Thanks for helping repair 4300, Mike, Trevor, Mark, Maury, Neil, etc

Tweakers' Asylum

Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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Hi the gang,
Remember the 4300 with 3 totally burned channels.
Well I eventually got them going again.
Took me a long time, mainly to get the parts and to train on ohter
dead
amps before the real thing.
I would like to thank all of you for your contribution.
Mike
Neil
Maury
Mark
Trevor
etc.
+ all the people I have forgotten.
What I did :
Managed to get my hands on the schematic ( this place here in Belgium
has them all).
Reworked all 4 channels.
Replaced driver with 2sa1358 and 2sc3421.
PWR TR with MJ15003 and MJ15004
Predrivers 2sc627 with 2n5320.
Other TR are the same type.
I guess I could have used more recent PWR TR but after what some of
you had written, I wanted to prevent instabilty due to an unadapted
feedback loop + TR with larger bandwidth.
I also plan to find better replacements for the predrivers.
The units works quite well. Sound is clean and "full". Bass really
deep - makes the furniture move ( almost at least).
The tuner is really great !
Things still bothering me a bit:
I do not dare to push the unit to its limits - 100 W in 2 channel
mode. But I do not need that much anyway.
The bias control has no effect at all ! + DC offset is = 0 ==> OK.
But clipping is perfectly symetrical.
Some reference voltage on the schematic to not match with the
measured voltages.
The PCB is badly damaged and I guess I will never be able to bring
the unit to its original specs. But that doesn't really matter. It
sounds OK and looks OK ( the previous owner scrubbed the top markings
off the top of the face plate - model 4300 + marantz , etc, would
like to do the same to him + buttons missing).
The next amp to repair will be an ARC D-52B.
Thanks again to all.
Robin

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Topic - Thanks for helping repair 4300, Mike, Trevor, Mark, Maury, Neil, etc - chj9183 07:09:17 12/25/00 (0)

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