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A question from the unwashed relative to: I built a TM500 mainframe tester...


 

Just a thought:

I wonder if there are TM500 modules which are particularly picky on correct functioning of the mainframe.

Such a module would
- use all or most of the interface
- show malfunction immediately, like no display, no output or such
- ideally does only use 1 bay

This would permit quick checking of mainframe slots, if you're sure the module is fine.

cheers
martin


Jared Cabot
 

The trick is a bad pass transistor can quickly kill a module, which can then go on to kill another slot in the mainframe, etc etc.
Using a module (that isn't the purpose built tester) to test the mainframe also won't allow you to test voltages, ripple, transistor beta, transistor leakage etc.

The Mainframe tester will allow for a full functional test without risking damage to a potentially expensive module.


Michael W. Lynch
 

On Sun, Jan 3, 2021 at 08:29 AM, Jared Cabot wrote:


The Mainframe tester will allow for a full functional test without risking
damage to a potentially expensive module.
Yes, These will cause a cascade of failures with certain modules. I always try to at least diode check those pass transistors before inserting any module or powering up.

So your Mainframe tester module does utilize or test the Pass transistors of the individual slot in some form or fashion?
--
Michael Lynch
Dardanelle, AR


Jared Cabot
 

Yep, the mainframe tester tests for short/leakage and beta, along with the DC and AC voltages, and phasing of the two floating AC windings.


Colin Herbert
 

If anyone else needs some more info on what the tester was intended to do when Tektronix came up with the idea, it is useful to check out Tekwiki (https://w140.com/tekwiki/wiki/067-1201-99), as indeed it always is. There are a couple of User Manuals there, plus the Tek construction notes.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jared Cabot via groups.io
Sent: 03 January 2021 15:30
To: TekScopes@groups.io
Subject: Re: [TekScopes] A question from the unwashed relative to: I built a TM500 mainframe tester...

Yep, the mainframe tester tests for short/leakage and beta, along with the DC and AC voltages, and phasing of the two floating AC windings.


Mlynch001
 

Tha me to all, I have not had the opportunity to review any of the literature or watch the video. I appreciate everyone filling in the blanks for me!

--
Michael Lynch
Dardanelle, AR


 

On Sun, Jan 3, 2021 at 03:29 PM, Jared Cabot wrote:


The Mainframe tester will allow for a full functional test without risking damage to a potentially expensive module
Does that include checking that the floating AC windings are really floating ?
I have had a TM503 with one end of one of the windings in one compartment shorted to ground.
Voltages looked OK but the plugin in that compartment didn't like it.
/Håkan


Colin Herbert
 

Wouldn't my idea of bringing the connections separately to the front panel solve this? Continuity between each end of each 25 VAC winding could be tested without the mainframe being powered up.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of zenith5106
Sent: 03 January 2021 16:29
To: TekScopes@groups.io
Subject: Re: [TekScopes] A question from the unwashed relative to: I built a TM500 mainframe tester...

On Sun, Jan 3, 2021 at 03:29 PM, Jared Cabot wrote:


The Mainframe tester will allow for a full functional test without risking damage to a potentially expensive module
Does that include checking that the floating AC windings are really floating ?
I have had a TM503 with one end of one of the windings in one compartment shorted to ground.
Voltages looked OK but the plugin in that compartment didn't like it.
/Håkan