Problem with P1. Out of the PSU, ~24V AC out from pins 1 & 3, check; ~-20V DC out from 3 & 4 at 33rpm and 4 only at 45 rpm, check. But when connected to motor P1 in (bottom left circuit), no go at either speed. However, connecting PSU 1 & 3 out to motor P2, it works at both speed settings.
Check the P1 cable and connectors at both ends. Check for appropriate continuity and also check for no shorts between pins. Use ohm meter and have power off.
Thanks - did all that and all good, so still mystified... I think the problem is limited to the AC side of the motor PCB (pins 1 & 2), because when I switch speeds I hear the relay switch (connected to 3 & 4) clicking.
I can work around it by just connecting AC to P2 and if I want to switch to 45 RPM, temporarily connect the 4-pin to 3 & 4 to switch the phasing circuit (or not bother, or run the PS at 33 and use the 45 wheel of the pulley).
Does P1 pin 1 measure 27R to sleeve of P2? What is the purpose of switch TB1? Is it open or closed? Other things to check are for trace hairline cracks, cold solder joints, or very fine whisker shorts between traces.
Ah - haven't tried going across that resistor - will give that a go. TB1 is the main TT on/off switch, made redundant by the PSU but required to be on if still in the circuit (checked, ok). Board & joints all look ok as far as I can see. Meantime though, a 4-pin socket to tidy up my hack 4-pin to 2.5mm adaptor has begun its journey.
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