BillM Blues Junior Mods

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BillM Blues Junior Mods

Postby WilliamC » Tue Mar 30, 2010 4:50 pm

A few weeks ago I mentioned in another thread that I was going to do the BillM Blues Junior mods. There was some interest so...

I managed it without causing any serious damage to self or amp and here’s how it went:

Unplug Amp. OK, no problem.

Remove back cover, knobs, jacks. The back cover is held on by 6 screws, it’s also a major part of the ground and shielding for the Blues Junior, so although you can operate the amp with the cover off, it’s not real happy about it. Knobs pull straight off with no problem. When removing the nuts that hold on the fat footswitch and speaker jacks, the speaker magnet will grab them right out of your wrench or nut driver. I also removed the power switch, giving me a little more room to remove the circuit board.

Remove transformer connections. This is a little tricky, particularly the connectors to the speaker jack daughter card since there are some thin wires going to the fat switch jack. You just have to wiggle them gently back and forth and eventually they come off. The connectors are color coded on the cream board amps, but I took notes anyway.

Remove circuit board. More screws; no problem. It’s a little tricky getting the top of the board out past the edge of the chassis; gentle but firm is the way to go (as in so many things 8) ).

Output Transformer. The output transformer is mounted to the back of the chassis, so that comes out (4 screws), then the two holding the transformer down. You have to wiggle the connectors around a bit to get the leads out through the grommets and do the same getting the new leads back through. BillM’s T020 transformer comes with two washers that lift the transformer a bit so the leads can pass under it to the holes in the chassis. You’ll be amazed at how wimpy the original transformer looks beside the T020.

Power Supply Stiffening. This involves a second capacitor in parallel with the existing one. Being lazy and frankly afraid to drill through the circuit board, I took the easy way out and carefully soldered the new cap to the original’s leads. A dab of silicone adhesive under the new one and between the two caps eliminates problems from vibration.

At this point I hooked everything up and tried it out, just to make sure everything was still working. With no shielding, there was quite a bit of hum but it sounded OK, so power off, unplug, wait a minute for it to discharge, discharge to ground just to be safe and…

Tone Mods. Three items here: short the center and left terminals of the mids pot together with a little piece of wire and replace the mid and bass filter capacitors. Just cut the old caps out and use a solder sucker to get the little bit of bent over lead out of each hole. This isn’t hard, but the traces on the BJr circuit board are incredibly thin and it would be very easy to burn through them. The new caps just drop into the existing holes; bend the leads to hold them in place, solder, trim them off, and you’re done.

Adjustable Bias. I didn’t do this because as noted I was a little nervous about drilling through the circuit board. I’m planning to replace the output tubes with JJ EL84s in the future, and I’ll do it at that point.

Re-tension tube sockets. This was actually a little trickier than it looks. The sockets are sort of awkward to get to and in my case some of the connector springs were pressed solidly to the sides, making it hard to get a little screwdriver in. The springs that hold the tube retainer on also seemed a little stretched, so I replaced them. If you have a BJr that occasionally makes a weird noise or has a farty sound in the bass until it's warmed up, your power tube sockets need to be tightened up.

Buttoned everything back up, and, just like everyone says, the difference in sound was like night and day. The flabby low end is completely gone as is amp hum at reasonable bedroom volumes. I can totally scoop the mids and clarity is better across the board. Everything is “as advertised”. Rather than subject you to my playing, BillM has just posted a video review of the mods by Anthony Stauffer which covers everything: http://billmaudio.com/wp/ Anthony doesn't really get into the completely clean tones but he's a Strat guy, so you can get some idea of what the BJr might sound like for Alligator era Jerry sounds. I think you can get a really decent Gibson era Bobby sound. I'm using an Ibanez AF-105 and it sounds darn good to me. If you do early rock, classic country or rock-a-billy type stuff a modded BJr is probably the most bang for your buck in a small amp - but honestly, it's probably not the best choice for general purpose Dead.

It’s been many years since I fooled around with electronic stuff and it was pretty enjoyable to do the mods. If I was gigging this amp, I’d put a more efficient speaker in (see the BillM website for his comments) and since I have the T020, adding external speaker is not out of the question either.

Now that I've got the tools - I'm thinking that an MXR Dist. + clone is up next :smile:
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Re: BillM Blues Junior Mods

Postby mkaufman » Tue Mar 30, 2010 6:20 pm

Bill's a great guy. He used to write for PC Magazine. I considered doing his mods to my BJ, however, instead, I sold the amp. I'm glad it worked out for you.

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Re: BillM Blues Junior Mods

Postby waldo041 » Wed Mar 31, 2010 6:08 am

very nice detail WilliamC! i did most of those mods on the BJr years ago, and i can say firsthand the biggest improvement is the speaker. you really lift the blanket off it by swapping that out. your mods will really be noticeable once you do that.

WilliamC wrote:Now that I've got the tools - I'm thinking that an MXR Dist. + clone is up next :smile:


AND THE BUG!! :smile:

check out these sites for more good projects and components.

http://www.generalguitargadgets.com/

http://www.tonepad.com/

http://www.smallbearelec.com/home.html

http://www.effectsconnection.com/oscommerce/


and this has a great forum for helping get some questions you may have one any of the builds. also a store!

http://www.diystompboxes.com/wpress/

peace,
waldo
"Tone is in the instruments. Technique in the hands. Do what you will." ~ quote from some guy at the TGP forum
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Re: BillM Blues Junior Mods

Postby strumminsix » Wed Mar 31, 2010 6:26 am

Did you first discharge the caps (only asking in case someone else follows your lead)
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Re: BillM Blues Junior Mods

Postby WilliamC » Wed Mar 31, 2010 6:37 am

strumminsix - yes I did. BillM mentions that it's perfectly fine to let the amp self-discharge. I did that and grounded the caps too. I see now that I didn't mention it in the first section but did later. So SAFETY FIRST kids!

Thanks Waldo! There is a real "wall of worry" for guys like me with no real experience to overcome - hopefully by going into detail some of the fence sitters will be encouraged to dive in too.

And thanks too for the links - I'd found DIYstompboxes but the others are new to me. It's hard to believe how much material is available these days!

Cheers,

-bill
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Re: BillM Blues Junior Mods

Postby strumminsix » Wed Mar 31, 2010 6:41 am

WilliamC wrote:strumminsix - yes I did. BillM mentions that it's perfectly fine to let the amp self-discharge. I did that and grounded the caps too. I see now that I didn't mention it in the first section but did later. So SAFETY FIRST kids!


Excellent and glad it worked out wonderful for you!

I've let a small amp sit and did find it discharge very much on it's own but I'm paranoid so did the caps to ground trick too.
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Re: BillM Blues Junior Mods

Postby waldo041 » Wed Mar 31, 2010 6:57 am

ALWAYS UNPLUG THE AMP FIRST!

and here are a couple ways to drain off the LETHAL VOLTAGES of the filter capacitors. granted these are not PCB amplifiers, but the same principles can be used if you know where the capacitors are and their polarity's. positive to ground!

SRV's Amp Tech Cesar Diaz BIG INSULATED screwdriver style;

http://www.youtube.com/watch?v=hedZTu7S4HE

And The Resistor Method;

http://www.youtube.com/watch?v=Rg3-dZC5 ... re=related


and finally what not to do until you drain off the filter capacitors by the great amp tech Gerald Weber!

http://www.youtube.com/watch?v=1lozkT1zrIU

peace,
waldo
Last edited by waldo041 on Wed Mar 31, 2010 7:12 am, edited 2 times in total.
"Tone is in the instruments. Technique in the hands. Do what you will." ~ quote from some guy at the TGP forum
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Re: BillM Blues Junior Mods

Postby strumminsix » Wed Mar 31, 2010 7:01 am

Hey Waldo, I still use the one you gave me a few years ago!
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Re: BillM Blues Junior Mods

Postby waldo041 » Wed Mar 31, 2010 7:20 am

strumminsix wrote:Hey Waldo, I still use the one you gave me a few years ago!


cool ss, and always glad to help!

i cannot stress how critically important it is to do one of these procedures! if you make it past your first jolt not doing one of these, you will always remember after, and that is not the way to learn why you should do this!

peace,
waldo
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Re: BillM Blues Junior Mods

Postby NeebruM » Wed Mar 31, 2010 7:41 am

waldo041 wrote:very nice detail WilliamC! i did most of those mods on the BJr years ago, and i can say firsthand the biggest improvement is the speaker. you really lift the blanket off it by swapping that out. your mods will really be noticeable once you do that.

WilliamC wrote:Now that I've got the tools - I'm thinking that an MXR Dist. + clone is up next :smile:


AND THE BUG!! :smile:

check out these sites for more good projects and components.

http://www.generalguitargadgets.com/

http://www.tonepad.com/

http://www.smallbearelec.com/home.html

http://www.effectsconnection.com/oscommerce/


and this has a great forum for helping get some questions you may have one any of the builds. also a store!

http://www.diystompboxes.com/wpress/

peace,
waldo

THANK YOU for these links! A spied a couple of tremelo boxes, one of which I need, and would be fun to build. Now I have to decide which one... My "bug" has been woken up for spring!
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Re: BillM Blues Junior Mods

Postby Stevo123 » Tue Jul 27, 2010 11:27 am

Just had several mods done to my Blues Jr (green board): Basic kit, Presence control, High voltage preamp mod, clean boost module, TO20 output transformer, and re-cap kit. Just got it back today and I have to say it sounds pretty great! It's almost like a whole different amp. Here's my initial impressions:

-There's a TON of bass available, especially when it's cranked. I used to regularly dime out the bass, but now at high volumes I only really need to keep the bass at around 1-1.5! Any more is just way too much bass. At lower volumes, though, the bass can be cranked up a lot more. The EQ has to be modified a lot as the amp is cranked more and more.
-Bass and mids, when dialed back to appropriate levels, are much tighter and crisp. The bass and low mids used to be pretty "muddy".
-I usually dial in so that the strongest strums get a little breakup, but it was hard find a good range for that previously and to my ears, the broken up tones sounded pretty bad. Now there seems to be a wider range of overdriven tones, and they are much more useable now. Seems like there's a good bit more dynamic range as well, which allows for more variance in breakup by how hard I play. The harder strums, when dialed in right, can give a nice increase in intensity without getting overly distorted.
-There's a little more clean headroom, but not as much as I expected. The clean boost module is cool, but I wouldn't say it keeps the sound 100% clean, as it does cause a very noticeable amount of breakup.
-So far I haven't been able to find a really good jerry sound out of the amp (which was easier to do before). It seems a bit too "punchy" to get that kind of sound. There's some good bob sounds, though, which is more what I play anyway.
-Higher register notes have a much thicker sound now, which was one of the big things I was hoping to get.
-The presence control is very nice to have, especially since the mids have to get backed off a little bit to keep the amount of distortion lower. It allows the higher mids to be boosted so the mids control can be backed off at higher volumes to keep the lower mids at bay in order to keep it cleaner.

Just got it today and haven't had a chance to play it with my band yet but I'll post more about how it performs in that context later this week.
Last edited by Stevo123 on Tue Jul 27, 2010 11:44 am, edited 1 time in total.
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Re: BillM Blues Junior Mods

Postby Stevo123 » Tue Jul 27, 2010 11:40 am

I take that back that it can't get a decent jerry sound. After cranking up the preamp gain a little bit to gloss things over a bit and cranking the treble and reverb it does a fairly solid job, especially considering my guitar isn't really optimal for that sound.
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Re: BillM Blues Junior Mods

Postby RiverRat » Wed Jul 28, 2010 8:13 pm

.
Last edited by RiverRat on Tue Feb 22, 2011 3:54 pm, edited 1 time in total.
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Re: BillM Blues Junior Mods

Postby strumminsix » Thu Jul 29, 2010 6:36 am

Interesting thread... I'll have my Fargen Blues Jr in a few days... Must compare notes :P
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Re: BillM Blues Junior Mods

Postby Stevo123 » Thu Jul 29, 2010 10:01 am

After messing around with it for the past couple days, my amazement continues. It just has such a wide range of great sounds. I had the lead guitarist of my band play some sick lead stuff on it yesterday and it was screaming! My only beef is that I don't think the stock speaker handles all the potential bass very well and it breaks up a bit too early for my taste. Thinking of putting an eminence c-rex in there and seeing how much better that performs.
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