Vintage Epiphone combo

[andresound]

Not to worry Bob, I will be doing a decent order from you sometime soon. As soon as this project is done . Dam.. I need counselling

[andresound]

Have you tried Antique Electronic Supply? They have lots of tube stuff, and they say they ship internationally, with lots of options: https://www.tubesandmore.com/customer-s ... d-delivery

Thanks Martin. I have placed an order for the caps (TVA series)

[andresound]

Thank you for the link Martin. I have bookmarked it. Here is what I intend to use. It will be neat and simple. Values are higher.

[Phil_S]

I used JJ can caps in my GA20-RVT. I modified the ring clamp with a pliers for sideways mounting because of the shallow chassis. I drilled out the rivet and used that hole for the screw.

[andresound]

On the home stretch now. Cleaned up step down transformer connections. Finished installing can cap and first stage coupling cap (will change to something better arrives), placed last filter cap close to first stage.

[andresound]

Reverb tank. Stripped and cleaned cabinet. The font baffle is easily removable (see the screws in previous post of speaker pic). Also now ready for tubing and testing/checking voltages. FYI, the remaining 6L6 tube measured 48ma in AVO tester (80%). Will replace with OS Sylvania 6L6's (coke bottle). This amp has seen very little playing time for a 55 year old girl. ALL preamp tubes (6EU7 and 1x 12AU7) tested 100%.

Will check voltages and post in the morning.

[andresound]

Restoration complete. Voltages are

V1 6EU7 pin 4 = 1.19
6 = 156.2
7 = 150.7
9 = 1.19
V2 6EU7 pin 4 = 1.42
6 = 165.8
7 = 124.1
9 = 1.186
V3 6EU7 pin 4 = 1.163
6 = 152.9
7 = 164.2
9 = 1.165
V4 12AX7 pin 1 = 152.7
2 = 53.5
3 = 93
6 = 233
8 = 9
V5 5881 pin 3 = 385
4 = 300
5 = 16mv
8 = 22.3
V6 5881 pin 3 = 383.2
4 = 298.8
5 = 10mv
8 = 22.2

Should there be such a big difference in voltages between plate and grid??

[andresound]

Finished, will leave grill cloth as is. Do have a slight 50hz hum. Will visit that later.

[Firestorm]

The EA10 schematic shows 59V difference between plate and screen grid across a 5K resistor, so depending on the tubes you could see 85V across the 6K. That implies that the screens are idling at almost 2W, so if those are actual 5881s (3W screen max), they may start to light up when signal is applied.

Is V4 split between reverb driver and phase inverter like on the BA15? If so it should probably be 12AU7 to provide enough current to shake the reverb springs. PI is cathodyne right?

[martin manning]

I believe V4 should be a 12AU7 too. Re the 50hz hum, with all the filters in one can you can't separate the grounds. I would try wiring in a separate cap for the first filter with its negative lead connected directly to the PT CT and chassis ground point, and a separate lead from the cap can to that ground, and see if that clears up the hum.

[andresound]

Finished, will leave grill cloth as is. Do have a slight 50hz hum. Will visit that later.

[andresound]

I believe V4 should be a 12AU7 too. Re the 50hz hum, with all the filters in one can you can't separate the grounds. I would try wiring in a separate cap for the first filter with its negative lead connected directly to the PT CT and chassis ground point, and a separate lead from the cap can to that ground, and see if that clears up the hum.

Sorry Martin my mistake....V4 is a 12AU7. Also redid the grounding scheme and all is well. This amp sounds Great!!! I must be getting deaf It does not seem to be that loud. Breaks up beautifully and the reverb is awesome. Had thoughts of converting to fixed bias... But she sounds good and leaving her stock is the way to go. Have thought about the Step down transformer which measured 125v out. I think this is one of the old ones that has a 220v primary, hence the high output. Even with this, my voltages seem to reflect the EA-10 schematic. Great amp for smaller spaces.

[andresound]

The EA10 schematic shows 59V difference between plate and screen grid across a 5K resistor, so depending on the tubes you could see 85V across the 6K. That implies that the screens are idling at almost 2W, so if those are actual 5881s (3W screen max), they may start to light up when signal is applied.

Is V4 split between reverb driver and phase inverter like on the BA15? If so it should probably be 12AU7 to provide enough current to shake the reverb springs. PI is cathodyne right?

Thanks firestorm. My mistake, yes V4 IS a 12AU7. Should I rather use 6L6. Might get a bit more clean headroom. Problem is... The only 6L6's I have at the moment are Coke Bottle type and they physically "'touch" each other (the socket spacing is CLOSE ). Won't they get to hot?? I would have thought 6L6's in 1961 were only available in "coke bottle" form???

[martin manning]

Should I rather use 6L6. Might get a bit more clean headroom.

I doubt it. The only real difference between 5881 and any of the various 6L6's is the power handling capability (max plate dissipation). The socket spacing is surely assuming the small straight-sided 6L6GC envelope, which dates back to 1959.

Good to hear you have the hum solved. What does the ground scheme look like now? Still using the cap can for everything except the last filter?

[Bob S]

Congratulations on resurrecting the old girl. Great thread too.
I love it when a plan comes together.

Edit - almost forgot - if you use JJ 6V6s & treat them like a 6L6. They'll fit fine.