Date   

Tek Temperature Coefficient on precision resistor

victor.silva
 

Can anyone confirm that Tektronix TC=T9 is equivalent to 25ppm temp coeff. on precision resistors.

On the 2465B Tektronix specifies TNPW1206-1006BT TC=T9, which I believe are 25ppm T/C resistors (the rest I know, 1206, 10k, 0.1%, thin film)
These are used in the reference for the A/D on the A5 module.

Thanks,
Victor


Re: 634 Monitor HV board issue

Dave Wise
 

Sounds like a well-known problem with Tek HV transformers of a certain era. They picked an impregnant which today becomes lossy when hot, and the transformer goes into thermal runaway. The best fix is to rewind. Chuck Harris has a machine, but I don't think he has a recipe for the 634.

It can also be done by hand, although it's tedious. For example, see topic and album "453 HV Transformer Rewind", where I developed a machine and procedure from ordinary household objects. Years later, my transformer is still working perfectly. You'll have to figure out wire sizes and turns, unless someone has the spec sheet.

HTH,
Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Adrian <Adrian@...>
Sent: Monday, July 09, 2018 8:41 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 634 Monitor HV board issue

Having spent some more time on this I'm now wondering if the issue could be the transformer 20V primary? Do these things tend to develop shorted turns? I ask because I seem to have a normal image for the 10-15 seconds before the primary current has ramped to the point (a) my nerve fails (~2.5A) and (b) the drive transistor is cooking, so I switch off which makes me think the voltage multiplier is working?

Thanks,
Adrian


Re: 634 Monitor HV board issue

Adrian
 

Having spent some more time on this I'm now wondering if the issue could be the transformer 20V primary? Do these things tend to develop shorted turns? I ask because I seem to have a normal image for the 10-15 seconds before the primary current has ramped to the point (a) my nerve fails (~2.5A) and (b) the drive transistor is cooking, so I switch off which makes me think the voltage multiplier is working?

Thanks,
Adrian


Re: 7A13 Comparison Voltage coarse knob

Colin Herbert
 

Thanks for this info, Håkan. I was aware of the use on 7A22 (I own one) but not the others.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of zenith5106
Sent: 06 July 2018 22:35
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7A13 Comparison Voltage coarse knob

The Tek part number for the knob is 366-1084-00 and it just may be used on
some other item of equipment.
This knob was also used on AM502, 26A2, 5A19N, 5A22N, 7A22, 7S11 & 7S12.

/Håkan


Re: Kludging together a TDR or similar?

 

On Thu, Jun 28, 2018 at 01:49 pm, Siggi wrote:


Alan Wolke did a video on TDR using a scrap box ~1ns pulser: <
https://www.youtube.com/watch?v=9cP6w2odGUc >. For ~$2 and a few minutes
soldering, you might be able to get useful results :).
I think you beat me to it :

https://www.youtube.com/watch?v=9cP6w2odGUc

Yup you did, I see the URL is identical. Nice that it is still there.

I was prompted fo get it because someone on Usenet is picking on one of the better members there and he said, probably sarcastically "How are you going to determine the twist in a CAT 5e cable ? He didn't ask me but I decided to answer anyway and I remembered the video that was sent to me by a cohort.

I think the guy knows what he's doing.


Re: Kludging together a TDR or similar?

Tom Gardner
 

On 08/07/18 16:11, cheater cheater wrote:
Sorry, having trouble picturing the circuit, mind explaining it in a bit
more detail? Add a netlist maybe?

On Sun, 8 Jul 2018, 10:12 Tom Gardner, <tggzzz@...> wrote:

On 08/07/18 04:53, Ed Breya via Groups.Io wrote:
If you are concerned about setting or controlling the frequency, you can
drive the output stage instead from another with XO or a generator. My
preferred 74AC driver for fast, strong pulsing is the 74AC541, with eight
amplifiers that can be paralleled. Also, the pinout is excellent for this
sort of thing, layout-wise - all ins on one side, and all outs on the other.
My preference is 74LVC1G*, which have ~7ohms output impedance, 32mA
drive, and
work from ~1V to 5V albeit with different risetimes.

If you add a 143ohm series resistance and put three of those in series
(and
decouple them very well), then you get a clean 50ohm output. I can't
measure the
risetime; it is certainly sub nanosecond, another measure gives ~600ps,
and I've
seen a (poorly controlled) measurement of 300ps on a 1GHz scope.
I note that I wrote "put three of those in series". I meant parallel.

  - 74lvc1g* - 143R -
 |                   |
-+- 74lvc1g* - 143R -+-
 |                   |
  - 74lvc1g* - 143R -

We are into the third week of a heatwave here; it must be cooking
my brain. Well, that's the least worrying alternative.


Re: Kludging together a TDR or similar?

Tom Gardner
 

On 08/07/18 16:11, cheater cheater wrote:
Sorry, having trouble picturing the circuit, mind explaining it in a bit
more detail? Add a netlist maybe?

On Sun, 8 Jul 2018, 10:12 Tom Gardner, <tggzzz@...> wrote:

On 08/07/18 04:53, Ed Breya via Groups.Io wrote:
If you are concerned about setting or controlling the frequency, you can
drive the output stage instead from another with XO or a generator. My
preferred 74AC driver for fast, strong pulsing is the 74AC541, with eight
amplifiers that can be paralleled. Also, the pinout is excellent for this
sort of thing, layout-wise - all ins on one side, and all outs on the other.
My preference is 74LVC1G*, which have ~7ohms output impedance, 32mA
drive, and
work from ~1V to 5V albeit with different risetimes.

If you add a 143ohm series resistance and put three of those in series
(and
decouple them very well), then you get a clean 50ohm output. I can't
measure the
risetime; it is certainly sub nanosecond, another measure gives ~600ps,
and I've
seen a (poorly controlled) measurement of 300ps on a 1GHz scope.




Re: Kludging together a TDR or similar?

 

Sorry, having trouble picturing the circuit, mind explaining it in a bit
more detail? Add a netlist maybe?

On Sun, 8 Jul 2018, 10:12 Tom Gardner, <tggzzz@...> wrote:

On 08/07/18 04:53, Ed Breya via Groups.Io wrote:
If you are concerned about setting or controlling the frequency, you can
drive the output stage instead from another with XO or a generator. My
preferred 74AC driver for fast, strong pulsing is the 74AC541, with eight
amplifiers that can be paralleled. Also, the pinout is excellent for this
sort of thing, layout-wise - all ins on one side, and all outs on the other.
My preference is 74LVC1G*, which have ~7ohms output impedance, 32mA
drive, and
work from ~1V to 5V albeit with different risetimes.

If you add a 143ohm series resistance and put three of those in series
(and
decouple them very well), then you get a clean 50ohm output. I can't
measure the
risetime; it is certainly sub nanosecond, another measure gives ~600ps,
and I've
seen a (poorly controlled) measurement of 300ps on a 1GHz scope.




Re: Kludging together a TDR or similar?

Tom Gardner
 

On 08/07/18 04:53, Ed Breya via Groups.Io wrote:
If you are concerned about setting or controlling the frequency, you can drive the output stage instead from another with XO or a generator. My preferred 74AC driver for fast, strong pulsing is the 74AC541, with eight amplifiers that can be paralleled. Also, the pinout is excellent for this sort of thing, layout-wise - all ins on one side, and all outs on the other.
My preference is 74LVC1G*, which have ~7ohms output impedance, 32mA drive,  and work from ~1V to 5V albeit with different risetimes.

If you add a 143ohm series resistance and put three of those in series (and decouple them very well), then you get a clean 50ohm output. I can't measure the risetime; it is certainly sub nanosecond, another measure gives ~600ps, and I've seen a (poorly controlled) measurement of 300ps on a 1GHz scope.


Re: Source for 1/8" fibreglass or other hard plastic rod in UK

John Parkins G8KVP
 

Hello David,

If you have a local B&Q have a look in there. They do a small range of
both metal and plastic rods as well as small angle, flat and tubes.



Saturday, July 7, 2018, 6:26:57 PM, you wrote:

DCP> I'm looking for a UK source of 1/8" (0.125" or 3.2mm) diameter fibreglass
DCP> rods (or other hard plastic) such as is used in many 7000 series plugins.

DCP> For the specific application (the rod down the middle of plastic expansion
DCP> rivet) a 3mm rod won't do.

DCP> I only want a small quantity, so any suppliers with large minimum orders
DCP> would be a problem.

DCP> Thanks
DCP> David


DCP>




--
Best regards,
John mailto:john@...


Re: Source for 1/8" fibreglass or other hard plastic rod in UK

Michael A. Terrell
 

I have used the dowels from those 6" long cotton swabs to hold wood together for repairs. Drill a hole, glue the wood together, and drive on of the dowels in to hold it in position while it dries. They are also good for removing crud by cutting them to a sharp point to get into cracks and small areas. I'm sure you can find many uses for them, in repairing your electronics as well.


Michael A. Terrell

-----Original Message-----
From: "David C. Partridge" <@perdrix>

A great idea - Hobbycraft has 1/8" hard wood dowels


Re: Kludging together a TDR or similar?

Ed Breya
 

If you are concerned about setting or controlling the frequency, you can drive the output stage instead from another with XO or a generator. My preferred 74AC driver for fast, strong pulsing is the 74AC541, with eight amplifiers that can be paralleled. Also, the pinout is excellent for this sort of thing, layout-wise - all ins on one side, and all outs on the other.

Ed


Re: Source for 1/8" fibreglass or other hard plastic rod in UK

 

A great idea - Hobbycraft has 1/8" hard wood dowels

Dave

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Michael A. Terrell
Sent: 07 July 2018 21:44
To: TekScopes@groups.io
Subject: Re: [TekScopes] Source for 1/8" fibreglass or other hard plastic rod in UK

How about 1/" wood dowel rods? They are cheap, and fairly hard. They are used as sticks to make suckers, so they are fairly cheap. You might find then on Ebay, from China or at a bakery supply store.


Michael A. Terrell


-----Original Message-----
From: "David C. Partridge" <@perdrix>

Problem is the UK suppliers mostly have 3mm not 3.2mm


Re: Kludging together a TDR or similar?

n4buq
 

Okay, Bruce. I appreciate the explanation. I'll have to do the math and see where that puts the target frequency.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Bruce Griffiths" <bruce.griffiths@...>
To: TekScopes@groups.io
Sent: Saturday, July 7, 2018 6:12:50 PM
Subject: Re: [TekScopes] Kludging together a TDR or similar?

At low frequencies where propagation delay can be neglected the frequency
will be k/RC where in this case
where the output resistance of the 74AC14 can also be neglected:
k ~ 1/(ln(Vt+/Vt-)*((Vcc-Vt-)/(Vcc-Vt+)))
where
Vt+ is the upper input switching threshold of the 74AC14
Vt- is the lower input switching threshold of the 74AC14
Vcc (5V in this case) is the power supply voltage for the 74AC14
Bruce
On 08 July 2018 at 06:49 n4buq <n4buq@...> wrote:


No, I'm not overly concerned about the pulse width. I was just wondering
why there is a difference between the measured width (on the scope) vs the
fequency I'd expected with 1/RC. According to Bruce, there's more to it
than that and the hysteresis of the Schmitt trigger has to be taken into
consideration.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Michael A. Terrell" <mike.terrell@...>
To: TekScopes@groups.io
Sent: Saturday, July 7, 2018 9:14:23 AM
Subject: Re: [TekScopes] Kludging together a TDR or similar?

Both parts are 5% but that isn't important.

The time required for a pulse to travel to the discontinuity isn't
affected
by the error in the pulse width. If it bothers you, use a crystal time
base
instead of a simple one gate oscillator.

I have another schematic with multiple pulse widths that you can select
from,
but like this design, it is built with 5% parts. That one also allows you
to
select 50, 75 or 100 ohm output impedance by adding a 22 ohm, or a 50 ohm
resistor in the output path.

Even temperature has some effect on the frequency, along with the
propagation
delay on the gate.


Michael A. Terrell


-----Original Message-----
From: n4buq <n4buq@...>
Sent: Jul 7, 2018 9:03 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Kludging together a TDR or similar?

Looking at that schematic, it appears the frequency is determined by C3
and
R1. If I'm not mistaken, the exact values of those components would
result
in a frequency of 3.129 kHz; however, the oscilloscope images appear to
show 4.81 kHz. Is that difference due to component tolerances or is
something else at work here?

Thanks,
Barry - N4BUQ






Re: Kludging together a TDR or similar?

Bruce Griffiths
 

At low frequencies where propagation delay can be neglected the frequency will be k/RC where in this case
where the output resistance of the 74AC14 can also be neglected:
k ~ 1/(ln(Vt+/Vt-)*((Vcc-Vt-)/(Vcc-Vt+)))
where
Vt+ is the upper input switching threshold of the 74AC14
Vt- is the lower input switching threshold of the 74AC14
Vcc (5V in this case) is the power supply voltage for the 74AC14
Bruce

On 08 July 2018 at 06:49 n4buq <n4buq@...> wrote:


No, I'm not overly concerned about the pulse width. I was just wondering why there is a difference between the measured width (on the scope) vs the fequency I'd expected with 1/RC. According to Bruce, there's more to it than that and the hysteresis of the Schmitt trigger has to be taken into consideration.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Michael A. Terrell" <mike.terrell@...>
To: TekScopes@groups.io
Sent: Saturday, July 7, 2018 9:14:23 AM
Subject: Re: [TekScopes] Kludging together a TDR or similar?

Both parts are 5% but that isn't important.

The time required for a pulse to travel to the discontinuity isn't affected
by the error in the pulse width. If it bothers you, use a crystal time base
instead of a simple one gate oscillator.

I have another schematic with multiple pulse widths that you can select from,
but like this design, it is built with 5% parts. That one also allows you to
select 50, 75 or 100 ohm output impedance by adding a 22 ohm, or a 50 ohm
resistor in the output path.

Even temperature has some effect on the frequency, along with the propagation
delay on the gate.


Michael A. Terrell


-----Original Message-----
From: n4buq <n4buq@...>
Sent: Jul 7, 2018 9:03 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Kludging together a TDR or similar?

Looking at that schematic, it appears the frequency is determined by C3 and
R1. If I'm not mistaken, the exact values of those components would result
in a frequency of 3.129 kHz; however, the oscilloscope images appear to
show 4.81 kHz. Is that difference due to component tolerances or is
something else at work here?

Thanks,
Barry - N4BUQ




Re: TDS744

 

While looking for a replacement, I noticed that the later versions
have a different HT transformer,
Also the aluminum cover over the P/S is slightly different to fit the newer transformer.
/Håkan


Re: Source for 1/8" fibreglass or other hard plastic rod in UK

Michael A. Terrell
 

How about 1/" wood dowel rods? They are cheap, and fairly hard. They are used as sticks to make suckers, so they are fairly cheap. You might find then on Ebay, from China or at a bakery supply store.


Michael A. Terrell

-----Original Message-----
From: "David C. Partridge" <@perdrix>

Problem is the UK suppliers mostly have 3mm not 3.2mm


Re: Source for 1/8" fibreglass or other hard plastic rod in UK

stefan_trethan
 

I'm sure you can import some 1/8" stuff from the colonies?

3.2mm is a standard arrow shaft size, but most are probably carbon
(and conductive).

R&G in Germany has only 3mm, but that costs almost nothing.

ST

On Sat, Jul 7, 2018 at 10:26 PM, David C. Partridge
<@perdrix> wrote:
Problem is the UK suppliers mostly have 3mm not 3.2mm

Dave

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Artekmedia
Sent: 07 July 2018 18:30
To: TekScopes@groups.io
Subject: Re: [TekScopes] Source for 1/8" fibreglass or other hard plastic
rod in UK

David

I recently found a source for a similar item here in states at what we
call a "Hobby Shop" (Model planes, trains, ships, etc)

Dave
manuals@...

On 7/7/2018 1:26 PM, David C. Partridge wrote:
I'm looking for a UK source of 1/8" (0.125" or 3.2mm) diameter fibreglass
rods (or other hard plastic) such as is used in many 7000 series plugins.

For the specific application (the rod down the middle of plastic expansion
rivet) a 3mm rod won't do.

I only want a small quantity, so any suppliers with large minimum orders
would be a problem.

Thanks
David




--
Dave
Manuals@...
www.ArtekManuals.com








Re: Source for 1/8" fibreglass or other hard plastic rod in UK

 

Problem is the UK suppliers mostly have 3mm not 3.2mm

Dave

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
Artekmedia
Sent: 07 July 2018 18:30
To: TekScopes@groups.io
Subject: Re: [TekScopes] Source for 1/8" fibreglass or other hard plastic
rod in UK

David

I recently found a source for a similar item here in states at what we
call a "Hobby Shop" (Model planes, trains, ships, etc)

Dave
manuals@...

On 7/7/2018 1:26 PM, David C. Partridge wrote:
I'm looking for a UK source of 1/8" (0.125" or 3.2mm) diameter fibreglass
rods (or other hard plastic) such as is used in many 7000 series plugins.

For the specific application (the rod down the middle of plastic expansion
rivet) a 3mm rod won't do.

I only want a small quantity, so any suppliers with large minimum orders
would be a problem.

Thanks
David




--
Dave
Manuals@...
www.ArtekManuals.com


Re: Kludging together a TDR or similar?

Michael A. Terrell
 

You also have to deal with the input and output capacitance of the gate, along with the distributed capacitance in the circuit board. It's also possible that he took the photo from a hand built prototype.

I used to work with two stage Sallen-Key filters. They used 14, 1% components, plus either a wideband voltage amplifier, or a current amplifier for the higher frequencies. Both the ripple and the 3dB points had to fall within 5%, but they often needed components changed to get them to pass. Sometimes the resistance of the reflowed solder was enough to made it fail. Just a fraction of an ohm. Other times, swapping the pair of 100pF SMD caps in a stage would pull i into spec. There were 16 identical filters on these video boards, but minor variations in the distributed capacitance would cause major problems. I wrote a program to suggest new resistor values, based on how far out of spec a stage was.

Other people would just randomly select a new part, and try dozens of combinations to get it to pass. These filters ranged for 10 KHz to 20 MHz and they were in top of the line Telemetry receivers. One was put aboard the ISS as part of a kU band communications system. The multiple filters allowed the use of voice, video or wideband data uploads.


Michael A. Terrell

-----Original Message-----
From: n4buq <n4buq@...>

No, I'm not overly concerned about the pulse width. I was just wondering why there is a difference between the measured width (on the scope) vs the frequency I'd expected with 1/RC. According to Bruce, there's more to it than that and the hysteresis of the Schmitt trigger has to be taken into consideration.

Thanks,
Barry - N4BUQ