Ashdown MAG 300 amp, 2004

DVM-D cold test? Amps can become radio transmitters and fry themselves without any audible indication, other than maybe some "rizzing" on the violins. Are the output devices shorted?

No , output devices, cold test , seem fine. Looking at the Fronter datasheet, the bridge has to be derated to only 3 amps at 40 deg C, which seems surprisingly low temp. This amp was all day sitting outdoors in the cloudless sun and failed after 1 hour of use in a set. So 40 deg C was quite likely exceeded, so probably the reason for failure. As constricted in space , without going off board, I see a heatsink being bolted to the replacement same rating bridge, or wiring off board and bolting to the chassis

I have had 3 Ashdown Electric Blue 180 amps with failed mains transformers so far. (Shorted primary) The replacement toroid Ashdown supply is a lot bigger.

Gareth.

I cannot see how an honest rated 8amp bridge could be in a 15mm square pack. Replacement will be 4 amp 200V rating, with a hole to take a vaned heatsink, no hole in the original (perhaps to get 8A it uses the central area). The fan airflow in these amps is fine for the output heatsink but the bridge is sheltered by the main caps and wiring knot, vane will be off-centre poking into clear air, off the edge of the board

I picked up the wrong bridge, the original Frontier one does have a central hole