I used to rebuild Fisher amps & receivers. I would rebuild all on board power supplies, upgrade the coupling capacitors & replace 12AX7s with good sounding NOS vintage tubes. Also, replaced out of tolerance resistors. These Fishers were stunning sounding per my customers and most never pursued better gear after my sale to them. I did this as a hobby, not really a business. I charged about $500-600 for this service, but NOS tubes did cost about $150 adding to the rebuilding cost. I did sell the existing 12AX7 tubes to reduce the cost of best NOS 12AX7 tubes I supplied. If the amp or receiver needed new power tubes, add about $200 to final cost. I could rebuild these amps in about 6 hours including repacking the item for shipment. BTW- many rebuilders used awful sounding Sprague Orange Drop coupling caps. I used superior Russian K40Y-9 coupling caps. What did you pay for a rebuild?