Chicken or egg question

For now until someone comes over to help you, list it in as is condition for sale as a local pick up with the description of what happened. Whoever buys it will get it off that shelf with your help if no one shows up before it sells. 

Thanks much for the suggestion, however, that not working No.23 is very not working.....will not power up.  Now, can I ask a couple of forum readers to come to my house to help get that monster off a high shelf where I put that amp almost 30 years ago?  I worry about a very costly repair....and yes, I mean the cost of the impending hernia repair.

Connect the No.23 that does not work to the working RCA outputs at the preamp. The RCA inputs to the 23 are connected to the non-inverting (pin 2) XLR. If it still doesn't work then the amp is at fault.

Since the No.23 has two discreet circuit input stages -- one each for the 2 and 3 pins of the XLR -- there still will be sound even if one XLR leg is dead. A silent amplifier with balanced connections means that both legs of the XLR are dead. That would most likely be from a relay fault in the preamp or a broken XLR connection at the amp.