Gibson BR-6 repair

[Geno]

I have an old Gibson BR-6F could not locate serial number. It had metal tubes I replaced them with groove tubes.

I want to replace the caps which would be best Jupiter or Sprague? I have already replaced the electrolytic.

[bmccowan]

Love that amp - simple and great tone.
Unless the metal tubes were worn out - keep em - nothing wrong with metal tubes.
Signal caps - choose your flavor - choose your budget. Visit the Archive of Favorite Topics on this forum. Opinions will keep you busy for a while. I like lots of different caps: mallory 150s, various orange drops, the Xicon and Panasonic caps, etc. I hear only subtle differences. I usually use 150s in those older amps because (well truth is, I don't have a good reason) I do not spend extra for Jupiter, Sozo etc. - others do and are just as happy as I am.
Let us know how you make out.

[Geno]

Thanks for the advice.

[thetragichero]

restored a br-9 with the matching lapsteel for my dad so he could sell it. i didn't touch any of the coupling caps because it didn't need it, just replaced the original electro caps and added a properly-grounded three prong power cord. with the lapsteel it stays clean but with a regular guitar gets some nice grit

[Platefire]

I don't know if it's just me but those old ugly cheap ceramic caps seem to last forever. They put a lot of them in the old 40's thru 70's amps

[bmccowan]

I don't know if it's just me but those old ugly cheap ceramic caps seem to last forever. They put a lot of them in the old 40's thru 70's amps

Not just you. I seek out and rebuild a lot of Valcos and most are full of ceramic caps. They are almost always right on spec, and sound good.  Some folks make a mistake by replacing them with new caps IMO. I've recently built some new amps with ceramic tone caps - all good.
I think this model Gibson came with those waxy paper caps, and I have found they do not hold up all that well.

[Geno]

These are the old caps you referred to.  When I power the amp up it sounds like a motor boat or a siren and lasts 2-3 seconds. Then quiets down but almost sound like a fuzz pedal.

[bmccowan]

Then quiets down but almost sound like a fuzz pedal

Well that's the Gibson sound. Just kidding of course.
BTW does yours still have the field coil speaker? If so, and if it still sounds good, it is worth being gentle with it - they are rather rare these days. If replaced with a PM speaker, a choke or 1K 3+watt resister should be installed in the same spot in the B+ rail.

[Geno]

Is there anything I should know before I start replacing capacitors in an old tube amp. I do know how to use an oscilloscope, multimeter, and how to solder.

[Williamblake]

With motorboating going on you might want to check the powersupply. Bad filtercaps in the powersupply give bad decoupling give unwanted interaction.

[Geno]

Yes it has the field coil speaker but the cone needs to be replaced. I want to keep and repair the speaker.

[kagliostro]

Verify well if the voltage rating Is adeguate, happens that in some amp they have a voltage rating that Just suffice the needs, other thing to Remember Is the max temperature rate of the e-cap


Franco

[Williamblake]

Caps hold a charge. Caps have polarity. Filter caps can work differently depending on their location, meaning ground is not neccessarily the same everywhere, nor is B+. Everybody and their dog loves a doghouse but they are bad practice. There is a lot bad practice that works fine. But mostly, don't zap yourself, discharge. 

[sluckey]

Is this the same Gibson BR6 amp as in your other thread? If so, please keep all discussion about the BR6 amp in the same thread. I can combine the two threads if you like. LMK.

[Geno]

sorry yes it is the same amp.  Please combine 

[bmccowan]

Is there anything I should know before I start replacing capacitors in an old tube amp. I do know how to use an oscilloscope, multimeter, and how to solder.

Some of this was covered by others:
Capacitors store electricity - so check with your meter and be certain.
WB mentioned doghouses. Old Gibsons have none and there is no good reason to try to add one.
The BR6f is wired point to point (tube socket to tube socket) - nothing wrong with that, but the old capacitors had pretty stout leads. New caps tend to have wimpy leads. So its good to make sure that parts can't flop around and short. Heat shrink tubing and spaghetti sleeve can help.
Desoldering the old leads on the sockets lugs is usually harder than soldering the new leads. A spring loaded solder sucker works pretty well to remove as much solder as you can before you start torturing the lugs with needle-nose pliers.
Make sure you get the polarity right on electrolytic caps. Other type caps are not marked for polarity and work well either way.
I think you already did the filter caps. But old Gibsons used metal clamps to hold them in place. Its hard to reuse them. cable ties and adhesive cable tie pads (not Pad Thai) work ok.
As long as you have things opened up - check the resistors - if original, some may have drifted far off spec. And clean/lubricate that one pot.
Most important - read everything that Doug Hoffman posted here in the Library of Information. And you can't go wrong buying parts and supplies from Doug.

[tubeswell]

These are the old caps you referred to.  When I power the amp up it sounds like a motor boat or a siren and lasts 2-3 seconds. Then quiets down but almost sound like a fuzz pedal.

Filter caps need replacing.

[66Strat]

As noted by bmccowan, the replacement components may have less than robust leads that are not conducive to point to point wiring. Doug has terminal strips in his online store that may be useful in securely mounting components. Before you start work on the amp, take pictures of the circuit. You may find it useful for reference in developing a layout for your project.

[Geno]

I need a 20uf Electrolytic 500 and can I use a 22uf?

[sluckey]

I need a 20uf Electrolytic 500 and can I use a 22uf?

yes

[Geno]

Thanks

[Geno]

I need to replace the paper cone in my 10 inch field coil speaker and unable to find a source.

[bmccowan]

I would try Ted Weber as a first shot:
https://www.tedweber.com/other-stuff/recone-parts/page/2/

[Geno]

My Gibson BR-6F amp schematic shows 4 electrolytic caps and (1) .01 cap, and (3) .05 caps. My amp has an extra cap an AMCON capacitor which has + and minus on it, part# AE-13, not sure this is the extra cap. Well anyways I have 5 wax type paper caps.

[Geno]

Iam trying to identify a cap
The cap is a AMCON part# AE 18 20 MFD. 25 W.V. it has a plus and minus side. Where can I go to find out info about this?

[sluckey]

That's a 20µF @ 25V electrolytic. Most likely being used as a cathode bypass cap. You can buy them at any parts house. Hoffman sells a 22u@50V, 25u@25V, and 25u@50V. Any of those would be a suitable replacement.

     https://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=Capacitors&ORDER_ID=!ORDERID!