Blues Jr Mods

erniestrings

Member
Messages
79
i'm planning some mods for a Blues Jr I picked up cheap a few weeks ago. I needed a smaller amp than my Z/Port City to take around for smaller gigs, and I'd played a few Blues Jr's before, so I figured I'd give it a shot. I wasn't blown away by the tone right out of the gate, so I threw some tubes in it and swapped the stock speaker for a British Greenback... Huge improvement already!

After doing some research on the BillM Mods and a handful of others, I have a decent idea of what I want to do initially, and maybe a few I'd like to look at as eventual mods. I'm going to start out with swapping caps for the tone stack, filter, & coupling stages, doing the twinstack mod, changing the taper of some of the pots, cathode follower mod, and possibly doing the standby switch, sparkle mod, and presence mod. In some cases those cap/pot values will change to be more in line with a traditional blackface circuit.

Down the road, I may take on swapping the transformers, tube sockets, replacing pcb with turret board, etc., and possibly build a pine cab for it (I like woodworking). There seem to be a couple of mods that interest me, but I can't seem to find much info on though.

The first would be adding a tube driven reverb circuit. I realize I would have to add a couple of tube sockets for the driver and receiver, and a larger traditional tank. What I don't fully understand is how I would need to tap into the reverb circuit from the main pcb, whether there would be any voltage/impedance/resistance issues, or any other consideration I need to know about. The second would be adding a tube rectifier in place of the solid state transistor currently used. Again, many of the same questions/concerns.

I do realize that for the time and money invested, I could just go buy another amp that I liked more. I enjoy the process of getting to know the amp internals though, and I think the end result could be a pretty great sounding amp. If not, I can always gut it and build a classic circuit like the 5e3... :)

Any links or helpful descriptions on how to handle the tube reverb/rectifier would be greatly appreciated!
 

caspa

Member
Messages
1,182
i'm planning some mods for a Blues Jr I picked up cheap a few weeks ago. I needed a smaller amp than my Z/Port City to take around for smaller gigs, and I'd played a few Blues Jr's before, so I figured I'd give it a shot. I wasn't blown away by the tone right out of the gate, so I threw some tubes in it and swapped the stock speaker for a British Greenback... Huge improvement already!

After doing some research on the BillM Mods and a handful of others, I have a decent idea of what I want to do initially, and maybe a few I'd like to look at as eventual mods. I'm going to start out with swapping caps for the tone stack, filter, & coupling stages, doing the twinstack mod, changing the taper of some of the pots, cathode follower mod, and possibly doing the standby switch, sparkle mod, and presence mod. In some cases those cap/pot values will change to be more in line with a traditional blackface circuit.

Down the road, I may take on swapping the transformers, tube sockets, replacing pcb with turret board, etc., and possibly build a pine cab for it (I like woodworking). There seem to be a couple of mods that interest me, but I can't seem to find much info on though.

The first would be adding a tube driven reverb circuit. I realize I would have to add a couple of tube sockets for the driver and receiver, and a larger traditional tank. What I don't fully understand is how I would need to tap into the reverb circuit from the main pcb, whether there would be any voltage/impedance/resistance issues, or any other consideration I need to know about. The second would be adding a tube rectifier in place of the solid state transistor currently used. Again, many of the same questions/concerns.

I do realize that for the time and money invested, I could just go buy another amp that I liked more. I enjoy the process of getting to know the amp internals though, and I think the end result could be a pretty great sounding amp. If not, I can always gut it and build a classic circuit like the 5e3... :)

Any links or helpful descriptions on how to handle the tube reverb/rectifier would be greatly appreciated!

If you have a 1x12 extension cab, try just plugging it into that first and defeating the internal speaker altogether.

I had a blues junior that I did anything and everything to, but going through a good meaty orange 1x12 with a very, very broken in vintage 30 made it an absolutely incredible amp.

I personally think that funds are better funneled into a new amp... nothing remotely blackface about a blues junior without super extensive mods
 

erniestrings

Member
Messages
79
Thanks for the replies! I am definitely considering building a new cab for it, but that will take a little time. I've ran it through my Port City 212os with Scumbacks (huge sounding cab), and it was a pretty big improvement. It still lacked some of the punch in the lower register that I get from my Maz 38 and Sovtek Mig 50. I think swapping the caps out should take care of most of that hopefully. All told, the Cap job and pot swaps shouldn't cost more than $60-$70, which is worth it if it gets anywhere in the ballpark of what I'm going for.

Outside of those, the tube reverb mod was the one I was most interested in, however, I'm also considering building a separate tube spring reverb unit. That would give me more flexibility, but less portability (and I already have some great reverb pedals). May eventually do that just to use for recording...
 

picnic

Member
Messages
2,294
Emi Wizard went into my old BJ. Decreased the boxyness and increased clean headroom some. I think I also upgraded the reverb and that did make a difference too.
 

kingrazor

Member
Messages
3,946
I plan on getting the Fromel kit for mine. Would have done Bill M's mods but unfortunately he recently passed away and his shop is closed up. The Fromel kit is pretty similar. Beefier caps, power stiffening, twin stack mod and bias pot.

Also considering getting a Skumback speaker for it.
 

erniestrings

Member
Messages
79
I plan on getting the Fromel kit for mine. Would have done Bill M's mods but unfortunately he recently passed away and his shop is closed up. The Fromel kit is pretty similar. Beefier caps, power stiffening, twin stack mod and bias pot.

Also considering getting a Skumback speaker for it.

I looked at the Fromel kits, but I thought I'd save the extra $40-50 you pay for their instructions and just source the parts myself. I have a list of all the caps and values I'll need (F&T's, Orange Drops, etc.), and the install info is readily available if you do a little digging.

I think you'll like the Scumbacks. I have the M75 and Scumnico, and they are two of my favorite speakers I've used with any amp. I have a Greenback in my BJ right now, and it made a big difference, but I may end up with the scumnico in there by the end of it. I'm not 100% sure it will fit though, so that may need to wait for a custom cab...
 

erniestrings

Member
Messages
79
Let me know if your interested in a pine cab the size of a Hot Rod deluxe (Cover & large Reverb tank included), I have one I got for my blues junior but thinking of selling the cab. I'm using a different right now. As far as mods go they really do enhance the amps tone especially adding the coupling caps!!

PM'd
 

Boomstick

Member
Messages
313
I had a blues junior that I did anything and everything to, but going through a good meaty orange 1x12 with a very, very broken in vintage 30 made it an absolutely incredible amp.

I like the vintage 30 too, but if it was me, I would put an Alnico Tone Tubby in it.
 

sadhudude

Member
Messages
410
As a Blues Junior owner and user for three and a half years I would say sell it on before investing any more cash in it and get something that sounds great from the off (or get go as I believe they say in the USA). I have done a lot of the BillM stuff to mine and added a CRex speaker and whilst it sounds pretty good now it's not great and I am not sure it ever will be. The early Peavey Classic 30 that I stupidly sold some years back was a way better compact amp platform at small gig volumes and needed no mods to have a great sounding clean channel. I regret the purchase and the time and money spent trying to improve it.
 

erniestrings

Member
Messages
79
As a Blues Junior owner and user for three and a half years I would say sell it on before investing any more cash in it and get something that sounds great from the off (or get go as I believe they say in the USA). I have done a lot of the BillM stuff to mine and added a CRex speaker and whilst it sounds pretty good now it's not great and I am not sure it ever will be. The early Peavey Classic 30 that I stupidly sold some years back was a way better compact amp platform at small gig volumes and needed no mods to have a great sounding clean channel. I regret the purchase and the time and money spent trying to improve it.

Thanks for the info... just out of curiosity, which mods have you done? What shortcomings do you feel it still has after the mods? Do you think there is a key flaw in the circuit design (i.e. low plate voltage)?

This isn't my primary amp, and I enjoy tinkering with gear, so I'm mostly looking at this as an opportunity to have some fun and have a "decent" small amp to do smaller gigs. I've played those Classic 30's you mentioned, as well as some other boutique low-wattage (small) amps that have sounded huge (Matchless, Allen, /13, Goodsell, etc.), but so was the price tag. That said, plenty of them run on EL84's, and even share some commonalities to the BJ circuit (and differences). I guess I'm just trying to say that I'm tempering my expectations, and for $300, I don't think I could find a better amp. If $50 in parts will make it sound any better than it already does, it's worth it. Is it worth throwing $300 at? Probably not... I could just buy a silver face bandmaster at that point.
 

sadhudude

Member
Messages
410
Thanks for the info... just out of curiosity, which mods have you done? What shortcomings do you feel it still has after the mods? Do you think there is a key flaw in the circuit design (i.e. low plate voltage)?.

Power supply stiffening, tone caps, coupling caps, presence control, set bias properly for the UK, added a CRex (excellent speaker). All of which have made a difference but I think the folks who talk about the cabinet are right but a new cabinet built of decent material and finished well is going to cost an amount that I don't feel is proportionate to the quality of the amp (2/3 the cost of a used BJr?) You also end up with something that is never going to give you your money back if you sell, it's still a BJr. Better not to invest and put the money towards something that sounds right for you from the off IMHO. That's my experience with it anyway. I don't know much about the circuit design, I am not that techy, I do now think that the simpler circuits I have tried (Princeton, Harvard) sound better to my ears. It's been and education though, I would spend a lot more time choosing my next amp with my own ears in diffferent situations.
 
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gtrplr71

Member
Messages
3,685
I almost bought a BJ III yesterday got to the store played it for the 2nd time in a week and now it rattles, I dont know if thats an easy fix or not but they do sound good.
 

erniestrings

Member
Messages
79
I almost bought a BJ III yesterday got to the store played it for the 2nd time in a week and now it rattles, I dont know if thats an easy fix or not but they do sound good.

As lowpaygigs said, the tubes often become loose. The rubber grommets they added on the III are supposed to help with that, but I don't see the design being any more effective. I also had a loose back cover that simply needed to be tightened a bit that caused some rattle...
 

gtrplr71

Member
Messages
3,685
As lowpaygigs said, the tubes often become loose. The rubber grommets they added on the III are supposed to help with that, but I don't see the design being any more effective. I also had a loose back cover that simply needed to be tightened a bit that caused some rattle...
I think I will go talk with the guy. I can get it for $425 brand new if I do that I plan on using a 1X12 cab. I just dont want to buy someones problem if you know what I mean.
 




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