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In Reply to: RE: No! posted by xcortes on September 29, 2009 at 09:13:56
But it isn't like a lower value resistor so that it pulls more current. The tube won't operate at optimal value and will produce more distortion but I would still be able to see that it works without damaging the tube or the amp. Unless I am confused, which happens more often with electronics than I would like.Edit: there will be voltage on the 300B grid that shouldn't be there. Maybe that would cause a problem. Might just be best to wait and do the conversion first.
Edits: 09/29/09Follow Ups:
Without the proper heater (filament) voltage the cathode will get stripped.
The heater voltage conversion means re-wiring the filament filter choke, and using a different pad on the power supply board.
Other than the filament voltage, a 300B will work very much like a 2A3 in any 2A3 circuit.
The J/J 2A3-40 is essentially a 300B, but with a 2.5V, 2.5A filament.So, in a fashion, this may be equivalent to using a 300B in a 2A3-configured Paramount, without having to re-wire anything.
As usual, YMMV, etc, and all of the usual caveats apply.
As Paul stated in the previous post, a 300B (except for filament voltages) will behave like a 2A3 in a 2A3 circuit, so other than for technical curiosity, there is probably no real point in proceeding with this experiment.
/ed B in NH
real radios glow in the dark
Edits: 09/30/09 09/30/09
Not looking to see how it would sound. I ordered a pair of 300B that took a beating and each has a rattle. I am planning on converting the Paramounts back to 300B in a week and half when Grainger is here. I just wanted to make sure the 300Bs were functional in case I needed to order a new set before he gets here. Just want to have a working pair of Shuguang on hand since he is driving a good ways.
Tubes with a "rattle" are most likely in damaged condition.
If you have access to an emissions type tube tester, it can at least tell you if the tube is dead, shorted, or possibly still usable. Even better is a transconductance tester, which will show you the tube's real state of health (or lack thereof).
If you can't get access to a tester, try measuring the resistance of the filament between pins 1 and 4 (the two "fat" pins). This should be a low resistance value, a matter of an ohm or two, with a cold filament.
An "Open" reading means that the filament is broken.
(Look for little bits of filament wire rolling around inside of the tube's envelope).
Also check for any resistance between 1+4 and pin 2, and to pin 3, and between 2 and 3; these should all read as open. (or as infinity).
HTH
/ed B
real radios glow in the dark
Everything checked out to specifications with the meter. Nothing left to do but convert the amp and plug them in. As long as they don't damage anything, I have the original EH 300B that came with the Paramounts to use as well.
I'll just wait then. Thanks for the response.
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