zx475ti intermittent right rear rca input cutting in and out

[Schwongs]

I have a PG zx475ti I just bought, and it's already frustrating me. After driving around for a while, I began to notice the volume and "punchiness" of my sub going in and out. Half of a song would sound dull and have no punch whatsoever, while the other half would sound like it should. While listening at low volumes the sub would get drastically quieter, but if I gave the volume knob a quick turn up and back down it seemed to "kick" the amp back into shape temporarily. The sub volume would remain normal for 30 seconds or so but after a while at low volume it would cut the sub volume back down roughly in half.

I've dealt with signal problems with other amps in the past so this was my first assumption. When I got home, I tinkered with the RCA input cables to find that my right rear input wasn't working I swapped with known good cables, from a known good output on my HU, just to find the same problem so cables and HU are not the culprits. I've heard about potentiometer and crossover pot issues, so I gave all of the knobs and switches a good toggling but no dice. Problem continued.

I then saw my blue lights on the top blink out. Confused, I tapped on the top of the case and VOILA! The sub was clear and louder. I disconnected the LH RCA, and found the RH to be working again. Is this a common issue with the zx475ti amp? Are there any other issues that will cause these symptoms? Where do I start my diagnosis?

Here's my current setup.
PG zx475ti 4 channel.
Front - 4 ohm stock speakers x2
Rear - 4 ohm mtx thunder 6000 bridged

[ttocs]

sounds like some solder joints have gone bad. Technical taps are great for finding these and normally not too hard to diagnose the problem.

[Schwongs]

So this morning I decided to do a little more troubleshooting. I was trying to figure out if the problem was in the input or output side of the amp. I tried switching the rear outputs to feed off of the front input, and the problem followed. This makes me think the problem may in fact be more serious.

I decided to try switching the sub to run bridged off of the front channels, and run the speakers off of the rears. It seems to be working, but you know how these things go.

Any thoughts?

[ttocs]

now tap on the amp and see what happens. If the speaker changes that had the problem before then it is in the amp. If the same speaker/channel continues then it is something after the amp.

[stipud]

Wiggle around the RCA inputs. Likely either the RCA or the solder connecting the jacks to the board is intermittently cutting out.

[Schwongs]

UPDATE

Just as I expected.....back to square one. Last night on the way home, there was only a little (distorted and scratchy) sound coming from my right speaker (connected to the right rear channel). This is the same channel that was giving me problems before I reversed my setup. I've tried tapping, I've tried wiggling. The only thing that brings the sound back to normal is cranking the volume temporarily. It seems to kick the amp back into shape for a while, but only for a short while.

I pulled the case off last night to check the internals to look for obvious signs of damage, but couldn't see anything. I'm generally a good troubleshooter, but all these small components get a bit overwhelming.

I'll tinker with it a bit more today to see if anything changes.

[ttocs]

as he said it is probably nothing more then a bad/broken/cold solder joint that has developed some corrosion over the years. hook it up again with the top off and try some technical taps on the RCA connections. If nothing there then try some taps in other places to isolate the problem. You probably just need to find the bad connection and touch it with a solder iron or add a little solder to it to have it good as new again.

While it is apart take the time to inspect all the caps. Make sure they are not showing any signs of swelling and put a piece of paper under them to check for leaking.

[Schwongs]

Thanks for the help guys, I never did get it figured out. I tried the technical taps and everything else. Nothing. I returned it to the seller and found a SS VGA 400.2 which suited my needs better anyway, for 1/3 the price.

Thanks again, call this thread closed!