Power Acoustik TS980 sparks, blows fuses even without power on.

[BoeroBoy]

Hi all. Noob to this site here.
I've had an old Power Acoustik TS980 amp around from a previous car and I decided to put it in my sailboat lately. I wired it up in test fine bridged mono to my 12 DVC sub and it was great. Then I wanted to conceal the wires better so I drilled holes and rerouted them through hidden channels in the hull. Unfortunately I did it with all red wire and taped the ends of one to indicate ground. Naturally one end slipped off while pulling the wires through a hole and I wound up switching them like a dipsh1t. Touched the wire to the amp and sparks flew. Touched it again quickly thinking that the amp's caps were just empty and blew both 30 amp fuses... The remote was left unconnected and no sound source was connected. That's what it finally took for me to check my wiring and see it was backwards.

So I replaced the fuses and corrected my wiring. Same thing... Even without the remote, speakers, and input. I pulled the cover to look for any solder I may have melted and created a short but no luck. All looks good. Has anyone else had this experience or quick guesses as to what I may have fried?

Thanks

[Perry Babin]

Are there any large diodes near the power/ground terminals?

[BoeroBoy]

Yeah I suppose large diodes would protect a reverse hookup huh?

I don't remember seeing any, but I'll take another look.

Thanks

[BoeroBoy]

Hi Perry.
In fact I do see a large diode right next to the power terminals. Is that what typically blows in a bonehead situation like mine? Maybe I could just solder in a replacement and be on my way? Will have to dig out the multimeter I guess.

[BoeroBoy]

FYI a continuity tester shows current going both directions on that diode (unless 0there is another route). It also lights when connecting either way on the power terminals. Am I correct to assume the diode is bad?

Please excuse the blurry phone pic. Diode can be seen above power terminals separated by remote at bottom left.

[jean-paul]

Originally Posted by BoeroBoy

Unfortunately I did it with all red wire and taped the ends of one to indicate ground. Naturally one end slipped off while pulling the wires through a hole and I wound up switching them like a dipsh1t. Touched the wire to the amp and sparks flew.

Hi, it is in fact a very fortunate day for you as you have learnt a lesson why cables should not be the same color, be it AC or DC wiring. It is stupid, forbidden by law and initially seems to cost less time and money but often/always ends up in costing more time and more money anyway. Some very basic testing with a DMM would not have hurt either. In the cases where you get away with it (and sell the subject in question) the new owner will have a nice time troubleshooting a problem.

It is a bit in the same category like cutting off ISO connectors/cable harnesses (always too short too) in cars just to connect a big $ non-standard car radio without wanting to spend 8$ on an adaptor cable. If it is not yourself that will have to bother one day the new owner will. Just to mention another example of creating useless time and money consumption, mostly for other people

Please read the typenumber on the diode and replace it. Retest the device and keep some distance while switching it on and don't watch it directly. I suggest to use lighter fuses like 6A or 10A for testing. Don't even think of replacing blown fuses with wire as it falls in the same category I just mentioned. Check if there is no DC between + and - speaker terminals without shorting either one to GND. If both channels are OK you can connect speakers and a source to it.

You write that it lights and that is not normal behavior for a diode except when it is a LED If it measures continuity both ways it is definitely broken.

I hope the amp will only need a new diode. In any case please rethink this situation the next time you do a job similar to this.

[Perry Babin]

Measure the resistance across the B+ and ground terminals. If it reads approximately 0 ohms constantly, cut the diode loose from the board and measure again. If the resistance starts going up or down without the diode, the rest of the circuit may have survived.

As was suggested, power it up via a 10 amp fuse. Have ALL semiconductors tightly clamped to the heatsink BEFORE applying power.

If the amp powers up and produces clean audio, there may be no other damage. You should replace the diode. It's not absolutely necessary because the FETs will serve basically the same function but to consider it properly repaired, you'd have to replace the diode.

[BoeroBoy]

Right on! I snapped up a 863-1N5402G from Mouser and in she went.
Finally got it all hooked back up yesterday and I'm peachy keen.

Thanks guys! Lesson learned: mark that cheap red ground wire with a sharpy instead of electrical tape! Unless it's a system I care about enough to buy black wire...

J