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