BRYSTON 4 B NRB Stereo Amplifier Repair

ONE BAD CHANNEL WITH BLOWN OUTPUT TRANSISTORS AND SEVERLY DAMAGED PRE AMP BOARD COMPONENTS AND PCB TRACES

[athealth]

Greetings,
Thank you for the educational video. I have an old 1991 Bryston 4B NRB, that runs very hot and blows the right channel fuse every so often. I’m not an electrical engineer or tech, but would like to adjust the bias down to see if I can cool it down it a bit. If you have a chance, could you post more details on how you adjust the bias. How you set up your scope, and how you connect the connectors. Do you have the amp on or off. If it needs to be on, do you turn it on after you connect the meter to the test points? Do you connect to one test point and adjust the bias to 6, and then connect to the other test point and again adjust the same bias pot to 6? Also, when you adjusted the DC offset, do you have the amp on all of the time? Do you connect the meter first and then turn the amp on, or is it off? Thank you very much for the great video.

[dcjenkins]

I have a 4 b with one channel not total out but very staticy but has the square transformer

[raccoon]

*Bryston gave a crazy 25-year warranty on new amps ack in 1992*

[philipsu]

Hello sir, I have a Lexicon NT 225 which is a rebadge 4B ST and the right channel is dead. 1 blown fuse in back and 1 blown fuse inside by the power transformer, I replace blown fuses and same happened again. What you said in one of your videos is right, many clowns in the industry who does a half ass job and if you have the thing apart, do it right with quality parts that will last, 100% agree with you. Prior to the fuse blown, the right channel was getting static and popping sounds and when I jiggle the switches in the back, the issue would go away. Would like to know how much you would charge for a restoration? Im in CA and shipping both ways is not cheap. Thank you.

[laszlosokolai]

These amplifiers develop bad dc offset hence blowing tweeters and midranges and transistors. It was fixed in the ST and later models.

[MJM]

I have a 4B original, replaced pretty much everything including outputs, drivers, resistors, caps, bias pots, yet when on my variac, the PNP of one channel shorts, not the other channel nor the NPN. Bias pot doesnt seem to affect it, please advice.

[raccoon]

0:32 I kept looking for a dog outside my window.

[morksbeanbag]

Sorry but that is one poor solder joint. When reflowing you should add some fresh solder, or better still remove all old solder before reflowing, not a cold joint it like this. Really good effort, but extra experience is required here.