Eico Classic 2050 - sat idle for 3 decades

[lqpete11]

I replaced cap C16 (50uf/25v) and resistor R46 (125ohm/5w) and the distortion (and climbing bias) still remains.

All suggestions appreciated. I’m looking at PC3 and PC5 along with R43/44 as possible culprits. I don’t know enough to say if they could cause my symptoms.

 

[BuzzK]

I'll have to check, but I may have some of the knobs with inserts. I also have a fabricated bottom cover that may fit, if yours lacks one.

I'd change this to fixed bias; add cathode and screen resistors; and Dave Gillespie's EFB™ circuit. (If you do that, you'll need to drop the B+ voltage a bit). It'll lower distortion; increase output power; and optimize tube life. Plus you'll be able to measure cathode current through the 1 or 10 ohm cathode resistors. IMO it will improve the sonics, too.

Can you check the voltage across the R45-46 cathode resistors? From that you can compare currents for the two channel pairs.

 

[lqpete11]

I'll have to check, but I may have some of the knobs with inserts. I also have a fabricated bottom cover that may fit, if yours lacks one.

I'd change this to fixed bias; add cathode and screen resistors; and Dave Gillespie's EFB™ circuit. (If you do that, you'll need to drop the B+ voltage a bit). It'll lower distortion; increase output power; and optimize tube life. Plus you'll be able to measure cathode current through the 1 or 10 ohm cathode resistors. IMO it will improve the sonics, too.

Can you check the voltage across the R45-46 cathode resistors? From that you can compare currents for the two channel pairs.

Hey Buzz,

Thanks for the suggestions. I’m hoping to get it working correctly before I make any modifications.

Both R45 & 46 read 0 VDC across them, but Imay be doing someone wrong in my measurements. There are multiple components connected to the same terminals and I checked it there. They also both read .174 VAC if that’s helpful. I measured from 5 to 2 on R46 and from 4 to 2 on R45 using the build sheet attached for reference points.