Technics SL-1200 mk1 too fast

Just got replacement PCB. When I measure Pin 16/17, I'm getting 18V AC but meter is jumping around between 17.5V and 18.5V. Is this acceptable or do I need to replace motor? The 20V DC is the same, can't dial in to steady 20V, fluctuates around 19.5V and 20.5V. Any ideas? thanks
 
The AC fluctuations are suspicious but we don't know how stable your home PS is, or how good your meter and probes are, so let it slide.

The 20VDC fluctuations (depending where you're measuring it and what it is exactly that you're trying to dial in) can indicate a problem.

If it's after regulation (collector of TR13) - it's an issue. It's addressed in the first section of the trouble shooting guide in the service manual.
 
the 20V DC I'm measuring is by probing pin 7 and collector pin TR14? Is this before or after, I'm unsure?
 
if you can trust your meter it looks like you got a constant voltage problem (funky voltage regulation). The SM says to replace/clean VR1 and/or replace a bunch of diodes. check it out.
 
Think I've found the problem. C14 is showing as shorted on multimeter. I'll get that replaced then see what happens ;
 
C14 is showing as shorted on multimeter.
How so? If that's an in circuit continuity test, it's meaningless. Gotta pull at least one leg out. Test capacitance @120Hz and ESR no more than 1Ω. In any case, if it's faulty - replace all electrolytics.
 
I have no idea about electronics. Just youtubed a couple of test caps videos and guy reckoned I could test in circuit. I've only got basic multimeter so cannot test ESR, etc. Anyway, I had an old power supply board to test desoldering caps so I managed to get C14 replaced, ran deck for 30 min stable but jury still out. DC board voltage is fluctuating at 19.9 - 20.1v which is much better. Is there Caps inside the PU / Transformer that could be replaced? The guy I got the replacement PCB Control Board from reckons it can sometimes be caps in the PU that have gone? thanks again

Update:

Ran deck for 24hrs now. All pitch is now stable after replacing C14. Another thing I did do was remove the speed selector switch again and give it a proper clean.

Hope this helps anyone else with an old Technics Deck.
 
Last edited:
EC's don't age well through the decades but shorted ones usually bulge up, swell or leak. In lack of an LCR or ESR meter, If one EC is bad, it's safe to assume there's more, so just shotgun replace them all for new. There's just a dozen of them in there and they are run-of-the-mill caps. Do not replace old EC's from one old PCB for ones off another old PCB, that's useless. Order new capacitors from Farnell which is the safest and largest distributor in Europe with a hub in the UK, and avoid eBay Asian junk and counterfeit capacitors like the plague. You can use tighter tolerances and higher voltage rating - but not the opposite and you have to watch out for the correct polarity orientation (stripe is negative). Any main stream mfgr. modern general purpose or power supply EC would do. I've checked Farnell and found these in stock for less than $10 total.

EDIT: C16 axial - updated
 
Last edited:
Thank you for going to all the trouble of sourcing the caps. I'll get all them ordered up today, as well as another set for the spare board I have now. Once again, really appreciate all the help you've provided. I bought this TT blind on eBay and thought it was heading for the rubbish pile.
 
Hello guys I can't find help anywhere else so hopefully you can......technics 1200mk2 issue is the green led doesnt light up at all and is still good. I do have the service manual but I can't figure out how to read all of it. The pitch fader works and table does quartz lock I just want to figure out what needs t ok be replaced to get the green led to work when pitch is in the quartz lock position.
 
Привет. У меня sl-1200, при измерении переменного напряжения на контактах 16/17, показания 19,5 - 19,7 В. Конденсаторы заменили все, в соответствии с CM. Что может быть? Или оставить как есть? Буду благодарен за ваши рекомендации.IMAG1225.jpg
 
Has anyone put an MK II tone arm on a first generation SL-1200? I swear I read a thread about it, but now I can't find it anywhere.
 
Super thread, thanks for all the input! My TT 1200mk1 had speed issues, 45 to fast, 33 tooooo slow, cleaned all the pots, didnt help, just now replaced all the caps, this solved the problem! Especially cap C12 had problems, it leaked. One question: I want to set motor voltage at 20 dc. I dont understand were to measure, one probe on collector tr 14 , so were do i put the other probe........?
 
Back
Top Bottom