Subwoofer Power Supply
My sonís subwoofer blew out.
He has a Polkaudio RM6880. There
are other components to the set but they are whimpy so he only uses the
subwoofer with a low level signal from his big receiver.
When the unit failed I
looked inside and noticed the 1 amp fuse was blown.
this looked easy but there's no such thing in electronics. I
replaced the fuse and it blew again as i expected so I tried a 5 amp
fuse which held but blew out the transformer primary coil which had been
obviously shorted. When I put the bigger fuse in the circuit
heated up, smoked, stunk and finally opened.
The transformer was labeled 86H-4102 DCGM 0725A.
My suspicion was that the two secondaries were around 12 volts AC
or enough for the board to rectify to 12 volts DC. The
transformerís primary coil was shot as well as both secondary coils so
there was no way to test impedence of to find out anything.
I tried to get specs on this transformer and could find
absolutely nothing anywhere anyhow.
Nor could I find voltages required to drive the control board but
I estimated 12 volts looked good. I
went to the local electronics store and scrounged around in their
surplus room and located a transformer that looked more or less close to
this bad one. I tested the
primary and secondary coils on the surplus unit and they were OK.
The transformer took 110 volts through the primary coil with a 1
amp fuse. I have no idea
what voltages were needed but I hooked the secondaries up to the
subwoofer control board and everything worked fine.
It would be wonderful if companies published their wire diagrams and specs but sometimes you just have to guess or buy a new one.