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Valve Standard PT problem


ricach

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The heater windings on my power transformer are bad. The schematic rates the windings at 6.3VAC/1.6A. Doing the math, (taking the data from the tube spec sheets), the 5 tubes require 2.42Amps of heater current. My guess, that's why the windings are shot. Anybody else had a problem with their Power Transformer? Know a suitable (better) replacement? For now I'm just planning on adding a small transformer specifically to power the heaters.

 

Also, for those wanting to mod their VS, the tube signal path is totally interrupted by the whole DSP circuitry. (Sits between the 2nd preamp stage and the phase inverter/power stage) If you don't want/like/use the DSP, a simple jumper from the wiper of the treble pot to the high side of the volume pot will do away with all that and give you a true 'tube' signal path. My plan is to use the DSP footswitch jack as a means to do the bypass. Unfortunately this also bypasses the reverb.

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Instead of replacing the whole PT, I added a small 12VAC/3A (6.3V CT) PT ($12 from PartsExpress) just for the heaters. Works great.

 

Also, just placing a jumper from the wiper of the Treble pot to the R41 Resistor (need to utilize the 47K), is all that's necessary to bypass the DSP circuit. Since it's difficult getting to the pot leads, I soldered onto one side of R17. No need to pull out the PCboard. There is a huge! gain in volume - therefore using a foot switch to bypass is useless because of this. Turning up the reverb or turning on the DSP does inject noise, but no effects are heard so I know the bypass works. Just keep these down/off and it'll sound fantastic.

 

I still don't want to give up figuring some way to still utilize the Reverb. It has its own output from the DSP chip so I'm thinking of injecting it back somewhere into the Preamp circuitry to boost the signal and make it more useable.

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