In the UK in the mid to late 1970s, HH was the king of the pub band PA world.
A couple of weeks ago a friend asked me to have a look at two of his amplifiers which he bought around 1976.
One is a five channel mixer amplifier and the other is a slave amplifier. Both are rated at 100 watts and have two 2N3055 transistors in the output stage. Quite a basic design. HH together with Carlsbro had the majority of the market at that time but by the early 1980s we had been invaded by Peavey and pub bands started buying their superior designs such as the XR500 and XR600.
They didn't need a lot to get working again. There were a couple of loose crimp terminals on a bridge rectifier and a few wires which needed re-soldering... and a lot of contact cleaner sprayed into the pots.
Behind the front panels of these amplifiers, there is an electroluminescent panel - so when the power is on, all of the panel lettering glows bright green. The one on the mixer amp doesn't work any more but the slave one sort of works. It's a bit patchy.
is what they looked like when new: