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Old 3rd May 2008, 06:35 PM   #21
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A big problem with these turntables was the switches. Try cleaning all of the switch contacts with pure isopropyl alcohol/acetone and a Q-tip.
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Old 4th May 2008, 12:30 AM   #22
paki976 is offline paki976  Italy
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Weird, same answed I gave on vinylengine few hours ago:

http://www.vinylengine.com/phpBB2/vi...?p=79158#79158

By the way, I managed to make it almost work changing TR7-9. Now the turntable runs at steady speed, but a little fast but I can hear the pulsations of the direct drive system (not seen on the strobo).

Maybe someone more skilled than me could provide better equivalents for the transistors? Here in Italy is quite hard to find Japanese parts!

Thanks again,
Fabrizio.
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Old 4th May 2008, 01:54 AM   #23
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Check all the of the discrete parts for resistor drift (and the speed adjustment potentiometers on the pcb) and if the electrolytic capacitors are all still good (or just replace them).
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Old 4th May 2008, 04:59 AM   #24
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Yes, I agree with replacing the electrolytics, and checking for resistor drift. I had to replace two bad pots in mine. Just to double check, you say it runs fine at 33 rpm?

-Justin
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Old 4th May 2008, 08:23 PM   #25
paki976 is offline paki976  Italy
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Today the turntable started to work after i changed again TR7, but the transistor burnt few minutes later. Also the two diode packs were warm to touch.

Ok, I'll try changing ALL resistor AND caps.
I guess is not a big deal to unsolder, test and solder again, so better change!

Weird is that on VR3 i got something like 18V, instead of the 50mV specified on SM. Also on VR4 i cannot reach the 2.2V.

I'll post my results tomorrow after the changes.

Fabrizio
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Old 5th May 2008, 04:05 AM   #26
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I would try changing the caps first...
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Old 6th May 2008, 10:40 PM   #27
paki976 is offline paki976  Italy
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Ok, changed all Electrolytics and all the polyester caps (except one I forgot to buy ), also found originals 2sc1384. Now the TT is spinning again, but faster than normal.
I'm able to set 50mV on VR3, but cannot go lower of 6V on VR4.
Started to check many resistors, but found no appreciable drift on values.

I'm checking voltages on VR3 and VR4 with motor disconnected. Am I wrong?

Maybe some transistor I used is not really equivalent (expecially in the oscillator circuit)?

Any idea anyone?

Thanks,
Fabrizio
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Old 8th May 2008, 09:21 AM   #28
paki976 is offline paki976  Italy
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Difference found on my PCB over the service manual:

C4 on pcb 10mf, on SM 1mf

Maybe Could someone check on real-life if it is a SM error or a previous wrong repair? This morning prior going to work also found a discrepancy on a resistor in the R1-R6 range, (don't remeber which one seems to remember R5)
On my 1500 found many mods made by previous owners (for example, resistor in series over pitch controls)

thanks,
Fabrizio
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Old 9th May 2008, 08:38 PM   #29
paki976 is offline paki976  Italy
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Talking It works!!!

Ok, finally I was able to repair this beast.
Apart of burnt tansistors and leaking caps, found 2 open windings on the motor. It was a painful work of patience and magnifying glass, but results are great!

I would thank averyone who helped me sorting out, expecially despotic931.



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Old 10th May 2008, 03:16 AM   #30
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Default Re: It works!!!

Quote:
Originally posted by paki976
Ok, finally I was able to repair this beast.
Apart of burnt tansistors and leaking caps, found 2 open windings on the motor. It was a painful work of patience and magnifying glass, but results are great!

I would thank averyone who helped me sorting out, expecially despotic931.




Excellent, I'm glad to here you got her fixed up! I am sorry I couldn't help more than I did, but happy to have helped enough for you to get it all sorted out! Enjoy!

-Justin
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