I have an MX4000 that when I switch it on to TV at first it's a snowy picture and only after a few second the channel pictures comes up. It seems to loose the channel 1 or 2 times during the first minutes of operation. After that, when it's "warmed up" everything is fine. Anybody got a clue to what's happening?

Try tapping on the tuner module with something like a toothbrush to see if this gives any interference/dropout.

If so, usually it's bad solderings mostly on the edges of the pcb inside the module, where the pcb is soldered on the metal surrouding (you could check this with a magnifying glass).

Another troublemaker on that IF board is that big IC TDA8120 (or TBA ?); if it always goed the same way: cold start = problem, after a few mins = ok, try spraying that IC with freeze spray and see if the snowy picture returns when the IC get's cooled.

thanks iPaul I'll try that. I assume it's easy to reconize the tuner module and the IF board?

Yeah: the tuner module is actually the little ''tin'' with the aerial entry, so where you normally plug in your cable, the IF board is the board where this module is on, the TDA8120 is located on the triangle part on the upper half.