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Further MS2000 synthesizer problems

Here's the service manual for reference:

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I replaced C109 with a 100uF electrolytic temporarily, and also found that the power and ground planes were shorted together. Common mode choke L10-L12 had apparently burned and shorted, so I've temporarily replaced it with jumpers.

The +7 and +5 rails are up and running now, but the 3.3 volt rail is still down. I measure about 8.6 volts from positive to negative across C109, but I'm also seeing about 8.7 volts from the ground terminal of C109 to the ground fin of regulator IC7.

Reply to
bitrex
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There's no continuity between the top of C25 and where C50 would have been. Guess L13 is smoked as well.. :(

Reply to
bitrex

The schematic shows that L10, L11, and L13 are NU (Not Used). L13 is replaced by a jumper. Is the schematic for your unit accurate?

Reply to
John S

You're right. I believe it's accurate, I was just being dumb. The common mode choke was just 2 windings - it was scorched and shorted. I cannot find L13 anywhere on the board. Still, there seems to be a continuity problem somewhere as the buck switcher is not getting an appropriate input voltage.

I think I'm first going to take the other poster's suggestion, disconnect the switcher completely and see if I can get the logic working off a bench supply, as if I can't get it operating that way then this exercise is really for nothing.

Reply to
bitrex

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