Re: Help: Pioneer M4000 Home Stereo Amp
- From: "ampdoc" <ampdoc@xxxxxxxxxxx>
- Date: Thu, 15 Feb 2007 16:36:42 -0600
"Dani" <greeben@xxxxxxxxx> wrote in message
news:1171543785.245975.203220@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
You usually have to also replace the 2SC3181, as well as the 2SA1264
outputs, & look for surface mount 220 ohm resistors
right by the outputs. They usually go also, make sure the mica
insulators are in the right location. These Pioneer units use
a 'self destruct' trigger that activates if the bias drifts which is
designed to intetionaly destroy the ouput transistors & blow the fuse.
Use fresh heat sink compound on the outputs to keep them cool. Finally
make sure the speakers that were on
the amp before it blew have good woofers, as this will blow it all
again. Hope this helps, Dani.
Actually it's a fuse blow circuit that uses the audio outputs like a
crowbar to intentionally blow the fuse in the event of overvoltage on the
line. Same output design as the RX series all-in-one units, and VERY hard to
work on. I'd suggest finding the "Blow" line and check it to see if it's
going active, and certainly check all the 220 Ohm surface mount transistors.
With all the finals out of circuit the foil on the pcb should read 220 Ohm
between the base and emitter connections, if not your resistor is bad.
I've made a "test jig" using a NC latching relay and a FET, removing the
Fuse Blow line connection on the amp module ( be sure to ground the amp side
otherwise it'll float up and activate the fuseblow circuit) and using it to
turn on the FET and relay, thus removing power from the main transformer
instead of applying forward bias to the finals. This approach allows
troubleshooting without killing the finals every time, it functions kind of
like the powerdown circuit in the Pioneer PJTV's, removing Line voltage from
the main power xformer. Just reset and go again :-)
Good luck
Jammy
.
- References:
- Help: Pioneer M4000 Home Stereo Amp
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- Re: Help: Pioneer M4000 Home Stereo Amp
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