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Gibson BR-9 chassis

#1 User is offline   dkevin 

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Posted 20 September 2017 - 02:16 PM

I have been on a quest to find an early BR-9 amp to rebuild. Just the other day I was looking on the Bay and found a chassis with tubes in mostly original condition for $70 . Couldn't get my wallet out of my pocket fast enough! This particular amp appealed to me because it was exactly as the commonly available BR-9 schematic described. Most of these amps I have encountered have the 6SJ7 preamp tube and are single-ended, parallel output amps. Don't get me wrong! These are still great amps! But I always wondered what the original design sounded like and how it differed from the later variant. The amp showed up today and I tested the tubes. The 5Y3 was dead (probably due to the ancient paper-tube electrolytic caps). The 6V6GT's were strong. The 6SN7 tube socket had a 6X5WGT rectifier installed in the preamp position. Bet it had difficulty making sound! The 6X5 will go in my stock for several old Silvertone amps. I have 6SN7's and spare 5Y3's. The fuse holder was sheared off. I clipped the wires to the PT and tested it. It read; 391vac to the 5Y3 plates...5.5vac to the 5y3 heaters and 6.9vac to the preamp/output tube heaters. The interstage transformer (PI) tests out at 546ohms. I am hoping to be able to use it. As it stands, I need to replace the E-caps, wax-paper capacitors, power cord , output transformer and add a choke so I can use a permanent magnet speaker. The caps and such, I already have on hand. The transformers I will have to order. They should come to $70 (not including shipping).
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#2 User is offline   dkevin 

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Posted 20 September 2017 - 05:14 PM

Attached File  Gibson_BR-9.pdf (61.01K)
Number of downloads: 8
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#3 User is offline   badbluesplayer 

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Posted Yesterday, 03:30 PM

Sounds like a fun project. [thumbup]
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TENNESSEE AMPLIFIER COMPANY
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