Just starting restoration of 750B and 750C
Quote:
Originally Posted by
Chevelle
Yes, the 750C always have transformer hum. I fixed the transformer only with the four screws on the side with rubber grommets between the transformer and housing. I did NOT use the metal bracket that secures the transformer to the bottom and also put a piece of a rubber mat under the transformer. This all reduces the hum but you should not ship the 750C without the bracket, otherwise the transformer will get loose...
Also you can add a 100 Ohm resistor in series with the 300 ohm resistor in the fan supply. The fan will run slower at idle.
Hjalmar
This thread has been extremely helpful and even inspiring. I recently became owner of a BGW 750C quite accidentally through a friend, and expected a lot of power but the same faults I had heard with PA amps: a bit harsh, veiled, lacking detail. When I tried it with a good tube preamp and a set of high-efficiency speakers and was very pleasantly surprised, I decided to take it seriously and consider replacing caps etc. I bought a second one (actually a 750B, the one with the clipping lights) so I can keep listening to one while I work on the other. :)
The tips here are really useful. I'll try the same grommet and rubber trick used by Hjalmar, and may replace the original huge electrolytic caps too. I'm not sure on the small caps on the board... what to change, what to replace them with...
I ordered a pair of ultra-quiet 120mm x 120mm fans (made for computer cases) that I won't mind running all the time. They will need a 12vdc supply but I figure I can put a small wallwart inside the case.