Acquired an '82 blonde RD50 110 and 112 cab (both with EV speakers) from its original owner, all good except Limiter side has loud hum when turned up and barely passes any guitar signal. Tried all the obvious stuff, cleaned all pots and jacks, swapped tubes and ICs, did full electrolytic recap. Looks to be a Rev B board (dated 4-5-82, production label 6-82). All components I've measured so far are in spec. Voltages are correct. Limiter/Clean switch and footswitch check out fine. Owner said Limiter side worked when he bought it, but never used it. Thinking there is a bad ground/solder joint somewhere and/or some failed component blocking signal.
Using an audio probe, at the resistor and cap locations where you should get Clean or Limiter signal depending on switch setting, I am getting good Clean, but barely discernible Limiter. Locations include C17, C18, R23, R26, etc.
Suggestions welcome where to focus my attention vs checking every component.