50w Bias Question

gutpile · Post by **gutpile** » Sun Nov 25, 2007 1:54 pm

In between the 2 1M resistors on V3 the diagram say put a 470 there (yellow-violet-yellow) BUT in the pictures of George's amp it looks like he has a 47K there (yellow-violet-orange)... this might be why I am getting high readings on v3? I used a 470 (y-v-y)... what should be there?

Thanks,
Mike

mwm523 · Post by **mwm523** » Sun Nov 25, 2007 2:16 pm

Mike, it should be 470 ohm (yellow - violet - brown).

Yellow - violet - yellow is 470 Kohm.

This is a very common mistake. Change it to a 470 ohm.

gutpile · Post by **gutpile** » Sun Nov 25, 2007 2:21 pm

NICE! Thanks a million! maybe now I can get some sound!!

gutpile · Post by **gutpile** » Sun Nov 25, 2007 2:23 pm

so if I used 1/2w NOS AB for the 1M resistors, that should be OK, right?

Billy Batz · Post by **Billy Batz** » Sun Nov 25, 2007 3:52 pm

Uh huh

gutpile · Post by **gutpile** » Sun Nov 25, 2007 4:52 pm

Allright problem fixed.... All volts are right on... I tried biasing and I am getting 35ma on v4 and 21ma on v5??? Are the tubes not matched properly or did I do I have something wrong? again thanks for all your help....

Mike

mwm523 · Post by **mwm523** » Sun Nov 25, 2007 5:07 pm

Swap the power tubes around (V4 to V5, V5 to V4) and see if the mismatch follows the tube or stays with the socket. If it follows the tube, the tubes are mismatched.

gutpile · Post by **gutpile** » Sun Nov 25, 2007 5:35 pm

Bad Tubes... I took a pair out of my 100w and it biased right in!

This amp KICK ASS!! Talk about gain right off the bat!!! I'll post some pics later!... I have now completed the Metro Trifecta, JTM45, 100w, & 50w!!!!

Thanks to all that helped me complete this beauty!!!

Thanks,
Mike

mwm523 · Post by **mwm523** » Sun Nov 25, 2007 6:24 pm

Awesome! Glad to hear you got it sorted out.