I generally do not repair these amps as I was unable to obtain any technical information. This was certainly true for the briefcases of years gone by; maybe that situation has changed as I recently had some success with a BP-800.
BP-800 Amplifier
One of the problems I have come across with these is a problem with the stand-by function. This is a power saving feature that turns the amp off when there is no signal present. Sounds like a good idea but it is problematic.
Two variations of this problem seem to exist, and maybe more.
Problem variation 1 is where the amp completely fails to work, however the LED on the front is red indicating permanent standby and you guessed it no growling bass notes from the speaker.
Problem variation 2 is where the sensitivity is not suitable for the player / musical style or whatever. In this case during a quiet passage of music, the amp goes into standby and then just when it is your big moment, well we miss that and then a few seconds later an almighty pop through the speakers as the amp comes back into life. Prog-rockers take note this is not OK with the songs filled with dynamics.
In both cases the solution I have been asked for is to disable the circuit and fortunately this is possible. The mod keeps the original toggle switch doing what it does but it puts you back in control and makes your amp reliable again.
You can even send the amp in to me for a remote modification given these amps are so light weight the postage cost if fairly trivial.
