Re: Marantz 2275

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Re: Marantz 2275

GregS

27 Jul 2009 12:59

>>> Wondering if anyone is familiar with this series. I was
>>> testing it out and the bias circuitry is not
[quoted text clipped - 18 lines]
>H720 and H721 are for the bias of a couple stages back. I'll
>check that out too.

One mystery solved. There is a bias transistor. Its hidden under one driver
heatsink. There are two positions for it on the board. One
away from the heatsink. That position I first saw is vacant.

So far a bad pot on one channel is the only thing I have found wrong.
I still have to figure why the bias on the other channel is
not working.

greg

GregS	22 Jul 2009 13:20
>> Wondering if anyone is familiar with this series. I was >> testing it out and the bias circuitry is not [quoted text clipped - 15 lines] > >Good luck. H720 and H721 are for the bias of a couple stages back. I'll check that out too. greg

David Farber

21 Jul 2009 20:39

> Wondering if anyone is familiar with this series. I was
> testing it out and the bias circuitry is not
[quoted text clipped - 7 lines]
>
> greg

I found a service bulletin from 10/29/1975 that may or may not have an
effect on your problem. If your serial number is below US 7701 or Europe
51001, replace diode H720 and diode H721 with a 1S1555. When you say the
bias circuitry is not functioning, do you mean there is zero bias current?
It is supposed to be 10mv from TP701-TP702 and TP703-TP704.

Good luck.

Signature

David Farber
David Farber's Service Center
L.A., CA

GregS

21 Jul 2009 14:24

Wondering if anyone is familiar with this series. I was
testing it out and the bias circuitry is not
functioning. There is shown on the schematic a bias transistor
along with one diode and pot.
There is no bias transistor on the two stages, just looks
like one diode. I intend on adding a diode or two to get it going.

There is a place on the boards for the transistor, but it was never there.

greg

Re: Marantz 2275

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