I bought A old Fisher MT-6330 DD turntable, I would like to bring it back to spec performance. At best is has a peak 2S wow at 0.093% giving a DIN W&F at 0.037%, but more often the peak is 0.14 and DIN 0.05 . It is very sensitive to user adjusting speed pots, and speed oscillates several seconds if platter is disturbed.
Almost like the servo gain is too high .
spec is 0.035% presuming DIN as source is the german manual.
I can find settings for reference voltage and DC balance, but now setting for servo gain.
I am going to clean potmerers for speed setting both internally and the user speed pots, and set the motor drive DC balance according to service manual .
But What about adjusting the servo gain when there is no variable resistor for i?
What else can I do?
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I have deceided to simple start the upgrade by replacing the vibrating onboard transformer power supply , that is unregulated , by A SMPS with DC regulation. This I can buy complete and keep external to the chassis,.
I dont see a problem with that.
A suggestion would be to use the power supply from the unit and put it in a separate box. If you feel it needs regulation then do that in that box and connect with a umbilical cord.
An EI power transformer in my opinion is a more durable and frankly better power supply than a switch mode if all other things are equal id take the EIs.
I guess im saying before you consider doing stuff to it you should be sure that you're going to make an improvement vs just making it different.
A suggestion would be to use the power supply from the unit and put it in a separate box. If you feel it needs regulation then do that in that box and connect with a umbilical cord.
An EI power transformer in my opinion is a more durable and frankly better power supply than a switch mode if all other things are equal id take the EIs.
I guess im saying before you consider doing stuff to it you should be sure that you're going to make an improvement vs just making it different.
Many thanks. One purpose is to eliminate the vibrations that the transformer gives. And radiated “hum” even if no hum is audible. I made a dummy load and LC filter to put between the smps and the load . Added a protection diode and damping resistor for the LC, and a ferrit too..
Made of parts I had laying around.
Made of parts I had laying around.
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For my other turntable I am thinking about moving the transformer out from the turntable, also to move vibrations away..