Next up in the solid state power amp crawl, a late 1970s Heil Sound 400. This beast is in unknown/untested condition. I seem to recall the previous owner saying something about a dead channel, but this was in the mid 1990s and I was but a music store clerk. After spending over a decade gathering dust in the dead gear room in the attic I was instructed to haul it away with everything else.


Take note! These knobs go to 12.


Nice wide open guts.


Channel A looks to have been replaced in the early/mid 1990s, from the 40th week of 1991 manufacturing date code on the transistors. Looks like this amp is somewhat lacking in the sort of protection scheme that saved the actives in the RA7502, this notion is further punctuated by the fact that the driver board appears to have been replaced in its entirety as well. I'm thinking someone held a BBQ here.




Channel B on the other hand appears to be original equipment, bearing the 39th week of 1978 build date on most of the transistors. The part at lower right paints an interesting picture:


I'm trying to figure out how, in normal use, someone could achieve this sort of arc. Sort of makes me wonder about the internal conditions of this part as well. I'll sniff around for any dead shorts on both power rails, then perhaps apply a little voltage and see what happens.