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 Forum index » DIY Hardware and Software » The Repair Shop
Cheetah MS6 power supply
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phroggiey



Joined: Oct 24, 2013
Posts: 3
Location: Cambridge, UK

PostPosted: Thu Oct 24, 2013 8:35 am    Post subject: Cheetah MS6 power supply
Subject description: bypassing transformers
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Hello everyone,

I have recently had an issue with a Cheetah MS6. I was replacing one of the CEM3396 chips when one of the voltage regulators bent and snapped without me realising. When I turned it on - 'pop' - and a terrible smell from one of the transformers.

After replacing the voltage regulator, still no luck. I figure I've blown a transformer (they are infamous in the MS6 for going wrong).

The MS6 has two - one to bring it from mains to 15V, and one to bring it to 7V. From here, the positive-rectified signal goes to two separate diode-capacitor-voltage-regulator routes to give +/- 12V and +/- 5V.

Looking at the schematic I think it should be easy just to bypass the transformer and provide 12V AC to the circuit where the signals from the transformers would have come out. The diode-capacitor-voltage-regulator circuits should give the correct voltage output with a 12V AC supply to each; with a bit more heat coming out of the 5V regulators.

I've attached a PDF of what I mean.

Do you reckon this would work? Any feedback would be very helpful.

Tim


ms6 power.pdf
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phroggiey



Joined: Oct 24, 2013
Posts: 3
Location: Cambridge, UK

PostPosted: Thu Oct 24, 2013 8:36 am    Post subject: Reply with quote  Mark this post and the followings unread

I meant the positively and negatively rectified signals are converted to +/-12V and +/-5V DC... Look at the schematic for what I mean...
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L´Andratté



Joined: Sep 23, 2012
Posts: 60
Location: Hamburg, Germany
Audio files: 5

PostPosted: Fri Oct 25, 2013 10:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi!
I don´t know your device, but you should think about the first transformer has now to put out power for both circuits 5V/12V.
Is it capabale of that?

And: You probably know, but it´s exactly the part of circuit you better not go the try&error route. Go the p.i.t.a. calculation route!
scratch
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phroggiey



Joined: Oct 24, 2013
Posts: 3
Location: Cambridge, UK

PostPosted: Sat Oct 26, 2013 2:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Yup exactly. That's why I'm asking the forums! I've been in contact with a guy in Scotland who's dealt with similar problems on MS6 synthesizers before. He seems to have found transformers with the same pin layout that I can just solder back in. So I think I'll just go with those!

Apparently the published schematic is riddled with errors as well, and so can't be trusted!
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