Kicker XS100 Competition - 30vAC on speaker terminals

[Dr Zeus]

The amplifier is able to produce a rail voltage of +-29.5vDC, and the opAmps are getting +-14.9vDC at the power pins.

When nothing is connected to the speaker terminal outputs or RCA inputs, the speaker terminal outputs present a 0.8vAC clean sine waveform. There is also 0.8vAC from RCA shields to amp general ground. Powered off, meter reads OL resistance on RCA sheilds referencing amp ground. in fact, the meter reads OL on RCA shields referencing almost anything inside the amplifier.

As soon as I connect my frequency generator to RCA inputs the amplifier goes straight to 29vAC across the speaker terminals, and on the scope I see a waveform like I've not seen before.

10 Volts/Div and ~2mS

[Dr Zeus]

Reading now about a surface mount fuse.... hmm checking...

EDIT: looks like the under-board surface mount fuse blew.

[Dr Zeus]

Replaced the RCA shield fuse and the amp powers and plays outside of the heatsync. Installed it back into it's shell and now the amplifier will not power up at all while the following screw is installed - My power supply strains and trips do to this being the cause of a short:

[Deadly Sones]

Had a similar problem before. I'd check to make sure nothing is shorting to the case (including transistors).

[Perry Babin]

What is the resistance from the B+ terminal to the RCA shield?

You have to use a nylon screw in the location shown in the photo above. If you don't, you'll get a ground loop if the amp is mounted to the vehicle's chassis. I find it best if you use a nylon screw that will have about 1/2" of threads above the board when the screw is screwed down to the bottom of the mounting hole. Then use a nut and an insulating washer (if you're using a steel nut) to tighten the board down. You'll need to make sure that the plastic cylinders are under the board (assuming this is like the ZR series amps) so that the board doesn't contact the metal mounting boss. If there is no cylinder or insulator, insert insulating washers between the boss and the board. There is a note about this in the ZR600 folder.

[Dr Zeus]

You have to use a nylon screw in the location shown in the photo above

Hmm This sounds like Kicker may have a design flaw because the screw pictured is the one which came out of there. Seems Kicker amps of this series have several problems or easily malfunction grounding and shielding issues.

This amp is a very large kicker and has a lot of support... I'm tempted to just leave the screw out as there are a few others holding the board down. I'll have to check how stable this is, or just go and get a nylon screw. BTW this amp has the largest transformer coil I've ever seen in any amplifier (Except the JBL GT600 Crown amp).

I'll check shield to B+ resistence tonight.

Thanks!

[Dr Zeus]

What is the resistance from the B+ terminal to the RCA shield?

I see resistence from RCA Shield to B+ at 34 ohms. Powered and referencing amp general ground, RCA shields are measuring 13.8vDC.

This amp also appears to be having some kind of grounding crisis... Sometimes the amp will power up fine when other times it will just throw my ps into protection. If I have the screw installed pictured above, the amp always throws the supply into protection.

[Perry Babin]

With one meter probe in the B+ terminal and the other on the RCA shield (or the secondary center tap), twist the transformer to see if the resistance goes from low to infinity.

[Dr Zeus]

Theres definately some variation the transformer. After playing with it for a few minutes, I now have 20 ohms across those two points. Twisting or pressing the transformer only seems to reduce ohms of resistance temporarilly. If I power cycle on-off, the resistance goes back up to 35 ohms.

At no point was I able to get anything higher than about 35 ohms.

[Dr Zeus]

I think I just figured it out. The PS fets had a load of metal flake above and under their insulators. As soon as I loosened them from the sync the resistance went from 35 ohms to OL.