Alright, soundmonkey, I guess it comes down to how risk averse you are. The manual says not to do it, and some here say not to do it. Personally, I'd be willing to role the dice on an 80's-era receiver and just try it out. I don't think that it'll hurt it, but that's my own personal belief and my risk posture. Contrary to TLS's statements, though, I don't think that you have to worry about flying shrapnel from an exploding receiver.
In my decades of using audio/video gear, I've done things that others here say simply can't be done - and guess what? They worked. So, I have my own experience base that leads me to say what I do, as do they.