Blues Junior thoughts

[Mark]

I've spent Sunday modifying a Blues Junior. The first thing that amazed me was how small the transformer set is. The power transformer is smaller than the power transformer for a 5F1 Champ, the output transformer is also very small. I have found in the past that smaller output transformers have less bass response than the larger transformers which is why I was concerned.

The PCB quality is questionable too, if I buy a PCB from Mad Bean it's got eyelets on both sides of the board and is robust, the Blues Junior PCB is primitive by comparison. The ribbon cables I'm told are a nightmare,fingers crossed on that one.

Any thoughts on these amps?

[martin manning]

You've seen the Bill M mods pages for those amps? ( http://billmaudio.com/wp/ ) PT and OT upgrades, elimination of the ribbon cables, adjustable bias supply, and other tweaks.

All of what you say is true, and people have had some fun and success mod'ing them into decent little amps for a little money and a bit of effort. They are built to a price point, with all of the expected compromises.

[xtian]

Thoughts? One of my least favorite, most popular amps on the market.

[sluckey]

Hoffman has done some interesting things to a Blues Junior. There have been quite a few of the Hoffman based conversions done since Hoffman made the boards available. He dropped the lame reverb circuit. The end product is a decent sounding amp that is very roadworthy.

http://el34world.com/Hoffman/Blues_Junior_Build.htm

[pompeiisneaks]

Not much that fender has done in the last 30 years has been 'stellar' the Blues Deluxe (an amp I've owned since the 90's) still has basically teh same problems and weaknesses you mention of crap circuit board, jumper wires that start dying if you move them much at all. Poorly designed circuits and built down to a price. Even their 'reissues' are nothing like the actual amp they're supposedly emulating. They just happen to be so inexpensive a lot of young players buy them as a starter tube amp. Also a decent amount of playing musicians just ask for a HRD or the like as a backline amp when they travel without their gear since they can make it sound pretty neutral and still get the tube tone without busting the bank on a one off show here or there. Thus they still sell like gangbusters. But then again, this isn't much different from Vox either. I love the sound of a classic Vox, but the new ones are built pretty shoddily. One of the repair gurus from some facebook groups showed the guts of one of the top of the line "hand wired" series and they're atrocious. They use those turrets with the slotted top that you would usually use to bend leads around, and they just drop the components in and solder them as if the solder was the glue and the 'path' for the circuit. They use super inexpensive components just like the non hand wired ones so they basically doubled the price for an extra couple hours of labor on an identically designed amp that 'looks fancy'.

This just screams as to why custom built amps can and should be considered superior products pretty much always.

My 2c. Just too bad the musician community as a whole doesn't learn about this often enough. Additionally probably only 1 to 2% of true musicians can afford a hand built amp

~Phil

[Mark]

Thanks for your replies.

The reverb circuit also makes me wonder. I look at the 2200pF cap (C19 on the series 3 REV D cct) across the output of the reverb tank, I wonder why the reverb recovery circuit requires this cap?
One would think that the reverb would sound better without this cap. Any thoughts on the reverb circuit?

http://www.thetubestore.com/lib/thetube ... -Rev-D.pdf

The Hoffman valve socket board is gold, it allows the unused triode to be used. The cathode follower before the tone controls comes to mind.

[pompeiisneaks]

If I recall there's an identical 1500pF cap on the blues deluxe recovery of the reverb driver and a common mod is to cut that out since it does actually reduce the reverb a bit in a crappy way. No real good reason for it as I recall.

~Phil

[Mark]

Thanks for your reply Phil, it just doesn't make sense having it there unless there was a stability problem.

[jjman]

1970+ SF models have this cap. At least the DR and TR. I suspect it might curtail some of the highest highs coming off the reverb. Some people install tone controls in reverb circuits.

There are many things to dislike about the subject amp but that cap is very low on the list for me, if at all.

[Mark]

I understand what you are saying about the cap. What do you dislike about the Blues Junior?

I never understood why Fender didn't make remarkably different versions of the amp.

[Mark]

The Bill M mods worked in the amp, though the transformer set does limit what the amp can do. Personally I think you'd have to get the amp very cheaply to justify replacing the transformer set.

[M Fowler]

I sold my blonde BJ years ago.

The only good one is a dead one on my work bench from guys so mad at their amp that they request I strip the amp and build a good tube amp.

Can use the stock transformers or order Allen PT & OT to run 6V6 or EL84 though the plate voltage is too high in my opinion for EL84's.

Mark

[Mark]

The transformers are smaller than those in a Champ. One can only wonder what Fender were thinking. The transformers in Hot Rod Devilles are a good size and work well, too bad they skimped on the transformers in the Blues Junior.

I think all Blues Junior are either destined for the dump or to be rebuilt. The board holding the valves is the first board to go south. The beauty in replacing this board is you get another triode to use as a cathode follower or for more gain.

[jaysg]

I did some BillM mods to one. The tone stack mod is trivial but maybe the best thing to do. I replaced the plate resistors with RN65s. Speaker could undoubtedly be better...no idea what though.

[Mark]

I had the non modded BJ next to the modded BJ and the mods do make very noticeable difference. It's hard to say if it is the increased coupling caps (0.022uF as opposed to 0.0022uF) or the tone stack, but they are very different sounding amps.

I'm surprised there aren't mods such as increasing the screen grid resistors from 100 ohms to 220 ohms, as the screens would be running hot.

I've heard the Warehouse speakers ET-65's sound good in these amps.

There is a clone of the B.J. getting around, I believe it is a Belcat amp.