THULE IA100 Problem

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#3
That seems to be something on the 'digital side'.
I don't know if it's related, but it could be: I found a design fault with the stabilized low voltage supply to the logic and preamp. Maybe you have a bad logic supply voltage causing it to start to misbehave.

The voltage regulators are fed via resistors from the rails, and in standby, the current is low, so the input voltage before regulators goes high (35V). This is on the limit for the regulators, and over the limit for the capacitors chosen(16V). The regulators also run hot.
I suspect a lot of the failures of these amps are caused by oscillations due to destroyed caps, and oscillations then destroy regulators, and thereby all the electronics they supply..

To avoid disaster, the least you can do is to replace the capacitors around the regulators with new ones. Before the regulators (C40, C41, C76) they need to be min 36V rating (16V in schematic). Add some cooling fins to the regulators too.

I went a step further and installed a separate power supply for the low voltage. Other mods I did was new caps (monster caps on PS and a pre-charge circuit for power up), perforated top lid for better cooling, some cooling holes in the bottom to further cool hot spots on the PCB. Sounds beautiful and will probably last a very long time.
 
#4
I think it's bingo !!
I have just recovered an IA100 which has several problems and I went directly to the logic supply and found the same thing.
I think I will graft him another transformer to solve this problem, then I will see for the rest.
thanks Rallyfinnen 😉
 
#7

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