zerox 22" lcd psu help

[swampy]

Hi there everyone im new to the forum and could really do with some advise.
Im not getting any power what so ever to the monitor,
So far ive changed these caps :
Green - 470uf 25v
Red - 680uf 25v
purple - 220uf 25v
brown - 10uf 50v
and still nothing im wondering if the 100uf 400v cap might need changing.
Heres a pic of the unit.
Cheers swampy

[retiredcaps]

Re: zerox 22" lcd psu help

Im not getting any power what so ever to the monitor,

If you have a multimeter, then check the DC voltages of each of the pins on the connector on the left hand side of the power board. Your photo is too blurry, but there is a legend just above the pins. List the legend and each DC voltage.

[swampy]

Re: zerox 22" lcd psu help

cheers for that i'll get a clearer picture uploaded tomorrow.

[jetadm123]

Re: zerox 22" lcd psu help

Did you check the main fuse, F201? Also, check fuse F202, as that is for the 5V output.

If F201 checks good, try measuring the voltage across the main cap, C201. If you're in the USA, it should read 165VDC.

You should have also changed cap C206, since that is a startup cap.

[sabre504]

Re: zerox 22" lcd psu help

Looking at the burn marks on your board i would suspect the 2 mosfets
on the rear of the board are gone

[swampy]

Re: zerox 22" lcd psu help

Cheers guys the c206 start up cap is next as its dud.

[swampy]

Re: zerox 22" lcd psu help

I have'nt changed the start up cap yet but i set it up on my desk and plug'd it into the mains and you can here a tick,tick,tick sound coming from the board.
Also when i checked the dv voltage from the pins on the connector on the right hand side of the power board the voltage fluctuated.

[PlainBill]

Re: zerox 22" lcd psu help

I have'nt changed the start up cap yet but i set it up on my desk and plug'd it into the mains and you can here a tick,tick,tick sound coming from the board.
Also when i checked the dv voltage from the pins on the connector on the right hand side of the power board the voltage fluctuated.

The tick, tick, tick sound is typical of either a bad start up cap or excessive load. The fluctuating output would point to the startup cap.

PlainBill

[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.

[swampy]

Re: zerox 22" lcd psu help

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

[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

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.

[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.

[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).

[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

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

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.

[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.

[sabre504]

Re: zerox 22" lcd psu help

Forgot i had this may be of some help

[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?