A while back I got a BGW 500D. I nice amp but it developed a problem beyond my current ability to fix in the right channel. Then I found a deal on a 750C and jumped on it. I read a lot (mostly here) on these amps and saw what others did to theirs. I haven't done the cap mod yet but I did add in some bypass caps. Specifically 47uf electrolytics on the PS caps and 0.1uf film & foil caps for C1, C3, C11&12 on the amp modules. I also changed the 1/4" input jacks to RCA jacks, and added a much beefier power cord with a rhodium plated plug. I buttoned everything up, hit the power switch and no "magic smoke" came out so I shut it down and connected a source and a test speaker. I powered it up, the cooling fan spun, but no sound 
. After a bunch of trouble shooting, still no sound
Much head scratching ensued. What if... nah, couldn't be. Little voice says "check the test speaker, you'll feel like a doofus later if you don't".
Yup, after an hour or so of chasing my tail, the speaker was the culprit.
Fear not amp fans. The big BGW is now driving a pair of Maggie MG-2.5R's and sounding splendid.
. After a bunch of trouble shooting, still no sound Much head scratching ensued. What if... nah, couldn't be. Little voice says "check the test speaker, you'll feel like a doofus later if you don't".
Yup, after an hour or so of chasing my tail, the speaker was the culprit.
Fear not amp fans. The big BGW is now driving a pair of Maggie MG-2.5R's and sounding splendid.
UPDATE
I'm really liking this amp. One of the nice things about it is it's neutrality. It doesn't seem to add anything to the musical signal but gain. Since I've posted last, I have changed speaker cables and then IC's. The 750C has faithfully showed me the differences in both. One upgrade I heartily recommend to anyone with a vintage BGW amp is to at least replace the original power cord plug and the outlet you plug into if you haven't done so already. Spend a lot here if you want but it really isn't necessary. I found both from a seller on the bay and they cost me around sixty bucks.
I'm really liking this amp. One of the nice things about it is it's neutrality. It doesn't seem to add anything to the musical signal but gain. Since I've posted last, I have changed speaker cables and then IC's. The 750C has faithfully showed me the differences in both. One upgrade I heartily recommend to anyone with a vintage BGW amp is to at least replace the original power cord plug and the outlet you plug into if you haven't done so already. Spend a lot here if you want but it really isn't necessary. I found both from a seller on the bay and they cost me around sixty bucks.
BGW club
Hi,
I picked up a 6500, 750D and a 7500 at an electronics recycling center recently. My second son fell in love with the 6500 so off it went. I sold the 750D and am left with the 7500. I cannot find a schematic or manual for it. I even contacted BGW and they no longer have pdf or hard-copy.
It sounds good now and it is really good shape but I just want to know more I guess. Love it though.
Anyone have a service manual? Any manual?
James
Hi,
I picked up a 6500, 750D and a 7500 at an electronics recycling center recently. My second son fell in love with the 6500 so off it went. I sold the 750D and am left with the 7500. I cannot find a schematic or manual for it. I even contacted BGW and they no longer have pdf or hard-copy.
It sounds good now and it is really good shape but I just want to know more I guess. Love it though.
Anyone have a service manual? Any manual?
James
I designed many of the BGW amplifiers. The 7500 had two different versions. The 8000 was the basic amplifier module. It was NPN outputs (NEC 2SD746) later it was converted to PNP outputs (NEC 2SB706). 8000, 7500, GTA & GTB were fall outs of the family. Take a picture of the Amplifier module and if I have it I can send you a schematic.Duke duke.aguiar@ieee.org
