Tektronix CSA802A - anyone familiar with repairing this unit?

[JM]

I recently bought a CSA802A - a nice clean unit with low up time. Unfortunately it developed a fault in transit, and the extended diagnostics are showing the following faults :-

Timebase - Block M/F I/F - Comm T3112
Timebase - Block M/F I/F - Strobe Gate T3311

I pretty much stripped the whole unit down (I wanted to backup all the EPROMs anyway) and have checked all the supplies and all inter board cabling. All socketed IC's have been checked for correct seating. From a visual inspection there is nothing obvious. The unit was very well packaged, with nodamage to the packaging on receipt, and I'm confident that it was working when sent.

I thought I'd just post in the off chance that someone is familiar with theunit and can advise on the probable problem. Given that there isn't schematics available for these they are a pain to trouble shoot. I suppose it'll be cheaper in the long run to find a donor unit and swap boards until thefaulty board is identified, rather than reverse engineering the unit.

John

 

[JM]

Subject should have referred to the CSA803A ...

 

[JM]

That's the comm version of the 11801?





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John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com



Precision electronic instrumentation

Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

VME analog, thermocouple, LVDT, synchro, tachometer

Multichannel arbitrary waveform generators

Yes, on the hardware side two of the plug in slots supply power only, and it has an additional wide bandwidth prescale trigger. The direct trigger has higher sensitivity than the 11801, and has a higher bandwith. Software wise it has some standard inbuilt masks for pass/no-pass testing.

 

[JM]

Subject should have referred to the CSA803A ...



















I think there are a pair of battery backed ram memory chips on the timing pc

board (bottom of unit). With the power off, make a measurement of the

voltage between pin 14 and pin 28 on both of those chips (they are installed

in a Dallas battery backup socket). If the voltage is less than 2 volts, you

will need to replace both memory chips.



If that is your finding, report back and I'll post a source for a

replacement device.



tm

Yes, I should have mentioned that I checked all the internal batteries and they are all good (battery backed RAM sitting at over 2.9V).

 

[JM]

That's the comm version of the 11801?





--



John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com



Precision electronic instrumentation

Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

VME analog, thermocouple, LVDT, synchro, tachometer

Multichannel arbitrary waveform generators

Just for interest here's a photo of the prescale trigger hybrid
http://db.tt/Rx0tZyMx on the TBC board.

John

 

[tm]

I sure wish some ex-Tek person would smuggle out a set of schematics for
the
11801 series. The service manuals just say to replace boards.

Of course, Tek doesn't want those wonderful old scopes to get fixed.

Agreed. It's like they killed all the people that knew anything.

It really is a wonderful scope.