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Re: [Amps] TL922 failure - SOLVED

To: Amps reflector <>
Subject: Re: [Amps] TL922 failure - SOLVED
From: Victor Rosenthal 4X6GP <>
Date: Fri, 13 May 2022 11:18:49 +0300
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As usual, it turned out to be my fault.

I put a small ww resistor in series with the filament transformer primary to reduce the filament voltage to exactly 5.0v.

The resistor has been there for years, and it had migrated so that it touched the bottom plate of the amp. It was coated with some insulating material, but that ultimately wore through.

I made sure that that can't happen again. I had quite a scare, believing that it might be one of the transformers!

Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
On 13-May-2022 10:02, Victor Rosenthal 4X6GP wrote:
After about 10 years of almost daily use, my TL922 has failed.
When I turn it on, the GFI for my radio room immediately -- instantly -- pops.

An ohmmeter from either line pin on the power plug to the ground pin shows a resistance of 1.2k. I presume that explains the GFI's reaction! The resistance across the line pins (it is wired for 230v) is 27 ohms, which I think is normal.

The schematic shows a couple of 470pf capacitors from line to ground. It looks like it's either this or the transformer.

I haven't removed the amp from my desk and opened it yet, but does anyone have an experience with a similar problem?
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