by Rob-NYC »
Fri Aug 19, 2016 3:01 am
When the search motor run continuously it is caused by the wipers never hitting a 'hot" trace.
Causes are:
Worn wipers. ---Slightly-- flex the plastic holder to see that the wipers stay in contact with the traces. be careful as the plastic may be brittle.
inadequate contact at the edge connector on the search unit. The lower edge on your unit looks not to be fully on the board. Try pressing it to the left to fully seat it. Be careful not to press it outward or inward and crack the board. Also, the individual fingers can become spread and not make good contact.
Dirty keyboard or broken carry-through contacts.
Keyboards anywhere near this age need to be washed. I remove the latch solenoid, spray diluted floor stripper on it while working the buttons. This is followed by a rinse in hot, flowing water and dried with a high pressure blower (i use an electrolux vac w/clean hose and crevice too). After washing I place a drop of 20wt oil on the metal shafts of each button and the latch spline and linkage.
Any one of those may solve the problem, but they should all be checked and washing should be done.
BTW: Do yo have a service manual? What amp is in there. There were two transistor types offered; a "50 watt" and a 100w. These amps had thermal runaway problems and often the heatsinks idled hot. I have seen them replaced, somewhat awkwardly, with tube amps.
Rob-NYC
"If we believe absurdities, we shall commit atrocities" -- Voltaire