I added a couple of pictures here:
/g/TekScopes/album?id=301426. Please note:
1. CH 1 seems to be able to display the square wave from the
test/adjustment terminals.
2. CH2 and CH3 display a flatline, but no square wave (not quite sure
why).
3. CH4 - the one with the main issues, by all signs - doesn't display a
waveform at all.
Radu.
On Sun, Mar 23, 2025 at 9:37?AM Radu Bogdan Dicher via groups.io <vondicher=
[email protected]> wrote:
I'm reviving this thread, because I seem to have a very similar issue and
am not sure how to progress.
This is a 754D that had a plethora of errors, most of which got solved by
replacing SRAMs serving U200 (so, if the sequencing described by Jay
applies to this acquisition board, that'd be CH4, but it seems to impact
all channels apparently). The root cause was (possibly alongside other
types of failures of the SRAMs) a low-resistance condition between pins 2
and 3 of those SRAMs (corresponding to A16 and A14, all addresses being in
parallel across the eight ICs) of about 10 ohms. I had to remove seven of
the eight chips before this condition was eliminated (one original SRAM
left on that channel). Once I did that, all errors pointing to specific
U201 through U216 went away.
I've also reflowed all pins for U200 to eliminate cold joints being as a
possible cause.
I have on error left: "diagnostic test failure, digDataFormatDiag,
ERROR!!BYTE mode, in demux 200 ,i= 4 memBaseAdr 0x738000a= data =
fffffa00, expectedData[i] = aa00" This seems to generate some spurious
peaks, just like Jared seemed to experience (I'll enclose a picture
shortly).
Not sure what else to look for to narrow down the issue left.
Radu.
