Epi VJ with dyslexia

[super&plexi]

OK, I know I can get reversed and turned upside down when retubing and putting pwr tube in pre socket, and pre tube in pwr socket. Saw smoke, immediately unplugged. Know it worked  when I put it away.


What'd I fry? Heater windings? OT? .....my brain in the 70s? Didn't have meltdown smell, like catastrophic core melt, but couldn't have been good


Of course I'll get in there n find out, just wondering what I can expect. Thanks. And good to be back in So. Cal. .... H.B. right now JoeG!

[shooter]

Of course I'll get in there n find out,

I'd start with cathode n plate R's, PS rail voltages, NEW tubes, if it's a fixed bias amp, bias supply

did you blow a fuse?  If not, once it's fixed, maybe lower fuse rating so it blows 1st instead of last

[92Volts]

The most obvious problem I can see is the EL84's screen voltage supply would have been connected to pin 9 of a 12AX7. This is in turn connected to the heaters.

This actually shouldn't damage the heater winding of your power transformer because it should be happy to float at 300v +/-6.3v AC. However it's likely grounded for noise reasons and the resistors or other circuitry used to ground it could have fried.

The screen resistor also could have fried if the heaters are indeed grounded because a lot of current would have flowed.

It likely didn't damage the 12AX7 because a large amount of current compared to what the high-voltage circuit supplies is supposed to handle is still relatively small compared to what the 12AX7 heaters are meant to handle.

The plate voltage is connected to the grid of the 12AX7 which is scary, but the anode and cathode associated with that grid are potentially connected to nothing so that tube might have survived.

I haven't even looked at what could have happened to the EL84 in the 12AX7's socket yet. But it's less likely to cause a "major" problem because all voltages available to the 12AX7 are limited by large-value plate resistors (often 100k ohms). These resistors themselves may have fried though.

[super&plexi]

Wow thx for fast replies. Epi phone valve junior with few changes....like champ, marsh, vox, values but crappy versions of all sound wise.


. Anybody got good sounding versions of these with mods or do you think it's pretty Transformer based-  cardboard sort of sound I'm getting out of it.


I've had the idea to turn it into a Poweramp and get another head for a preamp I think I could get 50 well  know I can get 50 Watts out of it easy. But maybe something like ll c+ power with



Different Pwr tubes...trannys etc ....I got em already. Heck can't (Hopefully) be too hard to shoehorn in a Blues Meister or something.  I got to redo my Blues Meister since I dropped it out of chassis.

[92Volts]

I'm confused, the Valve Jr can put out about 5 watts, not 50. Do you mean to use the Valve Jr as a preamp, and get something bigger to act as a poweramp?

Bad sound from small, cheap amps like this can usually be blamed on the speaker. It's not only cheap but also small, there's a reason 12" speakers are popular when size and budget allows for one. The Valve Jr uses an 8" speaker.

The output transformer isn't large or expensive (and likely has poor bass response) but this isn't a big problem for a guitar amp. Even well-regarded amps like Champs (and other Fenders) used "undersized" OPTs.
Even if you want more bass response, and expect a bigger output transformer would help, the speaker is probably a more important change to make.

[sluckey]

That Epi VJ is worth exactly what you paid for it. Sow's ears and silk purses come to mind.   

[drew]

I'm confused, the Valve Jr can put out about 5 watts, not 50. Do you mean to use the Valve Jr as a preamp, and get something bigger to act as a poweramp?

I think they may have used the same PT in bigger amps in the Epiphone "Valve . . ." line.  I know it has a winding that isn't even used in the Valve Jr. - think it was used to power digital effects in the bigger amps.  Doubt that's it's good for more than a pair of EL84s or 6v6s, though. 

[brewdude]

EVJ was my gateway drug... it lead me to many much better builds.  Frankly, in my opinion, the Epiphone Valve Jr. is a terrible sounding piece of junk.

The fact is I messed with mine for a long time.  I probably gutted it and rebuilt it three times.  I eventually replaced everything except the PT.  I even replaced the chassis with a new aluminum chassis from Watkins amp forums. 

Currently, I have a point to point build with a paralleled 12AX7 input stage, a Bandmaster style TB tone stack (ala Merlin’s book) into a 6SJ7 pentode feeding a 6L6 PA and a big Hammond SE OT.  It uses the VJ PT (the only bit left from the Epiphone) and a large choke CLC pi filter in the PS. 

This amp actually sounds pretty good now, but has little to do with the Valve Jr. that started the quest.