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Vintage threads from the first ten years

Change from 6L6 to EL34

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12/21/1999 7:52 PM
lars	Change from 6L6 to EL34 I have a Bluesbreaker that I would like to test with EL34. What more do I need to do except change the resistor on the power tubes from 470/5W to 1k/5 and change the bias resistor so I can bias the amp.

12/21/1999 10:03 PM
peter	on 6L6's pin 1 and 8 are connected internally. on EL34's they aren't. So you need to make sure pin 1 & 8 get connected together in the amp (and that the extra pin isn't being used as a handy place to connect something in the amp) You can leave 1&8 connected if you go back to 6L6's.

12/21/1999 10:34 PM
Dwight	Make sure your power transformer can handle the increase in filament current. 6L6's draw .9a, whereas EL34's draw 1.5a. I'm not sure exactly how to test this. I just know it is something that needs to be considered when making this change. Maybe one of our more technicaly inclined contributors can enlighten both of us.

12/21/1999 10:44 PM

The two posts above are correct, although Dwight means filament AMPS, 0.9A for 6L6 vs. 1.5A for EL34; Both are 6.3 VOLT filaments. The power trans of your amp may not be capable of supplying this much additional filament current. The safest approach would be to add an auxiliary filament transformer - 120VAC to 6.3VAC at 3 amps. You could then run the preamp tubes from the existing power trans filament winding, maybe make it DC.

Anyone out there know if the power trans can take the additional load of EL34s?

12/22/1999 1:14 AM
stokes	I read in G.Webers book that if you check the fil.voltage after changing tubes,and the voltage does not drop from the 6.3v,your tranny is probably capable of the extra amps,if it drops it does not like the extra current.

12/22/1999 5:50 AM
jason	nice tip john! jason

12/22/1999 9:58 AM
Lars	Thanks for the tip. Lars

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