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PostPosted: Sat Apr 02, 2016 5:46 pm 
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Bottle Rocket

Joined: Mon Sep 07, 2015 4:07 pm
Posts: 6
Hey guys

i have just found out that some technician changed some resistors and maybe added a diode in my DC3. I need help to change it back.

There are several versions of the board. I need the DC23B, 1993 version. It's very different from the others design and there are also some variations from the DC3 standard schematic. I gave up trying to identify the mods. It will be easier by comparing it to one of its "brothers".

In the next days i will upload a photo of it.

thanks


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PostPosted: Sun Apr 03, 2016 6:57 am 
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Mark III
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Joined: Fri Jul 29, 2011 12:52 pm
Posts: 357
I am pretty sure this is before I did any mods to it. Mine was a DC3B from 1993

Image


For reference, this is the same amp post mods:

Image

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PostPosted: Mon Apr 04, 2016 8:59 pm 
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Bottle Rocket

Joined: Mon Sep 07, 2015 4:07 pm
Posts: 6
that's 98% similar, except in the v6 neighbourhood. And that's right there where the damage was done.

There are some resistors in different positions and also a diode crossing over a piggyback 120 k chinese-made resistor. It is hard to see (and to take a photo) because it is beside the 2 orange drops and right under those 4,5 wires wrapped up.

my idea is to restore the amp and then do the famous bias mod. Right now i have:

pin7= 429 volts
pin9= 320 v
bias= -8.5 v (!!!)

that's why the amp is not sounding correct, even though the JJs power tubes are (unbelievably) working fine.
I don't know how. The mistery is up to you.


thanks for the photo


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