I just started taking up car audio amplifier repair as something to do to pass the time and make a buck here and there.
At the moment I've got a Polk PA660 four channel that arrived in protect mode, running my bench supply hard. Tested all the output transistors and found a pair dead. Replaced them with similar, tested good transistors. The channel now just puts out near rail voltage. Checked all over the place and couldn't seem to find anything else that looked out of place.
As I said though, I'm fairly new to this whole deal, but I have a fair amount of knowledge, so anyone that's willing to work with me on this and could teach me more bits to use on other amplifiers, that would be awesome.
Thanks in advance.
At the moment I've got a Polk PA660 four channel that arrived in protect mode, running my bench supply hard. Tested all the output transistors and found a pair dead. Replaced them with similar, tested good transistors. The channel now just puts out near rail voltage. Checked all over the place and couldn't seem to find anything else that looked out of place.
As I said though, I'm fairly new to this whole deal, but I have a fair amount of knowledge, so anyone that's willing to work with me on this and could teach me more bits to use on other amplifiers, that would be awesome.
Thanks in advance.
Check all the pre driver transistors for that channel, quite often a blown output will take other transistors with it. Greg
That may be true but the car audio forum might have somebody familiar with that amp and it's circuit. Schematic available?
Craig
Craig
dont worry your right the only true difference for a car amplifier is the power supply which instead of the usual step down steps up since the voltage is low.
the amplifier after the PSU is pretty straightforward and also quite simple in most cheap brand cases.
it gives you rail voltage? nothing smokes while it does so ? either you have some solder dropped and shoprt circuiting some traces on the pcb or the output transistors are fully open and that menas their either short circuited themselves (read dead) or something has opened them up from the previous stage transistors in which case if they stay open for some time they will probably die ,
the amplifier after the PSU is pretty straightforward and also quite simple in most cheap brand cases.
it gives you rail voltage? nothing smokes while it does so ? either you have some solder dropped and shoprt circuiting some traces on the pcb or the output transistors are fully open and that menas their either short circuited themselves (read dead) or something has opened them up from the previous stage transistors in which case if they stay open for some time they will probably die ,
Well, there's a thread open in both then, hope the mods don't mind, if y'all don't.
I know technically it's not the right way to do it, but I check for closed transistors in circuit, since a 0 ohm closed will read no matter what else is hanging out in the circuit. However, one of the small signal transistors before the outputs will read 0.47 ohms while all others (4 identical channels, only one misbehaving) read something different (my DMM's diode test and resistance test are on the same switch) but the same as each other. I'm a bit out of it at the moment since my computer just took me for a fool, but if someone over here wants to help out, let me know and I'll continue this here as well.
I know technically it's not the right way to do it, but I check for closed transistors in circuit, since a 0 ohm closed will read no matter what else is hanging out in the circuit. However, one of the small signal transistors before the outputs will read 0.47 ohms while all others (4 identical channels, only one misbehaving) read something different (my DMM's diode test and resistance test are on the same switch) but the same as each other. I'm a bit out of it at the moment since my computer just took me for a fool, but if someone over here wants to help out, let me know and I'll continue this here as well.
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