Tektronix 7603 with 7B53A and 7A26 plug ins

[Refugee]

I am going to have to study the circuit diagrams and text in the manual to find out what signals should be on all the lines and check them with another scope.
There are a couple of places where the waveforms look a bit squashed. These need to be checked against the manual after some study.

[AlanBeckett]

There are a couple of places where the waveforms look a bit squashed.

Back in the day that was considered a good starting point - do all the Signals look like TTL?
If there are any that don't then the chances are something is wrong. Of course that's not necessarily helpful if there's a mixture of Analogue and TTL.

Alan

[Refugee]

There sure is an awful lot of analogue and the study is to establish what is supposed to be there and then measure it.
I see no point in changing a chip unless I have found a definite fault with it.
It is just as well the board in a place that has easy access.

[AlanBeckett]

Sorry R, I've lost track. What's wrong with the Display?
I've got a 7623A which very likely has the same Board. I could look at Signals for you.

Alan

   

[Nick]

The manual for the timebases is pretty good wrt. the on-screen display - generally all the Tek service manuals discussed the theory and practice in detail.

Whilst checking against a known-good unit would normally be a reasonable thing to do, here we have something that is 20 - 30 years old, so checking against the service manual would be safer...

Following this thread has made me rather regret getting rid of my 7904...

BTW. I did check about the extension - the only one I have left is for the TMS500/5000 chassis - I have a LOT of those plug-ins, so that must be why I kept it

[Refugee]

I have been doing some testing and a lot of reading and began to tackle U2126 first. On pin 12 the waveform is shown as roughly -6 volts and this is wrong on mine.
It varies with the display brightness control and will not budge above -0.5 volts. Pin 11 where the signal from the brightness pot connects also will not budge above -0.5 volts unless I power up with U2126 removed. This allows it to go from +4.5 volts for minimum brightness to -13.5 volts at maximum brightness on pin 11.
With U2126 in place disconnecting the Z amp cable does not restore it.
CR2124 and CR2125 have been tested as have R2122 and R2123.
Pin 12 has narrow positive going pulses and these are present also on pin 11 but these are narrow enough that a DVM ignores them and also they only come up to 0 volts.
The pulses vary with the settings on the plugins so that part is working.
Has anyone got a U2126 I could borrow?
The part No is 155-0021-01
Readings from pins 11 and 12 for maximum and minimum brightness would be useful if you have got the cover off..

[Refugee]

BTW. I did check about the extension - the only one I have left is for the TMS500/5000 chassis - I have a LOT of those plug-ins, so that must be why I kept it

My plugin is fine now that I have replaced the faulty FET with a 2SK43.
The 2SK43 should be fine as I pulled it from a BER posh video camera from about the same period and the data sheet says it is a special fast one for video. It has to pass a sawtooth with a maximum rate of 1mhz so it should be able to do the job without any problems.

[Nick]

The Tektronix 155-xxxx-xx parts are all custom ics. The usual souces that I would go to, Sphere and Qservice, don't have any 155-0021-01s left,  nor does eBay. Same is true for the board as a whole - 670-1900-xx...

Best bet by far at this point is the Yahoo! TekScopes group. ..

[Radio Fixer]

I haven't followed the thread a lot but admire the tenacity to get it working properly again. I wish you luck and slow progress is being made.

Whenever I see pics of these scopes inside and out I'm awed by the beautiful layout and construction.

Gary

[Nick]

It may help that the US military has a National Stock Number (NSN) for this part - NSN 5962002368572 or 5962-00-236-8572 with the correct formatting.

Seems it was used (i.e. in the Tek 7000-series scopes) in the support of various interesting US military projects (source:http://www.parttarget.com/5962-00-236-85...21-00.html):

• Strategic Weapon Systems(Poseidon and Trident)
  
• Aircraft, Eagle F-15
  
• Ballistic Missile Early Warning Sys. (Bmews)
  
• Support Equipment, F-15 Aircraft
  
• Ticonderoga Class Cruiser(47)
  
• Arleigh Burke Class Destroyer
  
• Fms - Knox Class Frigate
  
• General Purpose Electronic Test Equipment (Gpete)
  
• Calibration Standards Equipment
  
• Fms - Build Frigates Class Ships