TDS1002B not booting consistently

[cesare]

I've got a bit of an issue with a TDS 1002B which is not booting consistently. However, there's a spot on the circuit board which if I heat with a hot air gun reliably allows the instrument to boot. So, my thoughts were that this was either some sort of dry solder joint, a component which only works when hot, or a problem with a via.

I've checked and re-soldered all the components nearby, and can't measure any change in the board when cold or working.

Once up and running, the board works reliably, and will reboot if I restart it for a few minutes after powered down. If I start it from cold and leave it in the stuck failing to boot state (say for 5 minutes) it will then start without applying heat.

The PSU rails look to be stable and in spec, no undue noise, no obvious short between the rails and ground. I'm just unsure where to go next. Am I likely in the right area or is there something else i've missed I should consider?

[bidrohini]

This is the service manual of TDS1000B. You may find some similarities with your version: https://www.farnell.com/datasheets/1760369.pdf