Date   

Re: RM503 ongoing repair saga T620 UNWOUND.

ykochcal
 

Well the reason I set up and did the tests were for a couple of reasons.

1. It's another way to measure L with not much more then a scope and pulse
generator, and it covers a higher current mode then other methods. And it's
not clear to me yet where and when the loss are come in to play for at the
operating point. ( sort of like capacitors changing value with the DC
voltage applied)

2. I have not gotten there yet but I was interested in seeing if an arc over
can be "seen" in this test. ( I think one transformer I have does not yet
have a constant short but arcs over only at a higher voltage)

3. I think the properties of the core can be found, and I would like to look
for other cores of a similar nature to do some practice winding/testing on.

4. My interest is 25% to wind a new transformer and 75% to understand
inductors better.

So in terms of just winding a transformer I think I am doing a bunch of
stuff that is not directly necessary but is more educational for me.

John


Re: Multimeter Calibration and Voltage Referance

Benedikt Dienst
 

To calibrate my whole equipment, I only drive to work!

regards
Ben

From: mailto:TekScopes@...
Sent: Friday, March 27, 2015 6:10 PM
To: TekScopes@...
Subject: Re: [TekScopes] Multimeter Calibration and Voltage Referance


For voltage reference, I use a module I bought on eBay for $20 US. Just search eBay for "voltage reference ad584" (without the quotes) and you will get many examples. Some use the AD584L chip which is laser trimmed to +/- 5 mVolts which is good enough for most of us. Mine came with a hand written "final value" paper that gave the values to 5 digits.
If you want a step up, check out Low Cost Precision Voltage References . This seller offers several great references from simple DC voltage up to voltage (AC and DC), resistance, current, and frequency for $80 US.

| |
| | | | | | | |
| Low Cost Precision Voltage ReferencesCheck out http://voltagestandard.com! voltagestandard.com low cost precision DC voltage references |
| |
| View on www.voltagestandard... | Preview by Yahoo |
| |
| |

From: "henasau@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Friday, March 27, 2015 5:12 AM
Subject: [TekScopes] Multimeter Calibration and Voltage Referance

It would be interesting to know how members go about and keep in check accuracy of their workshop multimeters. I have 5 multimeters and each is giving slightly different results. It would be nice to calibrate them to a known voltage standard.


Of course I could pay the money and have them calibrated with the certificate but I am just wondering if there is an easy home made method to address this.

Henryk




[Non-text portions of this message have been removed]

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[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]


Re: Multimeter Calibration and Voltage Referance

 

For voltage reference, I use a module I bought on eBay for $20 US.  Just search eBay for "voltage reference ad584" (without the quotes) and you will get many examples.  Some use the AD584L chip which is laser trimmed to +/- 5 mVolts which is good enough for most of us.  Mine came with a hand written "final value" paper that gave the values to 5 digits.
If you want a step up, check out Low Cost Precision Voltage References .  This seller offers several great references from simple DC voltage up to voltage (AC and DC), resistance, current, and frequency for $80 US.
 
|   |
|   | |   |   |   |   |   |
| Low Cost Precision Voltage ReferencesCheck out http://voltagestandard.com! voltagestandard.com low cost precision DC voltage references |
| |
| View on www.voltagestandard... | Preview by Yahoo |
| |
|   |

  From: "henasau@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Friday, March 27, 2015 5:12 AM
Subject: [TekScopes] Multimeter Calibration and Voltage Referance

  It would be interesting to know how members go about and keep in check accuracy of their workshop multimeters. I have 5 multimeters and each is giving slightly different results. It would be nice to calibrate them to a known voltage standard.


Of course I could pay the money and have them calibrated with the certificate but I am just wondering if there is an easy home made method to address this.



Henryk





[Non-text portions of this message have been removed]

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Re: RM503 ongoing repair saga T620 UNWOUND.

Dave Wise
 

Chuck wrote:

Saturation testing is pretty meaningless in a gapped core. It
will be very hard to saturate, and will not saturate under any
condition that the primary will withstand.
Thank you for your knowledge and information, Chuck, but I respectfully disagree on this point. Although most of the energy is concentrated in the gap, if you push the flux high enough, the core will still saturate, and beyond that point your coil approximates an air-core coil. When I was making a replacement HV transformer for my HP 740B, I tested a gapped TV flyback core with a switched voltage source. There was a breakpoint where the current ramp went near vertical because of the loss of permeability at saturation. I blew up a few transistors exploring this. :)

Dave Wise


Re: handheld dvms Mastech MS8264

Kurt Rosenfeld
 

It would be funny if the fixtures from a Tek 575 also worked in the Mastech DMM.

On Fri, Mar 27, 2015 at 12:11 PM, Scott Singelyn scotts@...
[TekScopes] <TekScopes@...> wrote:

Jerry,

Here is a link to the user manual. It explains how hfe measurements are
done.

https://www.techshopbd.com/uploads/product_document/Mastech-MS8264-Digital-Multimeter-Users-Manual.pdf

===============================
Scott Singelyn - N8ZPJ
===============================


------------------------------------

------------------------------------


------------------------------------

Yahoo Groups Links



Re: handheld dvms Mastech MS8264

Scott Singelyn
 

Jerry,

Here is a link to the user manual. It explains how hfe measurements are done.

https://www.techshopbd.com/uploads/product_document/Mastech-MS8264-Digital-Multimeter-Users-Manual.pdf

===============================
Scott Singelyn - N8ZPJ
===============================


handheld dvms Mastech MS8264

 

Hi,

I recently junked my last meter with hfe and temp functions. Looking at Mastech MS8264 on ebay I see a hfe position but no xistor socket. does anyone know how transistors are tested on this machine. what low cost meter is recommended?

Jerry Massengale


Re: Multimeter Calibration and Voltage Referance

Dale H. Cook
 

At 06:12 AM 3/27/2015, Henryk wrote:

It would be interesting to know how members go about and keep in check accuracy of their workshop multimeters.
I own a vintage Hewlett-Packard VTVM calibration system (DC and 400 HZ), originally used by HP field techs. The last calibration run showed the output accuracy as 0.1% or better on all ranges.

Dale H. Cook, Roanoke/Lynchburg, VA
Osborne 1 / Kaypro 4-84 / Kaypro 1 / Amstrad PPC-640
http://plymouthcolony.net/starcity/radios/index.html


Re: Multimeter Calibration and Voltage Referance

n4buq
 

It all goes back to that old saying regarding a man with more than one watch never really knows what time it is...

I do the same as far as using a DMM. No, it isn't calibrated, but my DMMs pretty much agree with each other (and my voltage reference board) and I "trust" them for accuracy over their analog cousins.

For hobby use, that's good enough for me for most work.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "'J. L. Trantham' jltran@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Sent: Friday, March 27, 2015 8:13:37 AM
Subject: RE: [Bulk] [TekScopes] Multimeter Calibration and Voltage Referance

It's curiosity like this that leads to 'addiction' to metrology. Be
careful.



Since you will never actually know the exact value of any 'standard', you
have to have something in your lab that you would 'trust'. For me, it's a
high quality DMM. Once that is professionally calibrated, you can use it to
'measure' your 'standards' for future reference and act as a 'transfer
standard' to calibrate your other meters.



The 'standards' can be a collection of various devices (resistors, voltage
standards, inductors, capacitors, frequency standards, etc.) or a
'multi-function' calibrator. I like the Fluke 5100B series that can be had
relatively cheaply from time to time but may well need some repair to get
them up and running. It provides DC and AC voltage, resistance and current.




It also depends on what 'standards' you need in order to properly calibrate
your meters.



It's my thought to have such a 'metrology section' in my lab but I have a
long way to go.



Good luck.



Joe



From: TekScopes@... [mailto:TekScopes@...]
Sent: Friday, March 27, 2015 5:13 AM
To: TekScopes@...
Subject: [Bulk] [TekScopes] Multimeter Calibration and Voltage Referance





It would be interesting to know how members go about and keep in check
accuracy of their workshop multimeters. I have 5 multimeters and each is
giving slightly different results. It would be nice to calibrate them to a
known voltage standard.


Of course I could pay the money and have them calibrated with the
certificate but I am just wondering if there is an easy home made method to
address this.



Henryk














Re: Multimeter Calibration and Voltage Referance

J. L. Trantham
 

It's curiosity like this that leads to 'addiction' to metrology. Be
careful.



Since you will never actually know the exact value of any 'standard', you
have to have something in your lab that you would 'trust'. For me, it's a
high quality DMM. Once that is professionally calibrated, you can use it to
'measure' your 'standards' for future reference and act as a 'transfer
standard' to calibrate your other meters.



The 'standards' can be a collection of various devices (resistors, voltage
standards, inductors, capacitors, frequency standards, etc.) or a
'multi-function' calibrator. I like the Fluke 5100B series that can be had
relatively cheaply from time to time but may well need some repair to get
them up and running. It provides DC and AC voltage, resistance and current.




It also depends on what 'standards' you need in order to properly calibrate
your meters.



It's my thought to have such a 'metrology section' in my lab but I have a
long way to go.



Good luck.



Joe



From: TekScopes@... [mailto:TekScopes@...]
Sent: Friday, March 27, 2015 5:13 AM
To: TekScopes@...
Subject: [Bulk] [TekScopes] Multimeter Calibration and Voltage Referance





It would be interesting to know how members go about and keep in check
accuracy of their workshop multimeters. I have 5 multimeters and each is
giving slightly different results. It would be nice to calibrate them to a
known voltage standard.


Of course I could pay the money and have them calibrated with the
certificate but I am just wondering if there is an easy home made method to
address this.



Henryk


Re: Multimeter Calibration and Voltage Referance

n4buq
 

I made a very simple board using one of the voltage reference chips. It's plenty accurate enough for an analog meter. A few high-precision resistive dividers are handy for other voltage ranges. Just a few dollars will get you some pretty good accuracy.

They ones on eBay have some calibration values printed on them and may be just a bit closer (same type of scheme, however) but are, as mentioned, in the $40 range.

Regards,
Barry - N4BUQ

----- Original Message -----
From: "Stefan Trethan stefan_trethan@... [TekScopes]" <TekScopes@...>
To: "TekScopes" <TekScopes@...>
Sent: Friday, March 27, 2015 6:49:17 AM
Subject: Re: [TekScopes] Multimeter Calibration and Voltage Referance

I don't think a chemical voltage standard would be all that useful,
since the voltage does change as they age.
In a cal lab they would be periodically compared wih a superior
standard, and they'd keep track of that change.
So if you got an old dusty standard cell somewhere that change may not be
known.
Also temperature and stuff has a big influence.

I think there are some reasonably accurate semiconductor references
for sale on Ebay and elsewhere, in the $40 range.
Those may well be your best option for checking or calibrating low end
multimeters.

ST



On Fri, Mar 27, 2015 at 12:01 PM, Gary Robert Bosworth
grbosworth@... [TekScopes] <TekScopes@...> wrote:
Henryk:

I have seen certified voltage standards at some of the companies where I
worked. They usually had their voltage stamped on the outside to 5-digit
accuracy and traceable to the National Bureau of Standards. Perhaps you
could find one of these cells on eBay.

Gary
On Mar 27, 2015 3:13 AM, "henasau@... [TekScopes]" <
TekScopes@...> wrote:


Re: Multimeter Calibration and Voltage Referance

stefan_trethan
 

I don't think a chemical voltage standard would be all that useful,
since the voltage does change as they age.
In a cal lab they would be periodically compared wih a superior
standard, and they'd keep track of that change.
So if you got an old dusty standard cell somewhere that change may not be known.
Also temperature and stuff has a big influence.

I think there are some reasonably accurate semiconductor references
for sale on Ebay and elsewhere, in the $40 range.
Those may well be your best option for checking or calibrating low end
multimeters.

ST



On Fri, Mar 27, 2015 at 12:01 PM, Gary Robert Bosworth
grbosworth@... [TekScopes] <TekScopes@...> wrote:
Henryk:

I have seen certified voltage standards at some of the companies where I
worked. They usually had their voltage stamped on the outside to 5-digit
accuracy and traceable to the National Bureau of Standards. Perhaps you
could find one of these cells on eBay.

Gary
On Mar 27, 2015 3:13 AM, "henasau@... [TekScopes]" <
TekScopes@...> wrote:


Re: Multimeter Calibration and Voltage Referance

Gary Robert Bosworth
 

Henryk:

I have seen certified voltage standards at some of the companies where I
worked. They usually had their voltage stamped on the outside to 5-digit
accuracy and traceable to the National Bureau of Standards. Perhaps you
could find one of these cells on eBay.

Gary
On Mar 27, 2015 3:13 AM, "henasau@... [TekScopes]" <
TekScopes@...> wrote:



It would be interesting to know how members go about and keep in check
accuracy of their workshop multimeters. I have 5 multimeters and each is
giving slightly different results. It would be nice to calibrate them to a
known voltage standard.


Of course I could pay the money and have them calibrated with the
certificate but I am just wondering if there is an easy home made method to
address this.



Henryk





[Non-text portions of this message have been removed]



[Non-text portions of this message have been removed]


Tektronix 485

alan shields
 

Havingretired in Nov 2014 at 59 after a long career in electronics,  I decided to pursue my passion

         for guitaramps and have taken on a couple of commissions to design and build some valveequipment.

        I own several  TEKTRONIX  scopes including a 485, a 2230 and a TDS320which over the years I have           fully 

 Re-furbished, except for the 485 which is missing a handle        and would appreciate any info asto where I 

Could obtain one,        maybe a swap for something  of mine.




[Non-text portions of this message have been removed]


Multimeter Calibration and Voltage Referance

henasau@...
 

It would be interesting to know how members go about and keep in check accuracy of their workshop multimeters. I have 5 multimeters and each is giving slightly different results. It would be nice to calibrate them to a known voltage standard.


Of course I could pay the money and have them calibrated with the certificate but I am just wondering if there is an easy home made method to address this.



Henryk


Re: RM503 ongoing repair saga T620 UNWOUND.

Chuck Harris <cfharris@...>
 

Ok, there was a request for some measurements:

First, the primary of a 547 style transformer is wound:
#1.....#2.......#3
0 ---- 20T ---- 60T


It is universal wound with #38 gauge bifilar, parallel connected.

I tested 3 transformers. One of my manufacture, one known to
have the transformer epoxy disease, and one believed not to have
the disease (but unverified by me).

The first series of tests was done with a Sencore LC-102, and all
possible connections to the primary. The second test was done
using a GR-1650B LCR bridge. I only tested the full primary (1,3)
with the GR bridge, and it was tested at 1KHz.

My transformer:

Sencore:
1,3... 60T... 74 rings.... 1.22mH
1,2... 20T... 58 rings.... 158uH
2,3... 40T... 66 rings.... 395uH

GR:
1,3... 60T... 1.68mH, Q=2.15

Thought to be good original:

Sencore:
1,3... 60T... 50 rings.... 1.884mH
1,2... 20T... 35 rings.... 140.3uH
2,3... 40T... 42 rings.... 756uH

GR:
1,3... 60T... 1.94mH, Q=2.8

Known diseased original:

Sencore:
1,3... 60T... 51 rings.... 1.562mH
1,2... 20T... 37 rings.... 128.6uH
2,3... 40T... 46 rings.... 604uH

GR:
1,3... 60T... 1.76mH, Q=2.2

Bear in mind that the Sencore uses a rather different method of
measuring inductance. It applies a voltage source to the inductor
through a resistor, and times how long it takes for the inductor's
voltage to reach some specified value.

And,

The GR bridge is measuring at 1KHz, which is not the design frequency,
nor the frequency I measured the Q at using the Boonton Q meter.

The differences in inductance are probably due mostly to gap tolerance.
The "known diseased original" transformer was tested cold, so it
should not be too surprising that it tests about the same as the rest,
as it works fine when cold.

-Chuck Harris


Re: RM503 ongoing repair saga T620 UNWOUND.

Chuck Harris <cfharris@...>
 

Hi John,

Total gap on the center leg will be about 0.014" to 0.016"
under the tolerances tek built to. As I said earler, there
are 3 ways I have seen the gap done:

1) all legs equal, gapped using tape spacer on all three legs.
2) all legs on one half equal, 14-16 thousandths on center leg of
other half.
3) center leg on both halves shorter than others by 7 thousandths.

#1 was pretty smart from a manufacturing perspective, but creates
a transformer that radiates quite a high magnetic field.
#2 is less smart as it requires stocking two different core halves
that are visually identical.
#3 is smart from both an engineering, and a logistics perspective.

#3 is what they ended up with in all of the later scopes that I
have seen... The 503 is a very old scope. It doesn't surprise me
at all to see it is using #2.

Saturation testing is pretty meaningless in a gapped core. It
will be very hard to saturate, and will not saturate under any
condition that the primary will withstand. The core flux is set
by the gap dimensions.

When the core is ungapped, like if you use the back side to mate
with the half that has equal length legs, it will saturate pretty
easily.

More meaningful tests are inductance per turn.

-Chuck Harris



'John Snyder' Kochcal@... [TekScopes] wrote:

Chuck

Everything I have seen is consistent with what you have said here.

But for the gap size.

I went back and re-measured because I did quite a bit of cleanup after the
first set of measurements.

The 503 core that I have the two sides are not the same.
One half all the legs, left/middle/right are equal length.

The other half the middle leg is .013" to .015" shorter. Which is less then
the .018 reported from my earlier not as clean test, most likely from epoxy
on the two left/right legs that have the other epoxy that held the .020
plastic spacer in the outer two legs, the center was fairly clean from the
start.

That would match your measurements, if you mean each core half middle leg is
ground 0.007" lower and the total gap with two matching sides in there
actual position would have a total center gap of .014"

When I did some tests on the core with the saturation tester you can push
the two together and really change the curve if they are not very tightly
taped.

John



-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Thursday, March 26, 2015 11:03 AM
To: TekScopes@...
Subject: Re: [TekScopes] RM503 ongoing repair saga T620 UNWOUND.

There is something that needs to be said to all future
transformer hackers regarding epoxy:

First, in the failed brown epoxy, it is soft always, but
when heated to 130C, it becomes like chewing gum. It lacks
much cohesive strength. It is easily scraped, and picked
out of many things.

Second, not all epoxy is failed brown epoxy. The epoxy
tek used to glue the two outer core legs on the 647 core
is really good epoxy... unlike the brown stuff they potted
the coil in. 130C won't even faze it. You have to heat
the good epoxies to 150, or even 160C to soften them to
the chewing gum stage... I have seen some that needed
even higher temperature, but fortunately not on tek
transformers.

If the core halves are bound with fiberglass tape, the
epoxy is going to be the bad sort, and 130C will do. If
there is nothing binding the edges, it is good epoxy, and
150-160C will be necessary.

A nice way to separate the halves is to make 4 wedges out
of fiberglass PCB material, that taper from 1/2 inch to
5/8 inch over 4 inches, or so. Wedge them in pairs into
the slots on either side of the winding... be firm, but
not aggressive. Pop the transformer into an oven set to
130C, or 150C, and walk away for 15 minutes. When you
come back, there will be a pile of core pieces, and
coils and wedges. I hope you put something under the
transformer to catch any stray parts.

After you have separated the halves, without breaking
them, you need to take a knife blade and scrape the epoxy
from the joining surfaces. The knife won't harm the
ferrite, if you take it easy... and there is no reason to
work very hard... if it gets difficult, pop it back in
the oven for a few minutes.

The gap can be easily measured on a clean core by
assembling the core EE direction, aligned like my printed
text... legs to back. And using a feeler gage to measure
the gap. In every core I have seen, from the late 60's
forward, it will be 0.007 inch, which is 0.18mm.

[Old waxy 545 transformers can be ground on no legs, with
tape gap spacers, or ground on one core half with the
full gap, or ground on both core halves, each with 1/2
the gap.]

If your gap isn't rock solid stable, none of your measurements
will be stable. That is because the act of the gap not
shrinking as the magnetic forces increase is what stores the
energy in a gapped inductor.

Fortunately, the only really critical thing in these
transformers is the HV insulation techniques you use in
making them.

In the early days of experimenting, I used to wrap a cobby
old piece of electrical tape around the outside of the core
to hold the halves together while I was testing the winding,
and sometimes as the core heated, the tape's adhesive would
let go, and the core would flop open, and yet it still worked.

-Chuck Harris

'John Snyder' Kochcal@... [TekScopes] wrote:
Chuck

Any numbers would help me because the 547 winding spec is available.

And by the way when I say .020" gap I should be saying .020" additional
gap.

For the 503 core I have not measured the center gap directly with the two
halves together(which I should)

But one half of the core has a center leg of 0.612" and the outside leg is
0.631 on one side and 0.628 on the other side. As clean of epoxy as I
could
get.

The other half the leg is .630 on all legs from top to bottom.
So a ".020 gap core" as I have been saying would have three gaps of about
.020 right side, .38 center and .020 left side.
I measured the no side gap core configuration(which would be about a .018
center gap) with the same 16 turn 26 gage coil test coil at a saturation
of
about 9.5A and 110.8 uh (no resistance comp math)

And on the GR1657 at 1KHz Series .1080 mH with a Q of 4.4
And at 1KHz parallel .1135 mH with a Q of 4.4

With a DC resistance Rdc of 0.1496 ohms.

And I guess that is the measurement I would like to get some other
reference
for which I think your numbers could be turn adjusted for.

My GR1657 is repaired and not calibrated, clearly reads in the right range
based on a bunch of inductors, but I have no real calibration "standard"

Thanks
John


------------------------------------
Posted by: "John Snyder" <kochcal@...>
------------------------------------


------------------------------------

Yahoo Groups Links




2n3904 gone

 

thanks

Jerry Massengale


Re: RM503 ongoing repair saga T620 UNWOUND.

ykochcal
 

Chuck

Everything I have seen is consistent with what you have said here.

But for the gap size.

I went back and re-measured because I did quite a bit of cleanup after the
first set of measurements.

The 503 core that I have the two sides are not the same.
One half all the legs, left/middle/right are equal length.

The other half the middle leg is .013" to .015" shorter. Which is less then
the .018 reported from my earlier not as clean test, most likely from epoxy
on the two left/right legs that have the other epoxy that held the .020
plastic spacer in the outer two legs, the center was fairly clean from the
start.

That would match your measurements, if you mean each core half middle leg is
ground 0.007" lower and the total gap with two matching sides in there
actual position would have a total center gap of .014"

When I did some tests on the core with the saturation tester you can push
the two together and really change the curve if they are not very tightly
taped.

John

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Thursday, March 26, 2015 11:03 AM
To: TekScopes@...
Subject: Re: [TekScopes] RM503 ongoing repair saga T620 UNWOUND.

There is something that needs to be said to all future
transformer hackers regarding epoxy:

First, in the failed brown epoxy, it is soft always, but
when heated to 130C, it becomes like chewing gum. It lacks
much cohesive strength. It is easily scraped, and picked
out of many things.

Second, not all epoxy is failed brown epoxy. The epoxy
tek used to glue the two outer core legs on the 647 core
is really good epoxy... unlike the brown stuff they potted
the coil in. 130C won't even faze it. You have to heat
the good epoxies to 150, or even 160C to soften them to
the chewing gum stage... I have seen some that needed
even higher temperature, but fortunately not on tek
transformers.

If the core halves are bound with fiberglass tape, the
epoxy is going to be the bad sort, and 130C will do. If
there is nothing binding the edges, it is good epoxy, and
150-160C will be necessary.

A nice way to separate the halves is to make 4 wedges out
of fiberglass PCB material, that taper from 1/2 inch to
5/8 inch over 4 inches, or so. Wedge them in pairs into
the slots on either side of the winding... be firm, but
not aggressive. Pop the transformer into an oven set to
130C, or 150C, and walk away for 15 minutes. When you
come back, there will be a pile of core pieces, and
coils and wedges. I hope you put something under the
transformer to catch any stray parts.

After you have separated the halves, without breaking
them, you need to take a knife blade and scrape the epoxy
from the joining surfaces. The knife won't harm the
ferrite, if you take it easy... and there is no reason to
work very hard... if it gets difficult, pop it back in
the oven for a few minutes.

The gap can be easily measured on a clean core by
assembling the core EE direction, aligned like my printed
text... legs to back. And using a feeler gage to measure
the gap. In every core I have seen, from the late 60's
forward, it will be 0.007 inch, which is 0.18mm.

[Old waxy 545 transformers can be ground on no legs, with
tape gap spacers, or ground on one core half with the
full gap, or ground on both core halves, each with 1/2
the gap.]

If your gap isn't rock solid stable, none of your measurements
will be stable. That is because the act of the gap not
shrinking as the magnetic forces increase is what stores the
energy in a gapped inductor.

Fortunately, the only really critical thing in these
transformers is the HV insulation techniques you use in
making them.

In the early days of experimenting, I used to wrap a cobby
old piece of electrical tape around the outside of the core
to hold the halves together while I was testing the winding,
and sometimes as the core heated, the tape's adhesive would
let go, and the core would flop open, and yet it still worked.

-Chuck Harris

'John Snyder' Kochcal@... [TekScopes] wrote:
Chuck

Any numbers would help me because the 547 winding spec is available.

And by the way when I say .020" gap I should be saying .020" additional
gap.

For the 503 core I have not measured the center gap directly with the two
halves together(which I should)

But one half of the core has a center leg of 0.612" and the outside leg is
0.631 on one side and 0.628 on the other side. As clean of epoxy as I
could
get.

The other half the leg is .630 on all legs from top to bottom.
So a ".020 gap core" as I have been saying would have three gaps of about
.020 right side, .38 center and .020 left side.
I measured the no side gap core configuration(which would be about a .018
center gap) with the same 16 turn 26 gage coil test coil at a saturation
of
about 9.5A and 110.8 uh (no resistance comp math)

And on the GR1657 at 1KHz Series .1080 mH with a Q of 4.4
And at 1KHz parallel .1135 mH with a Q of 4.4

With a DC resistance Rdc of 0.1496 ohms.

And I guess that is the measurement I would like to get some other
reference
for which I think your numbers could be turn adjusted for.

My GR1657 is repaired and not calibrated, clearly reads in the right range
based on a bunch of inductors, but I have no real calibration "standard"

Thanks
John


Anyone know where to get r185 5k position control on 475

alan_w_global@...
 

Hi Everyone,


At last I have my power supplies working and the trace is back, but now I get down to the fix, the ch1 position pot is broken, its a dual 5k 0.5W (r185 311-1397-00 part no. 10M366A), i've seen it on ebay but it costs too much from the US, anyone in UK have one or know a supplier?


Also does anyone know the correct resistance to ground on the +5 -8 and other rails?


Regards


Alan

80821 - 80840 of 195487