Howdy y'all!
Been a while since I've been here, what with the pandemic and all. Losing my job, finding a new one, etc it's been crazy as I'm sure many of you have experienced.
Anyhow I've got a friend's modern Deluxe Reverb on the bench and it has an interesting issue. One of the power tubes is drawing more current than the other - resulting in a lower plate voltage - regardless of the tubes that are installed. Yes, I have tried multiple pairs of 6V6s and the issue remains. This being a modern amp I don't want to go messing with the delicate pcb until I have a decent idea of what's causing the problem.
Any suggestions are supremely appreciated!!
Best to everyone & good to be back!
Deluxe Reverb HELP!
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sluckey
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Re: Deluxe Reverb HELP!
What voltage do you measure on pin 4 and 5 of each of the 6V6s?
Re: Deluxe Reverb HELP!
Pull the PI tube and repeat your measurements. If you can confirm that the low voltage stays with the tube socket, you should suspect the supporting components for that socket: screen and grid resistors, coupling caps, bias voltage.
I build and repair tube amps. http://amps.monkeymatic.com
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WRC34
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Re: Deluxe Reverb HELP!
Extremely delayed conclusion: it turned out to be a “bias feed” or “grid bias” or plain ‘ol “grid” resistor. I replaced both, and boom the amp sounds great.
Thanks for your help as always everyone!
Thanks for your help as always everyone!
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Stevem
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Re: Deluxe Reverb HELP!
If you still have the guys amp I would check the PI plate load resistors.
I forget if they are 1/2 watt, or 1 watt, ( 100K and 82K ) but if they are not 1 watters then you should change them to such!
You can even make up the values needed with two 1/2 watt resistors.
1/2 watt resistors are only good for a max of 350 volts hitting them and amps power supply hits them with more!
I forget if they are 1/2 watt, or 1 watt, ( 100K and 82K ) but if they are not 1 watters then you should change them to such!
You can even make up the values needed with two 1/2 watt resistors.
1/2 watt resistors are only good for a max of 350 volts hitting them and amps power supply hits them with more!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Deluxe Reverb HELP!
Posting this for anyone like the OP tussling with the DRRI or '68 CDR. Great video on how to beef up these PCB amps.
https://www.youtube.com/watch?v=4h9AUyG ... e=youtu.be
The layout and grounding of these amps were less priority than production efficiency. High amperage heater circuit is placed on the PCB rather than run to the power tubes. The PT center tap, power, screen, pI, bias circuit and artificial center tap, etc. all ground via the pots rather than to the chassis. The screen resistors are mounted on the PCB rather than on the power tube sockets. All this can be improved a great deal by getting that stuff off the main PCB and wiring the amp conventionally.
https://www.youtube.com/watch?v=4h9AUyG ... e=youtu.be
The layout and grounding of these amps were less priority than production efficiency. High amperage heater circuit is placed on the PCB rather than run to the power tubes. The PT center tap, power, screen, pI, bias circuit and artificial center tap, etc. all ground via the pots rather than to the chassis. The screen resistors are mounted on the PCB rather than on the power tube sockets. All this can be improved a great deal by getting that stuff off the main PCB and wiring the amp conventionally.