viewsonic p220f part value needed

What's it's function?

These monitors regularly blow the vertical output IC, a protective zener, and one or both 1 ohm fusible resistors supplying power to the vertical IC resulting in a horizontal line on the screen. Is that what happened to this one?

If that's the case then you need to replace the 4N35 optocoupler in the power supply as that's the culprit.

At this point I have not checked any vert stuff. It had no hv and I found the resistor in the hot ckt open and the hot bad, also a couple of broken solder joints, one being burned in the yoke socket ckt. I cracked off the outer coating on the resistor and measured around 10 ohms at about the middle of the resistor to one end so that is why the guess of about 20 ohms. I surmise that the cracked and burned solder connection on the yoke caused the hot and resistor to do a fade out. I don't have a schematic and I could draw one up for the area I am in but I thought I might pick a few brains of those who have seen this unit before.

Thanks for the info on the vert, I will check that ckt before I fire the set up.

RH34 is 1.2 ohms 2 watts. It should be a fusable type film resistor. It connects the 80 volt supply to RH41 (1 ohm 5 watts) the other side of which goes to transformer LH01 which is driven by QH22 through RH42 (.15 ohm 1 watt) to ground. Something to do with horizontal centering or linearity or something.

Ziggy

Definitely check the zener diode ZDB01 near the vertical chip ICB02 like James says. If its open in the forward direction then the main power supply is overvoltaging and you must replace the 4n35 (ICA04). And check RB30 and RB35, both 1 ohm 2 watt resistors in the vertical section. If the zener was bad its likely ICB02 is bad also. Z

gstr> Anyone know the value of RH34 in a viewsonic P220f. It appears to be

Did they just get a bad batch of 4n35's or what? I've fixed a pile of Viewsonics with that same exact problem.

That must be the case. It spans several models, too. We,ve had a 17" PF790 and a 22" P220F with the same problem. Board layouts are almost identical. Ziggy

Same here, I've come across it in the 17, 19 and 22" models, first time it happened it took me ages to track it down because the monitor would work fine for weeks at a time then blow up when I wasn't looking. Never could make it happen with the cover off, I finally had to monitor the power supply and poke around with a hair dryer and freeze spray until I found it.

Hi guys. I just picked up a P220f with what looks like the same vertical deflection problem. I'm about to check the 4n35 optoisolator to see if that is faulty. Also about to check the ICB02. basically i'm going to do voltage measurements and compare them to the data sheet. Any suggestions on a better way or anything special to look for?

I have already checked ZDB01 and it looks ok.. it should be a 36v Zener?

any suggestions or help would be really appreciated.

Thanks

-J

The IC is often good, usually one of the 0.1 ohm fusible resistors feeding it opens.