My 4B-ST runs Hot


4B-ST owners, does your amp run hot? After an hour or so of listening at moderate levels my amp is so hot on top that I can't keep my hand on it for long. I do not think I am pushing it that hard, but I might be wrong. My speakers are some small floorstanding PMCs (FB-1). Curious if anyone thinks this is normal or might be a problem?
argent
Argent, there is something wrong with the amp. It is not your load. It is in need of repair if it gets that hot on one side.
Argent, I had the exact same "problem" with the 4BST as you have: The right side of the amp was damn hot! It was happen a month ago. I called Bryston, they suggest that I should switch the speaker cables. And then I found out that I connected the channel1 with right speaker and channel 2 with left speaker; also with my interconnect as well. But I have used the 4BST like that for almost 2 years with no problem. I thought that maybe the problem now, so I correct the connection: Channel 1 connect to left speak and channel 2 connect to right speak and also changed the interconnect. The funny thing is, after that, the right side become pretty steadily as normal as the left side?! Since then, I don't have the warm problem with the right side of the amp. And I don't have any idea why...?
Nope, my speaker cables and interconnects are hooked up correctly. The only other thing that might be causing this is my pre-amp. For anyone who owns a Conrad-Johnson product, you know that they are not phase inverting. This means that when I send the signal out from the amp to the speakers, the red terminal on the Bryston must correspond to the black terminal on the speaker. But even if I hooked that up wrong, which I did not, I still don't see how that could hurt the amp. Phase inversion really just affects the speaker, I think. Anyone else out there who owns a CJ product want to chime in?
Just got a response from Bryston. They want me to see if I can duplicate the problem after I switch my speakers around. Guess they want to rule out a bad speaker or cable. I'm going to try it again, but I've moved my system to different rooms in my house often enough to have switched the speakers around several times. This heat thing has pretty much been a feature of the amp since I got it. Oh well, I'll keep everyone posted on what happens.
Guys, I had this problem and here is the fix which I got from Bryston. I had the same problem with my 3B getting hottor on one side more than the other. You have is Biasing problem. Here is the procedure to fix it.

The bias procedure for the 3B amplifiers is as follows:
Remove the top panel of the amplifier, and locate the 2 pairs of test points on the PCB. They will be on the left side of the main board for each channel, between the large 5W power resistors.(The newest amplifiers have them at the top left corner of the

board). Using a millivolt meter, measure the Voltage between

each of the pairs of test points. It should read between 10 and 15millivolts on each pair, or a TOTAL of 20-3OmV. (One may be higher than the other, this is not important, only the total). If it is higher, or lower, than 20-3OmV total, the bias may be adjusted by the rotary potentiometer control in the center of the board,(clockwise is to increase the reading). When the reading is within

the correct range, with the amplifier idling and no input connected, temporarily place the top panel on the amp, and leave it for 15-20minutes. Repeat the reading, and adjust if necessary. The bias is properly set when the reading stays within the correct range for 2successive readings. Then re-install the top screws, and the amp is now set. (Note: on older amplifiers, the test points may not be present. The readings may be taken directly across the large 5Wresistors in that case, and only one resistor need be used for the test. In this case, the reading is only the 10-15mV reading of one).
Good luck
Mohamed