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Old 18th May 2006, 08:25 AM   #11
AndrewT is online now AndrewT  Scotland
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Hi,
that DC servo seems somewhat unusual.
Connected to two compensation pins to pull the amp1 level up or down.

Is amp1 an IC opamp (+-55V regulated) or a potted discrete?

Amp2 is also high voltage.

I don't understand the biasing. Any help coming?

1976 and a snubber on the PSU. Who says these are new?

What are all those diodes and Zener on the feedback loop into amp2? Bridged limiter for protection?
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Old 18th May 2006, 10:42 AM   #12
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Join Date: Sep 2004
Location: MN
Quote:
Originally posted by AndrewT
Hi,
that DC servo seems somewhat unusual.
Connected to two compensation pins to pull the amp1 level up or down.

Is amp1 an IC opamp (+-55V regulated) or a potted discrete?

Amp2 is also high voltage.

I don't understand the biasing. Any help coming?

1976 and a snubber on the PSU. Who says these are new?

What are all those diodes and Zener on the feedback loop into amp2? Bridged limiter for protection?
Amp 1 & 2 are potted "Magic" modules. have no idea whats in them. the cap cam off of one and inside is a black potting material filled with small cork bits so there is no way to see inside.

I got the bad channel repaired and back up and running last night. I just need to fix the fuse board and its done! there is a 1.8K 5 watt carbon comp resistor for the LED power light that was sitting right noext to a fuse and it ROASTED the board and the fuse to the point the solder leaked out of the fuse. My cals say that resistor is dissapating about 4 watts so i am going to move the resistor to a new location where it can get some air around it. Plus the board is burnt beyond use in that spot again.

It is a weird amp thats for sure. even A.R. claims it is not one of there best. the parts guy told me they have hundereds of them in the warehouse that will never see the light of day again. I tried to talk him into selling me some, but he said no way.

BUT, side note. WZJ was there! didnt get to meet him but he dark green Caddy was parked in his assigned parking spot! He isnt there much these days.


Zc
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Old 18th May 2006, 03:41 PM   #13
mlloyd1 is offline mlloyd1  United States
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Location: illinois
Default the mystical modules ...

the amplifier's voltage gain stages are made up of Supertex N and P channel MOSFETs. It's a fully complementary symmetry circuit. I used to have a schematic. I'll see if I still have it.

mlloyd1
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