Since shared resistor cathode bias is, by definition, shared bias, they *should* be reasonably well matched, at least per side, to even and balance current in the primary.
You can build a simple matcher (or temporarily rewire 1 socket) by wiring 1 cathode to ground with the proper resistor for a single tube and test *all* the tubes you have (less than 2 minutes per tube) and label each for future reference.
As of rewiring complexity, maybe you can draw and make a generic 5E3 eyelet board that fits in the chassis, then quickly wire it to proper tube sockets/pots/jacks/transformers.
Worth "wasting" time designing it if you'll later convert a bunch of Hammonds to Tweeds.
Think about it
You can build a simple matcher (or temporarily rewire 1 socket) by wiring 1 cathode to ground with the proper resistor for a single tube and test *all* the tubes you have (less than 2 minutes per tube) and label each for future reference.
As of rewiring complexity, maybe you can draw and make a generic 5E3 eyelet board that fits in the chassis, then quickly wire it to proper tube sockets/pots/jacks/transformers.
Worth "wasting" time designing it if you'll later convert a bunch of Hammonds to Tweeds.
Think about it
The 5K field coil is not a choke for B+ but a *load* , eating 285/5=57mA so by not using it you have extra 57mA available. Good.
The 250 ohms one is the cathode resistor *but* it drops around 55V, while those 6V6, *in that amp* , require only around 18V , that's why they use a voltage divider at the grids.
You didn't answer my voltage readings questions, by the way.
The 250 ohms one is the cathode resistor *but* it drops around 55V, while those 6V6, *in that amp* , require only around 18V , that's why they use a voltage divider at the grids.
You didn't answer my voltage readings questions, by the way.
Well, that's an option.
W=V^2/R=55*55/250=12W
I would use a wirewound 250 ohms 25W resistor instead of the 2nd speaker field coil.
As of the 1st speaker and its 5000 ohms field coil, I guess that simply not using it will *probably* rise +V a few volts, because of reduced power consumption.
How much?
It's anybody's guess, but some 10 to 20V extra wouldn't surprise me, and definitely should not hurt.
Remember to un-use that cathode feedback winding, just pull and tape the wires and send cathodes straight to ground .... or even better through individual 1 ohm resistors, so you can read individual current any time.
You do not want the gain loss caused by that feedback winding, not their "HiFiness", much less in a "Blues machine".
W=V^2/R=55*55/250=12W
I would use a wirewound 250 ohms 25W resistor instead of the 2nd speaker field coil.
As of the 1st speaker and its 5000 ohms field coil, I guess that simply not using it will *probably* rise +V a few volts, because of reduced power consumption.
How much?
It's anybody's guess, but some 10 to 20V extra wouldn't surprise me, and definitely should not hurt.
Remember to un-use that cathode feedback winding, just pull and tape the wires and send cathodes straight to ground .... or even better through individual 1 ohm resistors, so you can read individual current any time.
You do not want the gain loss caused by that feedback winding, not their "HiFiness", much less in a "Blues machine".
Last night I took an amp I had with 2 12ax7 and 2 6l6 tubes, installed a PPIMV, pulled the output tubes and used a couple octal plugs in the 6L6 sockets to wire it directly into the power amp inputs. I was quite surprised by what a deep full sound I got. Too bad I cant turn it up until I get the speakers replaced although I really like the sound of these old Jensens but I know they cant take much abuse at 70 years old, and they weigh a ton. I have a pair of P12Ns I plan to use instead, I have been told they can take 50 watts, can anybody verify this? I really like the 1 watt resistor per tube idea. I would like to thank everybody here for all the great suggestions and technical info you have given me on this project.
Cool.
Those Jensens have *killer* sound and are very efficient, only they can't be used loud.
Sell them on EBay to perfectionists who want to clone 40's and early 50's Fender/Gibson/Magnatone/etc. amps.
Anything with 2x6V6 , preferrably cathode biased.
In fact, if I weren't 8000 miles away, I would get them from you.
Just add to the description that the 5000 ohms coil needs some 300V across it , and the 250 ohms one would need an extra, inexpensive 55V DC supply, which can be hidden anywhere inside the chassis.
It would be sad to have such speakers, the "real deal" by the way, ending in a landfill.
Good luck.
EDIT: those P12N can take *up to* 50W RMS each, I would use them with a 30W per speaker amp, to have some margin when overdriving the amp.
Those Jensens have *killer* sound and are very efficient, only they can't be used loud.
Sell them on EBay to perfectionists who want to clone 40's and early 50's Fender/Gibson/Magnatone/etc. amps.
Anything with 2x6V6 , preferrably cathode biased.
In fact, if I weren't 8000 miles away, I would get them from you.
Just add to the description that the 5000 ohms coil needs some 300V across it , and the 250 ohms one would need an extra, inexpensive 55V DC supply, which can be hidden anywhere inside the chassis.
It would be sad to have such speakers, the "real deal" by the way, ending in a landfill.
Good luck.
EDIT: those P12N can take *up to* 50W RMS each, I would use them with a 30W per speaker amp, to have some margin when overdriving the amp.
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How does that work? I guess I don't understand the internal workings of the oil can caps. Are they not grounded to the can body anyways? How are they floating? I see it in the schematic how it makes sense(sort of), but looking at the amp I just don't get it. How is one section grounded and not the others?
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Ok, so how are they connected? I have 1 can with 3 terminals and a ground wire from the can case to the chassis, I just cant seem to figure out how this thing works. I can see that L3 and L4 connect to C5 and C6, I can see one lead connected to C7. How are they connected at the other end? The schematic shows C5 and C6 connected together and to R11 and C7 to ground, how? The can has only 3 point connected to it, the schematic seem to show more. I know it really simple but I just don't get it.
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