GPX 4500 Audio problem

Hi Folks,
Wondering if anyone has had a similar problem with the 4500. After detecting for a couple of hours the volume of the threshold and volume response just drops by about three quarters. One minute the sound is normal and then it just drops dramatically in volume. I have tried 2 different batteries, 2 different leads and 2 headphones as well as speaker but the problem persists. I sent it back to minelab but they said it tested fine. Just before the problem happens there is a click, clik,click sound almost like a crackle before the total volume dramatically drops. All i can think of is that there is a defective capacitor or something in there that after a while it gets hot and shits itself. Turning it back on does not help it, neither does a short turn off. Once it has rested like overnight it is ok but then after about 1-2 hours the problem is back. Can anyone shed any light on what they may think the problem is. Very annoying after planning a trip and this happens a couple of hours in. Many thanks for your replies. Chris

Hi Chris
I would change the box again with someone else who has a 4500/5000 just to rule out external problems,then I would look for a bad solder connection within the box itself or a partially broken wire.Bad earths commonly cause this issue I've changed many a headphone lead with this problem.

Chris,
Is this machine stock standard or has it been modified?

Yep had it happen but only when i was using a lucky lark battery. When i used the minelab one it didnt do it. Try getting a hold of another battery to test if it is that or not.

My guess is it's where the headphone jack connects into the unit. If you jiggle that, mine used to come good but i had to hold it there as i detected.

Thanks for the help guys. Deutran i like the test with another box i will do that this week and see what happens. Night jar she is stock. Hoolahoopa thanks should be able to tell with Deutran's advice and thanks Piston will check it out. Great response and now to get at it, once again thanks to all!
Chris