Fender Blues Junior power trans question

[J Luth]

I have a dead Blues Junior here that belongs to a good friend, it’s the same one I asked about the jfet in a previous thread.

After pulling the main and tube boards out, they are junk due to someone that worked on it that should have their soldering iron taken away.

Question is, can the power transformer be used in a different circuit similar to a single channel Fender AB763 like a Deluxe Reverb or other using SS rectifier, no tube rectifier, and eliminating the tremolo circuit. I would be adding 1 - 12AT7 tube, a reverb transformer and change from EL84 to 6V6GC power tubes.

The Blues Junior power trans is rated for 100 mA.

I would probably need to add additional small filament transformer and find a shorter reverb pan.

[Tom Phillips]

I would not recommend using 6L6GC power tubes in the new build with the blues Jr PT.
I think you would be OK using 6V6s but the overall power will be less, because of the lower B+ voltage and lower current available. That's not a bad thing or a show stopper. You could also just stick with EL-84 power tube. Especially since you already would have them from the donor amp.

I assume that you are planning to build a hand wired circuit into the salvaged chassis and cab from the Blues Jr. That saves a lot of cost and effort.

I don't think you would need to add an additional heater transformer if you change your plans as I've suggested.

[J Luth]

I would not recommend using 6L6GC power tubes in the new build with the blues Jr PT.
I think you would be OK using 6V6s but the overall power will be less, because of the lower B+ voltage and lower current available. That's not a bad thing or a show stopper. You could also just stick with EL-84 power tube. Especially since you already would have them from the donor amp.

I assume that you are planning to build a hand wired circuit into the salvaged chassis and cab from the Blues Jr. That saves a lot of cost and effort.

I don't think you would need to add an additional heater transformer if you change your plans as I've suggested.

Thanks Tom, I don't proof read it before I posted, you would think I would do that by now but NOOOOO..
I did mean to type 6V6GC tubes. That's why I mentioned Deluxe Reverb I'll change it.

The ELl84's a no good either and possibly the output trans. I have a bunch of 6V6 tubes and a couple of output transformers good for 6V6. I did it again and typed 6L6 but caught it this time.

Yes I would be using as much of the Blues Junior as possible. Already have most of the replacement circuit and the board layout done. It may be a bit tight but should fit. Only thing that wont fit is the new reverb pan I have here for a larger AB763 amp. It's a bit to long. I doubt the one that is in ti will work.

[mozz]

Hoffman (el34world.com) has a blues jr turret board, don't know about reverb though.

[J Luth]

Looking at power transformers for this amp, replacement ones run between 2.6 to 3 amp filament taps. I can't find a good listing for the filament tap on the stock fender transformer. One thread I found on a different site said it was 2 amps but I don't trust the info. If the Fender trans is 2 amp that would not be enough it needs to supply, if I did the math correctly, 2.4 amps to use EL84's and added 12AT7. If it is only 2 amps it should work with 6V6's and the added 12AT7. I did just locate a few EL84's from a local guy for short money.

[Justin Thomas]

J Luth if you're wondering about the heater current on the stock BJ PT, it's probably 2.4-2.5A. 0.75A for each EL84 & .3A for each 12AX7. If you use 6V6s you should have more than enough to add a 12AT, maybe two. I wouldn't count on that transformer to provide MUCH more than the bare minimum needed to power the stock tubes.

As to the confusion above over 6L6GC, 6V6s came in GT & GTA, not GC.

I think you've got a potential cracking good amp there...

Jusrin

[J Luth]

J Luth if you're wondering about the heater current on the stock BJ PT, it's probably 2.4-2.5A. 0.75A for each EL84 & .3A for each 12AX7. If you use 6V6s you should have more than enough to add a 12AT, maybe two. I wouldn't count on that transformer to provide MUCH more than the bare minimum needed to power the stock tubes.

As to the confusion above over 6L6GC, 6V6s came in GT & GTA, not GC.

I think you've got a potential cracking good amp there...

Jusrin

Thanks.
Yet another typo

He is going with the build. Luckily for him that he is a good friend and a band mate.

Will try using 2 - 6V6 power tubes and add 1 - 12AT7 for the reverb and see how it sounds.
If he doesn't like it maybe go back to EL84's
I will have a few more questions.

[J Luth]

Going forward with the build with 6V6 power tubes and see how it sounds..
Questions to follow.

[galaxiex]

I did a "make over" on my Blues Junior.

Converted to an eyelet board and all hand wired.
Added one 12AT7 for tube driven reverb and a reverb transformer.
The stock BJ has one half of a 12AX7 unused. I used that for the reverb recovery.
Made the reverb foot-switchable as well.
Preserved the BJ "Fat" switching too.

The circuit is "sorta" AB763 pre-amp, and all Blues Junior power amp.
Used the BJ power and output transformers.

From the Master Volume to the speaker it's all Blues Junior.

Pre-amp and Reverb is a mish-mash of vintage Fender circuits.

Here's a schem.



Here's a gut shot...
Tubes are now chassis mounted.
Was very tight getting all that in there.... but worth it.
Still has the original BJ speaker and this thing sounds amazing.
Can get just about anything you want from "smooth" clean sounds to very saturated distortion.
It won't do Death Metal....

Does NOT sound "boxy" like most BJ's and actually has very good bass response, despite the small cab.

[Tom Phillips]

Nice. And fast work!

[galaxiex]

Nice. And fast work!

Thanks.
Fast? I built this in 2018….

[Tom Phillips]

...Fast? I built this in 2018….

I got your project mixed up with L Juth's planned project.

[J Luth]

I did a "make over" on my Blues Junior.

Converted to an eyelet board and all hand wired.
Added one 12AT7 for tube driven reverb and a reverb transformer.
The stock BJ has one half of a 12AX7 unused. I used that for the reverb recovery.
Made the reverb foot-switchable as well.
Preserved the BJ "Fat" switching too.

The circuit is "sorta" AB763 pre-amp, and all Blues Junior power amp.
Used the BJ power and output transformers.

From the Master Volume to the speaker it's all Blues Junior.

Pre-amp and Reverb is a mish-mash of vintage Fender circuits.

Here's a schem.



Here's a gut shot...
Tubes are now chassis mounted.
Was very tight getting all that in there.... but worth it.
Still has the original BJ speaker and this thing sounds amazing.
Can get just about anything you want from "smooth" clean sounds to very saturated distortion.
It won't do Death Metal....

Does NOT sound "boxy" like most BJ's and actually has very good bass response, despite the small cab.

Nice looking. Similar to what I have in mind.

One question for you, Did you use the fender type reverb transformer 125A20B

Tom, the one I am working on will be a while.

[galaxiex]

Nice looking. Similar to what I have in mind.

One question for you, Did you use the fender type reverb transformer 125A20B

Tom, the one I am working on will be a while.

Thanks.

I used a Classic Tone reverb TX.
I "think" it's a Fender equivalent....not sure...




Many more build details on the TDPRI forum.

https://www.tdpri.com/threads/blues-...reverb.861251/

[mozz]

You can't get classic tone parts anymore.