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TM500 Tester


Errick
 

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.


robeughaas@...
 

I am working to finish the firmware and hope to have it out in a couple of weeks. The vintageTEK Museum will publish the circuit board layouts and schematics in KiCad and the firmware source code. We will also make programmed processors available. The design is entirely contained in a single-wide TM500 module -- no external load resistors. A "teaser" video is here: https://youtu.be/YLdaMePWttI This version has a 16x2 display. I have since changed over to a 20x4 display.

--
Bob Haas


Eric
 

Bob,

    This is great I cant wait for these to be available. Looking forward to this one.


Eric

On 5/26/2020 12:00 PM, robeughaas@... wrote:
I am working to finish the firmware and hope to have it out in a couple of weeks. The vintageTEK Museum will publish the circuit board layouts and schematics in KiCad and the firmware source code. We will also make programmed processors available. The design is entirely contained in a single-wide TM500 module -- no external load resistors. A "teaser" video is here: https://youtu.be/YLdaMePWttI This version has a 16x2 display. I have since changed over to a 20x4 display.


Michael W. Lynch
 

Bob,
This is great.  Another project for me to build. 

Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell Phonemlynch001@...@gmail.commlynch003@...

On Tuesday, May 26, 2020, 11:01:47 AM CDT, robeughaas@... <robeughaas@...> wrote:

I am working to finish the firmware and hope to have it out in a couple of weeks. The vintageTEK Museum will publish the circuit board layouts and schematics in KiCad and the firmware source code. We will also make programmed processors available. The design is entirely contained in a single-wide TM500 module -- no external load resistors. A "teaser" video is here:  https://youtu.be/YLdaMePWttI   This version has a 16x2 display. I have since changed over to a 20x4 display.

--
Bob Haas


Errick
 

Thanks for the update! I can't wait to see all of the details of the unit and see one on my bench working.


 

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