SL-1710 Mk2 - Help Needed

[lancejt]

I've recently acquired a SL-1710 Mk2. I've been diving through old posts and they're all from at least 3-4 years ago at minimum.

I've been scrounging around looking at parts, but before I started ordering I wanted to describe what I'm seeing and see if those who had done these repairs might have input on where to start to have the most impact with the least effort.

First, what's working:

• table spins at proper speed when arm is manually moved into position
• plays albums just fine
• speed control buttons (33/45) work to affect proper change to table speed
• variable speed dial/pot seems to be in working order
• tested auto-return switch with multi-meter, working properly

Now for the less good:

• cue motor running constantly in arm down direction when table powered on
  • disassembled, found that an o-ring had already been installed to replace a missing belt
  • cue button did not seem to function until both microswitches were depressed, then cue button simply stops motor, but never re-engages it
• small gear does have crack, but is surviving for the moment, i know it'll need to be replaced, looking for one of those replacements as well
  • manually spun, the gears drive the lowering/raising and return of the arm as expected
• stop button seemingly non-functional
• auto-stop / return does not engage
  • led for auto-stop is lit when switched on with button/switch

I appreciate any and all input, just looking to get to a functional place. Intending to start off at minimum replacing IC501 on the arm board (TC4011BP) due to perceived weirdness with microswitches and cue button logic not acting correctly per service manual.

 

[SaSi]

Hi and welcome to AK.
Pretty hefty first post. I have an SL-1710MkII myself in a similar dysfunctional state. Mine seems to function more but weirdly. I have also narrowed down the faults into the CMOS logic circuits in the tonearm PCB.
Do you have a scope or a logic probe?
Have you verified the correct operation of the microswitches? The symptoms you describe can be caused either by failed logic ICs or dirty switches that don't give correct input to the logic gates.
When you replace the CMOS ICs, bear in mind they are static sensitive (for real, not like all the other ICs that just need precautions). So be careful with static when handling them to mount them. Best to properly check if they function correctly before you try to replace them.

I would start checking:
dirty/failed switches
power supply problems (wrong voltage, high ripple)
check the function of the gates with a logic probe
identify faulty ICs.