Zenith Projector 1985

[mbates14]

and what concerns me is not even a hint of green. but if you want to know if your green tube is bad or not, your going to have to make an effort to do so. such as "stretch and reroute" those wires. Ive done it on this projector, and i know you can too. Like i said previously, My projector makes no noise, other than the normal whine of the sweep circuits, like you would hear in any TV. Any other noise is considered NOT normal and should be looked at seriously.

I got my projector when i was your age, and i was your age back in 2003. But ive come to learn alot with electronics since then. (i hold a degree in electronics engineering, though unemployed).

Before you go chasing around yourself in a gutter like a chicken with its head cut off. Your going to have to pull each board individually. I would start with the power supply. Then i would start with the sweep, I would then inspect the passive convergence module in the center of the unit. Then i would move on the video process board, which is the board to your right if your facing the projector with lenses in front. You could be missing a green drive, and have a corrupted blue drive. possibilites are endless here. youll have to go through each one individually and rule it out on a checklist. This is all basic troubleshooting.

When i mean pull these boards, I mean look at the underside for obviousness. Bad solder, ESR test all electrolytics, etc etc etc. Even might go as far as reading out all the resistors, and do a static check of each transistor and diode. Once you deemed the board is good, place it back into the unit. and check the next one. Also the CRT neck connection boards, dont rule these out either. zenith is known to have resistors change in value, and open on these boards, that supply critical voltages to the CRT guns. THIS IS WHY you need to swap places with CRTs to rule out the CRT and save you some headache. IF electronics is something your going to get into, your going to HAVE to learn these things, and learn to do them. (and correctly btw, ive got scars from my mistakes as a kid).

This is pretty much all i have to say at this point. When you decide to start putting some strong effort into doing these things, then let me know, and i can help you further in your endeavor.

My method of trying to figure shit out, and your parents may think your nuts if you try this, but I always pace back and forth in the room talking to myself, as if i was explaining something to another person. and when i do this, i usually catch shit that i forgot about, or overlooked. and then from there, i can figure things out.

History on my projector:

My projector was a VIP Mark 3 from lafayette. rebranded PV800 basically.

The projector came from my local school district, badly battered and abused from students. the blue CRT glass was cracked, and fluid all over the bottom of the unit and tube. some of the fluid got into the HV wires and caused an arc, which shorted out the Horizontal output transistor, or HOT.

So, yea i wasnt much off from you. hehe. first, i had to remove the gell in front of the cracked glass, and then take the blue CRT away from the metal manafold, which called for cutting off the silicone holding it into place. i then extracted the CRT, cleaned out the fluid, removed the glass and the RTV that held it into place. i never replaced the glass and fluid, i just stuck the CRT back into place once the mess was cleaned up. I proceeded to replacing the HOT. The set would fire up, and shut right back down. and this was due to a failed HV splitter off the flyback. I had to remove all the epoxy, which was NOT fun at ALL.. in the least bit. and i found the short in the windings. i rewound just that portion of the block, and dumped some 5 minute epoxy back into the block. seveal tubes of it. hehe. Then, the set fired up and worked perfectly fine. and has played since this day, and i ended up finding another splitter, so i just replaced it.

[JesusJones]

Ok I thought about the crt neck board switching last night and figured out a way to do it.
Then I went to sleep and forgot all about it hehe.

Now I'm almost half way through and need to know one thing.
AT the top of these boards connecting to the white socket part are two larger wires.
I thought these might be heater lines BUT
One of the ends of the wire goes to the HV splitter
Then the video board
The other to ground.

Could still be for the heaters I don't know.
I ask because This is the one part that is proving to be difficult in moving. And if it is for heater's It's not exactly necessary to move it. Is it?

[mbates14]

any lines going to the splitter assy are focus/G2 lines.

[JesusJones]

Alright do I also need to switch the HV lines around?

Other than this it is ready to fire up.
And wild i had the board out I measured all resistances on it. They all check in OK. And the caps aren't open either.

[mbates14]

not for testing perposes no, all you need to do is swap the necboards, but leaving the original plugs in place. (so red gets green, green gets red).

if the problem shifts, your missing a votlage, most likely from an open resistor in the neck board.

PVR4663 Zeniths were bad for this.

[JesusJones]

Alright gimmi 5 minutes to tell you what happens

Okay So I'm pretty sure I did this right and....The green did not come back on. It was the same brightness and the red wasn't exactly as bright as before but that's about it.

The green stayed the same I'd say

So my tube IS dead then?

Also the red and blue are acting up now Wont keep a still image

[radiotvnut]

I know nothing about your unit; but, I recently had an RCA big screen with a dim, blurry red screen. The problem was the focus and G2 block that contains the adjustment pots.

[mbates14]

well if you swapped the neck boards and yoke connections, BUT you left teh connections on the neck boards the same (meaning not swap them). and it stayed the same, i woudl say yes you have a dud tube.

[mbates14]

youll have to elaborate on "keeping a still image"

like is said your going to have to go through all the caps. then look at the CRTs.

[JesusJones]

My input image had a bit of audio in it......don't ask how but that was the problem.

And yea I'm done with it for now. My ESR meter should arrive Monday or Tuesday hopefully and we'll continue on from there.

Would it be typical for a dud tube to show very faint picture. But nowhere near viewing brightness

Thanks for the help so far
Rudy

[JesusJones]

I am gonna do a full check on the G2 board on my unit. I have suspected it from the start but it looked very OK
I suspected it because the green control had been switched to high Unlike the other two.

I checked all resistors on my board and they are fine.
The pot for green also checks in the same as the rest. My problem does not lie there

Also I've heard before that Zeniths safety caps will fail. There is a safety cap in the power supply right by where the noise is coming from.
I'm just wondering if these caps had a specific value. The value is not printed on these particular capacitors in my unit. There is some writing though(letters and stuff)
Just wondering...
Rudy

[radiotvnut]

Originally Posted by JesusJones

My input image had a bit of audio in it......don't ask how but that was the problem.

And yea I'm done with it for now. My ESR meter should arrive Monday or Tuesday hopefully and we'll continue on from there.

Would it be typical for a dud tube to show very faint picture. But nowhere near viewing brightness

Thanks for the help so far
Rudy

Yes, it's possible for a bad CRT to show a dim, dull picture. CRT's usually die a slow death. The picture will generally get dimmer and dimmer and fuzzier and fuzzier until there's next to nothing left.

If you are going to work on TV's, it will pay you to obtain a decent CRT tester / rejuvenator. Something like a B&K 467 or higher model number should suit your needs. They cost several hundred $ new; but, can often be purchased for a little of nothing now since the CRT is not quite as popular as it once was. There are many test sockets available for these B&K testers that will allow them to test most CRT's. You can also rejuvenate weak CRT's with these testers. Rejuvenation is not a permanent repair; but, it will buy you some time and let you see the condition of the rest of the chassis. I've had rejuvenated tubes die in minutes and I've had others that were still going a year later. Try to stay away from the '70's and older testers. The rejuvenate functions on these older models often does more harm than good and sockets are not easily available for the later tubes.

[JesusJones]

Use the link at the bottom to veiw this properly.


I have no comments one way or another with respect to this device. Please contact the author for further information.

(From: Mario Di Stefano ([email protected]).)

Here is the 'gadget' I use to rejuvenate 'tired' CRT's:

T1
o---+--------+ +------------------------------->
| )||(
M | )||(
A | )||( 6.3 or 12 Vac To Filament
I | )||( Secondary CRT Tube
N | )||( (no Polarity)
S | )||(
| )||(
o---|-----+--+ +------------------------------->
| |
| ----------------------------------------> CRT Cathode
|
| +-----+ _|_
-------------------| LP1 |-----o o------------> CRT 1st Grid
+-----+ P1


Where:

* T1 is a standard mains AC transformer.
* LP1 is a standard FILAMENT LAMP (60 - 100 W) working voltage according to mains.
* P1 Hand Pushbutton.

Other things needed (not shown):

* Mains switch (best if with overload protection or with fuse)
* 4 ISOLATED clips like the ones used in electronics to make contacts with the pins of ICs. These isolated clips ARE IMPORTANT. You don't have to touch any connection during the cleaning.

I think this circuit works better if the mains voltage is 220 Vac.

How to use it:

First we have an tired CRT (BW or colour is the same). We have poor image contrast, 'strange' brightness, also strange colours. Next we have to remove (if present) the CRT socket to its circuitry (beware to disconnect mains voltage FIRST!!!!!). At this point could be useful to discharge the HV using an isolated wire FIRST connected to CRT grey body and then to the make the contact UNDER the suction gummy which carries EHT. to the tube. It is not a dangerous voltage, but could be better not to discharge it over the body!

Now we have to identify the filament pins. Usually on the schematic circuitry of the Monitor/TV it is clearly written. If the schematic is not available, using an ohmmeter we should find the two contacts which gives a few ohms. These contacts usually are put aside each other) have to be connected to the transformer secondary of the circuit above. The Cathode and 1st grids can be found looking very closely into the tube glass (use lens and good light if necessary). Keep in mind the way the CRT electron sources are built. These usually follows this:

Cathode
| (B/W CRT tube)
V
O------+ | |
+ | | <- 1st Grid
Filament + | |
+ |**| <-Spark (read text below)
O------+ | |
| |
| |
Cathode O---------+ |
Connection |
|
1st Grid O------------+ (Damn'd ASCII graphics!)
Connection


Try to connect and turn on the transformer. The Filament in the CRT should turn on in a not-so-bright red (if it is a colour tube, we have 3 filaments on).

Now turn off the transformer again. Connect the Cathode wire to the cathode pin of the CRT Tube. Connect the 1st grid accordingly.

Turn on the transformer. FIRE button P1. If there is dust (due to aging) between the cathode and 1st grid, the circuit will blow-up it. If this happens, you could (but not always) even see the LP1 turn on and off randomly (a good cleaning gives a lamp OFF) and some sparks inside the tube. The tube collar glass now becomes hot: it is normal. You can even 'force' better sparks if you 'ting' your finger against the CRT glass (not so strong, of course). If it is a Colour CRT, you have 3 Cathodes, 3 1st grids a anyway 1 filament. Useless to say that the procedure have to be carried out for all these electrodes. A good cleaning, gives a LP1 steady OFF. If it is a steady bright or dim, means that a 'bridge' has been formed between the electrodes and there is no way to recover the tube. Turn off the mains, remove the connections, and re-apply the original socket. That's all. I'm not tired to say: BEWARE OF THE MAINS VOLTAGE: IT CAN KILL!! If you are not so skilled, don't try to do this procedure. I used this circuit lots of times. It worked almost anyway. I recovered lot of thrown away PC monitors, and now are working well....


Borrowed from http://www.repairfaq.org/sam/crtfaq.htm#crtwir



It pretty much uses a light bulb connected to the mains to BLAST dust off from the cathode and first grid.
I don't much see the need for the heaters to be on but apparently that's how he does it



Worth a shot?

[radiotvnut]

You'd be better to get a real tester so you can read the condition of the tube on the meter. You don't want to rejuv a good tube! You'll actually make it worse and/or decrease it's life. Rejuvenation not only removes the trash; it removes some of the cathode coating that emits electrons. On a good tube; there is obviously minimal gunk on the cathode. Rejuvenating such a tube will remove the material that emits electrons from the cathode. You can probably pick up a quality tester on epay for $50 or less if you play your cards right.

[JesusJones]

Alright I wont mess with it then.
And can I try changing the red and green or blue and green HV lines around.
I just want to try it out. But want to know if it will have any Bad effects
Thanks
Rudy