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TL Audio dual pentode preamplifier (PA-1) schematic
Old 4 weeks ago
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TL Audio dual pentode preamplifier (PA-1) schematic

Hi everybody!

I have a TL Audio dual pentode preamplifier (I think is the PA1 first version, without the meters), that has a very strange behaviour: only on channel B I have:

- a very loud noise when switching the gain with the selector (it looks like a square wave on the scope). It has been mitigated by adding 100 pF capacitor in parallel with the existing 100 pF cap from grid of the EF86 to ground)

- a buzz noise that kicks in few seconds after switching it on, and fades away 2-3 minutes after the unit has been on. The strange is that the noise is present only with the fader knob (the big one) is at the minimum. As just I turn it up slightly, the noise disappears.

Also, the led indicating the signal presence works in a weird way (on without signal).

Is there anyone with the schematic of the machine?

The TL audio site is completely unavailable, and I have found nothing more than a simple block diagram.

Also some suggestions are welcome! I already tried to swap the tubes with he channel A (that works fine) but without any change.

If someone could help me, I would appreciate it a lot!

Thank you very much for the support!

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