FDP Forum / Substituting Power tubes / 4 messages in thread.

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USA / Sesame St.

Dec 18th, 2016 11:43 AM        

When the 6L6GC tubes are substituted with 6L6WGB tubes is there anything else that typicaly needs to be moddified like resistors, caps or checked in the Bias circuit other than changing out the GZ34 Rec with a 5U4GB and adjusting the Bias?


USA / Sesame St.

Dec 19th, 2016 08:35 AM        

From what I've read the 6l6WGB cannot simply be used to replace a 6L6GC tube without some changes.<br /> <br /> Most amps calling for 6L6GC tubes will exceed the ratings of the 5881/6L6WGB and may overheat or arc over, so check first before subbing these! <br /> <br /> Guitar amps that call for a 6L6GC cannot use these tubes without bias circuit adjustments or even modifications. Consult an amp tech if you are unsure.<br /> <br /> When I got my 67 Pro Reverb it had the JAN 6L6WGB tubes in it so that explains why there was a JAN 5U4GB rec tube installed. I didn't know all this previously, I just started looking into this.<br /> <br /> I was told by the previous owner that his amp tech put the JAN 5U4GB in because he liked the B+ readings better. I didn't realize that it was because of the specs of the 6L6WGB was different from the 6L6GC tube. <br /> <br /> Obviously the Bias will have to be adjusted if you change back to using the 6L6GC tubes and GZ34 rec. I don't know why there would have been any other mods done to the amp previously with the other tubes.



Dec 19th, 2016 10:21 AM        

I can see no good to come of this. Just use a 6L6GC set.



Bobby Roadrunner
Feb 12th, 2017 03:47 PM        

Also sometimes a 6l6WGC is good also

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