BGW amp 750B anyone familiar with it ?

funllbb- can you post a picture of what you are describing? I have a BGW 500D that is very similar to the 750 A model, there are some metal can type driver transistors in wells with compound around them on my boards. I know later 750 models went to plastic body transistors. The outputs are metal TO-3 in all of them.

Sorry I can't do pics. I'm new here and having trouble even figuring out how to navigate! Thought I'd get an email to notify me of any activity in this thread-nope! I suspect the 500 is very similar to the 750 as it was it's predecessor. I have an idea what your drivers (actually probably pre-drivers) look like. I'm betting if the heat sinks are the same they just have different boards, and a slightly smaller power supply. They look like good old amps though!
 
Not sure if anyone already mentioned this site for manuals but I've been very pleased with "HiFi Engine" for sourcing hard to find manuals and literature. It's easy to use as well as free. Just sign up and go. No affiliation. Got a service manual for my 750B and I know they have other models manuals etc.

This site? I didn't see a link to any other. I'm new here and still trying to figure out how everything works......
 
We never had very good luck with BGW amps in pro use. Our pro audio company bought 3 500's back in 1978. All were cooked and out of the racks by fall. We replaced them with DC300's and later PSA2's. These racks went to pool parties, frat parties, and mega disco dances and ran near the full output for hours. Crowns would be too hot to touch and same with the BGW's but if the BGW's cut out, they were cooked.
 
BGW 750C stereo or mono?

I have two BGW 750C monaural amps. Whenever I find a 750C user manual online, it appears to be for a stereo amp. So, did BGW make both mono and stereo versions and give them both the same model number? Does anyone know where I can get a manual for the mono version? Are the specs of the mono version the same as for one channel of the stereo version?

I was pretty lucky to acquire these two amps. About 12 years ago someone put them on Ebay with a starting price of $60 for both of the amps. The seller said that both amps were broken, but a buyer should be able to put together one good amp out of the two broken ones. So, I put in a bid of $60. No one else bid on them so I won them for $60. This included free shipping! The seller sent them to me and then sent me a friendly email that said that I got a great bargain. It cost the seller $70 to send them to me by UPS.

So, I opened them up, it turned out that the only thing wrong with both of them was that their power switches weren't working. They are a very unusual power switch. They are a circuit breaker and on off switch combined into one. I went to a local electronics surplus store that dealt in oddball parts and used equipment. They had several cases of that exact same switch for $3 each. So I fixed those two amps and they have been sitting unused underneath my pool table ever since.
 
Hi TRWong,

Welcome to AK and nice 1st post. Would you still have any info on the shop that had the power switches/circuit breakers? Would love to get some spares for my BGW amps. Also, were they white or black switches, or did they have both?

Now, since they've been sitting under your pool table, how about some pics?

:worthless
 
PS, never heard of them producing a purpose built Mono 750. That's where pics might come in handy to see exactly what they look like. My bet is that its a bridged stereo amp and configured only for mono, but if they have specific mono-only metalwork and labeling, well, there would be something new about that.
 
BTW- when BGW went out of business, Peavey (the musical instrument and PA company) hired many of the engineers from BGW, and bought much of the documentation from them. The Peavey CS800- the original model, as seen here:

attachment.php


... IS just a BGW 750, with a few mods for durability and usability in a PA environment (more aggressive protection scheme, compressor/limiters built in, and such).

So, if you can find a tech that's familiar with the CS800, they can pretty much inherently work on the BGW 750, should it ever need service. The same caveat as the CS800 applies here- you do need to remove the top cover, and blow out the dust once in a while... that heatsink design seems to just catch dust and hold it, until it piles up into a "carpet" and smothers the heatsink. Barring that, they're nearly indestructible, from a normal-use standpoint...

Regards,
Gordon.

I thought they looked awfully similar....and I made a post on DIY Audio documenting my repair of one. http://www.diyaudio.com/forums/solid-state/169909-cs-800-repair-pics.html
 
BGW 750C is stereo!

Gentlemen, my apologies. After dragging the two BGW 750C's out from under the pool table, I find that they are indeed STEREO amplifiers. So I was completely mistaken when I thought they were mono amps. So you fellows were right when you said that there was no record of BGW making a mono version of these amps.

I have included pictures including one of the on/off circuit breaker switch. It appears that everything inside of the amps is original except for that on/off circuit breaker switch that I replaced.

Front.jpg

Back.jpg

Circuit board.jpg

Inside.jpg

Circuit breaker.jpg

The on/off switch that I found were made by Matsushita. They are called Aromat miniature circuit breakers CP-A. Cat # BA A1215111U. Fast Trip 15 amps. I bought them at a surplus electronics shop called HSC in Sacramento. However they closed that location about 5 years ago. I called HSC in Santa Clara today, but they didn't have any more of those switches.

I do have a question about waking up these amplifiers from their 10 years of sleep. I was going to check the esr of all of the electrolytic capacitors first. I didn't see any soft start circuitry in the electrical schematic so it seems that the power supply capacitors are directly connected to the bridge rectifier. So it seems that using a variac might be the best way to bring up the voltage slowly in the main caps. Does that sound correct? Thank you for any help you can give me.
 
BGW repair in Japan

Holy Moly! I'm astounded that they got that amp working again. I've bought a lot of broken stuff on Ebay but nothing was even remotely as bad as that BGW amp in Japan.

For a while that was my hobby, buying broken appliances on Ebay and fixing them. Everything from George Foreman rotisseries to steam irons to amplifiers. I would fix them and then put them in the garage. One morning the UPS man dropped off 13 packages at my doorstep. I then knew that I was seriously addicted to Ebay. So, I quit cold turkey. Didn't buy a thing for years after that.
 
any bgw 750 fans out there ?

Just picked up a 500D for $65. Owner claimed it worked but did not have any speakers to test it. For that price I didn't care.

Replaced a shorted cap on one of the amp boards. Thing just sounds amazing!

I picked up a Marantz 250M needing repair from a guy who told me he put a working BGW 750 on the curb!
 
Keep us posted about the 500D, Ray. I have one that still works, I paid about double what you did a few years ago. I need to find a quieter fan for it- I'm running a 12V DC fan at 6V & I can still hear it during quiet passages. It powers my maggies with authority!
 
...I picked up a Marantz 250M needing repair from a guy who told me he put a working BGW 750 on the curb!

I recently bought a 750C at a bar auction for $65. After claiming it I sniffed around the fan and realized it was blown. Got it home and both channels had gone down. The lack of +/-DC fuses resulted in extensive damage. It took a while to rebuild, but it lives again.

I can't imagine dragging one to a curb. They're to heavy.
 
Keep us posted about the 500D, Ray. I have one that still works, I paid about double what you did a few years ago. I need to find a quieter fan for it- I'm running a 12V DC fan at 6V & I can still hear it during quiet passages. It powers my maggies with authority!

Interesting, I have a pair of Maggies I was considering resurrecting after getting this amp. Nice to hear they're a good match!
 
I recently bought a 750C at a bar auction for $65. After claiming it I sniffed around the fan and realized it was blown. Got it home and both channels had gone down. The lack of +/-DC fuses resulted in extensive damage. It took a while to rebuild, but it lives again.

I can't imagine dragging one to a curb. They're to heavy.

When I got the 500D the crowbar circuit was preventing the power switch from staying on, due to the shorted cap on the amp board. I'm surprised there was that much damage. Was the protection circuit compromised?
 
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