Date   

Tektronix tds 2014

phillip.prokop@...
 

Hello everyone. Found this group researching my problem. Non working tds 2014. Powers up, backlight comes on, LED’s come on, does not boot up. Began the troubleshooting steps in the service manual and found an IC on the main board getting extremely hot that the gold plating on the underside of the board for that IC, a portion of it is gone. While I haven’t gone through the full troubleshooting I am fairly certain that is the problem. Can anyone suggest any strategies for fixing that? Other than replacing the board.


Re: In Defense of the 7A19

tek_547
 

On Fri, May 29, 2020 at 10:23 PM, Dennis Tillman W7pF wrote:


HP wasted no time touting the superior performance and lower cost of their new
lab scopes with an industry wide advertisement. Within Tek this became known
as the HP "Foxtail" ad. It didn't mention Tek but it mocked the new features
of the 7K scopes as irrelevant "bells and whistles". One of those bells and
whistles was Barrie Gilbert's revolutionary on-screen readout.
Interesting story Dennis, thanx for that.
René


Re: Advice about buying a 7904

Jim Ford
 

I think the modularity of the 7000 (and 5000 and 11000) series Tek scopes is a big part of their appeal and superiority over the HP scopes. How cool is it to be able to mix and match plug-ins to your needs at any given time?!

Jim Ford

------ Original Message ------
From: sdturne@q.com
To: TekScopes@groups.io
Sent: 5/29/2020 10:08:34 PM
Subject: Re: [TekScopes] Advice about buying a 7904

Reg,

To add to Harvey's excellent response, yes indeed most (all?) 7k plugins will work in any 7k mainframe. HOWEVER, there are at least a couple plugins (I cannot recall which ones right now, perhaps someone else knows off the top of their head) that explicitly must never be used in a 7104 because the way they drive the crt can cause damage to it. You absolutely could simply use the plugins you have for your 7104 in a 7904(A).

Sean

On Fri, May 29, 2020 at 05:53 PM, Reginald Beardsley wrote:


Please forgive me my ignorance, but for most of my life these things were pure
unobtainium for budgetary reasons. And as I was not an EE and not allowed to
touch the ones at work, there was no incentive to torture myself by looking at
catalogs of things I could not afford. Getting a 465 was a huge event for me.
And I don't mean all the work it took to repair it. I am acutely aware of how
fiddly adjusting the vertical amplifiers is. But when you get it right, wow!
Though in all honesty, I like my Dumont 1062 better as it does not have a fan.
It's only 60 MHz, but otherwise matches the 465 in features.

Can I use my 7104 plugins in a 7904 mainframe, albeit with reduced BW and
sweep speeds? That would greatly ease my concerns about using the 7104 on a
regular basis. And make getting a 7904 mainframe pretty much a no-brainer.
Just a question of getting a good deal.

Is there a matrix which shows which plugins will work in which mainframes? I'm
really only interested in the vertical and horizontal plugins. For the other
stuff I have HP gear. I'm not aware of anything Tek made that can compete with
an 8566B or 8510C.

Thanks,
Reg


Re: Advice about buying a 7904

Dick
 

Using the Plug-Ins designed for the 7104 in a 7904 is like
bring coal to Newcastle !!

The 7104 Plug-Ins are rather rare and worth a lot more
than the 7904 counterparts.

73, Dick, W1KSZ
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of sdturne@q.com <sdturne@q.com>
Sent: Friday, May 29, 2020 10:08 PM
To: TekScopes@groups.io <TekScopes@groups.io>
Subject: Re: [TekScopes] Advice about buying a 7904

Reg,

To add to Harvey's excellent response, yes indeed most (all?) 7k plugins will work in any 7k mainframe. HOWEVER, there are at least a couple plugins (I cannot recall which ones right now, perhaps someone else knows off the top of their head) that explicitly must never be used in a 7104 because the way they drive the crt can cause damage to it. You absolutely could simply use the plugins you have for your 7104 in a 7904(A).

Sean

On Fri, May 29, 2020 at 05:53 PM, Reginald Beardsley wrote:


Please forgive me my ignorance, but for most of my life these things were pure
unobtainium for budgetary reasons. And as I was not an EE and not allowed to
touch the ones at work, there was no incentive to torture myself by looking at
catalogs of things I could not afford. Getting a 465 was a huge event for me.
And I don't mean all the work it took to repair it. I am acutely aware of how
fiddly adjusting the vertical amplifiers is. But when you get it right, wow!
Though in all honesty, I like my Dumont 1062 better as it does not have a fan.
It's only 60 MHz, but otherwise matches the 465 in features.

Can I use my 7104 plugins in a 7904 mainframe, albeit with reduced BW and
sweep speeds? That would greatly ease my concerns about using the 7104 on a
regular basis. And make getting a 7904 mainframe pretty much a no-brainer.
Just a question of getting a good deal.

Is there a matrix which shows which plugins will work in which mainframes? I'm
really only interested in the vertical and horizontal plugins. For the other
stuff I have HP gear. I'm not aware of anything Tek made that can compete with
an 8566B or 8510C.

Thanks,
Reg


Re: Advice about buying a 7904

Sean Turner
 

Reg,

To add to Harvey's excellent response, yes indeed most (all?) 7k plugins will work in any 7k mainframe. HOWEVER, there are at least a couple plugins (I cannot recall which ones right now, perhaps someone else knows off the top of their head) that explicitly must never be used in a 7104 because the way they drive the crt can cause damage to it. You absolutely could simply use the plugins you have for your 7104 in a 7904(A).

Sean

On Fri, May 29, 2020 at 05:53 PM, Reginald Beardsley wrote:


Please forgive me my ignorance, but for most of my life these things were pure
unobtainium for budgetary reasons. And as I was not an EE and not allowed to
touch the ones at work, there was no incentive to torture myself by looking at
catalogs of things I could not afford. Getting a 465 was a huge event for me.
And I don't mean all the work it took to repair it. I am acutely aware of how
fiddly adjusting the vertical amplifiers is. But when you get it right, wow!
Though in all honesty, I like my Dumont 1062 better as it does not have a fan.
It's only 60 MHz, but otherwise matches the 465 in features.

Can I use my 7104 plugins in a 7904 mainframe, albeit with reduced BW and
sweep speeds? That would greatly ease my concerns about using the 7104 on a
regular basis. And make getting a 7904 mainframe pretty much a no-brainer.
Just a question of getting a good deal.

Is there a matrix which shows which plugins will work in which mainframes? I'm
really only interested in the vertical and horizontal plugins. For the other
stuff I have HP gear. I'm not aware of anything Tek made that can compete with
an 8566B or 8510C.

Thanks,
Reg


Re: Advice about buying a 7904

ChrisBeee
 

:-DDD
Know what you are talkin' about!
Chris

On Fri, May 29, 2020 at 08:12 PM, Chuck Harris wrote:


I find all of the fans get quieter as I get older.

I wonder why that is?

-Chuck Harris

Bob Koller via groups.io wrote:
The fan on my 7904A is very quiet, a non issue on mine at least. I suggest
that the most important thing will be finding the best instrument available
around your location. Packing properly is difficult and shipping is expensive.




Re: 475 questions

ciclista41@...
 

Oops! I meant that for Chuck, but thank you, also, for prompting that informative discussion!

On Fri, May 29, 2020 at 09:07 PM, <ciclista41@yahoo.com> wrote:


Hi Raymond!

Wow! Thanks for the thorough explanation. I had been wondering about the
so-called capacitor "reforming."

Bruce

On Fri, May 29, 2020 at 10:58 AM, Chuck Harris wrote:


Hi Raymond,

Old fashioned electrolytic capacitors have a fairly reactive,
(to aluminum) highly conductive, water based electrolyte.

The capacitor's leakage current creates an electrolytic cell
with the aluminum plates, and removes the oxide layer from the
cathode plate, and builds an oxide layer on the anode plate...

The oxide layer on the anode plate is the dielectric (insulator)
for the capacitor.

This reaction is the "reforming" process that lives on in
electrolytic capacitor lore... Even today. It is also a process
known colloquially as anodizing aluminum.

The aluminum oxide dielectric layer has competing issues:

As the oxide grows thicker, it became a better insulator, and works
to stop the leakage current necessary to grow the oxide layer thicker.

As the oxide layer ceases growing, the electrolyte dissolves the
oxide layer, allowing the leakage currents to increase... growing the
oxide layer thicker.

In normal operation, a balance is reached between leakage current
and growing the oxide layer.... A "working voltage" rating results.

The only way to increase the thickness of the oxide layer once
it reaches equilibrium, is to increase the voltage across the
electrolytic cell, making the cell's current increase, and in turn,
the oxide grow thicker... creating a new higher voltage equilibrium,
and a new "working voltage".

As long as the heat created by the leakage current doesn't raise
the temperature of the electrolyte to a point where the it boils,
the capacitor is fairly happy.

This means that higher than working voltage surges will start to
heat the electrolyte, but as long as the surge goes away before the
electrolyte boils, the capacitor will live to see another day.

One other factor needs mentioning:

The thinner the oxide dielectric layer, the higher the capacitance,
and the lower the working voltage.

The thicker the oxide dielectric layer, the lower the capacitance,
and the higher the working voltage.

The manufacturer had to balance all of these conditions when they
wrote the specifications for their old style electrolytic capacitors.

If you used these old electrolytic capacitors at a lower than working
voltage, their capacitance would increase, and their ability to
operate safely at their specified working voltage would diminish.

Unless you reformed the capacitor... safely limiting the current
until the oxide layer thickened...

Modern electrolytic capacitors use a nonreactive (to aluminum)
electrolyte and as a result, reforming is no longer necessary.

Modern electrolytic capacitors have their oxide layer created, and
their voltage rating determined, before the capacitor is even
assembled.

-Chuck Harris

Raymond Domp Frank wrote:
On Fri, May 29, 2020 at 04:07 PM, Eric wrote:


There are 2 fundamental differences that need to be taken in to account
when
replacing “vintage” caps. And I use the term vintage loosely. One is
tolerance. In the worst case I can remember a capacitors value was +150%
-%100
tolerance. The means that for a 1 uF the measured value of anything
between
2.5 uF to .1 uF would be considered “in spec” old radios still amaze
me
they ever worked. Now a days +-20% is the normal. The service manual will
tell
you the tolerance of the filters. From memory I am guessing it is going
to
be
+100% to -20 % so pretty wide design tolerance on the filters.

The other important spec is the voltage rating of the cap. And here
vintage
caps and modern caps differ greatly. Vintage caps were very tolerant of
over
voltage especially given how tube gear warms up before the tube’s comes
in
to operation the B+ will spike some times as high as 200 to 250 volts
higher
then when the device is operating and can hang there for about 15-30
seconds.
This is not an issue in your 475 as it is solid state. However modern
caps
are
completely intolerant of over voltage so if you have the physical space
it
is
always good to bump up the voltage rating of the cap it wont effect
anything
to replace a 63V cap with a 400V cap excepta little cost in $ maybe one
or
2
and physical space it will be slightly bigger then it’s modern lower
voltage
counterpart. However both are usually smaller then their vintage counter
part
even doubling the voltage the modern can will be smaller physically.
I don't think anyone would have accepted caps with +150/-100% tolerance,
not
even electrolytics...

Any information on the inability of modern caps to withstand overvoltage
more than vintage caps used to? Maybe WV was just very conservatively
spec'ed?
I'd rather have known the actual max.

For (wet) Al electrolytics, choosing a spec-voltage very much higher than
it's ever going to experience, has a deformation effect, so is not
recommended.

Raymond




Re: 475 questions

ciclista41@...
 

Hi Raymond!

Wow! Thanks for the thorough explanation. I had been wondering about the so-called capacitor "reforming."

Bruce

On Fri, May 29, 2020 at 10:58 AM, Chuck Harris wrote:


Hi Raymond,

Old fashioned electrolytic capacitors have a fairly reactive,
(to aluminum) highly conductive, water based electrolyte.

The capacitor's leakage current creates an electrolytic cell
with the aluminum plates, and removes the oxide layer from the
cathode plate, and builds an oxide layer on the anode plate...

The oxide layer on the anode plate is the dielectric (insulator)
for the capacitor.

This reaction is the "reforming" process that lives on in
electrolytic capacitor lore... Even today. It is also a process
known colloquially as anodizing aluminum.

The aluminum oxide dielectric layer has competing issues:

As the oxide grows thicker, it became a better insulator, and works
to stop the leakage current necessary to grow the oxide layer thicker.

As the oxide layer ceases growing, the electrolyte dissolves the
oxide layer, allowing the leakage currents to increase... growing the
oxide layer thicker.

In normal operation, a balance is reached between leakage current
and growing the oxide layer.... A "working voltage" rating results.

The only way to increase the thickness of the oxide layer once
it reaches equilibrium, is to increase the voltage across the
electrolytic cell, making the cell's current increase, and in turn,
the oxide grow thicker... creating a new higher voltage equilibrium,
and a new "working voltage".

As long as the heat created by the leakage current doesn't raise
the temperature of the electrolyte to a point where the it boils,
the capacitor is fairly happy.

This means that higher than working voltage surges will start to
heat the electrolyte, but as long as the surge goes away before the
electrolyte boils, the capacitor will live to see another day.

One other factor needs mentioning:

The thinner the oxide dielectric layer, the higher the capacitance,
and the lower the working voltage.

The thicker the oxide dielectric layer, the lower the capacitance,
and the higher the working voltage.

The manufacturer had to balance all of these conditions when they
wrote the specifications for their old style electrolytic capacitors.

If you used these old electrolytic capacitors at a lower than working
voltage, their capacitance would increase, and their ability to
operate safely at their specified working voltage would diminish.

Unless you reformed the capacitor... safely limiting the current
until the oxide layer thickened...

Modern electrolytic capacitors use a nonreactive (to aluminum)
electrolyte and as a result, reforming is no longer necessary.

Modern electrolytic capacitors have their oxide layer created, and
their voltage rating determined, before the capacitor is even
assembled.

-Chuck Harris

Raymond Domp Frank wrote:
On Fri, May 29, 2020 at 04:07 PM, Eric wrote:


There are 2 fundamental differences that need to be taken in to account
when
replacing “vintage” caps. And I use the term vintage loosely. One is
tolerance. In the worst case I can remember a capacitors value was +150%
-%100
tolerance. The means that for a 1 uF the measured value of anything between
2.5 uF to .1 uF would be considered “in spec” old radios still amaze me
they ever worked. Now a days +-20% is the normal. The service manual will
tell
you the tolerance of the filters. From memory I am guessing it is going to
be
+100% to -20 % so pretty wide design tolerance on the filters.

The other important spec is the voltage rating of the cap. And here vintage
caps and modern caps differ greatly. Vintage caps were very tolerant of
over
voltage especially given how tube gear warms up before the tube’s comes
in
to operation the B+ will spike some times as high as 200 to 250 volts
higher
then when the device is operating and can hang there for about 15-30
seconds.
This is not an issue in your 475 as it is solid state. However modern caps
are
completely intolerant of over voltage so if you have the physical space it
is
always good to bump up the voltage rating of the cap it wont effect
anything
to replace a 63V cap with a 400V cap excepta little cost in $ maybe one or
2
and physical space it will be slightly bigger then it’s modern lower
voltage
counterpart. However both are usually smaller then their vintage counter
part
even doubling the voltage the modern can will be smaller physically.
I don't think anyone would have accepted caps with +150/-100% tolerance, not
even electrolytics...

Any information on the inability of modern caps to withstand overvoltage
more than vintage caps used to? Maybe WV was just very conservatively spec'ed?
I'd rather have known the actual max.

For (wet) Al electrolytics, choosing a spec-voltage very much higher than
it's ever going to experience, has a deformation effect, so is not
recommended.

Raymond




Re: Tek 4041 GPIB Controller

Dave Brown
 

Very interested in how you find those tapes. If they are OK then programming them might be a challenge?
I dug out my 4041 and checked the ROMS- photo of the ROM carrier in my Dropbox here-
https://www.dropbox.com/s/8kg7w45pn4jlmv3/4041%20ROM%20carrier.jpg?dl=0
I was always under the impression that a boot tape was required to kick it into life and facilitate changing control to the serial port - based on recent posts I now see that may be wrong? Or is that just to use the keyboard? I need to read those posts again. My 4041 has been stashed away waiting for a boot tape to be acquired for quite some time but is that really necessary? The 25 pin RS232 connector on the back of mine is labeled comm 0.
Must admit I have not looked at this problem in some years.
I have no idea re condition of the tape drive in mine but visually it looks OK, as does the whole instrument, both internally and externally.
DaveB, NZ

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Monty McGraw
Sent: Saturday, May 30, 2020 13:17
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek 4041 GPIB Controller

Gary,

I have ordered 15 NOS 3M DC100A tapes from EBAY. They are scheduled to arrive Sunday.

I hope the drive bands are still ok - but I may have to replace them with Plastibands.

I will try to format and create a System Verification tape from the files I have recovered and report the results here.

Does your 4041 have the Option 30 Programming Development Option ROMs?

Monty


Re: Advice about buying a 7904

Harvey White
 

Please see interleaved comments:

On 5/29/2020 8:53 PM, Reginald Beardsley via groups.io wrote:
Please forgive me my ignorance, but for most of my life these things were pure unobtainium for budgetary reasons.
Tell me about that one.
And as I was not an EE and not allowed to touch the ones at work, there was no incentive to torture myself by looking at catalogs of things I could not afford.
I was allowed to touch them.  It's worse....
Getting a 465 was a huge event for me. And I don't mean all the work it took to repair it. I am acutely aware of how fiddly adjusting the vertical amplifiers is. But when you get it right, wow! Though in all honesty, I like my Dumont 1062 better as it does not have a fan. It's only 60 MHz, but otherwise matches the 465 in features.
Much depends on how many channels you need, (most need 4 or less), what the bandwidth needs to be (most need 150 Mhz or less)
Can I use my 7104 plugins in a 7904 mainframe, albeit with reduced BW and sweep speeds? That would greatly ease my concerns about using the 7104 on a regular basis. And make getting a 7904 mainframe pretty much a no-brainer. Just a question of getting a good deal.
In a sense, there are no such things as 7104 plugins.  If you mean the  7B10, 7B15, 7A19, 7A24, and 7A29.  The overall answer is yes, you can with reduced performance at the high end.  The bandwidth of a plugin and scope frame work a bit like parallel resistors.  With a plugin of infinite bandwidth, the scope frame is the limiting factor.  A 7A29 will give  you closer to the frame's bandwidth than a 7A19, but not more.


Is there a matrix which shows which plugins will work in which mainframes? I'm really only interested in the vertical and horizontal plugins. For the other stuff I have HP gear. I'm not aware of anything Tek made that can compete with an 8566B or 8510C.
Practically any vertical plugin can be used in any frame.  The bandwidth is effectively the lower of the frame or the plugin. Yes, you could use a 7A22 with all the bandwidth limitations in a 7104.  I tend to be careful of the CRT, though, so the 7904 is the workhorse.

Not sure where there is a chart, but there is one.  The scope horizontal sweeps are recommended for the various series.  Tek made 100 Mhz, 200, 400, 500, and 1Ghz frames.  Each one has a recommended horizontal sweep pair.  7B10 and 7B15 for the 7104/3 for example.

IIRC, and this is only what I remember...

7B92 is for 500 Mhz as is 7B8x

 7B7X is for 200 and perhaps 400, not sure on the 400

7B5x is for 100 Mhz.  7B50/7B55, 7B53 work in the 100 Mhz frames.

What I have is mostly 7B92, 7B8x, 7B5x, 7B10, and 7B15 depending on the scopes, IIRC.

Harvey


Thanks,
Reg



AM503B and A6302 Probe - Error 588 - No DC Output Signal

davidwebster511@...
 

I recently bought a AM503B amp and A6302 probe from ebay. It has been found that the A6302 probe is bad and will elicit a 588 error from known working AM503B amps. The probe will not degauss. Degaussing is what causes the error. The AC amp function will provide an output signal but the DC function does not provide an output other than a positive DC offset that cannot be corrected by the amp trimmer pot. Does anybody know if this is an indication that the hall effect sensor is bad?

Thanks,

Dave


A6302 Current Probe - AM503B 588 Error, No DC function

davidwebster511@...
 

Hello,

I recently purchased a A6302 current probe from eBay and keep getting 588 errors on my AM503B amplifier. I purchased another AM503B amp and A6303 current probe to compare since I couldn’t determine whether it was the amp or probe causing the error. The 588 error follows the A6302 probe.

When I try and degauss, I get the error. I can use the AC amplifier and get a scope waveform similar to my working current probe. But when I put the amplifier in DC mode, the probe doesn’t give a signal at all, apart from a DC offset that cannot be adjusted with the amplifier pot. I’m trying to follow the schematics but am not seeing why this might be right off. Does anyone know why I would able to get an AC signal but not a DC? Is this the hall sensor that might be defective?

Thanks,

Dave


Re: Tek 4041 GPIB Controller

Monty McGraw
 

Gary,

I have ordered 15 NOS 3M DC100A tapes from EBAY. They are scheduled to arrive Sunday.

I hope the drive bands are still ok - but I may have to replace them with Plastibands.

I will try to format and create a System Verification tape from the files I have recovered and report the results here.

Does your 4041 have the Option 30 Programming Development Option ROMs?

Monty


Re: In Defense of the 7A19

 

LOL! I like HP's screwdriver with bells and whistles! And yes, that add was something very cheap, unbecoming of HP.
Thank you Dennis for the piece of Tektronix history. It keeps raising my appreciation for the brand.

I have always found the Hewlett Packard oscilloscopes odious. I hate the way the 180 looked, starting with its knobs
and continuing with its ridiculous bezel. Maybe that style appealed to girls, and Tektronix style is for men?

I LOVE the look of the 7000 series. And its readout adds a strong touch of elegance
I don't get tired of glancing at the 7704A full of plugins in one corner of my office,
and seeing at its side the 547, the most aesthetic oscilloscope ever (in my humble opinion).

Ernesto


Re: Tek 4041 GPIB Controller

Gary Robert Bosworth
 

We would like to see working cassette tapes with 4041 functional programs
that can boot-up and test the 4041.
.

On Thu, May 28, 2020 at 7:58 PM Monty McGraw <mmcgraw74@gmail.com> wrote:

I just finished creating the binary files for each of the Option ROMs v2.1
and also a 16bit binary that could be used for disassembly and posted them
in the ROMs folder on my github repository for the 4041:


https://github.com/mmcgraw74/Tektronix-4041-GPIB-Controller/tree/master/4041%20ROMs



--
Gary Robert Bosworth
grbosworth@gmail.com
Tel: 310-317-2247


Re: Advice about buying a 7904

Reginald Beardsley
 

Please forgive me my ignorance, but for most of my life these things were pure unobtainium for budgetary reasons. And as I was not an EE and not allowed to touch the ones at work, there was no incentive to torture myself by looking at catalogs of things I could not afford. Getting a 465 was a huge event for me. And I don't mean all the work it took to repair it. I am acutely aware of how fiddly adjusting the vertical amplifiers is. But when you get it right, wow! Though in all honesty, I like my Dumont 1062 better as it does not have a fan. It's only 60 MHz, but otherwise matches the 465 in features.

Can I use my 7104 plugins in a 7904 mainframe, albeit with reduced BW and sweep speeds? That would greatly ease my concerns about using the 7104 on a regular basis. And make getting a 7904 mainframe pretty much a no-brainer. Just a question of getting a good deal.

Is there a matrix which shows which plugins will work in which mainframes? I'm really only interested in the vertical and horizontal plugins. For the other stuff I have HP gear. I'm not aware of anything Tek made that can compete with an 8566B or 8510C.

Thanks,
Reg


Re: TM500 Tester

 

Hi Errick,
The vintageTEK Newsletter may have been referring to me.

6 years ago I designed and tested versions of the individual circuits that were necessary to perform tests for everything that can possibly go bad in a TM5xx or TM5xxx slot. My concept of how this tester would work is based on an entirely different concept than Bob Haas came up with.

My TL501 (TL stood for Test Load) had to be entirely self-contained in a single wide TM500 plugin which would perform all of its tests the instant it was plugged into any powered TM5xx/TM5xxx slot regardless of which supplies were functional.. The circuitry could not depend on any of the slot’s supplies since you don’t know in advance which, if any, are bad until you test them. It relied on the clever little circuits I designed to perform its tests instantly and automatically without user intervention. Problems it identified were instantly indicated by the color of LEDs that reported the test results. Some features of my design:
* The AC and the DC voltages that were present each powered their own independent colored LED bar-graph display which showed how far in percent that voltage was above or below nominal. There were 6 bar-graphs. If a voltage was not present that display was dark but this had no effect on the other bar graphs because they were powered only by the supply they were measuring.
* When pressed a momentary pushbutton applied the maximum specified load, 30W to 35W, (spread proportionally across the six supplies) of that slot's specified power rating
* A fully automatic circuit checked the functionality of each pass transistor and displayed the results on a multi-color front panel LED: Green for good, Red for shorted, and clear for open.
* The leads of the pass transistors were brought out to the front panel for further testing on a curve tracer.
* There was a Monitor Out BNC which went to a 6 position rotary switch connected to the six supplies for that slot. The monitor let you check any supply to see what it was actually doing.
* A header on the front panel brought out all 56 (28 X 2) pins of the TM500 rear interface connector so you could conveniently monitor the activity on any pin with a simple 0.025" square pin jack like the ones that attach onto the tips of a Tek probe.
* The Reverse Winding detector compared the phase of each of the 25VAC supplies to be sure they matched the phase of the 17.5VAC supply.

When I had a PC board made that connected all the circuits together I discovered I made some rookie mistakes. The entire thing was one huge short circuit. By that time I was tired of working on it and I set it aside and began working on TL501’s successor, the TL502. I got part way before something else distracted me (which happens all the time).

The announcement of the museum tester got me interested again. I thought it was quite interesting to see someone else solve the same problem using an entirely different approach. So much has changed since I stopped working on TL502 that new solutions are available that do not have the drawbacks I was dealing with. The multicolor bar-graphs were mesmerizing but far too complicated and they took up too much space on the front panel. The parts of my designed that created all the shorts are now much simpler to do. I did a little test the other day to see what a new version of my Test Load, TL503, might look like and I was pleased by what I saw. The idea of reassembling the separate circuits I already designed might be quick to do.
There are a few things I saw Bob Haas’ tester do that I overlooked in the TL501 and TL502 and at the moment the wheels are turning in my brain as I consider possible ways to accomplish the same purpose in the future TL503. I have so many TM500 slots that need testing that it would be very valuable to have a way to test them all. That is the entire reason I needed TL501 in the first place.

At the moment it will have to wait. I have another plugin I have designed, built, tested, and completed. I am in the final stages of documenting this plugin before I decide what to make next.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Errick
Sent: Monday, May 25, 2020 12:04 PM
To: TekScopes@groups.io
Subject: [TekScopes] TM500 Tester

From the April vintageTEK news letter "Another volunteer is developing an automated tester for the TM500 mainframes." Does anyone have any details on what is being done? I know the power module tester subject has come up many times in the past, and it will again.
I am/will/hope to build a tester soon.





--
Dennis Tillman W7pF
TekScopes Moderator


Re: In Defense of the 7A19

Mlynch001
 

Dennis,

This is one of the primary reasons that I enjoy this group so much. The history and technical details are priceless!

--
Michael Lynch
Dardanelle, AR


Re: In Defense of the 7A19

 

On Fri, May 29, 2020 at 10:23 PM, Dennis Tillman W7pF wrote:


The 7A19/7A19 Opt 4/7B90/7934 combination was the fastest lab scope ever made
and it was ahead of its time in 1972.
I guess that should be the 7A19/7A19 Opt 4/7B90/7904 combination

Raymond


Re: 475 questions

 

On Fri, May 29, 2020 at 07:58 PM, Chuck Harris wrote:


Modern electrolytic capacitors have their oxide layer created, and
their voltage rating determined, before the capacitor is even
assembled.
Thank you *very* much for that information, Chuck! My hearsay knowledge has been replaced with some insight.

Raymond

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