This: (one of the L15D boards in my 7-channel amplifier):
Not actually sure what caused it as all I did was change an opamp in the phase inverter buffer.
But it was quite exciting, with 
flames, noise, and magic smoke everywhere! And it even blew the VCC leg off the opamp "Is something burning?" asked my wife, "Nothing to see here, move on", I replied sheepishly 😱. Lucky I have a spare board and inverting buffer.
But I have a question. Should I have fuses between the +/-55V 500W SMPS and the L15 boards, and if so, what value fuses should I use? And should I put one fuse in the +55V rail and another in the -55V rail?
TIA, Jon.
Not actually sure what caused it as all I did was change an opamp in the phase inverter buffer.
But it was quite exciting, with flames, noise, and magic smoke everywhere! And it even blew the VCC leg off the opamp "Is something burning?" asked my wife, "Nothing to see here, move on", I replied sheepishly 😱. Lucky I have a spare board and inverting buffer.But I have a question. Should I have fuses between the +/-55V 500W SMPS and the L15 boards, and if so, what value fuses should I use? And should I put one fuse in the +55V rail and another in the -55V rail?
TIA, Jon.
IMHO you should aleays have a fuse between a power supply and the poweramp. It protects the power supply from a fault in the amplifier and as crude as fuses are. they save a lot of heartache in my experience.
Thanks, now waiting for fuseholders and fuses to arrive. I'll see if I can fix the burned L15D board, as I think I have some spare chips, mosfets, zeners etc.
Until then, I've resurrected the amplifier with a spare board and here are some photos of it temporarily back in service 🙂.
Until then, I've resurrected the amplifier with a spare board and here are some photos of it temporarily back in service 🙂.
I wondered the same, but no, it was the right way around - it's in a socket for easy replacement, rather than soldered to the board. Must have been a short somewhere but too much damage to investigate much further. Anyway, after checking it thoroughly, I've re-used the buffer with its original op-amp on the replacement board and it's all working fine, so maybe just a shorted op-amp chip. I must stop fixing things that ain't broke!
