The story starts with the X11's original owner (in Japan) listening to some music, there is a 'pop' and it loses a channel. Sounds pretty serious, but it does still power-on and looks and seems normal apart from the missing channel. Somehow it gets sold on Rinkya, and the new owner is a UK based AK member, who passes it directly to me for attention.
I'm going to guess here that either the (Japanese) owner, or possibly some numpty from a (Japanese) repair shop tried to fix the fault. When I inspect the inside of the amplifier I can see one new capacitor on the Power/Protection board, a UB152 bridge rectifier squashed right down onto the board with all the leads bunched up together. And almost all of the screened leads going to the upper group of rear panel RCA connectors (MM/MC, Tuner, AUX) have been untidily de-soldered.
Some of the rear panel RCA connectors on the X1/X11 are special 'shorting connectors' to stop extraneous input noise entering the amplifier - so only when they have a cable plugged in are they non-shorting. Just a guess, but I think this is what confused the numpty, I am guessing that as he found he had shorts across the input connectors, he assumed that they must be wired incorrectly
- or something? - anyway he removed most of the connections and started putting them back with the screen and inner transposed.
but stopped after he had done 2 - and must have decided the amplifier was too broken?
The squashed bridge rectifier had small explosion marks on at least two of the leads, (DC side shorted), tested and found it was 'open'. In trying to understand the above, initially I misidentified the bridge rectifier as being for the +/- 11V supply to one the MC Head Amps, possibly explaining the disconnected RCA sockets?
anyway I have now realised that it was for one of the +/- 47V low current supplies for one of the Power Amps. So I begin to tidy up the solder on the RCA connector PCB and find that the connector board has been snapped in half ! - whoever worked on it before can't have realised that you need to remove
4 screws (not 2) to release the RCA connector board containing 2 separate groups of RCA connectors. I noticed he thoughtfully
filed the snapped edges of the PCB, which means there is now a gap between the 2 pieces of board when mounted - making it much more difficult to repair.
thankfully there are no disconnected/damaged tracks). I'll be leaving it like that, as the 2 groups of connectors still have 2 securing screws each which I think is good enough.
So I ask AK member
SanthoshA for a picture of his RCA connector wiring which he kindly and quickly provided. I remount the now '2' RCA boards, and re-wire the connections. I replace the bridge rectifier, and I note that the soldering on the single replaced capacitor I mentioned was neatly done. The usual round of short circuit checks (all OP transistors are OK, drivers look fine too), and I am ready to power up for the first time via DBT and step down transformer.
It powers on fine, DC offset is fine, Bias current adjusts and although 'drifty' is predictable and as I would expect. After checking the bias and leaving it on for about ½ hour I can see no problems. I powered it up on full mains, all rails present and correct, a reset of bias and DC offset checks OK. Subsequent listening checks reveal that the amplifier is OK (both channels!) - it sounds tired, not nearly as nice as my AU-X1 - but there is a touch of class shining through nevertheless.
So, now I am now going to restore this beauty.
There is already an excellent live X11 reconditioning thread, so I won't bother to post mine here - maybe a few pictures at the end.
