Multimedia projector, blown psu

[madan1]

Hi everyone.
This is PSU from a NEC projector.
A spring got loose and shorted to ground under q201.
Blown parts found so far:
top side
fuse ( t5ah/250vac )
r115
q201
r214 ( no ohm readings )
d301 ( passing current in both directions )
d302 ( passing current in both directions )
bottom side
r208 ( no ohm readings )
r207 ( no ohm readings )

If I change the above parts will this psu work fine or there are other components which might have blown?
Also, can anyone help with the specs of r208 and r207?
I found a service menu, but there are no schematics for the psu there .

[R_J]

Re: Multimedia projector, blown psu

Have you tried to get a used one? search for ZSNE834I might be cheaper to replace than repair.

[jiroy]

Re: Multimedia projector, blown psu

The way i see it , R208 is 180 Ohms and R207 is a fuse bridge 000..
It's not bad to check all the SM resistances for outranged values .

[madan1]

Re: Multimedia projector, blown psu

Have you tried to get a used one? search for ZSNE834I might be cheaper to replace than repair.

There are few second hand ones, but I wouldn't call them "cheap". I do not know how many hours are on the lamp, so I prefer to keep the repair costs as low as possible.

The way i see it , R208 is 180 Ohms and R207 is a fuse bridge 000..
It's not bad to check all the SM resistances for outranged values .

Yeah, I also thought so.
The fat path from the burnt resistor goes straight to IC202. Unfortunately the label has faded and it reads something like 2A09d23 which is not recognized as IC . IC101 is a switch/booster and with a totally different label.

[jiroy]

Re: Multimedia projector, blown psu

There are few second hand ones, but I wouldn't call them "cheap". I do not know how many hours are on the lamp, so I prefer to keep the repair costs as low as possible.


Yeah, I also thought so.
The fat path from the burnt resistor goes straight to IC202. Unfortunately the label has faded and it reads something like 2A09d23 which is not recognized as IC . IC101 is a switch/booster and with a totally different label.

Since the label is missing , no schema , the only option now is to bet on a blown bridge fuse R207 while IC202 remained protected after it . You can put a temporary 1 or 2A Fuse for more safety testing .

[budm]

Re: Multimedia projector, blown psu

R207 is part of the Gate drive circuit which is driven by SMPS IC202 which is probably bad for sure now.
Can you read all the printings on top of that IC202 and tell us what they are?

[madan1]

Re: Multimedia projector, blown psu

Here are the best images I can take of that IC.


line 1 - *A*9D23
line 2 - 5528

I'm almost 100% sure that the first character is "2", but the third one is a mystery

[petehall347]

Re: Multimedia projector, blown psu

5528 ..
http://www.datasheet-pdf.com/PDF/FA5...lectric-729037

[madan1]

Re: Multimedia projector, blown psu

5528 ..
http://www.datasheet-pdf.com/PDF/FA5...lectric-729037

THANK YOU!

I didn't even think about searching for the 4 digits.. I thought this was a production date or something

The IC seems to be fine.. no shorted pins, but the diode d209 between the ground and the output ( pins 4 and 5 ) was shorted ( current in both directions ).

Also, in the IC documentation, page 16, the connection to the mosfet is straight, so the guess for "000" r207 was correct ( points go to jiroy ).


So the things are starting to get clear - the power surge got almost everything in that rail

[R_J]

Re: Multimedia projector, blown psu

Maybe have a look at page 33 two resistors in series one is 100 ohm one is 10 ohm

[madan1]

Re: Multimedia projector, blown psu

Maybe have a look at page 33 two resistors in series one is 100 ohm one is 10 ohm

No "1" for sure.

By the way, in the sample, for transistor is used 2sk3687.
Will it be ok to use 3687 ( which seems to be more easily obtainable ) instead of 2sk3564?

[budm]

Re: Multimedia projector, blown psu

For that Gate drive resistor to burn up like that, large amount of current has to flow through the resistor and through pin 5 output pin of that IC, so more likely the circuit om the output of the IC has gone open circuit. I WOULD replace that IC for sure.