Zenith Projector 1985 - Videokarma.org TV - Video

JesusJones · #1 10-20-2008, 01:51 PM

Found this CRT projector at a garage sale. It was only 10$ and I hoped it would be something simple that was wrong with it.

After cleaning the entire thing and powering it on. You can hear a loud crinkly/static noise coming from the HV area right after powering up. Like most Tv's do (I think this is normal, and mention it for elimination from troubleshooting)

The other thing I hear is a buzzing/ticking from near the power supply's transformer. This starts a couple seconds after powering on. Either the power supply is screwy. Or something else is making the power supply trip out. One thought was the large 680uf 200 volt capacitor. It's large and looks just slightly bulgy. Anyone think a 28 year old cap would dry up?

I have also seen the crt's flash when you flick the power off. (mainly the red one)

I post this here because the projector is basically a color TV but it has a CRT for each color. And should be similar in trouble shooting.

Here's a picture of a working one. Anyone remember ever watching one of these?
http://farm4.static.flickr.com/3248/...0c5e4c.jpg?v=0

Thanks for reading
Rudy

JesusJones · #2 10-20-2008, 08:47 PM

Alright Regardless of what I have said I now think it is an HV problem.

Using a fluorescent bulb in the dark I put it near the heavily insulated Hv lines. That go to the suction looking cups on the CRTs. When you flick power on the bulb glows momentarily. I could also see some HV leakage arcing.(Should this happen at all) Then it stops glowing. Once again when you power it off, the bulb glows momentarily.

Also when you power off the projector the CRT's often give there only sign of life at that point with a quick flash. Much like the bulb did when turning it off. This leads me to believe HV failure.

I have a few questions about the HV wires. Do these wires slowly loose there ability to insulate?

Do these wires change resistance like spark plug wires?

Or should I be more focused on the HV transformer area and horizontal deflection sections of this projector?
Any one had a similar problem with solid state?

Thanks for your time
Rudy

JesusJones · #3 10-20-2008, 11:03 PM

Okie doke

I got this bad boy singing! But it's not total victory yet. The green tube is not lighting up at all. But both blue and red are working strong.

I'm guessing i'll need a replacement crt or rebuild. Does any one know of a place I could get this done Or find the new one?

Thanks Rudy

I'll post pics once my computer will let me

Duane · #4 10-21-2008, 09:32 AM

I remember these Zenith projectors back in the 80's.Not equal to most of the data grade projectors of the same period, but good enough to give you a large picture (if you didn't mind the scan lines). I think most of these were basically video grade only, but I could be wrong.

As far as hunting down the problem with the green gun, you could start here and ask Curt
http://www.curtpalme.com/
If it's a crt rebuild,Curt could direct you to a company that still does this.

or you could take your chance with the AVS forum (CRT projectors).

rcaman · #5 10-21-2008, 10:34 AM

swap the crt boards from the red to green or blue to green i mean unplug the green board an move either the red or blue over to the green tube. dont disconnect the connectors on any board just move the red or blue to the green crt and see if you have video. you might have bad green drive from the chassis or a bad green crt board. steve

JesusJones · #6 10-21-2008, 01:05 PM

beleive it or not I've already sent curtpalme an email, he hasn't replied yet though.

Swapping the crt boards is an excelent idea. I planned on checking all the voltages on all three boards but swapping them for more instant and rock hard results sounds even better.

I'm hoping the tube is OK. I don't think finding it would be very easy. And rebuilding from what I've heard is rare and expensive.
Thanks
Rudy

mr_fixer · #7 10-21-2008, 01:45 PM

I know that you already know this, but i will say it in case you don't. Crt projectors usually have switches to turn off individual crt's during the set up and alignment process. sometimes a previous person might have flipped switches just because they can. Also Does the green crt filament light up? swapping out the crt boards is also a great idea as mentioned before.

JesusJones · #8 10-21-2008, 02:17 PM

OOOOOO switches eh? I did not know this, but it makes sense that it would.

I will take a good look over for some switches.

And yes all three filaments are glowing red as they should be.

And don't asume I know anything! I am only 17 and very clever and know alot about electronics. And have fixed and worked with tubed devices mostly.(amps, tvs)
This is my first solid state challenge. But it's the same principals.
And I am more than eager to learn.

So everything you guys tell me helps.
Thanks again
Rudy

bgadow · #9 10-21-2008, 03:01 PM

Getting a tube for that might not be too bad-I think there are a few places that do rebuilding on them. Since they are monochrome and rather small they wouldn't be so hard to do. I have seen projector crts on ebay on a regular basis.

I know where I can get a Panasonic similiar to this-the guy said I could have it, but I really don't have the room.

JesusJones · #10 10-21-2008, 07:50 PM

OK so the green is working. But it is not very bright.

Dead tube or other....???

It was probably working the whole time. I just never starred directly into it.

I tried switching the baords around but it proved to be difficult with tied in wires that didnt wanna move that freely.

But I hope the fact that it is actually working just not bright enough will bring some more conclusions...like weak crts....??(Also I noticed that the green focus or something was set to "high" unlike the red and blue that were set to medium)
Also the picture is upside down. Maybe this has to do with distance or something.....I donno

Rudy

brokenbroken · #11 10-21-2008, 11:39 PM

Have you tried injecting a video signal into this and projecting it onto a wall or something to see how it looks? You might be able to turn up the screen control on the green gun if that is even needed and get a decent picture out of this thing. Never know, you just might end up with a great ten dollar find.

JesusJones · #12 10-22-2008, 12:41 AM

Yes I tried playing some Friends.

The red plays strongly. And blue is there.
But the green plays much to weakly to get any effect from it.
And I cannot find any brightness control on this unit.

And still the picture is upside down. Was this thing ever mounted upside down?

Rudy

mr_fixer · #13 10-22-2008, 12:51 AM

Yes, It probably was a ceiling mount, but most projectors i've seen have a way to reverse the picture, some had a menu option you could select, some like my antique Barco V-star you had to individually reverse connectors on the yokes.

Bill R · #14 10-22-2008, 01:20 AM

I have a Provision 750 which is a Zenith comercial projector. To change the settings for floor/ceiling, and front/rear projection there is a board with jumpers (I think) that are changed. All you are doing is changing the yoke connections though. You really need a service manual to help with setup. There may be a service menu that will allow you to turn down the red and blue to match green. This will reduce brightness, but may make a useable picture in a dark room. These weren't very bright to start with. You may be able to find a complete set of projection tubes on ebay which would be a good idea. If you replace only green you will likely not be able to get good gray scale. And by the way do not look directly into the front of the projection tubes, it could harm your eyes.

Bill R

Duane · #15 10-22-2008, 09:15 AM

Since this is your first experience with a front projector, you really should try to find a user/install manual or seek advice from someone that knows this particular projector. If your intention is to learn how to fix them,seek some help from those who have the experience. This is not to say that there isn't anyone here that can help you, but since you are a novice, you can really cause some further damage or hurt yourself if you go at it willy nilly.I speak from experience..

The green gun gets most of the work in a 3 crt configuration.Maybe this is why it's weak. There are some G2 controls on projectors, but I'm not certain about the Zenith you have. Also, there usually is a switch that turns off each gun for sizing,geometry alignment,purity,etc. If not, then you would cap off each gun on the front and only allow the channel you want.
Some projectors have a switch that changes the image from a floor mounted position to a ceiling mount.Others have option pins that you change with jumpers.

Again I would suggest that you try posting on the AVS forum.Bunch of crt projector people who are very knowlegeable and someone may very well know your projector.

Good luck and let us know how things are progressing. Attach some pictures if you can.