I didn't either. I just connected the heater pins of a nearby EL34 to a power supply with clip leads and touched my voltmeter to the cathode and grid pins. The voltage reading is highly dependant on the meter impedance which is unknown since I am using a $4 meter. I have seen 10 volts on an 833A, which I have only seen in a guitar amp once.
I don't think so. Jack for "extra" speaker means it's in parallel. That means plugging anything into it can only LOWER the impedance. When you go from 4 tubes to 2 you need to INCREASE the impedance.
Well I think so. I have the schematic and it shows that the manufacturer is using a switched jack in order to change from the 16 ohm winding to the 8 ohm winding. But thank you for your for the reply.
Sorry you got the wrong idea.
There wasn't really that much information in your posts.
Usually, people have the amp in front of them...
When I said "he won't know", I should have made it clear that I do not think it a good idea to alter someone's amp without their agreement. I was trying to say that it will make no functional difference to the user, it will work exactly the same.
It's still the better idea.
A better "feature".
Think it is still a good idea to suggest the change to the amp's owner... cut pins somehow do not sit right with me.
Sorry for the misunderstanding.
_-_-bear
Glad it worked out for you and the owner of the mystery amp anyhow.
There wasn't really that much information in your posts.
Usually, people have the amp in front of them...
When I said "he won't know", I should have made it clear that I do not think it a good idea to alter someone's amp without their agreement. I was trying to say that it will make no functional difference to the user, it will work exactly the same.
It's still the better idea.
A better "feature".
Think it is still a good idea to suggest the change to the amp's owner... cut pins somehow do not sit right with me.
Sorry for the misunderstanding.
_-_-bear
Glad it worked out for you and the owner of the mystery amp anyhow.
Yes it may be a problem. Hard to tell without seeing the circuit, but yes, if you heat the cathode and drive the grid positive you now have a rectifier in parallel with the other (active) tube input.
Kind of figured that but thought I would ask anyway. Nothing special about the circuit, four EL84's, 200k grid resisters with 68k stoppers and fixed bias fed by a cathodyne PI.
If he likes the effect I could suggest the rewiring to him and he has a buddy that does work on his amps. I am not in the habit of working on others equipment and prefer to keep it to a minimum. Due to health reasons I am trying to back away from many of the things I used to do for people.
If you want to KILL 2 tubes in the 4 tube amp....
AND you don't want to have to modify it...
THEN you make 2 small "male to female" octal plugs to put BETWEEN the two tubes you want to KILL....
Only bypass the heaters ...from male to female...PINS 2 and 7 ....
Or , provided it is not a vintage amp, you go in the amp and mount a small switch in the back that disables the voltage to the SCREENS PIN#4 on the two tubes you are looking to KILL....
CERREM
AND you don't want to have to modify it...
THEN you make 2 small "male to female" octal plugs to put BETWEEN the two tubes you want to KILL....
Only bypass the heaters ...from male to female...PINS 2 and 7 ....
Or , provided it is not a vintage amp, you go in the amp and mount a small switch in the back that disables the voltage to the SCREENS PIN#4 on the two tubes you are looking to KILL....
CERREM
The tubes are not octal but 9-pin. Much easier just clipping the pins off a couple of old tubes and filing down the excess, took me ten minutes. Pin 2 is the grid and pin 7 is the plate, bypassing the heaters is not a good idea because two tubes are in series, that would put 12v on a 6v tube. Was not planning on modifying the amp, but thanks anyway.
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