I recently acquired this tuner as a birthday gift. Fortunately there is a lot of info and the schematic on the net, such as this:
http://www.glowbug.nl/radio/A5X83A.html
I was told it was working by my benefactor. However, being sceptical by nature, and having learned from my mistakes, I set about replacing the main electrolytic can comprising of C1, 1a & C2 before powering up. I'm not a believer in "reforming" old caps.
Nothing!
In addition, the steel portion of the AM dial cord kept slipping off
My fix once rewound was to bend a lip on the outer edge of the cup around which the dial cord is wound on the tuning gang cap. Not a pretty sight, but it worked!
I am very grateful for all the info on this site, it's has been immeasurably useful in gaining knowledge during these fixes.
For some reason, I found C71 missing, and a ,47micF cap from Pin 9 of B5 connected to the centre of the output RCA socket. Not sure what the previous person intended achieving there! I removed the offending item and fitted the correct cap in position.
There was now some faint audio, lurking under a terrible hum from the valve amp through which I was testing the receiver. I researched sources for hum for days, particularly on this site. I was sure the problem lay in a coupling capacitor. Tried various aerial configurations as per the diagram on the backing plate of the unit, and earthing. Nothing improved things. Using my signal tracer, I had RF clearly through to Pin 2 of B4, and around the IF can comprising S38-42. Realising the signal had gone pear-shaped between B4 and B5, I set about taking voltage readings. I had found voltages generally to be high, and had already adjusted the mains voltage selector from 220V to 245V. I found no voltage at Pin 8 of B4. Powering off, I found R19 to be open circuit. Once replaced, I powered up and got a rather much higher reading of 110V. Not the 45V I was expecting from the schematic. Anyway, to my amazement and relief, that did it. How sweet the sound. FM and AM stations all perfectly received. Hum completely gone.
My next challenge was to determine why the EM84 was so dim. An easy fix, R14 was also open circuit!
Should this unit go on the blink again, I'll start targeting resistors for sure.
