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I am after receiving a lot of help here on this forum so I thought I'd post this and maybe it will help somebody out.... I have an NX750P powered cabinet.....(Yorkville)... for repair...Fuse was blown...speaker was burnt to shit.........and had some weird readings on one of the mosfets...there are two...Q14 and 15....I cut them out of the ckt and then hooked up a 100w light blub in place of the fuse.....The light blub glowed bright at first. then dimmed down to off..so I thought this is was the problem....Left the lamp hooked up and connected a speaker I had here...now the lamp glowed bright all the time.. so, put a volt meter across the woofer output harness with no load....120 volts....hooked the harness up to an 8 ohm 175W resistor and again measured the voltage.....6 volts dc across 8 ohms.....further checking showed that an 18v zener had a low resistance reading in both directions in ckt but the readings were different......There is an ic chip there.... an IR2110 and it tested kind of strange in circuit on certain pins......(D16 in parallel with another resistor and this network is connected in parallel to pins 1 and 2 on this ic.).....Removed it, installed a socket and installed a new one....before I installed the new one I did a reading on D16 again and this low reading was gone....so I went ahead and replaced both mosfets and their associated gate zeners, and this ic chip....left the lamp in circuit and connected a volt meter to the woofer output.......zero volts...hooked the output up to the resistor load.....zero volts...hooked it up to a good speaker and it worked fine.....now all I need is the proper speaker for the unit....Hopefully this should help somebody out at some point in time.....also....The NX55P which is a lower wattage out is basically the same board layout and component set-up as the 750......
Cheers,
Bernie
P.S. I checked the bad ic after I removed it and pins 1 and 2 were leaky in both directions but had different readings.....however the readings across D16 were much lower than the readings on the chip when this chip was in the circuit....
Cheers,
Bernie
P.S. I checked the bad ic after I removed it and pins 1 and 2 were leaky in both directions but had different readings.....however the readings across D16 were much lower than the readings on the chip when this chip was in the circuit....