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Hoffman Amps Forum image Author Topic: EL34 pin 1 connected via resistor to pin 3???  (Read 605 times)

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Offline neskor

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EL34 pin 1 connected via resistor to pin 3???
« on: April 26, 2025, 03:25:06 pm »
Hi.
I just received stereo amp with parallel SE EL34 on output with cathode bias.
It has a blown Power transformer.
I can see that pin 1 on El34 is connected to pin 3 with 1K resistor. Never seen that before.
Is that normal practice?
Usually pin 1 is connected to pin 8.
Also pin 4 is also connected to pin 3 with 150R resistor, triode mode?
Thank you in advance!

Offline Merlin

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Re: EL34 pin 1 connected via resistor to pin 3???
« Reply #1 on: April 27, 2025, 05:23:34 am »
Yeah it's in triode mode, with both the screen and suppressor grids tied to anode. The resistors are a just-in-case measure to ensure the grids don't pass more current than they can handle, as well as discouraging oscillation.
It's rare for a triode amp to blow an output transformer, I wonder what happened.

 


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