Headunit Volume Problem

[Joey-is250]

I have a problem with volume on a standard headunit in a 07 is250.It just the ordinary one,not sat nav or ML system

After about half hour to an hour of driving the sound goes totally off but headunit still functions perfect just no volume even with the volume number up to max.

First time it happened turning on and off headunit made no difference but stopping car and restarting the car the head unit worked perfect again.When no volume working turning on the head unitthere 2 popping noises true speakers which isnt there when its working 100%

Today it did it again but this time turning on and off car didn't fix it but came back to car after about an hour and it working again perfect.

Does it sound like the amp in the boot the problem?Checked all connections and used contact cleaner after first time it done it and all seem good.Also amp does not fell overly warm or over heating.

Thanks for any help or if anyone has an amp for sale at reasonable money that i could buy to rule it out please let me know.

[jackcramerr]

if there is an amp in the boot check it's inputs and outputs. that's how I will approach this. if you don't have an oscope use a DMM set to AC and play a sine wave (50hz tone). you should see higher voltage after amp and much much lower before amp. check power gnd and fuses as well.

[bobmc]

These people claim to be specialist repairers

http://www.cartronics.co.uk/Cartronics-blog/Lexus-Mark-Levinson-amp-repairs

Just found with an internet search. I've not used them or know anyone who has.