Just found your channel, good stuff man. I've never liked the sound of these Blues Jrs, nor understood why other people like em so much. With your changes it actually sounds good now! At least to my ears
Another great video Brad! It's amazing how much better this amp can be with a bit of work. Vibration and heat are electronics two worst enemies. Folks that are lucky enough to be close to you for their repair or mod needs don't know how lucky they are. 🤗
A grid stopper resistor of sufficient value probably could have tamed that oscillation as well but in case of PCB, it is not as easy to install as it would be in case of classic point to point wired amps. Very nice videos! 👍 I just recently noticed them and subscribed immediately.
@@BradsGuitarGarage No, to PI. If that bypass cap of PI plate resistor did the job, as I understood, probably grid stopper would have done the same thing if the PI was oscillating or had too wide frequency response at higher frequencies.
By the way it cracks me up whenever I see one of these Cannabis Rex speakers. When I was young, we hemp-infused our speaker cones the old fashioned way: by setting fire to a certain dried vegetable matter! 🙂
Nice series! Go 🇦🇺 Just a couple of quick questions if I may: 1) was that “adding bass into the first gain stage” cap still snipped when you did the final play through? I could still hear the bottom end caving in when you had the bass turned up past halfway, even with the volume and master opened up to 6. 2) to get this amp sounding better with overdrive pedals, is my best bet to swap out the Jensen speaker I have in the tweed version or to change the tone stack? At the moment I run it: bass 0, treble 8, mids 6, volume 6, master 2-3. A tech has already upgraded the jack for me and put in better caps and screen grid resistors.
Wow that was brilliant. I learned more about guitar amps in watching this vid ... Brad is the man. And what knowledge ... Brad what is a good guitar amp to buy... I was thinking Fender Blues Junior, but not now...I do like the Tweed sound... Any advice for a 15 watt - 25 watt amp???? Cheers
Nice work there Brad... Do you play any music? ..oh I nearly forgot... Have you ever had the occasion to replace the push on push off boost button and can a conventional toggle switch work in it's place without adding any noise? Thanx in advance Cheers
Clean the speaker terminals prior to soldering with a pencil eraser or (better, more abrasive) ink eraser, or a fiberglas-bristle "scratch brush", prior to soldering. It's important to solder the connection quickly, getting in and out fast, before the heat melts the solder joints of the braided tinsel-lead that goes from the terminals to the voice coil.
@@BradsGuitarGarage , more for future viewers; and although a scotch bright pad will work, every electronics hobbyist, or professional, really should have a fiberglass bristle scratch-brush. Those things are awesome. As for using a pencil eraser, I recently watched an instructional video on training people to solder to military and aviation specs back in the Fifties, and they were cleaning the pads on brand new circuit boards with a pencil eraser prior to soldering. I learned this trick from old ham radio guys but you almost never see anybody on RU-vid videos do it.
I do it routinely on molex and IDC headers. I'm pretty sure I've shown that in a video. Your usual white rubber eraser is kind of useless. What you need is the ones whith that very mildly abrasive blue rubber on one end. They used to make dark grey erasers and they were very slightly abrasive. they were marketed as biro erasers. Not sure if they're still available or not.
@@BradsGuitarGarage Modern white erasers are usually referred to as "plastic" erasers. They're latex free which means that they don't dry up with age like older erasers do but they are soft and have no grit in them whatsoever, and are useless for polishing.You are correct that *usually* if the eraser is gray or blue it will have some silica, sand or pumice, in it. At the electronics repair shop I work for we frequently use powered draftsman's erasers that utilize a quarter inch diameter, 8" long, rubber eraser rod ---- pink for light polishing, gray for removing heavier corrosion or paint/anodizing ---- presumably made from natural latex because they do unfortunately dry up and get brittle with age (and getting properly abrasive replacement rubber rods that aren't dried up has become difficult). I also have several small battery powered artist erasers designed to take 4 mm Erasers and although the white plastic erasers that come with them are useless, I found some very abrasive gray "sand" erasers made by Sun Seed Dolphin that, although slightly smaller diameter than the usual erasers, a wrap of tape or layer of shrink tubing on one end of them will allow them to fit the battery powered eraser. These work quite well for cleaning and polishing circuit board traces; and I also use the battery powered eraser to spin a leftover short stubby nub of fiberglas scratch brush. This works fantastically well, its my go-to cleaning tool prior to most soldering, and it will even remove the green solder resist from circuit-board foils. I also have a refillable, retractable eraser pen with fiberglas embedded in the rectangular eraser rod, the Pentel Click Hyperaser.
@@BradsGuitarGarage , ps, here in the States I buy Scratch brushes and the fiberglass refills from Esslingers which is a watch and jewelry repair supply company. The higher quality scratch brushes they sell are German-made and the cheap ones I think come from India. You can buy them with brass and steel bristles as well but be aware that the cheaper scratch brushes cannot be refilled. They even sell an ultra skinny scratch brush with a 1/16th fiberglass brush which I've never seen anywhere else. If you have any favorite supply houses or online companies for this type of stuff in your corner of the world it would be good to share it with viewers.
Not a criticism, but just wondering why attach the new switch craft jack directly to the board? I’ve seen it done with wires so as to not stress the board. 🤔
Swap the EL84's and see if the problem follows the tube or stays with the socket. If the former, you need a new set of EL84's. If the latter, you need to figure out why the amp is causing such an imbalance.
The measurements on pin 2, 7 and 9 are about the same on both tubes, but this measurement between red to brown and red to blue are different. I'll try swapping the tubes and check. I think it'll be a great idea to swap the 4 bigger caps and change the tube circuit plate to a newer one. Thanks @@BradsGuitarGarage
That's a very open ended question. Keeping it to a well-known brand and without pushing too much into the esoteric market and one-off builders, I'd say Ceriatone.
10:40 I'm not a fan of this idea. You're better off isolating the jack ground with some fiber washers and leaving the factory chassis ground as-is. If the jack were to work itself loose, as they often do, you'll have an intermittent ground.
Fiber alone washers do nothing. The bushing of the jack would touch the edge of the hole and create a ground loop. You'd need a shouldered washer, and that requires a larger hole, so you'd need to drill out and permanently modify the chassis and cover plate. This is a good option (if you can source a shouldered washer - not the easiest to source unless you're in the know) on other amps which already have a larger hole in order to accommodate the courser threaded Cliff-style jacks.
@@BradsGuitarGarage , I have a bunch of nylon shoulder washers but as you mentioned those require rather a large hole in order to fit. Back in the olden days they used to use fiber shoulder washers and the shoulder itself was very thin so the hole didn't have to be as large, or required minimal enlargement to add shoulder washers when a new jack was installed. I haven't seen the thinner fiber type shoulder washers for sale anywhere. Nylon ones are somewhat commoner because they're often used for mounting RCA jacks on audiophile-grade amplifiers, but the ones that fit RCA jacks are usually too small to fit a quarter inch guitar Jack. The disadvantages to nylon shoulder washes is that they are soft and slippery and tend to compress, and they make for a loose fit so that the jack tends to work loose and spin or wiggle, and also they are usually an off white color and often easily visible underneath the shaft nut holding the jack in place.
@@BradsGuitarGarage , It should also go without saying that if replacing a plastic insulated input jack with an uninsulated Switchcraft type jack, and the interior of the amplifier has a painted or anodized chassis, you need to clean off the anodizing around the mounting hole so that the jack will make a good ground. And, use a shiny toothed washer, not a black oxide washer ( thank Lyle for the frequent reminders).
