zerox 22" lcd psu help

[sabre504]

Re: zerox 22" lcd psu help

Check ZD203 on the underside of the board

Also check Q201 for short

Have had both of these go on one board which caused the fuse ,thermistor and resistor R217 to blow

[swampy]

Re: zerox 22" lcd psu help

I just got my fuses today and a new 100uf 400v cap and i replaced the thermistor that had blown.
Now my new problem is that everytime i give power to the pcb the main fuse blows? I give up the damn thing

[Th3_uN1Qu3]

Re: zerox 22" lcd psu help

i need a 33uf 275v primary switching transistor

Um, never heard of a transistor rated in microfarads.

Im wondering if the primary switching transistor is causing the tick, tick, tick sound?

That sound indicates the transistor is working but the power supply is in protection mode. That usually happens when something's shorted in the secondary side. It could also be a bad controller startup cap so try replacing that too. It's a 50v cap, usually 10 or 22uF but can be other values, next to the SMPS controller IC.

[swampy]

Re: zerox 22" lcd psu help

I deffinatly used the right fuse im thinking that the thermistor got damaged when it blew the first time around.
Im having a look through my bits and i need a 33uf 275v primary switching transistor but as of yet im only finding 22uf's and 47uf's but theres time yet.
Im wondering if the primary switching transistor is causing the tick, tick, tick sound?

[Th3_uN1Qu3]

Re: zerox 22" lcd psu help

Just jumper it for now, it doesn't do much except protect the mains from the spike that occurs when the primary cap is charged.

If the thermistor blew the fuse should have too. Are you sure you used the same rating of fuse? Anyway, this indicates a short in the primary. Either the primary switching transistor or the bridge rectifier.

[swampy]

Re: zerox 22" lcd psu help

Just done some reserch and the NTC201 054 that i blew is a Thermistor im still quite new to this game.
Now im just wondering where to go from here, what to replace it with and/or where to get a replacement from.
How also can i tell what rating i need and how to check them as the only writing on the blown one is NTC 054.
Cheers guys in advance

[swampy]

Re: zerox 22" lcd psu help

Just replaced the main F201 fuse and the 400v cap and ive just blown the NTC201 054 ceramic cap.

[Th3_uN1Qu3]

Re: zerox 22" lcd psu help

Yes, but the 100uF cap has nothing to do with your issue.

[swampy]

Re: zerox 22" lcd psu help

Cheers sabre504 thats great help
Would it be ok to swap the 100uf 400v cap for a 120uf 400v cap?

[sabre504]

Re: zerox 22" lcd psu help

Forgot i had this may be of some help

[Th3_uN1Qu3]

Re: zerox 22" lcd psu help

You don't need to change the cap. And you can substitute a regular glass fuse with the same specs, there should be enough room for a fuse and a fuse holder.

[swampy]

Re: zerox 22" lcd psu help

Does anyone know of a good supplyer in the uk of these fuses T3.15A/250VAC.
On my board it is a little red box.
Im also im going to change the c201 cap (400v 100uf) as that was what i was testing when i got the blow out.

[Rtech]

Re: zerox 22" lcd psu help

Following on,F203 feeds the +14v to both the connector,and to the inverter side of the cct,so when you get it running again,one test I would do would be unsolder one side of the fuse,and then measure both the outputs,and see if the fault may be in the inverter side.

[swampy]

Re: zerox 22" lcd psu help

Confirm that of the 4 x 680uf caps,the left hand pair,have their negative side facing the other pairs negative side ?? ( cannot see if they are from the photo).

Yes they do Rtech they were one of the first things i changed .
Im not too bad with caps its just everything else
I've got another monitor that ive changed every cap in but its still having trouble to kick in, (but thats another thread )

[Rtech]

Re: zerox 22" lcd psu help

Confirm that of the 4 x 680uf caps,the left hand pair,have their negative side facing the other pairs negative side ?? ( cannot see if they are from the photo).

[jetadm123]

Re: zerox 22" lcd psu help

Thanks for the help so far peeps
I've just tested the voltage on the pins and this is what i get,
on the +14v pins im getting a bouncing reading from 0 to 1.5v
on the +5v pins im getting a bouncing reading from 2 to 3.5v.

I think i've just fubar i got a spark while i was testing the c201 cap (400v 100uf) and now it smells of sulphur and im not getting any reading at all
I've just blown the F201 fuse T3.15A/250VAC.

Hopefully, once you change the fuse, you'll be back to where you started.

[swampy]

Re: zerox 22" lcd psu help

Thanks for the help so far peeps
I've just tested the voltage on the pins and this is what i get,
on the +14v pins im getting a bouncing reading from 0 to 1.5v
on the +5v pins im getting a bouncing reading from 2 to 3.5v.

I think i've just fubar i got a spark while i was testing the c201 cap (400v 100uf) and now it smells of sulphur and im not getting any reading at all
I've just blown the F201 fuse T3.15A/250VAC.

[Th3_uN1Qu3]

Re: zerox 22" lcd psu help

I've changed the start up cap and its still ticking?

Short on one of the outputs. Check the diodes mounted on heatsinks.

[swampy]

Re: zerox 22" lcd psu help

I forgot to say the board is a Mirage PI-190DTLB board.

[swampy]

Re: zerox 22" lcd psu help

I've changed the start up cap and its still ticking? and the dc voltage from the pins on the connector on the right hand side of the power board is still fluctuating.
2 of the pins are 14+v and 2 are 5+v.