Repairing an original Boss Chorus Ensemble CE-1

[edvard]

I'm no stranger to basic electronic repair, but LFOs and modulation effects are a bit above my pay grade.  Here's the symptoms:
-I'm getting output whether the effect is in or out, but the "Peak Level" LED, and the LFO indicator LED are both solid on.
-Switching between "Vibrato" and "Chorus" does nothing.

I first suspected the LFO, so I swapped out the 4558 op-amp.  No change.  Then, after leaving the thing on for about a half-hour, the LFO LED started going on and off, but I couldn't get the thing plugged into my interface fast enough to catch it, and it went back to solid on.  That tells me that some capacitors are out. Where do I start?

Schematic is here: https://schematicsonline.com/wp-content/uploads/2022/11/Boss-CE-1-Chorus-Ensemble.pdf
or here: https://www.synthxl.com/wp-content/uploads/2019/05/Boss-ce-1-schematics.pdf

[PRR]

So are there any voltages in there?

Bright light and magnifier to find dry, cracked, or dubious solders?

These PDFs have typical waveform drawings. You can't see 440Hz without a 'scope, but you can see few-Hz wobbles on a DMM even if only as random numbers.

[edvard]

Ok, I got solid 14v at Q15 emitter and -14v at Q17, so we're good there.  Power is good to all ICs, the only discrepancy being there is 4.5v between pin 7 and pin 1 of the MN3002, where the schematic says it should be 5v.  I wish I had an O-scope to check the clock lines at pin 2 and 12, but I'll check the LFO output after dinner. 
BBIAB.

[edvard]

I'm back.  I've poked around, and everywhere the schematic says a voltage, the voltage I measured is exact, except for between pin 1 and 7, and I think that +5v is supposed to be between pin 1 and the other side of R20, not pin 7.  Now to find R20...  tomorrow.