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Old 17th November 2010, 08:07 PM   #1
diyAudio Member
 
Join Date: Nov 2010
Location: Toronto
Default Help fixing my Alphason Sonata

Hi all.
I have owned this Sonata for 20 years.
It is a 110/120V version for North America with one motor.
For quite some time it has had an issue with strongly preferring to run at 45rpm regardless of the switch position. Usual a few pushes of the switch would eventually get it to run at 33rpm, but after powering it down to change the record, it invariably starts in 45rpm again. The switch itself seems fine, so maybe it is the OSRAM relay?

Anyway, it has completely died. During operation it stopped and emitted a nasty smell. Looking at the board, I can clearly see a toasted part. That is the 1.2K resistor R1. My experience with SS electronics tells me that the resistor is probably fried as an effect of the fault, rather then being the cause.

I have built my own valve electronics for many years and have a good range of tools including an oscilloscope. My experience with SS electronics is more limited. Any suggestions or assistance would be greatly appreciated. I have some questions about the operation of the motor electronics, and hope someone more knowledgable can offer help. The motor electronics schematic is located as a PDF on vinylengine.

The schematic is for version 1.22 of the board and I have a version 1.1 but it seems part for part exactly the same. The color the motor wires is different on my turntable compared to the schematic. My T1 wire to the motor is blue, my T2 is magenta and my T3 is grey.

The other unusual thing is a wire which is not shown on the schematic. It seems to be a ground of some sort, attached to the shielding tin ground plane mounted on stand-offs to the bottom of the circuit board and to the casing of the motor. It was tied up and buried in the turntable housing and appears to have never been used. The wire is a good 1.5M long. Maybe it is supposed to be attached to the phono pre-amp case ground along with the tone-arm ground wire??

My gut feeling is that the failure is related to the problem of speed control I had but that is a guess...
Thanks and regards, David
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