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swapping OT tubes for troubleshooting

8/17/2005 10:59 AM
Roland swapping OT tubes for troubleshooting
Hello all,  
I am wondering - for quickie troubleshooting purposes if the 6V6's can be replaced with 6L6s or EL34s to test my amp (briefly) I have a crackle that goes away after the tubes really warm up we tapped the output tubes one seems to be a bad (harmonics)- so i would like to toss in the other tubes to see if the crunch goes away. I have buttloads of 6L6 and EL34 but no 6V6 to test with (yet) thanks guys - Rock'n Roland  
PS if this doesn't make the crunch go away I will scope the amp and see if I can find the problem - if not tube related  
currently i'm using 6V6EH's
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8/17/2005 4:19 PM
Bruce /Mission Amps

No to El34s... OK with 6L6s for a very short time in testing.  
8/17/2005 9:06 PM

Definitely NOT EL34s. Too many issues, not the least of which is the pin 1 thing. The excess current draw is another.
8/19/2005 10:04 AM
Al Lang

Stock 5E3, no EL34s but you can mod the amp to run on them. A lot of work. Ground pin one of power tubes, change out you PT, OT, change power tail resistor's, and rebias the cathode resistor for current draw of a EL34. Probably someother suff I forgot, too.  
I did it, kind of cool sounding and a little Marshally but I went back to 6V6's and 6L6s so...?  
8/19/2005 12:08 PM
Bruce /Mission Amps

The 6v3 filament tap of my 5E3 PT is 4 amps.  
The stock power tranny is only about 2.5a to 3a.  
The El34s alone will draw more then that, over 3 amps and in some EL34 tube cases, 3.4 amps.  
The screen current in two EL34s is 5 to 10 times that of a pair of 6V6s let alone the possible +200 ma of plate current.  
The OT is probably around 100ma.  
Don't take a chance with the PT and OT using El34s in a vintage stock 5E3 or for that matter, a homebrew one with small trannys.  

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