Danelectro amp

[Valvehead]

Ive got a Danelectro Envoy here with a dead socket , V1 (6sj7) . No filament voltage. The rest of the tubes light up and work. V1 and V2 are wired differently as far as the heaters. V2 is fine and works .
Anyone familiar with these amps ? I should have AC to pins 2 and 7 ? I am seeing ac to pin 7 but nothing to pin 2 . I will post the scem but its kinda blurry.......

pin 2 , V1 doesnt simply go to the heater supply like most amps ..Fender , etc... I cant figure out where its supposed to get its ac

danelectro_envoy.pdf

[Enzo]

No you should not find AC on pin 2 and pin 7, you should find AC BETWEEN pin 2 and pin 7. Don't measure to ground, measure from pin to pin. The tube doesn't care about ground, it cares about getting 6v across its heater.

Look at your schematic, all the heaters are in series. Four 25v heaters plus two 6v heaters. That adds up to 112v of heater plus a series resistor to soak up the last few extra volts.

This amp is a widowmaker, no power transformer, it rectifies the mains directly. Dangerous amp. Also not the only portion of the circuit using chassis as "ground" is the first tube. The rest of it does NOT use chassis as a ground.

Unless something is funny, if any of the tubes are open heater, they ALL will go dark.

What exactly does the amp do wrong?

[The Dude]

I hate to use the word impossible, so it's EXTREMELY unlikely with series filaments for all tubes to light but one. As Enzo said, check AC voltage between pins 2&7. Not all tubes filaments glow brightly when filament voltage is applied. Are you sure it's not lit? Maybe turn off the lights and have a closer look. Also, if you plan to actually use or sell this amp, install an isolation transformer so it is safe.

[Helmholtz]

I hate to use the word impossible, so it's EXTREMELY unlikely with series filaments for all tubes to light but one.

Except if something shorts the filament pins of the "one" tube.

[Valvehead]

No you should not find AC on pin 2 and pin 7, you should find AC BETWEEN pin 2 and pin 7. Don't measure to ground, measure from pin to pin. The tube doesn't care about ground, it cares about getting 6v across its heater.
Look at your schematic, all the heaters are in series. Four 25v heaters plus two 6v heaters. That adds up to 112v of heater plus a series resistor to soak up the last few extra volts.

This amp is a widowmaker, no power transformer, it rectifies the mains directly. Dangerous amp. Also not the only portion of the circuit using chassis as "ground" is the first tube. The rest of it does NOT use chassis as a ground.

Unless something is funny, if any of the tubes are open heater, they ALL will go dark.

What exactly does the amp do wrong?

Yes -- between 2 and 7 .
This amp has been worked on before. It DOES have an Iso power transformer , all new caps and looks like some added parts , like 3 47uf/450v filter caps ?

The amp has hum out of the speaker , and i can hear a faint buzz when touching V2. V1 is cold and does not have AC between pin 2 and 7. The rest of the tubes do. So , no guitar signal from input jacks .

V1 is not wired directly in series as far as heaters. pin 7 IS direct to pin 7 of V2....however , v1 pin2 goes to a network of parts on a turret strip. = a 78k res / a .33uf/630v cap / and the neg side of 2 47u/450v electrolytics . Guessing those are added when using a Iso trans? Ive never installed one so I dont know .

So , at V1 between pin 2 and 7 i have .02vac

[g1]

You have two 6SJ7's in there, swap them around and see if the heater problem follows the tube.

[The Dude]

Except if something shorts the filament pins of the "one" tube.

Exactly! That is why I didn't say "impossible". It would be a rare occurrence.

[Valvehead]

You have two 6SJ7's in there, swap them around and see if the heater problem follows the tube.

yes tried that..i have 3 of those tubes here. Its not a tube. No ac with or without tube in

[Valvehead]

I hate to use the word impossible, so it's EXTREMELY unlikely with series filaments for all tubes to light but one. As Enzo said, check AC voltage between pins 2&7. Not all tubes filaments glow brightly when filament voltage is applied. Are you sure it's not lit? Maybe turn off the lights and have a closer look. Also, if you plan to actually use or sell this amp, install an isolation transformer so it is safe.

It has the Iso. Cant see in the tube--these are the old metal style. V1 is cold , rest are hot to the touch

[Helmholtz]

Exactly! That is why I didn't say "impossible". It would be a rare occurrence.

YEs, but I wouldn't exclude an accidental wiring short as someone seems to have messed with the amp.

[The Dude]

All of the tube filaments are in series (think a string of Christmas tree lights). If one filament goes open, none of the tubes would light. Since swapping tubes didn't work and only one tube lacks filament voltage, there must be an external short from pin 2 to pin 7 of the tube socket. Aside from the wires for filament power, what else is connected to socket pins 2&7? Is it possible someone rewired that socket for a different tube? Maybe a picture would help.

[Valvehead]

pics

[Valvehead]

V1 is not wired directly in series as far as heaters. pin 7 IS direct to pin 7 of V2....however , v1 pin2 goes to a network of parts on a turret strip. = a 78k res / a .33uf/630v cap / and the neg side of 2 47u/450v electrolytics.

in this picture the pointer is showing this ..where the big orange cap connects , pin 2 is the black wire

under the orange .33 , there is also an orange wire connected at that spot that runs to V4 , pin 6

[Helmholtz]

Best make a drawing of the heater wiring.

Did the amp ever work after the mod?

[Valvehead]

Best make a drawing of the heater wiring.

Did the amp ever work after the mod?

I dont know..its a mystery amp , the owner passed away and i dont know who worked on it