Technics Sp10 Woes

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Nick
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Re: Technics Sp10 Woes

Post by Nick » Thu May 09, 2019 3:31 pm

Great news. Well done. It may be that all that needs doing now is to set the phase lock adjustment as detailed in the service manual. If thast not set, as it falls out of lock you get a kick as the platter speed changes while it tries to acquire lock again.

But the fact its going around is a huge thing.

It may be worth checking the frequency of the 50kHz oscilator, it may need adjusting to get to frequency with your new coils. Test probe on C2, Test ground on 0v or chassis.
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Wolfgang Felber
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Re: Technics Sp10 Woes

Post by Wolfgang Felber » Fri May 10, 2019 12:33 am

Hi all, thank you for your kind comments, this certainly is a labour of love. These turntables are very serviceable unlike a lot of other stuff around.
Build quality is pretty awesome. If maintained properly, I assume they should last forever. I have learnt so much in the last two years, that is how long it has taken.

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Re: Technics Sp10 Woes

Post by Mike H » Fri May 10, 2019 4:18 pm

Fabulous! Image
 
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Re: Technics Sp10 Woes

Post by Wolfgang Felber » Mon Jun 17, 2019 12:44 pm

Hi all, I have just returned from a well deserved holiday and have a renewed energy to finish off the SP10 Mk2. This have given me both joy and heartache. I managed to get it going but it it is not running smoothly, there is a vibration. In my effort to get it back to life, I replaced one set of driver transistors and I think this may have caused an inbalance. I shall check the voltages of each of the drivers to ensure they are all the same as well doing what Nick has suggested, test the 50K oscillator.

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Nick
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Re: Technics Sp10 Woes

Post by Nick » Mon Jun 17, 2019 6:35 pm

Check the phase lock setting first. If it's almost working then it may just need the setup in the service manual following.
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Re: Technics Sp10 Woes

Post by Wolfgang Felber » Sun Jul 07, 2019 11:52 am

Hi all, finally got time to sit down and do a bit testing. OK
1. Adjusted T1 to get 50K Hertz from the oscillator.
2. Got 50K Hertz at P1
3 Put probe on A1, A2 & A3, get a shitty wave form, voltage appears to be OK 17.2 volts
4. Attached a couple of photos, hopefully they are clear enough to make sense of them.
5. one photo shows the 50k hertz signal
6. other photo is the signal coming A1 A2 & A3, pretty horrible, is that normal, would not have thought so.
Attachments
UNADJUSTEDNONRAW_thumb_1489.jpg
UNADJUSTEDNONRAW_thumb_1487.jpg

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Nick
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Re: Technics Sp10 Woes

Post by Nick » Sun Jul 07, 2019 12:15 pm

Looks fine to me, remember its using that waveform to control the speed of the turntable, so you would expect it to vary in amplitude. Try putting the platter under load and see if the level increases.
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Re: Technics Sp10 Woes

Post by Wolfgang Felber » Tue Jul 09, 2019 1:32 am

Hi Nick, did what you suggested, put a bit of load on the platter. I could not see a huge increase in amplitude, in fact the more load I applied the wave started to flatten out. Does that sound right to you? Does this waveform originate from the frequency generator coil in the motor? If so then I understand why it flat lines, this is because the platter is slowing down and the FG will not produce as much frequency????

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Re: Technics Sp10 Woes

Post by Nick » Tue Jul 09, 2019 9:08 am

Can#t see for certain, but looks to me that the timebase of the two displays is different. One seems to be 5us, the other 5ms. In which case you are looking at different things. The service manual doesn't show a wave at A1-3, so assume the best instead of looking for problems where there may not be one. Have you tried checking the phase adjustment yet?
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Re: Technics Sp10 Woes

Post by Wolfgang Felber » Tue Jul 09, 2019 11:43 am

Hi Nick, yes I did but I think I didn't do it right. You are talking about the test points O S & T? I put one probe on T and one on S, I think where I stuffed up was I used two ground clips. The reason I say this is I got two identical saw tooth wave forms. They are supposed to be quit different. I will try again. Still got the rumble. The bearing is perfect as I replaced the cap. So it has to be something else causing it, possibly in the driver stage.

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Re: Technics Sp10 Woes

Post by Nick » Tue Jul 09, 2019 12:33 pm

Ok, focus on the test points, you should get a sawtooth and pulse. If you are getting two sawtooths then either something is wrong, or the probes are shorted.
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Nick
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Re: Technics Sp10 Woes

Post by Nick » Tue Jul 09, 2019 12:34 pm

If the drive is trying to lock and failing, you will get a rumbuling sound from the drive as it tries to obtain a lock fails, and will try the next time.
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Re: Technics Sp10 Woes

Post by Neal » Tue Jul 09, 2019 10:23 pm

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Re: Technics Sp10 Woes

Post by Nick » Tue Jul 09, 2019 11:04 pm

Was about to congratulate you till I realised it was Neal showing what the trace should look like.

I wondered if you had a different scope :-)
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Re: Technics Sp10 Woes

Post by Wolfgang Felber » Wed Jul 10, 2019 1:08 am

Hi Nick and Neal, thank you both for your comments, that does make sense now. This is another issue. It never did this before but it always drifted off speed. So at least now it is trying to lock. How do I fix this problem? The photo that Neal sent, is that the correct setting for the time base? Will this fix the grumbling sound of the motor?

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