That 108 is the pre-regulator voltage. I don't think that ripple is of
great concern. There's not a lot of bulk capacitance on the 108 because it
is the feedback to the inverter controller (A12U75), so it's going to have
some ripple.
Did you check all the supplies coming off the A12 board, or just the
voltages listed in table 4-4?
You need to check all of the supplies for level and ripple.
The digital supply mentioned is generated by the auxiliary regulator,
assembly A7, schematic sheet <38>.
This is where the +5VD (D = digital), -5VD, and +12VD are generated; these
are the voltages that run the processor/digital half of the scope and thus
the most likely to cause your specific problems.
There are test points on A7, but you should also check the supplies from
the A12 and A22 boards, as they are the inputs to the auxiliary regulator,
which can only clean up a dirty input so much. Except for the -5VD rail,
most of the filtering for the digital supplies happens beforehand in the
analog supplies along with all the caps for localized filtering at the ICs.
Dave Casey
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On Sat, Sep 5, 2020 at 12:36 AM Nick Corvid <awsomedrack@...> wrote:
Alright I've checked all the power supply test points I knew the location
of (A12,A22,A17) Except I didn't get that digital supply David mentioned,
which I'm not sure where the test points are, how to reach them, or what
the specs are for that.
Of the stuff I checked though everything came out relatively normal from
what I could measure with my less than great instruments, well all but one
thing, TP126 for the +108 volts that read 108.5 volts which is barely in
spec but had some funky ripple pictured here on my auxiliary scope:
/g/TekScopes/photo/252782/0?p=Created,,,20,2,0,0 . That
was the only thing I saw that was out of the ordinary so far.
