PV Penta

ty_tone · 03-06-2009, 05:31 AM

Hello everyone. Please be kind to the noob! I just got a new penta. The preamp tubes are not layed out like you normally see them. I'm trying to figure out v1-v4. The distortion is a bit on the buzzy side. Any suggestions? I need to pull the chassis and bias it correctly. I am sure it is cold from the factory. Any help and comments greatly appreciated! Frank

Enzo · 03-06-2009, 07:58 AM

I am not sure just what your confusion is, so here: All the tubes are in a row across the back except V1, which is towards the front. V1 is in the front corner, then straight back from it the tubes are: V3-2-4, and not that it matters much, but the three power tubes are in order V6-7-8-5.

V4 is the phase inverter next to the power tubes.

The V number assignments are printed on the parts layout in the schematic.

There is one path through the amp, the clean. The other two "channels" are created by switching in extra tube stages. The medium gain setting switches in the other half of V1. The high gain setting switches in the two triodes of V3. This is common PV circuitry.

SO if you don;t like the Ultra, or whatever they called the highest gain on this amp, the circuits around V3 would be the place to start.

03-06-2009, 05:31 AM	#1
ty_tone Junior Member Join Date: Mar 2009 Location: Ohio Posts: 3	PV Penta Hello everyone. Please be kind to the noob! I just got a new penta. The preamp tubes are not layed out like you normally see them. I'm trying to figure out v1-v4. The distortion is a bit on the buzzy side. Any suggestions? I need to pull the chassis and bias it correctly. I am sure it is cold from the factory. Any help and comments greatly appreciated! Frank

03-06-2009, 07:58 AM	#2
Enzo Senior Member Join Date: May 2006 Location: Lansing, Michigan, USA Posts: 10,301	I am not sure just what your confusion is, so here: All the tubes are in a row across the back except V1, which is towards the front. V1 is in the front corner, then straight back from it the tubes are: V3-2-4, and not that it matters much, but the three power tubes are in order V6-7-8-5. V4 is the phase inverter next to the power tubes. The V number assignments are printed on the parts layout in the schematic. There is one path through the amp, the clean. The other two "channels" are created by switching in extra tube stages. The medium gain setting switches in the other half of V1. The high gain setting switches in the two triodes of V3. This is common PV circuitry. SO if you don;t like the Ultra, or whatever they called the highest gain on this amp, the circuits around V3 would be the place to start. __________________ Education is what you're left with after you have forgotten what you have learned.

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