Roksan Kandy LIII amp , 2 years old

Owner has seen this thread

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and would rather I looked at it rather than the maker

Easy to blame PbF as printed all over as such. Problem is different to that above thread. For ages now the R ch has failed occassionally at switch on. Switch off and most of the time it comes up. Very rarely that ch dies in use, Then last week both ch failed at sw on , so he decided something needed doing

Anyone know how to find mechanical data on 16 amp output relays Make Finder 40.615 , clear cased so can see the contact gaps About .75mm for the R one and .5mm or so for the L. Thinking fine contact contamination and not enough mechanical punch-through. Both relays in series from one supply and TA3717 ptotector IC Or any other ideas other than checking phones socket, if wired in to affect output somehow, PbF solder looks fine. Wanging with engraver and nylon bolt has only highlighted a microphonic capacitor.

Looks like another amp where I'll make an LED mod that the owner can view through the phones socket. Bring out pcb mounted, relays-on LED ,and add a different colour one for the main rails supplies on, both viewable through the phones socket transparent plastic panel at its rear

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N_Cook
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Finder Relays search on

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just gives me a useless run around

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N_Cook

Got the combined phones socket and motorised vol pot board removed now. Phones uses switched ground contact for cutting speaker output , via relays, so not a suspect now. Can see why there are "pot" problems with these amps but not this one - YET. The PbF soldering on this board looks terrible compared to main board , no chance of the "green ring" of concave sided volcano mirror PbF finish here under a 30x . Matt grey crystalline and cracking solder so the "ring crack" of PbF likely in a few years with normal localised user induced vibration from using phones or turning the vol knob.

A technical issue - if anyone is up on the matter as twice in one month , different makers. I've found PbF solder being used on boards apparently made from substrate not specified for PbF , or rather the extra temperatures/heat reached in the soldering process. From the UL.com E number and type number these amp boards are tin-tinned for PbF use but the board material is rated 260 deg C/ 8second dwell (270 /10 for PbF , 260/10 for SnPb and 288/8 for polyimide high temp material ) so lower spec than the already lower spec (8 second dwell time) of traditional solder formulation boards.

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N_Cook

Another problem with this amp. a small DPST 5V relay switches in minor

+/-15V rails but one pole contacts welded closed. Supply side cap 220uF/ 25V and switched line has 68uF/35V which is blown on the permanent welded set of contacts, other rail ok so far. There is 000 ohm resistor down stream of each contact , any suggestions of ohmage to try replacing it with now the relay is out for replacement? contacts are 1 amp DC rated and is probably just supplying 4 dual opamps and no transistors or anything else active in the phono preamp and tape-in and tape out section. Presumably in the range 2R to 15R in each rail to limit switch on current. Presumably all those , user unused , opamps were permanently "powered" unipolar, never checked phono inputs on initial testing
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N_Cook

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