bonedog569
350 posts
Jun 29, 2011
5:46 PM
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Joe Genius left the speaker unplugged on his lil baby - a very pretty old Gibson BR-9. El power transformer is now a slightly burnt smelling paperweight. Anyone know of a workable replacement?
here's the schematic
http://www.gibson.com/Files/schematics/BR-9%20Amp.pdf
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MP
1743 posts
Jun 30, 2011
10:36 PM
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wow! dude! dunno. sorry. incredible gibson amp. as an aside, i know the BR-1s had field coil speakers. same w/ BR-9?
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MP
doctor of semiotics and reed replacement.
"making the world a better place, one harmonica at a time"
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Mojokane
419 posts
Jul 01, 2011
12:15 AM
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hey Bonedog,
great shot of you and your harps.
..ATTENTION!
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Why is it that we all just can't get along?<
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tmf714
700 posts
Jul 01, 2011
8:55 AM
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I just spoke with Paul at Mercury-he said more than likely it's the OUTPUT transformer if the speaker was left disconnected.
He has to make one-between $160-$200,and about 3 weeks time.You need to send the old power/output transformer as well.
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chromaticblues
899 posts
Jul 01, 2011
9:23 AM
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Yes tmf714 That is absolutly right. Not having your speaker plugged in has nothing to do with The power transformer. It will overload the output transformer and burn it up in about 20 to 30 seconds though. Which sucks because its easy getting a power transformer with similiar specs, but that old output transformer you just burntup was a big part of why it sounded the way it did! The best thing to do is find someone (like Gerald Weber) that will rewind your transformer exactly like it was! You will not find another transformer made anywhere that will sound like that one did! Email Skip Simmonds and ask him if he would rewind it. Maybe one of these guys has one lieing around?
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tmf714
701 posts
Jul 01, 2011
9:32 AM
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Paul at Mercury said the rewind would be very expensive due to labor involved in the winding process-it's all done by hand,and he said if you want the amp to sound the way it did before the tranny dumped,it needs to be hand wound. He blueprints the tranny as he rebuilds it,making sure to rebuild to factory specs.
Paul said it's easier and more cost effective to build one from scratch.
Last Edited by on Jul 01, 2011 9:35 AM
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bonedog569
351 posts
Jul 01, 2011
10:11 AM
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hmnnn -Thanks everyone. I thought output transformer first too- and ordered a weber that has been used by others for this amp (the mercury would have cost more than the amp is worth) - but something else is still going on. - I'm getting a very bad sound from near the power transformer when I plug it in -like it's cooking, I'll have to do more testing.
re field coil - yes it had a field coil speakler. I changed it to a standard weber speaker and sub-ed in a resistor in the circuit to compensate. That's when I put in a simple female/male speaker connector on the cord that led to this bonehead move- duh. I could have/should have wired in a jack that would have kept the internal speaker inline till I plugged in an external. - NEXT TIME!
I may put a choke there instead of the resistor once I resolve this. It was working really well - and was one of my fave harp amps till this sillieness.
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chromaticblues
902 posts
Jul 01, 2011
10:30 AM
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Good luck Bonedog. Those amps are great for blues harp. Its worth the effort getting her back up!
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5F6H
761 posts
Jul 01, 2011
10:45 AM
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@ Bonedog "I'm getting a very bad sound from near the power transformer when I plug it in -like it's cooking, I'll have to do more testing."
Do you still get this bad sound with the power tubes & rectifier removed & the amp powered up? If the amp powers up, without blowing a fuse, without tubes installed, then there is a possibility that the PT might be OK (though no guarantee).
If you have dispensed with the field coil speaker a Fender Princeton type OT (mates 2x6V6 in push pull to 8ohms) will work well enough, they're pretty inexpensive. Beware there were some BR9s that were parallel single ended...so be sure which type you have before buying anything.
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jimr
19 posts
Jul 01, 2011
11:06 AM
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One BR9 schematic on the web shows a phase inverting transformer instead of a tube driven inverter circuit. I suppose this could go bad. Does your amp have three trannies? If the PI trannie is bad, you could look for one that is suitable for a Fender Musicmaster Bass amp, which also uses push pull 6V6 tubes driven by a PI tranny. I got a phase inverting tranny from Allied Electronics for a 6L6 amp a few years ago.
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bonedog569
354 posts
Jul 02, 2011
10:11 AM
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There is a small third trannie. I need to get back in the shop and break out the meter again - or call in help. Meanwhile I may be going down the road to look at a Silvertone 1333. I'd sworn off new amp purchase - but this thing is so darn cute and bluesy.
If I get it I'll probably sell my little SE airline amp - Stop me before my pile of amps grows any higher!
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KingoBad
787 posts
Jul 02, 2011
7:15 PM
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Nothing says "Power Tranny" more than Wesley Snipes...
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Danny
Last Edited by on Jul 02, 2011 7:20 PM
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bonedog569
358 posts
Jul 03, 2011
10:07 PM
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The 'power tranny' (Wesley asside) - does in fact test good. I obviously know just enough to get myself in trouble. Now that I cut my color coded wire leads too short and desoldered them from the tube sockets and grounds - I've got a project just getting it wired back into place.
I'll look at that PI trannie next. Meanwhile - i picked up the 1333 and it is a project too. Intense odd order harmonic tone, as loud as the actual fundamental tone -like a harmonizer set to the wrong key. - Any
ideas on that one?. - A trip up to Skip Simmons may be in my future.
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Last Edited by on Jul 03, 2011 10:07 PM
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