[sdiy] Do Electros Die Slowly?

[megaohm]

Here is the problem. It concerns my Multivox MX-201 tape echo. The delay
time (motor speed) control is not changing the speed. I should say that
SOMETIMES it funtions (as in, it changes the motor speed). Even when it is
working I feel the speeds could be faster and slower (maybe). There are two
circuits on the board that are identical. Both use rectifier chips (black
cylinder)(schematic shows that these contain four diodes) followed by a
470uF 16V electrolytic cap. I measured at the caps and one circuit reads
14.75VDC which is close to the 15VDC shown on the schematic. The other
identical circuit measures 12.38VDC (this is the one that feeds the motor
regulator).
  I'm wondering if I have a cap that's gone/going bad. If I had the correct
value cap to replace it I would. Placing a Mouser order but I'd like to be a
little more certain this is the right fix.

  I find it strange that sometimes there's no problem and then other times
the delay time pot has no effect. In fact, I'd rather it be fully NOT
functioning instead of half and half. It's making it difficult to
troubleshoot. Any input/thought would be great.

Thanks,
peng
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