This unit presented with a broken cover down switch lever. It has other issues.
Power is good, clean with a scope. The turntable motor spins if I force it on by grounding the base on Q102 (motor run). The CPU clock (MN1421FPB) is running in the right range, strobe signals where they should be. I can't find a data sheet on that chip to show me any signals that put it in reset or some halt mode. The tonearm motor returns properly automatically if I rotate it out and turn the unit on.
I hate logic issues without enough clear documentation. I have the manual. Any pointers would be very helpful.
Thanks, Chris
Power is good, clean with a scope. The turntable motor spins if I force it on by grounding the base on Q102 (motor run). The CPU clock (MN1421FPB) is running in the right range, strobe signals where they should be. I can't find a data sheet on that chip to show me any signals that put it in reset or some halt mode. The tonearm motor returns properly automatically if I rotate it out and turn the unit on.
I hate logic issues without enough clear documentation. I have the manual. Any pointers would be very helpful.
Thanks, Chris
Hi, apologies in advance if you have already considered what I have to say. I'm making no assumptions (best starting point for troubleshooting).
Background: I have rebuilt and serviced about 10 Technics compact DD turntables (SL-5/SL-Q5/SL-Q6) and have never had a problem with the main PCB. I also have about a dozen of the motor units from these turntables that I have bought as parts (I repurpose them) and I have never found one with a faulty microprocessor.
Have you fixed the lid switch? The motor will not run if the lid switch is open.
Have you done the "measurements and adjustments" per the service manual? I always start with the calibration of the turntable as if any of the tonearm sensors are not calibrated correctly then strange things can happen.
Does the motor (when you force it to) run at the correct speed?
Cheers, Mike
Background: I have rebuilt and serviced about 10 Technics compact DD turntables (SL-5/SL-Q5/SL-Q6) and have never had a problem with the main PCB. I also have about a dozen of the motor units from these turntables that I have bought as parts (I repurpose them) and I have never found one with a faulty microprocessor.
Have you fixed the lid switch? The motor will not run if the lid switch is open.
Have you done the "measurements and adjustments" per the service manual? I always start with the calibration of the turntable as if any of the tonearm sensors are not calibrated correctly then strange things can happen.
Does the motor (when you force it to) run at the correct speed?
Cheers, Mike
Hi Mike,
Thank you!
The simplest suggestion can point to something I forgot, so thanks. I do the same thing. Your experience is valuable.
Yes, I fixed and verified the lid switch. This was the first thing I noticed. I glued a metal tag to replace what I think is a broken lever. I have no idea what the original looked like, but it now works. Also cleaned the switch (open when lid down).
Good point. No, I noticed that the "repeat" lamp didn't illuminate and looked at the processor after checking the power supply voltages and reset. The tone arm does return and stop if I take it out of the rest position. I assumed that meant the sensors were working there. I didn't run through the adjustment procedure as I feel I am dealing with a processor stuck in a state where it doesn't detect an album. I don't know what it normally does when you first hit play. This one does zero. I can see a red LED on up by the arm. Probably for tracking error. I'll wait for your response before diving into that. I did take the record detect lever out and made sure it wasn't damaged, then reinstalled it.
The motor runs smoothly when forced on. The waveforms look like the speed is hunting a bit, but a smooth rise and fall. The CPU clock is steady, slightly high.
I typically try to solve major faults before adjusting anything.
- Chris
Thank you!
The simplest suggestion can point to something I forgot, so thanks. I do the same thing. Your experience is valuable.
Yes, I fixed and verified the lid switch. This was the first thing I noticed. I glued a metal tag to replace what I think is a broken lever. I have no idea what the original looked like, but it now works. Also cleaned the switch (open when lid down).
Good point. No, I noticed that the "repeat" lamp didn't illuminate and looked at the processor after checking the power supply voltages and reset. The tone arm does return and stop if I take it out of the rest position. I assumed that meant the sensors were working there. I didn't run through the adjustment procedure as I feel I am dealing with a processor stuck in a state where it doesn't detect an album. I don't know what it normally does when you first hit play. This one does zero. I can see a red LED on up by the arm. Probably for tracking error. I'll wait for your response before diving into that. I did take the record detect lever out and made sure it wasn't damaged, then reinstalled it.
The motor runs smoothly when forced on. The waveforms look like the speed is hunting a bit, but a smooth rise and fall. The CPU clock is steady, slightly high.
I typically try to solve major faults before adjusting anything.
- Chris