I friend of mine gave me a couple of 1960's PA heads a few years ago and I just stumbled upon them in my basement this weekend. I am wondering A) what I should do to make sure they're safe to use and B) what I have to do to hook them up. They are both Bogen brand amps, Challenger series, one being a CHA 10 and the other a CHB 35. They are all tube. There is no watt rating on the CHA 10 (I assume its 10W), but the CHB 35 is rated for 35W (150W with auxilary power -- how does that work?). I may end up using one or both for guitar as they'd probably be pretty quiet on bass. I've never had any experience with vintage equipment. There is no 1/4" input jack (just screw-on mic inputs and RCAs), no 1/4" output jack (just a series of small "holes" in a circle with different ohm ratings next to them), and one has a bunch of wires coming out of the back that looks like it may have been attached to an old Jensen pre-amp I found beside the amps (which also just had a bunch of wires hanging out of it). I'm pretty sure I should have it looked at... I know you can get adapters for the input (so I can use a 1/4" jack), but I don't know about the output. Does it use just regular speaker wire? How would I get it to drive a cab? If you can give me any advice I'd really appreciate it.