failure in the K3.

The Sticky Pad, is suppose to help transfer Heat from the Fet to the Bottom Cover.

They Work, but are NOT as Good a the Old Original Thermal Compound.

I went to the Computer Parts store and purchase a small syringe of Thermal compound

And applied some to Each Tab of the Fets, and re-assemblied the bottom cover.

Making Sure to get the Star Lockwashers on each…. Tighten with a Hefty Fist.

I would order 2 Each, One to keep as a Spare! 

 

Oh Yes, we use to call the thermal compound, FBI Finger print ink !

It will get on Everything if your not Careful.

 

Great Job…. So far.

When you get the Fet installed, Run the Gain Caliberation Test,

So the radio will Reset to the Correct Power output…..

Use dummy Load if at all possible.   ……….. VAB 

   

 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Sunday, June 7, 2020 8:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 

 


 

 



 

 


 


 


Mel Farrer, K6KBE
 

Hello David,

As a reference on the junction of the RF transistor and the heat sink, I speak from personal manufacturing experience.  There are two issues.

First, the flatness of the mating heat sink surface.  Flatness can be measured with a micrometer or by using a straightedge and lay down a slick of heat sink compound and look for areas of white, none should be visible.

Second, is the flatness of the transistor base.  If one wishes to know if the transistor is seated properly with maximum contact with the heat sink, before soldering it down, one must put a .005 mil slick of heat grease compound on the two hole mounted transistor base plate and finger tighten the screws down, then take the screws out, remove the transistor and look at the morue pattern.  If the pattern is spectacled, that is, has a uniform pattern across the surface with lots of metal showing through, the surface tension was adequate for the test.  If areas that show white grease that is not compressed, the flatness of the base plate is a problem.  Address that problem now.  Then when final assembly is made, only go another 1/4 turn----no more.  On Stud mounted transistors, the ring around the stud must be uniform in display. 

There is a manufacturing MIL spec on this, but memory fails.

I hope this helps a little.

Mel, K6KBE

On Mon, Jun 8, 2020 at 11:19 AM David Cutter via groups.io <d.cutter=ntlworld.com@groups.io> wrote:

It's a lot easier to achieve correct and even pressure using a spring clip that presses on the body of the device, rather than one end.  Several shapes available.  I can understand the desire to use a screw that you tighten to the limit of the thread.  It's the same syndrome as turning off a tap with all your strength: it's simply unnecessary and can lead to premature failure. Sorry for the drift.

David G3UNA/G6CP

On 08 June 2020 at 15:12 Ray Maxfield <wa6vab@...> wrote:

around 0,8Nm for T0-220 …….   Let me see What range my torque wrench is Calibrated in.

I will check the Flatness of the Devices, and if needed.. File it Flat( or Lap the surface) and use Thermal compound.

Non Flat devices have been around for Years.   They were Found in Motorola Power devices

In the 70’s, I was repairing RF Amplifiers Then. ……

Ray  WA6VAB. 

 

From: CUTTER DAVID
Sent: Monday, June 8, 2020 2:11 AM
To: Elecraft-K3@groups.io; Ray Maxfield
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

I would caution against the Hefty Fist technique.  This can distort the tab and/or the panel it is attached to so that part of the tab is no longer in contact.  I recall a torque setting for optimum contact pressure and it's not very much.  Even for very large devices (as big as your hand) it's only 5Nm from memory. 

Have a read through this document, it recommends around 0,8Nm for T0-220 

https://www.infineon.com/dgdl/Infineon-AN2013_12_Screw_Tightening_Torque-AN-v1.0-en.pdf?fileId=db3a3043429a38690142a3a1f142107f

 

David G3UNA/G6CP

 

 

On 08 June 2020 at 05:57 Ray Maxfield <wa6vab@...> wrote:

Hi Robert………… Thanks for the Feed Back. 

This seems to be a Somewhat of a failure in the K3.

The Sticky Pad, is suppose to help transfer Heat from the Fet to the Bottom Cover.

They Work, but are NOT as Good a the Old Original Thermal Compound.

I went to the Computer Parts store and purchase a small syringe of Thermal compound

And applied some to Each Tab of the Fets, and re-assemblied the bottom cover.

Making Sure to get the Star Lockwashers on each…. Tighten with a Hefty Fist.

I would order 2 Each, One to keep as a Spare! 

 

Oh Yes, we use to call the thermal compound, FBI Finger print ink !

It will get on Everything if your not Careful.

 

Great Job…. So far.

When you get the Fet installed, Run the Gain Caliberation Test,

So the radio will Reset to the Correct Power output…..

Use dummy Load if at all possible.   ……….. VAB 

   

 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Sunday, June 7, 2020 8:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 

 


 

 



 

 


 


 


Robert W5AJ
 

FET FAILURE – update > fixed

 

Many thanks to Ray WA6VAB for his FET testing technique of checking temperature of the three FETS in 10watt section.

 

Found one FET burned out (To recap).   It was one of two in parallel or Push/pull type configuration, rig still put out and worked but LOW power output on six was the clue.

 

Thought I’d save a buck and ordered RD15HVF1 from a seller in China.   Those took a while to arrive and didn’t work once here..    There is good news in that didn’t ruin the K3.

Stories abound about discrete electronic parts from China but one that rings is what is being sold isn’t RD15 – markings added, not original.  (Tab even looked different, but I’ve noticed the seller has updated his photo to match RD15 tab….)  

Got refund but lot of wasted time….

 

RF Parts has made very positive impression.  I talked to their tech support on Friday – about lunch break time for CA.   Very informative.    The earlier FET with -101 is the one to get for K3.   A great conversation on differences.   Put some on order & RF Parts got them out door, same day (Impressive, thank you RF Parts).  FETs arrive here this Monday morning.   Soldered in one replacement using my 4X readers.  Those readers really help seeing smaller stuff on PCB. 

 

Had a person of interest walk through the repair area and now be doing carpet repair due to soldering iron burn spot.

I knew not to leave the room….

Surely someone might have (quick) good idea on carpet repair to share directly?   (Yes I have matching spare carpet piece)

 

K3 FANS:   did calibration test, K3 passed but did comment on the 20meter test, stopped transmitting unexpectedly.

After calibration test, put rig on 80 watts & key down.   PA temp got up to 45C before I stopped transmit, no change in fan speed.

That doesn’t seem right but I can’t find information on what should happen (Fan settings when in NOR)

For now, running fans in fixed speed mode until can review this one.    This K3 is one bought used as 10 watt version and added the 100watt section – 10+ years ago.   in past RTTY contests, the fan has speeded up.   Ideas on where to start?   Maybe a busted firmware version?

 

As far as the heat conductive material used on FETs – I’m changing out the pad thing on other K3 to the paste &

make note to re-paste in ten years.

 

 

73 W5AJ

  

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Mel Farrer, K6KBE
Sent: Monday, June 08, 2020 1:41 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hello David,

 

As a reference on the junction of the RF transistor and the heat sink, I speak from personal manufacturing experience.  There are two issues.

 

First, the flatness of the mating heat sink surface.  Flatness can be measured with a micrometer or by using a straightedge and lay down a slick of heat sink compound and look for areas of white, none should be visible.

 

Second, is the flatness of the transistor base.  If one wishes to know if the transistor is seated properly with maximum contact with the heat sink, before soldering it down, one must put a .005 mil slick of heat grease compound on the two hole mounted transistor base plate and finger tighten the screws down, then take the screws out, remove the transistor and look at the morue pattern.  If the pattern is spectacled, that is, has a uniform pattern across the surface with lots of metal showing through, the surface tension was adequate for the test.  If areas that show white grease that is not compressed, the flatness of the base plate is a problem.  Address that problem now.  Then when final assembly is made, only go another 1/4 turn----no more.  On Stud mounted transistors, the ring around the stud must be uniform in display. 

 

There is a manufacturing MIL spec on this, but memory fails.

 

I hope this helps a little.

 

Mel, K6KBE

 

On Mon, Jun 8, 2020 at 11:19 AM David Cutter via groups.io <d.cutter=ntlworld.com@groups.io> wrote:

It's a lot easier to achieve correct and even pressure using a spring clip that presses on the body of the device, rather than one end.  Several shapes available.  I can understand the desire to use a screw that you tighten to the limit of the thread.  It's the same syndrome as turning off a tap with all your strength: it's simply unnecessary and can lead to premature failure. Sorry for the drift.

David G3UNA/G6CP

On 08 June 2020 at 15:12 Ray Maxfield <wa6vab@...> wrote:

around 0,8Nm for T0-220 …….   Let me see What range my torque wrench is Calibrated in.

I will check the Flatness of the Devices, and if needed.. File it Flat( or Lap the surface) and use Thermal compound.

Non Flat devices have been around for Years.   They were Found in Motorola Power devices

In the 70’s, I was repairing RF Amplifiers Then. ……

Ray  WA6VAB. 

 

From: CUTTER DAVID
Sent: Monday, June 8, 2020 2:11 AM
To: Elecraft-K3@groups.io; Ray Maxfield
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

I would caution against the Hefty Fist technique.  This can distort the tab and/or the panel it is attached to so that part of the tab is no longer in contact.  I recall a torque setting for optimum contact pressure and it's not very much.  Even for very large devices (as big as your hand) it's only 5Nm from memory. 

Have a read through this document, it recommends around 0,8Nm for T0-220 

https://www.infineon.com/dgdl/Infineon-AN2013_12_Screw_Tightening_Torque-AN-v1.0-en.pdf?fileId=db3a3043429a38690142a3a1f142107f

 

David G3UNA/G6CP

 

 

On 08 June 2020 at 05:57 Ray Maxfield <wa6vab@...> wrote:

Hi Robert………… Thanks for the Feed Back. 

This seems to be a Somewhat of a failure in the K3.

The Sticky Pad, is suppose to help transfer Heat from the Fet to the Bottom Cover.

They Work, but are NOT as Good a the Old Original Thermal Compound.

I went to the Computer Parts store and purchase a small syringe of Thermal compound

And applied some to Each Tab of the Fets, and re-assemblied the bottom cover.

Making Sure to get the Star Lockwashers on each…. Tighten with a Hefty Fist.

I would order 2 Each, One to keep as a Spare! 

 

Oh Yes, we use to call the thermal compound, FBI Finger print ink !

It will get on Everything if your not Careful.

 

Great Job…. So far.

When you get the Fet installed, Run the Gain Caliberation Test,

So the radio will Reset to the Correct Power output…..

Use dummy Load if at all possible.   ……….. VAB 

   

 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Sunday, June 7, 2020 8:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 

 


 

 

 


 

 


 


 


Ray Maxfield
 

Hi Bob……… Great work….Repair job too !

Ill take a look at the Fan problem also.

Mine works at lo Heat level turn-on……

73  My Tech Friend.    Ray WA6VAB 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Monday, July 20, 2020 4:16 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

FET FAILURE – update > fixed

 

Many thanks to Ray WA6VAB for his FET testing technique of checking temperature of the three FETS in 10watt section.

 

Found one FET burned out (To recap).   It was one of two in parallel or Push/pull type configuration, rig still put out and worked but LOW power output on six was the clue.

 

Thought I’d save a buck and ordered RD15HVF1 from a seller in China.   Those took a while to arrive and didn’t work once here..    There is good news in that didn’t ruin the K3.

Stories abound about discrete electronic parts from China but one that rings is what is being sold isn’t RD15 – markings added, not original.  (Tab even looked different, but I’ve noticed the seller has updated his photo to match RD15 tab….)  

Got refund but lot of wasted time….

 

RF Parts has made very positive impression.  I talked to their tech support on Friday – about lunch break time for CA.   Very informative.    The earlier FET with -101 is the one to get for K3.   A great conversation on differences.   Put some on order & RF Parts got them out door, same day (Impressive, thank you RF Parts).  FETs arrive here this Monday morning.   Soldered in one replacement using my 4X readers.  Those readers really help seeing smaller stuff on PCB. 

 

Had a person of interest walk through the repair area and now be doing carpet repair due to soldering iron burn spot.

I knew not to leave the room….

Surely someone might have (quick) good idea on carpet repair to share directly?   (Yes I have matching spare carpet piece)

 

K3 FANS:   did calibration test, K3 passed but did comment on the 20meter test, stopped transmitting unexpectedly.

After calibration test, put rig on 80 watts & key down.   PA temp got up to 45C before I stopped transmit, no change in fan speed.

That doesn’t seem right but I can’t find information on what should happen (Fan settings when in NOR)

For now, running fans in fixed speed mode until can review this one.    This K3 is one bought used as 10 watt version and added the 100watt section – 10+ years ago.   in past RTTY contests, the fan has speeded up.   Ideas on where to start?   Maybe a busted firmware version?

 

As far as the heat conductive material used on FETs – I’m changing out the pad thing on other K3 to the paste &

make note to re-paste in ten years.

 

 

73 W5AJ

  

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Mel Farrer, K6KBE
Sent: Monday, June 08, 2020 1:41 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hello David,

 

As a reference on the junction of the RF transistor and the heat sink, I speak from personal manufacturing experience.  There are two issues.

 

First, the flatness of the mating heat sink surface.  Flatness can be measured with a micrometer or by using a straightedge and lay down a slick of heat sink compound and look for areas of white, none should be visible.

 

Second, is the flatness of the transistor base.  If one wishes to know if the transistor is seated properly with maximum contact with the heat sink, before soldering it down, one must put a .005 mil slick of heat grease compound on the two hole mounted transistor base plate and finger tighten the screws down, then take the screws out, remove the transistor and look at the morue pattern.  If the pattern is spectacled, that is, has a uniform pattern across the surface with lots of metal showing through, the surface tension was adequate for the test.  If areas that show white grease that is not compressed, the flatness of the base plate is a problem.  Address that problem now.  Then when final assembly is made, only go another 1/4 turn----no more.  On Stud mounted transistors, the ring around the stud must be uniform in display. 

 

There is a manufacturing MIL spec on this, but memory fails.

 

I hope this helps a little.

 

Mel, K6KBE

 

On Mon, Jun 8, 2020 at 11:19 AM David Cutter via groups.io <d.cutter=ntlworld.com@groups.io> wrote:

It's a lot easier to achieve correct and even pressure using a spring clip that presses on the body of the device, rather than one end.  Several shapes available.  I can understand the desire to use a screw that you tighten to the limit of the thread.  It's the same syndrome as turning off a tap with all your strength: it's simply unnecessary and can lead to premature failure. Sorry for the drift.

David G3UNA/G6CP

On 08 June 2020 at 15:12 Ray Maxfield <wa6vab@...> wrote:

around 0,8Nm for T0-220 …….   Let me see What range my torque wrench is Calibrated in.

I will check the Flatness of the Devices, and if needed.. File it Flat( or Lap the surface) and use Thermal compound.

Non Flat devices have been around for Years.   They were Found in Motorola Power devices

In the 70’s, I was repairing RF Amplifiers Then. ……

Ray  WA6VAB. 

 

From: CUTTER DAVID
Sent: Monday, June 8, 2020 2:11 AM
To: Elecraft-K3@groups.io; Ray Maxfield
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

I would caution against the Hefty Fist technique.  This can distort the tab and/or the panel it is attached to so that part of the tab is no longer in contact.  I recall a torque setting for optimum contact pressure and it's not very much.  Even for very large devices (as big as your hand) it's only 5Nm from memory. 

Have a read through this document, it recommends around 0,8Nm for T0-220 

https://www.infineon.com/dgdl/Infineon-AN2013_12_Screw_Tightening_Torque-AN-v1.0-en.pdf?fileId=db3a3043429a38690142a3a1f142107f

 

David G3UNA/G6CP

 

 

On 08 June 2020 at 05:57 Ray Maxfield <wa6vab@...> wrote:

Hi Robert………… Thanks for the Feed Back. 

This seems to be a Somewhat of a failure in the K3.

The Sticky Pad, is suppose to help transfer Heat from the Fet to the Bottom Cover.

They Work, but are NOT as Good a the Old Original Thermal Compound.

I went to the Computer Parts store and purchase a small syringe of Thermal compound

And applied some to Each Tab of the Fets, and re-assemblied the bottom cover.

Making Sure to get the Star Lockwashers on each…. Tighten with a Hefty Fist.

I would order 2 Each, One to keep as a Spare! 

 

Oh Yes, we use to call the thermal compound, FBI Finger print ink !

It will get on Everything if your not Careful.

 

Great Job…. So far.

When you get the Fet installed, Run the Gain Caliberation Test,

So the radio will Reset to the Correct Power output…..

Use dummy Load if at all possible.   ……….. VAB 

   

 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Sunday, June 7, 2020 8:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 

 


 

 

 


 

 


 


 

 


Ray Maxfield
 

Hi Bob.. Found this post on Fan Temp.   hope it helps….. Ray   VAB

 

 

Yes, I think that PA Temp setting *may* be too high, but it 'all depends'.
The PA Temp indication will follow the actual temperature of the
heatsink, so if your K3 has been on for a while, that 27 degC may be normal.
Follow the instructions in the manual to set the temperature.
First turn off the K3 and leave it off until the heatsink acclimates to
room temperature (at least 15 minutes, I recommend 30 minutes).
Then turn it on and go to the PA TEMP menu - set it to the room
temperature in degC.  For a 73 degF room, that would be 23 degC.

If I recall, the fan will not turn on until the PA Temp reaches 40 degC.

If you want the fan to come on sooner, set the PA Temp to a higher value.

73,
Don W3FPR

 

 

From: Robert W5AJ
Sent: Monday, July 20, 2020 4:16 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

FET FAILURE – update > fixed

 

Many thanks to Ray WA6VAB for his FET testing technique of checking temperature of the three FETS in 10watt section.

 

Found one FET burned out (To recap).   It was one of two in parallel or Push/pull type configuration, rig still put out and worked but LOW power output on six was the clue.

 

Thought I’d save a buck and ordered RD15HVF1 from a seller in China.   Those took a while to arrive and didn’t work once here..    There is good news in that didn’t ruin the K3.

Stories abound about discrete electronic parts from China but one that rings is what is being sold isn’t RD15 – markings added, not original.  (Tab even looked different, but I’ve noticed the seller has updated his photo to match RD15 tab….)  

Got refund but lot of wasted time….

 

RF Parts has made very positive impression.  I talked to their tech support on Friday – about lunch break time for CA.   Very informative.    The earlier FET with -101 is the one to get for K3.   A great conversation on differences.   Put some on order & RF Parts got them out door, same day (Impressive, thank you RF Parts).  FETs arrive here this Monday morning.   Soldered in one replacement using my 4X readers.  Those readers really help seeing smaller stuff on PCB. 

 

Had a person of interest walk through the repair area and now be doing carpet repair due to soldering iron burn spot.

I knew not to leave the room….

Surely someone might have (quick) good idea on carpet repair to share directly?   (Yes I have matching spare carpet piece)

 

K3 FANS:   did calibration test, K3 passed but did comment on the 20meter test, stopped transmitting unexpectedly.

After calibration test, put rig on 80 watts & key down.   PA temp got up to 45C before I stopped transmit, no change in fan speed.

That doesn’t seem right but I can’t find information on what should happen (Fan settings when in NOR)

For now, running fans in fixed speed mode until can review this one.    This K3 is one bought used as 10 watt version and added the 100watt section – 10+ years ago.   in past RTTY contests, the fan has speeded up.   Ideas on where to start?   Maybe a busted firmware version?

 

As far as the heat conductive material used on FETs – I’m changing out the pad thing on other K3 to the paste &

make note to re-paste in ten years.

 

 

73 W5AJ

  

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Mel Farrer, K6KBE
Sent: Monday, June 08, 2020 1:41 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hello David,

 

As a reference on the junction of the RF transistor and the heat sink, I speak from personal manufacturing experience.  There are two issues.

 

First, the flatness of the mating heat sink surface.  Flatness can be measured with a micrometer or by using a straightedge and lay down a slick of heat sink compound and look for areas of white, none should be visible.

 

Second, is the flatness of the transistor base.  If one wishes to know if the transistor is seated properly with maximum contact with the heat sink, before soldering it down, one must put a .005 mil slick of heat grease compound on the two hole mounted transistor base plate and finger tighten the screws down, then take the screws out, remove the transistor and look at the morue pattern.  If the pattern is spectacled, that is, has a uniform pattern across the surface with lots of metal showing through, the surface tension was adequate for the test.  If areas that show white grease that is not compressed, the flatness of the base plate is a problem.  Address that problem now.  Then when final assembly is made, only go another 1/4 turn----no more.  On Stud mounted transistors, the ring around the stud must be uniform in display. 

 

There is a manufacturing MIL spec on this, but memory fails.

 

I hope this helps a little.

 

Mel, K6KBE

 

On Mon, Jun 8, 2020 at 11:19 AM David Cutter via groups.io <d.cutter=ntlworld.com@groups.io> wrote:

It's a lot easier to achieve correct and even pressure using a spring clip that presses on the body of the device, rather than one end.  Several shapes available.  I can understand the desire to use a screw that you tighten to the limit of the thread.  It's the same syndrome as turning off a tap with all your strength: it's simply unnecessary and can lead to premature failure. Sorry for the drift.

David G3UNA/G6CP

On 08 June 2020 at 15:12 Ray Maxfield <wa6vab@...> wrote:

around 0,8Nm for T0-220 …….   Let me see What range my torque wrench is Calibrated in.

I will check the Flatness of the Devices, and if needed.. File it Flat( or Lap the surface) and use Thermal compound.

Non Flat devices have been around for Years.   They were Found in Motorola Power devices

In the 70’s, I was repairing RF Amplifiers Then. ……

Ray  WA6VAB. 

 

From: CUTTER DAVID
Sent: Monday, June 8, 2020 2:11 AM
To: Elecraft-K3@groups.io; Ray Maxfield
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

I would caution against the Hefty Fist technique.  This can distort the tab and/or the panel it is attached to so that part of the tab is no longer in contact.  I recall a torque setting for optimum contact pressure and it's not very much.  Even for very large devices (as big as your hand) it's only 5Nm from memory. 

Have a read through this document, it recommends around 0,8Nm for T0-220 

https://www.infineon.com/dgdl/Infineon-AN2013_12_Screw_Tightening_Torque-AN-v1.0-en.pdf?fileId=db3a3043429a38690142a3a1f142107f

 

David G3UNA/G6CP

 

 

On 08 June 2020 at 05:57 Ray Maxfield <wa6vab@...> wrote:

Hi Robert………… Thanks for the Feed Back. 

This seems to be a Somewhat of a failure in the K3.

The Sticky Pad, is suppose to help transfer Heat from the Fet to the Bottom Cover.

They Work, but are NOT as Good a the Old Original Thermal Compound.

I went to the Computer Parts store and purchase a small syringe of Thermal compound

And applied some to Each Tab of the Fets, and re-assemblied the bottom cover.

Making Sure to get the Star Lockwashers on each…. Tighten with a Hefty Fist.

I would order 2 Each, One to keep as a Spare! 

 

Oh Yes, we use to call the thermal compound, FBI Finger print ink !

It will get on Everything if your not Careful.

 

Great Job…. So far.

When you get the Fet installed, Run the Gain Caliberation Test,

So the radio will Reset to the Correct Power output…..

Use dummy Load if at all possible.   ……….. VAB 

   

 

 

Sent from Mail for Windows 10

 

From: Robert W5AJ
Sent: Sunday, June 7, 2020 8:19 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Ray,   thanks what a GREAT test method – a testing tool that is universal and easy to understand!

 

Checked the K3 schematics and figured that the single driver in 10W stage was good or nothing would happen.

Of the two finals in 10W section, appear to be in push/pull of some type, one is COLD!

 

Should have part / repair done by FD, so this is all good.

 

Noted the FETs had sticky pad between them and bottom cover

wonder if that needs to be replaced every five years or so type thing….

I plan to use same grease used on CPU to fan on the repair.

 

73 W5AJ

 

Robert

Midland, Texas

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Ray Maxfield
Sent: Friday, June 05, 2020 11:06 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Hi Robert…….. I would look for a bad Driver Fet Transistor

There are 3 Fets that are Heat sinked to the bottom of the radio.

Check your manual for the Correct location……

They are connected to the bottom plate for use as a Heat sink

Using Phillips head screws……..

Place the radio so it is raised up using the Front Bail.

Place your fingers on the 3 Screw that are holding the 3 Fets.

Key the PTT so the XT is on.   All 3 should get Warm, Not HOT

Or Cold.   Hot= Shorted, Cold Open,  Warm Operation normal.

I found one of my Fets was Cold……  Give it a try……… Ray WA6VAB  

 

 

 

From: Robert W5AJ
Sent: Friday, June 5, 2020 6:36 PM
To: Elecraft-K3@groups.io
Subject: [Elecraft-K3] Transmitter gain calibration

 


K3/100 -> noted that K3 was indicating 50watts output when the RF power was set at 100watts.

opened the K3 utility (1.16.7.25) and started the Calibration test

5 watt test, failed first band - 160 - gets to about 4 watts out and fails.

50 watt test, everything going fine until six meters, fails - couldn't get 50 watts out....

anything that I can tweak or check local or is the party over....

73 W5AJ

 

 

 


 

 

 


 

 


 


 

 


Bob McGraw - K4TAX
 

Why not order the parts from Elecraft and be done with it? Overall, less expensive and less hassle.

Bob, K4TAX


Ray Maxfield
 

Right now, they are responding to Slowly………………..

Over a week to get an email response.     Ray  WA6VAB

 

 

Sent from Mail for Windows 10

 

From: Bob McGraw - K4TAX
Sent: Tuesday, July 21, 2020 7:50 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Why not order the parts from Elecraft and be done with it?   Overall, less expensive and less hassle.

 

Bob, K4TAX

 

 

 


Kent Trimble, K9ZTV
 

They're in lock-down.

What did you expect?

Kent  K9ZTV



On 7/21/2020 10:22 AM, Ray Maxfield wrote:

Right now, they are responding to Slowly………………..

Over a week to get an email response.     Ray  WA6VAB

 

 

Sent from Mail for Windows 10

 

From: Bob McGraw - K4TAX
Sent: Tuesday, July 21, 2020 7:50 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Why not order the parts from Elecraft and be done with it?   Overall, less expensive and less hassle.

 

Bob, K4TAX

 

 

 



Virus-free. www.avg.com


Ray Maxfield
 

They can work from Home ……….

 

Sent from Mail for Windows 10

 

From: Kent Trimble, K9ZTV
Sent: Tuesday, July 21, 2020 9:08 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

They're in lock-down.

What did you expect?

Kent  K9ZTV


On 7/21/2020 10:22 AM, Ray Maxfield wrote:

Right now, they are responding to Slowly………………..

Over a week to get an email response.     Ray  WA6VAB

 

 

Sent from Mail for Windows 10

 

From: Bob McGraw - K4TAX
Sent: Tuesday, July 21, 2020 7:50 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Transmitter gain calibration

 

Why not order the parts from Elecraft and be done with it?   Overall, less expensive and less hassle.

 

Bob, K4TAX

 

 

 

 

 

Virus-free. www.avg.com