02-03-20, 07:45 PM
Hi Mike,
as you've ruled out all other potential fails, I suspect it's the control circuit inside the cockpit. I've detected and reapired such a defect a while ago. Maybe it's the same in your unit.
The picture shows the affected part of the pcb. Most likely transistor TR34 is not working. Ignore the red coloured parts, that's from another, older discussion about manually activating the fan.
According to the marking code (DF) it's a standard NPN transistor, maybe 2SC2463-F (55V, 100mA) (those markings are not clear without ambiguity). Any similar type should also do fine. Also replacing with a wired (non-SMD) type will work. I know, it's not an easy job..
For testing you could replace the temperature sensor by a wired resistor of less than 1700 ohm. That equals ~105°C. The voltage at anode of D32 should drop from 12V down to ~1.5V, the collector of TR34 accordingly (fan relay or equivalent load must be attached).
Hope that helps.
Regards,Christian
as you've ruled out all other potential fails, I suspect it's the control circuit inside the cockpit. I've detected and reapired such a defect a while ago. Maybe it's the same in your unit.
The picture shows the affected part of the pcb. Most likely transistor TR34 is not working. Ignore the red coloured parts, that's from another, older discussion about manually activating the fan.
According to the marking code (DF) it's a standard NPN transistor, maybe 2SC2463-F (55V, 100mA) (those markings are not clear without ambiguity). Any similar type should also do fine. Also replacing with a wired (non-SMD) type will work. I know, it's not an easy job..
For testing you could replace the temperature sensor by a wired resistor of less than 1700 ohm. That equals ~105°C. The voltage at anode of D32 should drop from 12V down to ~1.5V, the collector of TR34 accordingly (fan relay or equivalent load must be attached).
Hope that helps.
Regards,Christian