there has to be a way to make the Blues Jr reverb better!!

[phsyconoodler]

I have a cream board blues jr and the reverb is too metallicy sounding.There must be a way to get it darker and richer sounding.I don't understand opamps so I don't really know which caps come into play here.The tone is so bright with reverb it's almost unuseable.
  Any insight into how to darken it up would be welcome!

[jjasilli]

Have you checked the bill machrone mods?

[Geezer]

Keith, not sure if this is the right schem (I'm sure you have the correct one, being a Fender repair rep) > http://support.fender.com/schematics/guitar_amplifiers/Blues_Junior_schematic.pdf

The "bright cap" on the reverb pot seems excessive to me (C23/3300pf)....lower that value, trying different values using alligator clips to see what sounds better to your ears. I'd start with .001, or even lower (470Pf or so)
You might also try raising the value of C22 from the stock .015 to .022/.033/.047 to see if it fattens up the verb any.

G

[PRR]

It looks like a bright reverb circuit.

Who made the tank? Beautiful women in the US, or Korea? Some say the new Korean production does not sound the same as the old stuff.

C26 0.0033uFd is 4KHz at lowest. It could be smaller, sure. I'd cut it out and see where it stands.

R47 470K, try 22K. Similar effect to heavy load on naked guitar, takes the scream/ring away. 22K may be much too mellow, work your way back 50K 100K 200K.

C22 affects the peak frequency of the recovery ring. 2000pFd seems reasonable, but try 200pFd and 10,000pFd (0.01u).

C24 10pFd is extreme (50KHz). Try 100pFd (5KHz).

There are three bass-cuts.

C20 330pFd against its resistors cuts below 500Hz. This is very traditional Fender. Too much bass in-to the tank makes heavy boing/bang racket. You could try 500p or 1,000p, but it may be ugly.

C23 0.47uFd against R49 cuts below 180Hz.

C12 0.015u against pot cuts below 220Hz.

Both are resonable defenses against excess mudd coming out of the tank, but you could increase one or both for more ballz.

[phsyconoodler]

The amp I have here does not match the schematic shown on this thread and it is not the Blues Jr.III either.
 There is a schematic somewhere that has this reverb circuit which is different from either of those two,but I can't seem to find it yet.
  Hmmm...
I did make a change to C9 which is present on my amp and the green board amps but just has a jumper wire on the III's. I upped the value to .0068uf and it significantly reduced the reverb brightness.However,it made the rest of the amp dark.So I came up with a compromise of 1500pf which made the amp about perfect with single coils(all the customer uses) but the reverb was too bright again.Changing this cap has a significant effect on the whole amp's circuit.I ended up swappimg the accutronics tank with one from a traynor and it is almost perfect.
  I wish I could just do it with the existing tank but I have to find the crcuit first!!
Thanks for all the help guys,it is always appreciated!!!

[jjasilli]

Bill Machrone seems to say that toying with component values in the BJr reverb circuit is a losing proposition & does screw with the tonality of the whole amp.  The real culprit is where the wet signal is re-injected into the signal path -- which is supposedly cured by the cream vs. earlier green PCB.  Anyway his site is worth reading though organization is an issue.

Some BJr's use the 7027 opamp just like their bigger brothers like the Deluxe's & Devilles in your other thread.  So, once again, clipping a bypass cap might help. 

Interesting about the tank.  Traynors often use cap driven reverb, off a 12ax7 tube, & I have found that their reverb tanks are matching impedance to SS driven tanks.  Such tanks are often small and uninspiring, but they do function at least well enough for the average pedal effects reverb.

[phsyconoodler]

I've got the amp back where it should be.The C9 cap is back to stock.It was .022uf stock.
  This tone stack matches the III schematic but the reverb is neither.Very odd indeed.
I left the Traynor tank in there as it sounds good.MUCH better than the stock tank.It was so bright and splashy that it was totally useless.
 I changed the mid and bass caps to .015uf and .1uf respectively.The stock speaker is not great but not a total loss.I backed off the bias to 9watts.It's perfect there.
  I'm at a loss as to why this reverb is different but it's working now so I'm done with this amp for now.

[Fresh_Start]

IME every time you touch the insides of a Blues Jr. to fix one thing, you risk having something else get messed up.  Cold solder joints, those damned ribbon cables and generally cheap construction make it a hard amp to work on successfully (despite all of the Bill Machrone admirers).

If a new reverb tank makes it sound better, I say "hallelujah!"

Adding adjustable bias so you can cool it down and have power tubes last longer is the one mod I consider absolutely essential.  Sounds much better too.

Respectfully,
Chip

[phsyconoodler]

I find them rather easy to work on but when you run into anomalies like this one it makes it tougher.
The reverb really sucked on this one with the stock tank.

I find Devilles to be more problematic with cold solder joints and ribbon cable issues.