Tube Amp Archive

Meant to also say that after replacing the coupling cap off of the EF86 (0.047 uf), the input grid on the EL84 is still sitting at 40 mV.

After checking all the resistors (and de-soldering a few to double check), several have drifted more than 20 - 50%. I'll be placing an order for these this week and I'll let you know how it all turns out.

Right on about the heaters. Rookie mistake. Thanks for the advice and help everyone. Looks like I'm going to be digging a little deeper here.

Ooo, good stuff here. Thanks guys. The cathode resistor on the EL84 reads 156 ohms on the meter. Not too far out.

I'll replace that coupling cap and see what happens.

BUT, the heaters are only getting 3.5 VAC!! Maybe the power transformer has some issues?

Thanks!

Thanks, guys. I have traded out the EL84 and 12AX7 for known good tubes, but I don't have an EF86 lying around. I've ordered one though, so we'll have an answer later this week. The amp makes sound, it's just kinda muddy and pretty low volume. I know it's only on EL84, but it still seems very low. T...

Hey, I'm troubleshooting an old Vox AC4 for a friend that's saying it just isn't as loud as it used to be. It recently had it's filter caps and cathode bypass caps replaced. Tubes seem to be ok as well. In fact, about the only thing that I can see that's different than expected is that the B+ is run...