Basic monitor test? (WG-19K7681)

[Rob2D]

Hello all! Noob here

I acquired an old cab from a friend which I hope to put running again with a PC inside. However before I get started I'd like to know if there's any life in the thing at all! My friend bought this cab and it's twin many years ago from a guy who claimed they were in perfect working order before being stored. My friend then stored them for years and now in turn, it's in my possession.

The thing is, I have no jamma board to plug into it. The guts of it look to be tidy enough, so I was wondering if I just plug this thing into the wall, will the monitor show any signs of life? Or will I just end up damaging something/myself? The transformer and power supply look OK.





Forgive my ignorance; I am trying to read up on as much as I can around here, but there's a lot to take in! I'm just eager to get going on this project

[baritonomarchetto]

The most basic test you can do is: turn on the monitor, raise the "screen" potentiometer a little (it's placed on the flyback body generally) and check your image: does it fill the visible area of the screen? Is it grey/white?
If your "image" is there (raster) your monitor is very likely good.

[Rob2D]

Thanks, I'll do that this evening so.

[Rob2D]

OK, so I plugged her in and she came to life! 

I adjusted the "screen" potentiometer as suggested (it was marked "G-2" on my flyback) and the first thing I saw was this:



After that I turned it up a bit more and then observed this:



I went a little more and the same image as above turned to white. I stopped at that, not being sure if it was OK to keep going or not

So I assume this is good news and I can press on with the build???

[Kevin Mullins]

Good... aside from being vertically collapsed. It should fill the entire screen.
See if there is a vertical size adjustment.

[baritonomarchetto]

The test shows that your high voltage unit is very likely good, but as said the image is vertically collapsed, so keep your soldering station ready!
If it was mine, i would start by replacing every single electrolithic capacitor of the chassis and see if it fixes the issue.
At this point, source a cheap board for your next tests.
Do not keep the monitor turned on for too long or your screen phosphors will suffer.

[Rob2D]

Ah I see. I'm going to print out the manual later today so I'll take a look for any vertical adjustments I can try this evening.

I also have a cap kit and soldering station on the way courtesy of ebay. Now to learn how to solder

Time to get to work on this! Much obliged fellas

[lilshawn]

replace all the caps. it's old a tired. it's going to need them.


 IC3... this is the vertical deflection IC. if there are some bad caps here it can cause all kinds of ruckus. your vertical isn't total flatline, so you may have a chance.

if it flatlines though, IC3 will probably have to be replaced.

replace c48 (100uf 35volt) for starters. i'll bet the rater will smarten up even with just that one.


but still, consider picking up a capkit for it. it's damn near 30 years old. capacitors are rated in the thousands of hours. 6000 hours is only 250 days if left on 24/7.

[Rob2D]

replace all the caps. it's old a tired. it's going to need them.

Cheers for the reply Shawn. Cap kit is already on the way, although it might not be here for a couple weeks. Has to come all the way from New Hampshire. Took a couple snaps of the chassis in it's current state just to have for reference.

See if there is a vertical size adjustment.

Yes, so I printed off the manual and gave this a go. Vertical size adjustment had no effect at all; results were the same more or less. The only noticeable differences today were that the flatline remained on screen for a lot longer this time before the stunted image showed up. No green today, only white. Also, the image was flickering like crazy. Couple of pics below for anyone interested.





This is the cap kit I have on order from syracusesemiconductors on ebay.

[baritonomarchetto]

Capkits are a very US deal, but in all the other countries you write down the rating of the bigger caps and buy some spare of the others: in the end you have all the caps your monitor needs and some spare left at the same price... and WAY FASTER

[Kevin Mullins]

Is that a Zenith made K7000a flyback I see?

Be sure to pay attention to capacitor polarity as you remove and replace them.
Check the entire chassis for cold solder joints (cracks).

[baritonomarchetto]

... and do not rely too much on the capkit caps specs: replace capacitors with spares with the exact same capacity and same or higher voltage rating. The values on the chassis caps are the right one, not those of the "per-model-universal" capkit

[lilshawn]

do the caps one at a time... note which way they are oriented... there are cases of boards with incorrect silkscreening showing wrong polarity. putting in a cap backwards is bad news bears.

[Rob2D]

I'll be sure to check and double check everything!

[Djrouge]

Hi mate, I have the same monitor - different problem but wondered if you ever got this working ok in the end?

Cheers,

Tony.

[Alaska]

Is that a Zenith made K7000a flyback I see?

Be sure to pay attention to capacitor polarity as you remove and replace them.
Check the entire chassis for cold solder joints (cracks).

Definitely a zenith flyback. I have the same make but in 25". Thankfully mine didn't need replacing. Pretty tough to come by.