Tektronix 7603 with 7B53A and 7A26 plug ins

[Refugee]

The reason the on screen display is not working is due to the timebase fault and no meaningful diagnosis can be made at this stage apart from establishing that the logic circuit is powered.
It is now down to checking that all is present and correct at the plug the plugin connects to.
We will have to see if I can diagnose it more quickly than the 40 minutes each way to take up Alan's offer to plug into a known good frame.
I will visit the Tektrinix forum and see if the users can shed some light on the elusive 7B53B plugin manual.
What I do have is the diagram for the frame so the signals there can be looked at sooner.

[Nick]

My understanding was that the "free running" mode was the default - never used anything but that on any of the 7xxx-series scopes I've owned or used.

Simple first test would be to determine the mode the unit thinks its operating in.... its very rare that they are put into single-shot mode (only for photography really)...

From page 4-35 of the 7603 service manual:

   

Going to the forum is a good start - the folks there know these 'scopes inside-out...

[Nick]

Just found my CDs of Tektronix manuals - there's a 7B53A and an 7B53AN, but no 7B53B...

Is 7B53B on the tab or is it marked elsewhere on the unit - its interesting as I can't find any references to the "B" variant...

[Refugee]

That is exactly the same conclusion I came to when looking on the web for circuits. The boards appear to be the same as the A variant so the difference must be small.
It requires a lot of patience and I need to stick to times when I can give it my full attention or else it will end in tears.
I have been off the restore for a few days due to domestic stuff and having banged mi toe while out in the garden.

[Alan Douglas]

I checked my stash also: found three 7B53A manuals, no Bs. Oh well.

[Refugee]

Yes it is very frustrating that all the manuals are there except the illusive one for the very plug in that needs work done on it.

[AlanBeckett]

I don't want to be a Pessimist but apart from Mainframes I've never come across a 'B'. I wonder if it's a Special or it was modified by a Third Party. There were Third Party Plugins for Tektronix 'scopes and also 'Normal' ones that were Modified for special uses.
There are a couple of Plugins for the 564 which look perfectly ordinary but are designated 'Engine Diagnostics' if I remember rightly. I failed to buy one recently

Alan

[Refugee]

I have been off this restore doing the garden and getting all the indoor plants outside for there summer vacation.
I have made a mistake with the part number of the timebase plugin. I will PM a moderator if it is not spotted in this post. It is indeed a 7B53A. My fault for not cleaning the finger prints off my glasses

In the switching it is the resistor bank that looks like it has something wrong in it and I am going to have to check every contact in the switch bank. I am pretty sure at this stage that the special chip is all right.

MOD: Title changed - note that if you can edit the first post in a thread, you can change the title there....

[AlanBeckett]

That's good because it solves the mystery.
Onward and upward.

Alan

[Alan Douglas]

If you would like a real manual instead of a pdf I'd be happy to send you one.