Zenith 19EC45 Vertical Problem? - Videokarma.org TV - Video

jblmar · #1 12-02-2005, 03:36 PM

Hi gang,
I have a Zenith 19EC45 with what appears to be a vertical problem. The picture is as bright and sharp as usual but the top and bottom of the picture is black. When the set is first turned on the bottom 3 to 4 inches and the top 1" or so are black. As the set warms up for a few minutes the area shrinks to
to around 1 to 2". A thermal intermittent problem would be the opposite. I suspect either the driver transistor which is commom to both the top and bottom screen transistors as well as the bias diode for the output transistors. I'll check the vertical module over the weekend. The problem is on all channels with or without the antenna connected.
Anyone have experience with this chassis?

Ron

kc8adu · #2 12-02-2005, 07:07 PM

replace all the lytics on the vertical module.
the wraparound or over heatsink ensures they get baked.
make sure the fuse is a 6/10a fast blow.often see these overfused in sets with v-out issues and these modules can start fires if overfused.

jstout66 · #3 12-02-2005, 10:51 PM

If you want, let me know the Vertical module number and I can send you one if needed. I have a ton of Chromacolor 2 modules, and actually a set with the same chassis as yours. Anyway, I'm having a senior moment and can't recall the module number off the top of my head. It's either 9-88 or 9-90 IIRC. Those Chromacolor 2's have a fantastic picture.

jblmar · #4 12-02-2005, 11:18 PM

Thanks for the responses. jstout66, thanks for the offer. I'll believe it's a 9-92 but I'll check over the weekend. I believe that the bias diode for the output transistors may be bad.
Ron

kx250rider · #5 12-03-2005, 01:24 AM

If it's a 9-92 still in there, that's the PROBLEM! That board was discontinued in the early 80s due to trouble. The update is a 9-147. Don't even fool with a 9-92... And I second kc8adu's comment on the fuse. It must be correct, and also another note is that if that fuse is open, the screen will stay black like a high voltage loss. That confused alot of techs early on

And one more comment: That is probably the best 19" TV ever built. That has the 19VDZP22 HyperFocus tube in it. Black matrix and very nice phosphors.

Charles

holmesuser01 · #6 11-08-2006, 11:18 PM

And one more comment: That is probably the best 19" TV ever built. That has the 19VDZP22 HyperFocus tube in it. Black matrix and very nice phosphors.

Charles[/QUOTE]

Its also one of the heaviest sets I've ever hauled around, too!

jstout66 · #7 12-03-2005, 07:45 AM

jblmar, I do have a 9-92 AND a 9-147. PM or e-mail me if interested. And Charles, my 19EC45 seems to have developed an intermittant problem within the last few days. Once in awhile it looks like it looses all contrast (lkooks like a negative almost) and the color gets weak at the same time. If I turn it off and back on it's fine and may not do it all day. I also notice tho that the picture isn't as good as it was. It tends to bloom if the picture control is turned to the normal range. Which module should I be looking at? It used to be fine when I used it as a daily watcher, I've had it in storage about a year, and put back in service recently.

kx250rider · #8 12-03-2005, 12:06 PM

Quote:

Originally Posted by jstout66

jblmar, I do have a 9-92 AND a 9-147. PM or e-mail me if interested. And Charles, my 19EC45 seems to have developed an intermittant problem within the last few days. Once in awhile it looks like it looses all contrast (lkooks like a negative almost) and the color gets weak at the same time. If I turn it off and back on it's fine and may not do it all day. I also notice tho that the picture isn't as good as it was. It tends to bloom if the picture control is turned to the normal range. Which module should I be looking at? It used to be fine when I used it as a daily watcher, I've had it in storage about a year, and put back in service recently.

2 things pop into mind: The Chromatic switch pushbutton is famous for the loss of contrast and flashing in & out. It's sealed, so very hard to sprayclean. Try just pressing it in & out a whole lot, and see if that fixes the problem. Otherwise, the 9-88 luminance module may have loose pins. (ALL the modules get that way once they're pulled and reinstalled). The fix for that is to tighten each pin socket with a dental pick or tiny screwdriver. You remove the module, then carefully poke each side of each pin socket so that the contact tabs are almost touching eachother. That way, when the module is pushed back onto its pin headers, the pins slip tightly between the socket contacts.

The blooming, especially when you say the TV was stored for awhile, may be a slightly gassy tube. I wouldn't worry about it, as long as the picture is sharp when the contrast is set slightly down and the sharpness is in the middle. So the tube is #1 suspect, and secondly I would look toward the HV tripler not delivering enough focus voltage at times. Any corona smell or arcing???

That's step 1 anyway...

Charles

jblmar · #9 12-04-2005, 11:09 AM

I checked the tv last night. When I disconnect the antenna, the bottom of the screen returns to normal while the top is still black, but only about 1/4". Reconnecting the antenna, the problem returns. It's a real pain to setup the oscilloscope at my parents house, so I have to do it the old fashioned way. Trial and error. It appears that when a signal is present, the wave form must be distorted. Perhaps a bad capacitor? Anyone know what the "switch" transistors function is?
TIA
Ron

jstout66 · #10 12-04-2005, 02:44 PM

Ron, I'm almost certain your problem is in that module. I'll send you one (9-147)for the cost of postage. PM or email me with your address if interested. Jamie

jblmar · #11 12-04-2005, 03:01 PM

Thanks Jamie. Is the 9-147 the same as the 9-92? I did find that tuning to and un used station or disconnecting the antenna produced different results. Without a signal, I was able to get a full screen while turning the consumer usable front panel Vertical Hold control. The problem is most likely in that circuit,
Jamie, I'll most likely take you up on your offer. Thank you so much.
Ron

holmesuser01 · #12 12-04-2005, 03:51 PM

I've seen your symptoms a hundred times, at least, on Zeniths. I used to simply replace the electrolytics on the vertical module first thing. In the rare case that there was something else wrong with the module, I always had spare modules in stock. Used to make use of a large module rebuilding service in Indiana that was pretty good, too.

jstout66 · #13 12-04-2005, 04:01 PM

yup. The 9-147 is a sub/upgrade for the 9-92. I do have a 9-92, but there is a word written on the box which I can't read, which looks like "intermittant" but am unsure. I have a large amount of Chromacolor 2 modules as I buy out dealer stock whenever it comes on eBay, as those modules are impossible to get now. I have over 80 modules due in at any time tho and most likely will have a 9-92. I can send both if you wish.

jblmar · #14 12-04-2005, 08:22 PM

holmesuser01, that's what I think too. A wave form should be produced at the cap. It should rise and fall as the small value cap charges and discharges. Next weekend I'll replace them. The problem I have is that I can't set up the 'oscope in a safe mannor at my parents house, otherwise I'd check wave forms and voltages to see what's going on. Thanks for your input.

jamie, it's good to know you as a source for parts. The picture on that set is fantastic! As for the problems you're having, clean all the contacts pins on each board with deoxit. Clean the tuner with a high quality cleaner. If you press the color switch slowly, you'll see that it has an effect on the contrast, color etc. At one point, the picture will become foggy. Similar to your problem. Don't over look the VRs behind the door. Both the manual and pre set controls should be cleaned. They're located on the bottom inside of the set. That should clear up your problems.
Ron

jstout66 · #15 12-05-2005, 05:36 AM

Thanks for the tips on my set. I will clean the contacts on the boards. My set does not have the Chromacolor button, so it isn't that problem. My set is the "low-end" one without that feature. I remember selling them new. It was an "entry level" set and IIRC sold for 349.95. Anyway... will check the contacts on the boards and will try to pop in a new 9-88. My set had the same vertical problem as yours Ron when I got it. I popped in a new 9-92. I have a 1975 Zenith 23" console in my office and it is fantastic. NO "glitchy" problems which is nice. I know the plug in module connections have been a week point on these sets as they've aged.