Author Topic: Marantz 1090 amplifier  (Read 1910 times)

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Offline Kenceu

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Marantz 1090 amplifier
« on: June 04, 2015, 08:31:30 pm »
Hello everyone!

I'm a newbie in electronics and tried my hand at repairing this old amplifier (simple circuity). And noticed that the output stage is beyond saving without spending loads and loads of money.
See attached pic below this was after soldering new transistors and biasing the circuit. It blew 3 unrelated resistors.
Now the pre amplifier circuit is still in pristine condition and completely in spec. Now I was wondering if it would be possible to separate the pre amplifier from the output stage so that the whole main amplifier part doesn't get any power anymore?

I have the schematic if anyone could push me in the right direction or tell me which wires to cut i'll be very grateful!

Offline mzacharias

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Re: Marantz 1090 amplifier
« Reply #1 on: June 06, 2015, 12:03:16 pm »
I would simply disconnect the main power from the main amp stage, put bleeder resistors across the main filter capacitors (if there aren't any already) and use the convenient pre-amp out jacks on the rear panel.

As an aside - I repair this sort of stuff all the time. My only concern in fixing it would be that this type of output transistor is an obsolete package and it might be necessary to hack in a different physical package. Ugliness potentially ensues.

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