Hi,

I've got my hands on a used TDS540 in hopes that at least once channel
would work. No luck.

The box comes up with two self-tests failures :
FAIL ++ Acquisition
FAIL ++ Attn/Acq interface

After that, channels 1 and 2 show nothing.
Channels 3 and 4 show 'saw' pattern when there's no input signal
applied. If I connect it to the probe compensation signal I can see
sum of square wave pattern and the 'saw'.

I've followed Tektronix' troubleshooting chart and it looks like
acquisition module A10 is probably bad.

I wonder if anyone here had to deal with the similar issue before.
Looking at the ebay, I've noticed that quite a few TDS* scopes sold
there had failed acuisition and/or attenuation modules. Looks like it
must be a fairly common issue. Does anybody know what are the most
common failures for the tds5xx family scopes?

Thanks,
Artem