- Posted by Russ57 (A) on September 10, 2003 at 07:25:14
In Reply to: Ghetto Tube Matcher posted by Chris on September 10, 2003 at 02:33:50:
You will need the power supply and bias circuity to be in good working order and you will need the output transformers with a suitable dummy load attached. From there I would advise replacing the stock shared 15.6 ohm resistor, going from the cathodes of the EL34's to ground, with individual matched 10 ohm resistors. There is a wire going from the cathode side of each 15.6 ohm resistor to the sockets up front to check bias voltage. Add another wire for the new 10 ohm resistor so that each resistor has a connection to the front socket. Then bias tubes to 1/2 volt instead. That will be 50 milliamps per ohm's law. Matched tubes would have the same voltage drop across each 10 ohm resistor when the bias pots were adjusted so that each EL-34's grid was feed the same grid voltage. Hopefully this makes sense to you but if not post again.
Russ
Follow Ups:
- Re: Yes, you can but.... - chris 12:42:41 09/10/03
(2)
- In Reply to: Re: Yes, you can but.... posted by Russ57 on September 10, 2003 at 07:25:14:
I understand you so far as I have changed these resistors to 10 ohms before and biased each individually on a previous rebuild project. I guess what I'm really asking is what parts can I leave out? Do I need the driver board? Do I need the output transformers? Can't I just power the tubes up without the output circuitry? Thanks for your help.
- Re: Yes, you can but.... - Russ57 16:15:39 09/10/03
(1)
- In Reply to: Re: Yes, you can but.... posted by chris on September 10, 2003 at 12:42:41:
You don't need the driver board just the grid resistors. But again if you have the board it is easy to just use it and pull the 7199 tubes. You must have the output transformers and they must be connected to a suitable dummy load such as a 40 watt non-inductive 8 ohm resistor. I suppose one could use a resistor instead of the output transformers but I figured you did have the transformers and that would be the easy way.
Russ
- Re: Yes, you can but.... - chris 12:08:30 09/11/03
(0)
- In Reply to: Re: Yes, you can but.... posted by Russ57 on September 10, 2003 at 16:15:39:
Thanks.
- Re: Yes, you can but.... - chris 12:08:30 09/11/03
(0)
- Re: Yes, you can but.... - Russ57 16:15:39 09/10/03
(1)
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