[JohnR]

I need more channels for my latest "plan." Bought an old Rotel multichannel amp the other day for next to nothing with two channels not working, tonight I thought I may as well have a look inside for anything obvious. Turns out each channel has an output fuse, and guess what, two of them were blown. Dangnab those dangnab engineers for engineering in such an obvious safety mechanism!

So that's the amp for a 3-way surround pair. At $12.50 per channel, it's sometimes hard to justify DIY...

[Chris Adams]

Nice! I'll bet there are a bunch of deals like that. The problem is knowing which ones.

[Davey]

The engineers safety mechanism turns out to be your opportunity.    You now have a nice amplifier for next to nothing.
Those engineers do have some good ideas......occasionally. 

Dave.

[JohnR]

Exactly

While I would rather have a root canal than attempt a proper repair of a solid state circuit (I'm more of a system person), it's fun to poke around inside this thing. Each pair of channels has its own pair of transformer windings, bridge rectifier and capacitor pair (and another pair of fuses). They didn't have to do it that way. The signal wiring to each board is terminated with wire wrap! That surprised me, haven't seen that in a while.

[Davey]

More than likely the blown fuses were just a result of an accidental short circuit on the speaker posts by an inexperienced user.

Actually, I don't like fuses in that application because of the non-linearities and slow response.  There are alternatives....if a user feels the need.  Or, a knowledgeable user who's aware of the risk can just install a really large current "fuse."

Dave.

[Mike B.]

If you have a multimeter with decent resolution you might what to check the DC offset at the speaker binding posts. That is the first thing I do with older amps. It does not need to be terminated. Plug it in, turn it on and measure each pair of speaker outputs.

[JohnR]

Good idea, thank you. All channels are 12-15 mV, all measure fine (freq response).