orangeart
KJF Audio Ltd.
I've managed to let it out again.
I successfully swapped my NAPA 6/3 boards for NCC 200 boards recently, all went well.
Last night I decide to change feedback caps from the standard BC128 to some FFBs, Again all went well. I decided I should re-check the bias. The method I normally use is Malcolms method of setting 7.2mV across both emitter resistors. I unfortunately managed to slip with one of the probes, not for the first time and had very brief continuity between the resistor shown in the pic and the heatsink on the collector of TR8. Note the pics are not of my board, i borrowed them from Les' site. Anyway the resistors with circles round them spectacularly set of fire. The cap next to one of them has melted as well, although I think this is collateral damage from the inferno next to it. There was smoke coming from under the board as well, i've not had a chance to look under there yet, but the resistors were so hot that it could have been the solder melting.
Anyway, apart from the obvious resistors and cap where should I start? I've got most spares available although maybe not exact models, I have the NAPA 6/3 board I could steal some parts from to get it going then replace what I need to.
Any help appreciated.
Thanks
Stefan
I successfully swapped my NAPA 6/3 boards for NCC 200 boards recently, all went well.
Last night I decide to change feedback caps from the standard BC128 to some FFBs, Again all went well. I decided I should re-check the bias. The method I normally use is Malcolms method of setting 7.2mV across both emitter resistors. I unfortunately managed to slip with one of the probes, not for the first time and had very brief continuity between the resistor shown in the pic and the heatsink on the collector of TR8. Note the pics are not of my board, i borrowed them from Les' site. Anyway the resistors with circles round them spectacularly set of fire. The cap next to one of them has melted as well, although I think this is collateral damage from the inferno next to it. There was smoke coming from under the board as well, i've not had a chance to look under there yet, but the resistors were so hot that it could have been the solder melting.
Anyway, apart from the obvious resistors and cap where should I start? I've got most spares available although maybe not exact models, I have the NAPA 6/3 board I could steal some parts from to get it going then replace what I need to.
Any help appreciated.
Thanks
Stefan