Alpine CDA-9833

[Carm99]

Alpine CDA-9833
Ive got this stereo open at the moment and the small 12v fan won't run. I've tested it by itself with a Bench PS and it's working ,just not when plugged into the board when the stereo is switched on.
Any help is welcome.
Cheers.! 🙂

Here is the Service Manual.

https://data2.manualslib.com/pdf5/11...52&take=binary

[Carm99]

Here's part of the circuit.

[R_J]

The fan circuit is controlled from IC501 pin 44 so I suspect the fan won't run until it is required, if the fan is for cooling the outputs I suspect it only comes on when required, there is a HI-TEMP input on IC501 pin 87, controlled by TH501

[Carm99]

Hi
It never comes on at all.
cherrs

[R_J]

What have you checked other than applying 12v to the fan? What are the voltages on Q813 pin 4 and pin2? maybe Q812 or Q813 are bad, ZD801 could be bad, maybe R826 is open?

[redwire]

Could also check the thermistor voltage at MCU pin 87 "HI-TEMP". It seems to be 100kΩ at 25°C with 5V power and R543 15kΩ so I would guess 4.35V at room temp and it drops as things heat up. If it's 5V then the thermistor is likely open-circuit. It's an 0603. Could heat it up a little with a soldering iron. My math:
25°C gives 4.35V
40°C gives 3.79V
50°C gives 3.32V

ERTJ1VV104J

[Carm99]

Thanks for the interest and help guys. I'll get back to this at some point. Too busy at the moment.
There's no diagram for the circuit board and some have no reference so it might be difficult to find components.
Cheers