audio-talk

For any SP10 owners who may experience this problem:

Went to play a couple of new albums today and found the SP10 playing up.

Turned on and noted the strobe light pulsing strangely. Tried to start the motor and it attempted to start up but immediately went into reverse!

Tried 45rpm and 78rpm, same result. Stopped the motor and tried to rotate it forward by hand with the power supply still switched on....the motor resisted and started buzzing

So, first point of investigation was to check the service manual and tackle the easiest option first, the PSU. Voltages where seemingly OK but the 5v line wouldn't settle. Put the scope on it and found a large amount of ripple. I knew the caps where the originals and a quick google search brought up a couple of hits with similar issues so out they had to come.

The 5v smoothing caps to replace are C412 16v100uf, C411 16v100uf and C410 16v1000uf

This cleared up the 5v supply and the voltage settled at 5.05v without any further adjustment, before it bounced about, around 5.6v...

A quick check with the motor unit saw it all working so I decided to replace all the other 'lytic caps just as a precaution.

Hope this may be useful in the future.

Yep, been there, done that. But in my case after fixing it I shorted the 5v and 21v line and took all the logic ICs out

And what did you do then? I only ask as I expect Neal would like to know - it might be relevant.

Good point Andrew, I think Nick replaced them but with what? And did it work correctly afterwards!

Bah! My troubles are back.

Same problem as before. Press start, platter tries to go in reverse or not move at all. Sometimes it will start though or with a small push.

It was working fine, I wanted to go back in though and replace some caps that I'd not done the last time it was on the bench...all seemed to be OK but whilst checking the spin up and spin down I blue a fuse on the 32v rail.

Replaced the fuse and all seemed OK then it started playing up....I've checked all the voltages and the three adjustments that can be performed but still no joy. I've checked the drive voltage, timing etc but cant work this one out...I'm stuck!

Found no output on one phase from the driver board. Seems I managed to take out TR5 a 2SB512 PNP power transistor, 25W, 3A, 60v Anybody know if there is an equivalent or similar part available? TO-220 package...

http://www.bdent.com/2SB512-p/2sb512.htm

http://www.ebay.it/itm/new-rare-2SB512- ... 0432456592

Thanks Phil, I'll keep those links in mind.

I did a cross reference on both parts and it came up with BD242 / BD244 and BD241 / BD243 (complimentary) As these are available from RS I;ll try these first.

Also, for reference, TIP41 / TIP42 may be suitable as well...

Seems like I'm talking to myself!

Anyhow, it lives again!

For reference the original PNP transistors 2SB512 can be replaced with BD242C. Thats TR1, 3 and 5.

For the NPN transistors TR2, 4 and 6 the original part 2SD389 could be replaced with BD241C, although I've not tried it.

Higher power replacements for BD22/241 are BD244 and BD243.

Well done Neal, I have been watching.

Me too. I didn't have anything useful to say so I stayed shtumm.
(shtumm is something my Dad says - anyone else use that expression?)
Anyway, well done for getting it going. Is the SP10 your prime turntable?

Hi Max, yes SP-10 is the prime one and the PL-71 is backup.

Another data point (I've found precious little on the internet about servicing these decks, it all seems to fall back on RTFM and interpreting the manual can be a challenge).....There is an adjustment possible on T1 for TR28 which generates the Phase control reference signal (50Khz).

In the manual its listed as 180uS and 10v P-P measured at C2, this appears to be incorrect as 180uS works out to be 5.555Khz where 18us = 55.55Khz...Also I was unable to set this and get 10v pk-pk, it was either or so I went for timing and the pk-pk worked out at 8v...

Neal wrote:Seems like I'm talking to myself!

Best way of getting a sensible answer.

Know nowt abaht SP10's so I stayed shtumm as well.

Yes Max I do.

To end a blooming awful week my SP10 is buggered again Should have left it alone. Wasn't happy about replacing just the one power transistor and Dave Crawley advised to go back and check the phase outputs for balance....sure enough the repaired one was higher than the other two.

Swapped out all 3 pairs and all was good. Used D44H8 and D45H8 ...

Then I noticed some strange spikes on the outputs and also the same spikes on some of the timing signals.....hmmm.

By accident I knocked one of the boards and noticed the display on the 'scope spiked...hmmm some more.

Turns out tapping the boards produced more of these random spikes. Tapping certain ceramic caps and moving a few just under finger pressure did the same. Aha! Microphonic ceramics...

So I systematically set about replacing them all checking operation of the deck as I went....all was going swimmingly well until the last few caps on the controll board where replaced...now on any speed the deck spins too fast with a chugging noise! Poo....

I'll have to check each signal on the controll board and hope I've not taken out one of the transistors...replacements for which will be hard to find especially the FETs...

Not ignoring you Neal, watching with interest, I was lucky in that the fixes I had to do were all on the control board, where its easy to understand. I guess you have checked that the phase lock is set correctly again, it may just be free running.