Cambridge Audio A640 repair
My Cambridge Audio A640 integrated amplifier has been suffering from drop-outs and clicks for years. I discovered that it got better after switching sources a couple of times, which forces the output relays to open and close. This led me to believe that there could be a bad contact in the output relays.
I ordered a couple of new relays, put them in and the problem is fixed! Crystal clear sound again!
Update Februari 2021: it's still working perfectly, more than 5 years after the repair and several people have told me they also fixed their A640 this way and have clear sound again. I wish everyone many more years of crystal clear music.
Overview of the main board and -encircled- the output
board
Probably needless to say: disconnect the power plug before you start
working on this!
Detailed view of the output board and indication of
the connections of the two relays. There is one relay for each channel.
I didn't take the trouble of getting the board out, as that required
disconnecting and unmounting too many other things. Just take off the
speaker connectors to loosen the board somewhat and replace the relays
from below the output board.
The new relays: Omron G2RL-2, 12V coil,
8A switching current, 250V/AC switching voltage
Alternative, if the Omron ones are unavailable:
TE Connectivity RTE24012 12V 8A DPCO Relay RTE24 (made in Switzerland)
The original relays were
MASSUSE ME-11 012-24 8A 250VAC
Dimensions: 29 x 12.7 x 15.7 mm