Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

[quattro alex]

This is a Panasonic DVD & PVR combo that starts up and then shuts off after 30secs or so.

I got the device into service mode and this highlighted an H19 fault ( this relates to the case fan). The was not moving at all, and on closer inspection I found some polystyrene trapped in there. This was removed but the fan did not operate still, I disconnected fan from connection P7502 and tested on 9v battery and this worked fine.

I believe the fan getting stuck might have caused an over current issue at the fan motor transistors Q7505 an Q7511.

Questions:
1. Does that scenario sound likely?

2. Would a diode test confirm whether these are good/bad, if so is it positive on the single leg and probe the other 2?

[tom66]

Re: Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

What voltage do you get at FANOUT? What about at the 12.4V rail?

For Q7511 to turn on, the base-emitter voltage must exceed approx -0.6V (i.e. more negative.) For this to happen then the base voltage relative to ground should be less than about 11.8V.

Q7511 is controlled by Q7505, which pulls the base of Q7511 low. For this to happen Q7505 must receive a signal through R7660.

[quattro alex]

Re: Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

What voltage do you get at FANOUT? What about at the 12.4V rail?

For Q7511 to turn on, the base-emitter voltage must exceed approx -0.6V (i.e. more negative.) For this to happen then the base voltage relative to ground should be less than about 11.8V.

Q7511 is controlled by Q7505, which pulls the base of Q7511 low. For this to happen Q7505 must receive a signal through R7660.

I have 0v from the FANOUT

I have checked resistance values for R7660, R7574, R7540, R7583, R7539, R7538, R7525, R7571 and R7538 they're all correct.

I can confirm continuity between R7660 and Q7505 (bottom left leg)

Will I be able to test those voltages without the other boards connected?

[tom66]

Re: Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

I don't know if you can check without all boards connected but there's nothing stopping you soldering colour coded wires to the places I indicated.

[quattro alex]

Re: Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

I don't know if you can check without all boards connected but there's nothing stopping you soldering colour coded wires to the places I indicated.

Just to confirm I'll be soldering 2 leads, one onto the base and one onto the emitter of Q7511 and then negative lead of DMM will go to ground and the positive will be connected onto the other lead (take reading) , then the swap with the remaining lead?

Thank you for your suggestions.

[tom66]

Re: Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

I would also do base of Q7505. But yes like that.

[quattro alex]

Re: Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

I would also do base of Q7505. But yes like that.

Base on Q7505 is 0v on standby and when the unit is switched on

Base on Q7511 is 12.27v standby and on, but after 2 mins this drops to 11.62v and 30secs later the device powers down (standby) and the voltage goes back to 12.27v

Emitter on Q7511 is 12.30v standby and 12.27v when on.

Does this confirm an issue with Q7505 or is it further up the line?

[tom66]

Re: Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

Q5705 is not receiving a signal. Check C7587 is not shorted and R7660 is approx 10k. Trace back signal from R7660. Try checking voltage on other end of R7660, away from base of transistor.

[itacipri]

Re: Panasonic DMR-EX77 with H19 fan fault (unit shuts off)

Hello quattro alex.
Did you get the fix done?
What did you do?