Restoring vintage H/K Citation 19 Power Amp

I have one of the nicest products from Harman's "golden age" - a Citation 19 power amp, purchased back in '78. Weighs about 40 pounds and still works, though after all these years it probably merits a restoration. Sound isn't quite as tight as I'd like and if I leave it on continuously it exhibits a low level hum (in the 300 Hz range, not 60 Hz). But if I power off and disconnect the preamp, the hum is gone when I power back on.

I'm wondering if any readers have experience restoring these amps, and have some guidance to offer. I don't trust the local service shops to tackle this - one did a mediocre job on a Denon CD deck, the other overcharged me repairing an Integra HT receiver. I know Blue Sky used to do such work - and they were expensive - but have since retired. I have a copy of the Service Manual, but have never tackled a job like this, and would probably mess it up.
I have three of these amplifiers as well, but have yet to perform any serious rehabilitation.  Unfortunately, there is not allot of information out there but if you have the time and patience, internet searches will provide you with a handful of forum discussion that are helpful.  Most I have found were from here.  I believe that the 19 shared some components with the 16, so include it in your search as well.  Good luck.

Something this old will need new filter capacitors in the power supply. That is the source of the buzz (its a 'buzz' if its anything over 60Hz FWIW), and the reason its not there if you cycle it off.

If the filter capacitors are not replaced, the power transformer is at risk, as the filter caps can start drawing energy, and thus heating up the transformer. Good caps store energy, they don't consume it!

This is straightforward work. You might find more information about technicians and the amp itself over on in the 'solid state' forum.
You should contact Don Sachs — Sachs Consulting I think.  He used to rehab vintage HK gear and now makes and sells his own products.  Not sure if he still refurbs old stuff anymore, but I’m sure he’d at least have some good info and recommendations for you if nothing else.  Best of luck. 
I contacted Jim McShane and he advised he doesn't deal with H/K solid state, and unfortunately couldn't recommend anyone. 
I contacted Jim McShane and he advised he doesn't deal with H/K solid state, and unfortunately couldn't recommend anyone.
FWIW we can handle stuff like that. And I can strongly recommend Jim should you ever get any of the h/k tube Citations.