Blues Jr gut and rebuild

[M Fowler]

Guy was complaining about having to fix his Blues Jr all the time only have OT fail/EL84's blow. I offered to gut the chassis and rebuild. He tried out some of my 18w amps, TW Rocket, Marshall, and Matchless Spitfire. He liked the Spitfire the best with his pedal board setup.

Since the Blues Jr has more knobs then a Spitfire, I reused a loaded Matchless Lightning board I had laying around, drilled/fitted new tube sockets and CTS pots. Isolated Switchcraft input jack, 120v pilot light and bright switch. Reverb knob is now a cut control.

Ordered Bill M./Allen Amps Heyboer PT-24 so need to build rectifier board yet. This PT has more voltage but fits exact hole 2.5 x 2 inch. Used a Mercury OT 18w Marshall 8k to 4/8/16R that colossal gave me. No choke using 1k/5w resistor instead. Bias resistor is 150R instead of 120R due to increased HT voltage. Waiting on the PT.

Not necessary but I did it anyway: removed the speaker baffle board and rotated it so speaker offset to right side. Rotated speaker so wires can reach speaker jacks better. Drilled 3rd speaker jack hole and installed 3 Switchcraft jacks might isolate those jacks.

[M Fowler]

Some more photos.

Need to drill for fuse holder yet and build rectifier board.

Screen resistors are 1k/5w instead of 100R.

PPIMV

Patrick at Mercury Magnetics came through for me providing the wiring diagram for the MM OT Colossal gave me, thanks Dave and thanks to Patrick (MM).

[Blindog]

Great work Mark! I'll be keeping an eye out for a busted Blues Junior to experiment on

Mark

[Colossal]

Very nice Mark, that amp is gonna sound really good. Sorry about the OT. It is the Marshall 2061 20W 2xEL84 OT. I think it is 7k6 or 7k8 primary (unless Patrick told you otherwise).

[M Fowler]

Trying to get PT supplier to tell me if they shipped the PT yet no replay so far.

This is such an easy project, nice to work with and very little prep work to convert.

Dave, thank you for the OT it should sound great buddy.

[dorrisant]

Love this concept! Use what you can in a junk amp. Build what you want, much better. I have a Mayer Sig going together... when get done winding.

Mark, That has to be the prettiest Jr gutshot porn I've ever seen.

Dave, what do I have to do to earn an MM OT? Lol!

TD

[M Fowler]

Tony you mean better looking porn then this one

[sixstringer]

Looking good Mark, great idea. Now.... How about a Lighting Reverb in a BJr chassis so you can use up more of those holes control panel.

[dorrisant]

Tony you mean better looking porn then this one

I think I threw up just a little bit.

TD

[M Fowler]

Looking good Mark, great idea. Now.... How about a Lighting Reverb in a BJr chassis so you can use up more of those holes control panel.

The owner didn't want reverb so I said okay a cut control then. But yeah a lightning reverb or Rocket Reverb 18w, or even 6V6 Fender controls with reverb would be better then the stock amp.

[M Fowler]

The amp just went out the door with owner and onto some nice church gigs.

Fender Blues Jr converted to Matchless Lightning

B+1 376vdc
B+2 362vdc
B+3 328vdc
B+4 340vdc
B+5 276vdc
EL84’s Plates 369vdc Screens 355vdc pin 3: 12.86
12AX7 PI 1&6: 250vdc 2&7: 48vdc 3: 71vdc
12AX7 1&7: 163vdc 3: 1.3vdc 6: 276vdc 8: 163vdc
12AX7 1&6: 140vdc 3&8: 1.3vdc

[xtian]

I'll bet your client was thrilled! Were you happy with the end result?

[M Fowler]

I'll bet your client was thrilled! Were you happy with the end result?

Yes it sounded good but I would have gone with 6V6 or 6L6's but owner didn't want to.

[Milkmansound]

Tidy!

One BsJr down - millions more to go.

[M Fowler]

http://el34world.com/Forum/index.php?topic=17845.0

Doug has been working on new boards to retro fit the blues jr. He has a nice layout as well.