The Amp Garage

- I'm struggling to get my head around the operating point of the splitter/mixer stage from the Brown harmonic tremolo circuit. If I re-conceptualize that stage's shared 4.7k/2uF shared cathode as a split cathode arrangement, I think it'd have 9.4k cathode resistance with a 1uF bypass capacitor. Th...

It's also possible you got a pot with an odd taper. I've only messed with one original 6g7 and my revibe, so not a great sample size of harmonic trems, but both had noticeable tremolo on 1 or 2. Might be worth checking out Sluckey's revibe project if you are planning to build another. He has nicely ...

jer_vic wrote: ↑Fri May 24, 2024 7:22 pm The layout for the Weber Maggie kit...shows resistors across the switch.

Yep, it's generally a good practice to add them when you are switching caps in and out. I like the input jack drawing on webers layout much better, and the 220k bleeder resistor on the first filter cap is also a good idea.

Thanks. I think the voice/boost is that kind of thing. Here's the part of the circuit for that: Yep, my way only gives you one boosted setting but you get to keep the hi/lo input settings and get a footswitch option. If you add a pair of resistors across your switch it won't pop when you change set...

I don't think it should be subtle early in the rotation. Might be worth subbing in a new tube like johnnyreece suggested or double checking your wiring if it bugs you.

Thanks for the picture. I think it's one of these: https://www.piris.com/wp-content/upload ... sb-esb.pdf They're stated as both temperature and current protectors. I've not run into those before. Thanks for the link! I know how bimetallic strips work but didn't think of thermal protection. I guess...

Looks nice so far! Good on you for doing multiple test fits. For future builds, if you want to keep the two input jacks and have a hidden boost switch, here's a way to do it with an optional two button foot switch. https://ampgarage.com/forum/viewtopic.php?f=6&t=36383&p=454393&hilit=cloacal#p454393 ...

Any alcohol should do. Don't spill adult beverages on your shellac finish or you will have a bad time. I add a coat of paste wax for protection, lacquer then wax is even better.

xtian wrote: ↑Thu May 23, 2024 1:54 am The Fender Bassman RI (tweed 4x10) has a 3A fuse (accessible outside chassis) followed by a 4A fuse in series, inside the chassis. Strangely, the 4A fuse had gone open when the client brought it in.

Weird, do you know if the client replaced the 3A?

Weird. Was this factory wiring? Bimetal strips are weird in an amp. I wonder if it's a thermal cutout for the whole amp when the inside air is too hot, just in a glass tube package. Glass tube is stock to the Musicman. I have worked on several, all have it. I'm speculating about bimetallic strip, b...

The amp could have an oscillation that is causing the power transformer to sag when you hit certain notes pulling down the filament, could also just be some oxidation on the bulb or a bad solder joint.

The original was 10M. Weber sells them for the revibe, not sure if anyone else makes something better. https://www.tedweber.com/wp106ra/. Could also play with adding resistors to get a better usable range.

Are you using a reverse audio pot for the intensity?

I have a few marginally related fuse questions/observations to ask the hivemind. 1: I worked on a couple amps in the past week that have series mains fuses, presumably to hedge against user error. Curious if anyone has thoughts or opinions about this. One was in an swr workingmans amp, the other was...

I believe you want "garnet" shellac. It takes more coats than you might expect to get a deep color. I mix it so it's a pretty dark brown in denatured alcohol, but not so thick that it won't dry properly. I have only used it on wood, so YMMV with tweed.