Xtron head unit thump noise

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I have an Xtrons head unit that's been laying around for years, it has a 7" touch screen and nav on board., the DVD did not work for some reason and I replaced it with a working one but had to swap out the boards to keep the ribbon cable connections that run from the DVD board to the main board. While i was doing that i touched my soldering iron to the screen and had to replace it as well, :eek:

All is fine now and I tried it out in my car finally, I do not use deck power for any speakers on any set ups i have installed, I currently have a very simple 2 amp system with a 4 channel amp for front and rears and a Mono block sub amp with 4 x12" subs.
I have been running a Pyle 7" DVD Deck with SD and USB slots with a multi card reader connected to the rear USB. Lately the Pyle has started to cut out sound on the left front RCA preout. I changed amps, (I have a number or them ready for use) still had the problem, changed out my long RCA cords from front to back (I have plenty of those on hand as well) took the HU out and checked the Preouts directly from board to RCA connection all wires were good, reinstalled, now I have lost the right front unless I hit a bump in the road it will start working then cuts back out again, So I gave up on that deck and enter the Xtrons.

First thing i noticed upon start up was the incredibly loud THUMP! At initial start, I turned down my amp inputs and tried again and this time it wasn't as loud but also the head unit started in a different way so it didn't send any signal to the amps as it did the 1st time.

But as soon as I made a selection on the HU to start setting it up, the THUMP was there, even just when I hit the settings button or the set time button. Plus what's even more strange is in between tracks of MP3 files, where they are recorded individually and each file is played then the next is loaded, I got the THUMP in between consecutive tracks. It's like the automatic audio mute is non existent.

I would think that every model and make has this built in as a given, what's weird is there is no noise coming from any blinkers or brake pedal, as other noisy HU I've dealt with in the past. All noises are generated directly from the circuits inside the HU? I have to ask if anyone else has owned an Xtrons HU and had similar issues or is this limited to this one and I might have a chance of repairing it? If this is common then I will have to sell it to someone who is not going to use the preamp outputs and they will be happy with it. I have turned everything way down and still it remains, it's like it's getting way too much power to the HU and it's passing every noise from a switch or even internal IC switches noises right out the Sub channel.
The good thing is all 5 channels are staying working at all times so i was correct that my Pyle has something strange going on inside it somewhere, i found nothing that would cause intermittent shorts or loss of contact inside it. For it to start working when turning or hitting a bump makes no sense when there's nothing that could be moving.

Any advice on either deck would be appreciated, I've never had these problems before and I've been doing car audio for 40 years.:geezer:
 
Head units have muting circuits that clamp the output when changing functions, settings, tracks, etc. The muting circuit in your head unit appears to be defective. I know nothing about xtron. For head units like pioneer, the muting transistors for the RCA outputs are in the circuit just before the signal leaves the head unit.

If you connect a speaker to the speaker output wires, do you get the pop?
 
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