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Author Topic: Cooked Super Amplifier  (Read 2210 times)

solidstate2199

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Cooked Super Amplifier
« on: May 20, 2018, 07:45:20 AM »
Bought an old Superlead Style Amp, its not here yet.

One burned out EL34 Socket and what looks like the
negative feedback resistor is shot, plus collateral
to the surrounding parts.


There is a cable coming from the 16ohm speaker jack going
to that resistor so i guess it is the 100k seen on the schematic.

Can i suspect output transformer damage?

I make better pics when i have it here.


schematic
https://drtube.com/schematics/londoncity/dea100-early.gif

g1

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Re: Cooked Super Amplifier
« Reply #1 on: May 22, 2018, 12:21:58 PM »
A burnt feedback resistor is pretty rare.  The only thing I can think would cause it is the same thing that would toast the output tube socket, running signal with no load connected.
So yes, you need to be somewhat suspicious of a damaged OT.

solidstate2199

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Re: Cooked Super Amplifier
« Reply #2 on: March 09, 2020, 02:16:20 PM »
Im in the process of getting this Superlead repaired in the next couple
Weeks, the Feedback resistor is not bad, it had Carbon residue on it
From blown screen resistors next to it.

FIRST The filter and reservoir caps need to be Done. Currently there
Is a voltage of over 1200 volt inside due to the leaking caps, i couldnt
Believe it, i measured with different multimeters.
I think the dmm is not getting the right reading because of the stray
Ac...but nevertheless...it also needs a thorough cleaning because
There is carbon everywhere...the pt sockets need to go.

I hope the transformers are alright.