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The Incredible Technics SP-10 Thread
The Incredible Technics SP-10 Thread
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Old 21st August 2018, 03:35 AM   #1091
BrianL is offline BrianL  United States
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The Incredible Technics SP-10 Thread
Not necessarily. But it's not uncommon for regulators to 'want' some minimum load in order to operate correctly. I would hope that since the supply and turntable can be disconnected from each other, the supply's outputs would be stable with no load. Adding some amount of load is nice but not necessary, I believe.

Another thing to do would be to check the supply voltages with the turntable connected and running (before it starts misbehaving). Assuming that the no-load measurements are in spec, they should not vary much with the turntable connected.
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Old 22nd August 2018, 06:19 PM   #1092
ra7 is offline ra7  United States
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The Incredible Technics SP-10 Thread
Update on backwards rotating table.

See the two images below. The strobe is set to 5 ms per div, and the two waveforms are exactly as in the service manual, with the delta T close to 6.3 ms. The strobe (which fortuitously came back on) is locked on at all three speeds. Just that it is spinning backwards.

If I rotate VR101, it goes back out of lock and visibly spins faster/slower and the scope shows the pulse waveform jumping around.

The caps in the PS have been replaced and all the voltages are good. I ordered new caps for all the electrolytics in the internal boards, and my next step is to start replacing one by one and keep testing. Start with the motor caps.

Any other thoughts or suggestions?
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Old 23rd August 2018, 02:08 AM   #1093
BrianL is offline BrianL  United States
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The Incredible Technics SP-10 Thread
If you're going to replace the electrolytics, I wouldn't waste time with changing out one-by-one. That is going to be a big pain and take a lot of time. I'd just swap all of them and see what happens. I doubt that in doing it one-by-one, you'd stop swapping if one cap magically cured the problem, so the only thing to be gained is to satisfy your curiosity as to the likely cuplrit.
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Old 23rd August 2018, 06:46 PM   #1094
Retrosoulman is offline Retrosoulman
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Does anyone knows if the sp 10mk2 p/l got the same circuit boards with the sp10mk2
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Old 23rd August 2018, 08:20 PM   #1095
Aleks1 is offline Aleks1  United Kingdom
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No the Mk2 boards are not all the same.
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Old 24th August 2018, 06:23 AM   #1096
ra7 is offline ra7  United States
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The Incredible Technics SP-10 Thread
Thanks BrianL, that makes sense!

Going through the troubleshooting flowchart again, I checked the voltages, and there is 4.95V on C2 at the connecting board. Can I consider that to be 5V? If it is under 5V, the flowchart says to check the constant voltage output circuit. The two variable resistors on the power supply board control the output voltages. The one controlling 5V is turned all the way, and I cannot get it above 4.95V. I was able to turn the 32.5V resistor to adjust that rail to exactly 32.5V (earlier, it was reading 32.7V). What are others measuring on the 5V rail? Is 4.95V within the margin of error?
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Old 24th August 2018, 06:30 AM   #1097
BrianL is offline BrianL  United States
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The Incredible Technics SP-10 Thread
I would think a 50mV difference is not the issue.
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Old 24th August 2018, 01:51 PM   #1098
JP is offline JP  United States
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5V is sensitive but 50mV low won't matter. That you can't get higher than 50mV is tell-tale of a issue, as is the overheating - seems something is drawing too much current.
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Old 24th August 2018, 03:28 PM   #1099
ra7 is offline ra7  United States
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The Incredible Technics SP-10 Thread
Hi JP, I am not having overheating issues. That's someone else's deck. I'm the one with the backwards rotating table with speed locked at all three speeds.

If 4.95V is OK then I'll proceed with the flowchart.
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Old 24th August 2018, 03:36 PM   #1100
JP is offline JP  United States
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Still very odd that's the extreme of the adjustment range.
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