This customer’s RCF active speaker was apparently lent out and came back broken – unfortunately the negative rail mosfet and output transistors are short circuit, blew rail fuse – the woofer appears to have overheated and voice coil resulted in shorted turns which would have taken out the power amp (overdriven, probably clipping for ages!). 🙁
The SAP16P part was discontinued a while back and UK supply are around £15 each, however found another supply, just may take a bit longer to arrive. The mosfet no issue.
The driver itself though – not 100% sure on spec but I think it’s 10″ 8 ohm, rated for 300/350W with 2.5″ voicecoil, neodymium magnet. For the Direct original replacement woofer the only place found was £170 delivered, but the customer also said they may have a suitable donor.
Customer brought a 2nd RCF 310 speaker which had more issues (had attempted repair to XLR connectors and volume pot) but wanted the woofer transplant to the first unit after repair anyway. We can make good, surely!
The second module volume control was falling apart, as didn’t have mechanical support to back panel and was pulling away from PCB if nut tightened up, it was also was missing a connection pad on top side pcb, so repaired all that and added spacers to support the pot to the panel. There was further PCB trace damage to the top side of the board by the XLR connectors which needed repair.
I noticed chassis ground was tied to signal ground which wasn’t right, and this was traced to the replacement XLR connectors – interesting, the ones the customer had installed had chassis grounding to pin 1 (there are quite a few variations by Neutrik), so removed the grounding strap from the female XLR and modified the male to isolate pin1 and provide ground to chassis as it should be (same as the 1st speaker):
Now after replacement we had the expected impedance between chassis and signal ground, and after the repair and pot install:
Adjusted the quiescent current on both, tested fine, delivering 224W into 8ohm at clipping.
Customer happy got two working amps, just woofer required to complete. Customer actually has 3 of these speaker cabinets so now has a spare!