Bridge Rectifier?

Discussion in 'Amps and Cabs [BG]' started by bass_drum, Aug 2, 2005.

  1. bass_drum


    Feb 13, 2005
    Hey guys! Today I was jamming with my friend. My guitarist left his amp here, so we plugged my friends guitar into it. all was fine, and we were playign very quietly, and all was well. 2 minutes after turning the amp off, my friend plugged his guitar in and turned the amp on, except, it didnt turn on, instead, it started smelling really bad. So I turned the amp off and unplugged it. After that my dad took the back panel off and checked it out. he said the bridge rectifier may be gone, so he told me to turn the amp on. As soon as i tuerned the amp on, the rectifier started smoking.

    So does anyone know where I can get a bridge rectifier for a tagus RB5104 guitar amplifier? (It is a combo amp with 4 ten inch speakers). Also, what would cause the bridge rectifier to break?

    Thanks for your time.
  2. Hey

    Firstly, not cool, never play with someone elses amp without them knowing :scowl:

    Secondly, this is a bass forum :p , however, try or, im assuming its a rectifier valve, what is the valve/model number printed on it?

    Thirdly, not cool, never play with someone elses amp without them knowing :scowl:

    oh, and Hi :)
  3. A bridge rectifier is a diode whose value is determined by the amp's voltage requirements. Oughta cost 50-75 cents max, IF that's all that's wrong with the amp, because if it went, chances are there's something else badly wrong, probably a shorted output transistor. You most likely didn't do anything to cause it to happen.
  4. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    while this may be my first post on the talkbass forum and i may be new to bass stuff, I'm NOT new to guitar amps. (designer/builder of tube gear)

    Anyway- i've never heard of tagus amps, but seen reference on this forum only, maybe they're bigger in the bass world.

    first of all, is this tube or solid state? (this makes a big difference). because of the "bridge rectifier" comment, i'm guessing solid state. most (not all though) tube amps use full wave rectifiers and not bridge rectos (there are plenty of exceptions, fender twin reverb comes to mind for anything post, er, 72?)

    Secondly, do you know how hard it is to blow a rectifier? VERY. They also don't particularly smell. It's possible something ELSE went first and took a rectifier with it.

    If it was a really FOUL smell (instead of just a burning electronics smell), chances are some big electrolytic caps blew up. (both solid state and tube amps have these). This is generally a problem when using older gear (more than 20 years, but sometimes as little as 10, depending on design/quality/use). Ask your vintage tube amp guitar friends about their last cap job, you'll find out.

    unfortunately, when these bad boys blow, they can take other stuff out with them.

    If the smell was more just an "electrical fire" type smell... you may have toasted some of the transistors in the power section. (the preamp ones generally wouldn't be put under enough stress to blow and cause a smell).

    But yeah- I've never heard of tagus amps, let alone guitar ones, and a google search didn't turn up with squat for them.

    Until I know tube or solid state, I can't really give you more specific advice...

    (unless, this was NOT a bridge rectifier, was actually a tube full wave rectifier,and happened to be made by Shuguang/ValleyArts/"The Chinese Tube plants". They've consistently had problems with their GZ34/5ar4... their 9th generation 12ax7 and KT66 are outstanding though.)
  5. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    Make sure you notify the amp's owner BEFORE undertaking repairs. If the repair fails or doesn't solve every problem, he'll be doubly pissed that you did such invasive meddling.
  6. My bad, i instantly thought recifier tubes
  7. bass_drum


    Feb 13, 2005
    Oops, sorry if it sounded liek i plasyed it without him knowing. I asked him first asnd he said it was ok.

    Anyways it is a solidstate amp. And it smelt liek burning electrical stuff.

    Also, Im sorry, i knwo this is a bass forum, its just this is the only place I know well enough, that will respond. Thanks! ~JB~
    P.S> this is a bridge rectifier (for sure) with a heat sink built into it (it has single bolt pertrudiing out the back and it had compound for heat transfer) it sits about a half inch square three eights thick. There is four terminals, two marked AC, one marked + and one marked -. The part number of this component is S-6230, or perhaps S-6290 (there was a small chip buy the second last digit). There is a logo of an "S" on top of an "I" wich could stand for ST micro electronics, however this is quite different from there current logo, or could be for SI, impossible to tell.

    We considered wiring in 4 diodes to replace this, however we are hesitant to do so because because of the lack of a heatsink. What would yuo suggest doing?

    We are having trouble cross referencing this to a currently available component, do you know of a substitute/replacement for this bridge rectifier? If so, where could I get one?

    Btw I am a bass player in need of help and that is why I came here, i know it is a guitar amp, but I felt you where the most reliable people I could contact, Thanks again!
  8. zombywoof5050


    Dec 20, 2001
  9. That is indeed a bridge rectifier, but as others have said, something else has probably failed also.....send the amp to a tech. Linear power supplies are very easy to diagnose.
  10. bass_drum


    Feb 13, 2005
    Well, I bought a 5 dollar rectifier, put grease on the back of it (as a heatsink) and it works fine now. :smug:
  11. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    well, that's good... for now-

    just pay attention closely to the amp's behavior. Diodes are one of the few components that "can last 50 years, can last two uses" if they die a "natural" death. However- any kind of "natural" diode death is RARE at best.

    Also, just for some clarification. A bridge rectifier uses four diodes... also, a rectifier tube is also diodes (some are single, but most used in guitar amps are two diodes working as a full wave rectifier).

    tube vs. solid state is another story- but at the end of the day- a diode is a diode (be they tube diodes or solid state diodes). how's that for confusing?
  12. Glad it's working, but instead of grease, go down to Radio Shack and get a tube of heat sink compound for a couple of bucks. Use a very thin layer, it'll conduct heat much better than grease--when grease gets hot, it'll just migrate outward.

    You don't have to cross reference bridge rectifiers, they're more or less "standard" now. For higher-power applications like bass and guitar amplifiers, a bridge rectifier rated 25 amps or more will be fine.

    Check all over to make sure there aren't any loose connections or shorts that could've taken the bridge rectifier out.....
  13. Passinwind

    Passinwind I Know Nothing Supporting Member

    Do you mean thermal grease? Did you then attach a heatsink? That's what thermal grease is for, to allow efficient heat tranfer to a heatsink. OTOH, if the rectifier is similar to the one you originally described, you may be all set.
  14. bass_drum


    Feb 13, 2005
    Im not sure wat kinda grease it is, since its my dad who put it in. I'm ntot o worried though, because we got the grease from the guy who sold us the rectifier. Also, I dont think i'll be worying about how much this rectifier lasts, ive done everyhtignt he guy told me to do, and I'm sure the amp is working better then it was before, so Im happy. If it blows again, I'll let my guitarist deal with it, cause im nto even touching the amp again. All I know is that the rectifier was gonna blow up wether it was me or my guitarist playing through it and I jsut got unlucky.
  15. Sounds like you got the right "grease" then, so hopefully you're good to go.

    That's why I hate borrowing stuff, or lending stuff...what happens if something goes wrong? Whose "fault" is it, or more importantly, who's gonna pay to fix it??
  16. Passinwind

    Passinwind I Know Nothing Supporting Member

    You're a tech, you know you're gonna pay, on some level. :eyebrow:
  17. Exactly.... :eek: