TDS644A Advice needed


g4gjl@btopenworld.com <g4gjl@...>
 

I am presently working on a TDS 644A which fails its power-on tests Thus:

ACQ : FAIL
ATTEN / ACQ :FAIL

There are no displayed waveforms though as I run through various controls, occasional triggering occurs, as indicated by front panel LED.

I havnt yet opened the scope,but guess there is a multiplexer associated with the four channel inputs to the video processing circuitry, and also either a single or four separate A to D convertors.

Can anyone confirm in block diagram granularity, the signal path from attenuator to video processing stage?

I assume TEK never released any technical information or servicing manual or similar info for this scope.

Any help would be appreciated

Pete


Andy
 

The error log should give you more detailed information on the problem. It could be as simple as a loose connector. I don't know if the 644A suffers from leaking caps, but you should definitely check it before running more.

It's not much, but you can download the service manual here:

http://www.tek.com/oscilloscope/tds620a-manual/tds620a-tds640a-tds644a

This isn't your model, but it might be close enough to be helpful, and does have full schematics.



www.upc.edu/pct/documents_equipament/d_282_id-683.pdf

--- In TekScopes@..., "g4gjl@..." <g4gjl@...> wrote:

I am presently working on a TDS 644A which fails its power-on tests Thus:

ACQ : FAIL
ATTEN / ACQ :FAIL

There are no displayed waveforms though as I run through various controls, occasional triggering occurs, as indicated by front panel LED.

I havnt yet opened the scope,but guess there is a multiplexer associated with the four channel inputs to the video processing circuitry, and also either a single or four separate A to D convertors.

Can anyone confirm in block diagram granularity, the signal path from attenuator to video processing stage?

I assume TEK never released any technical information or servicing manual or similar info for this scope.

Any help would be appreciated

Pete


 

The TDS644A does in fact also suffer from the leaking caps issue. They will all need replacing and the boards need to be cleaned. There's many articles in the group about how to do this. The OP could also take a look here:
http://www1.tek.com/forum/viewtopic.php?f=5&t=4886&sid=771cea524a0c59598c5c806762e3385a

Jay

--- In TekScopes@..., "baltimora86" <acuffe@...> wrote:

The error log should give you more detailed information on the problem. It could be as simple as a loose connector. I don't know if the 644A suffers from leaking caps, but you should definitely check it before running more.
[snip]