G2 mod gigs well

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Structo
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Re: G2 mod gigs well

Post by Structo »

Yeah, I know it wasn't the same as you were talking about, I just came across it in my notes and remembered it was mentioned being used in the Marshall.

I think I'm going to try the Zener method.

But what would the specs be?

Take a 6L6GC

In my amp the plate voltage is 434v.
I think when I have measured things before I only came up with about 5ma on the screens.

Geez, try to find single diodes for sale any more is not easy.
Tom

Don't let that smoke out!
pdf64
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Re: G2 mod gigs well

Post by pdf64 »

That JTM45 screen supply arrangement is really interesting and works well. If an additional decoupling filter cap (eg 33uF) is added at the node of the 1k and 470ohm resistors, the waveform of a high power sine wave changes noticeably for the worse. There's a strange feedback mechanism going on there which I haven't got to grips with or seen an analysis of. Pete.
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Reeltarded
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Re: G2 mod gigs well

Post by Reeltarded »

Structo wrote:
Geez, try to find single diodes for sale any more is not easy.
Tell me about it. Before the internet, I could build a space needle with things commonly for sale all over town. Now with the internet, I have plans for a space needle, but I have to buy bulk, and ship everything in from Diodeganistan.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
Andy Le Blanc
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Re: G2 mod gigs well

Post by Andy Le Blanc »

Use a cap and bleeder...

a bleeder makes the difference, looking at the jtm 45, a bleeder allows any
value in place of the 1 k to set the voltage at the screens.
the bleeder doesn't have to so small a value that you encounter thermal
issues or impractical watt sizes either, the same if its tried with just a bleeder
right on the tube socket.
lazymaryamps
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Structo
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Re: G2 mod gigs well

Post by Structo »

The reason I wanted to try the diodes is because I don't want to experiment trying to find the right resistor value on an expensive quad of power tubes.
Tom

Don't let that smoke out!
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