Seeking help with an amp problem

Hello. I bought a B&K EX-442 amp used on Audiogon. It was trouble-free for a few weeks. Now, when it's first turned on, the right channel doesn't play at all, but after an hour or two it gradually comes on, but after awhile it becomes silent again. (There is no sound whatever from the channel when it's not playing properly, not even static or hissing.)

I tested the preamp and sources, and there's no question that it's the amp. I've had many amps over the course of many years and I've never had an intermittent problem like this.

My thanks for any guidance anyone can provide.
call B&K - ask for Jerry in Tech Support. He is by far the most familiar and forthcoming about the older amps. Describe the problem - he may be able to give you a fix over the phone (or at least what/how to check it). You'll probably have to send it in for repair, unless it's something simple like a loose wire. It doesn't sound to me like it can be fuses but I'd check them anyway. B&K can tell you where they're located (inside the amp). If I had to guess I'd expect the repair cost to be ~$100 plus 2 way shipping. They'll fix what's wrong and go through the rest of the amp too - give you all new fuses, power switch, reset the bias, etc . . . so it's not a bad deal for the money. Especially compared to most shops who'll charge tou a min $200.

Thanks. I called B&K. They offer just a conventional repair of $65/hr. plus parts. I've sent it in.