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Old 23rd November 2007, 12:53 AM   #1
d3imlay is offline d3imlay  United States
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Default GAS Thaedra

I just picked up a Thaedra. Where can I find a schematic. I've been to davidsaudio.com but only found a one line diagram.
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Old 23rd November 2007, 01:54 AM   #2
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What is wrong with the preamp?

Do you need it fixed?
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Old 24th November 2007, 02:23 AM   #3
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I just found a Thaedra Head Amp schematic and a Thaedra II Head Amp schematic.

I have nothing on the power supply but that should be straight forward with a B+ of 22volts and B- of 22 volts.
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Old 24th November 2007, 06:51 AM   #4
d3imlay is offline d3imlay  United States
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It's not working, so, yes I need to get it fixed. I'd prefer to repair it myself if i could find the schematic.
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Old 24th November 2007, 12:50 PM   #5
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Quote:
Originally posted by burnedfingers
I just found a Thaedra Head Amp schematic and a Thaedra II Head Amp schematic.

I have nothing on the power supply but that should be straight forward with a B+ of 22volts and B- of 22 volts.
Hi,

The supplies should be +/- 28vdc. There are two sets, one for the lineamp card and one for the two phono cards. There is also a muting relay circuit, which is highly suspect if you are getting nothing out of the main outs.

Hi Joe!

Regards, Mike.
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Old 24th November 2007, 01:06 PM   #6
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Hi Mike,

I will update my schematics to indicate + - 28 volts.

Damn, can't even get a good schematic anymore.

Come to think of it I replaced the relay in the unit I used to own.
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Old 24th November 2007, 01:23 PM   #7
d3imlay is offline d3imlay  United States
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My problem is the relay isn't pulling in. I've got a signal to the relay. Power supplies seem to be OK although there are a couple scorched caps near the power resistors.
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Old 24th November 2007, 07:00 PM   #8
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I don't have a relay circuit to give you. There is going to be a cap in the circuit and if I were to make a bet it would be the caps fault.

Carefully unsolder them and replace them. Check the transistor that is in the circuit if it doesn't come up and live.
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Old 24th November 2007, 07:06 PM   #9
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Quote:
Originally posted by d3imlay
My problem is the relay isn't pulling in. I've got a signal to the relay. Power supplies seem to be OK although there are a couple scorched caps near the power resistors.
Hi,
Is the relay circuit on the motherboard or a plug in ? If the scorched caps are electrolytics they might be the cause (dried out). I have a relay circuit schematic I'll dig out but there was a number of attempts by GAS at this circuit so it might not be of use. I'll try to post it when I finish what I'm doing. Basically it's charging an electrolytic and pulling the relay. The power transistor is an MPSU07 and they used to fail. Check (obviously) the drop across the power resistor to see if the circuit is trying to pull the relay.

Mike.
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Old 24th November 2007, 09:00 PM   #10
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Mike,

I think they are on the main board if my memory is correct.
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