MPS-2220 rev C master / slave mode

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slalomnut
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Joined: Fri May 06, 2016 6:15 am

MPS-2220 rev C master / slave mode

Post by slalomnut »

Greetings! I have a few of these little tanks and one is a rev C with the master/slave switch appearing to be mislabeled or backwards. The blue dot on the switch is away from the power inputs, unlike my others where the blue dot is on the power side and according to documentation, default setting should be master towards the power side. I've been refurbing this guy and have ran into issues with the fuse melting instead of blowing. It runs in stereo in a 1 ohm load, the 0 awg to distro blocks for power and ground, then 4 awg to an 8 awg reducer on the positive side and 8 awg direct to the negative., and 12 awg to drivers. Output = Str, Ground = Com. The melt down took out R[9-12] and Q[7-10], with burn marks on the traces. Prior to the failure, I had replace C[1-3,13-14,19-20]. I have replaced all parts that melted down, along with all caps with the exception of the ones in front of the low level input, D1, Q1, R1, R2, Q2, OP2, VIL mod: R[138-139,238-239]. It powers up but I haven't fed it any music yet.

I should note, that prior to these part swaps, it would always draw a little power. (i.e. the ON light would stay slightly illuminated unless battery was removed.) That is no longer the case after replacing these parts. May not be related to the melt down.

Questions: Should I ignore the blue dot on the switch and set it to the power side in master mode? (That was how it was during the melt) Any ideas what may be causing such large power draws that's causing the fuse to slowly deform / melt.

Cheers!
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