In comes the chap carrying his treasured Hacker Centurion. “Stopped working” was the fault summary. On closer interrogation under the angle poise lamp, I learned that the deck didn’t work and the fuses had blown. Ummm. It was nice to see all the original paperwork going back to the 1970s.
Well, open her up and see what’s going on. The deck, a Garrard SP25 Mk5 was removed and the cables all fell to bits as they were all rotten with damp. That worried me as the set uses these horrid end crimp resistors which fail in time, especially when damp has been around. Put the deck to one side to be played with later. Both 750mA fuses had blown. These are in the HT feed from the mains transformer. Well, not quite HT at a mere 40V! Check around we find that both rectifier diodes were short circuit. Wonder why? The big smoothing capdensor was found to be in good order. New fuses and diodes and power up using the current limiter after a check for obvious other shorts. Upon application of angry pixies, the current limit lamp flickered off and on, suggesting something awful and hideous was going on.
Removed both power amplifier modules and decided to check the pre amp section on it’s own. These things are so “old fashioned” made, separate boards, plugs and sockets, servicing heaven. Lucky as it would be had, apart from scratchy pots, the pre amp worked ok.
I admit to glaring at the output transistors blaming them for the excessive current being demanded from the national grid. Odd things marked a Z177. Yeah righ, 2N3055s I say. But on cold testing everything, nothing nasty was found. Powering up the amp modules using a bench supply showed that the excessive current was being caused by duff bias control pots. These cleaned and the speaker coupling electrolytic replaced, we now had a working system.
Attention turned to the record deck. The usual auto stop mechanism was gummed up so remove the cam assembly and clean up. The idler wheel had become hard. This meant that when the auto stop kicked in, taking it’s power from the rotating platter, it slowed and stopped. Best thing to do here is to boil the idler and rough up surfaces with a little wire wool.
All reassembled and we had a nice working bit of kit. Anyone know the record being played?