View Full Version : Zenith 19EC45 Vertical Problem?


jblmar
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
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
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
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
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

jstout66
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
12-03-2005, 12:06 PM
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
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
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
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
12-04-2005, 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
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
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
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.

jblmar
12-10-2005, 08:21 PM
Thanks to all for your help. The board is a 9-147. C701 measured open. The problem is still there. I can't check the set with the 9-92 schematic since they are different. Anyone have or know where I can get the 9-147 schematic. I don't have the time to trace the foil side, so the schematic would be handy.
Thanks again to all for your help.
Ron

kx250rider
12-11-2005, 12:28 PM
Thanks to all for your help. The board is a 9-147. C701 measured open. The problem is still there. I can't check the set with the 9-92 schematic since they are different. Anyone have or know where I can get the 9-147 schematic. I don't have the time to trace the foil side, so the schematic would be handy.
Thanks again to all for your help.
Ron

I'd try the Sams for a later chassis; F or G (25FC45, etc). I can't remember where the cutoff is for the changeover to 9-147, but it was early in the Chromacolor series.

Charles

jblmar
12-11-2005, 04:00 PM
Thanks Charles. I'll give them a call.
Ron

jstout66
12-11-2005, 04:35 PM
Charles, was the 9-147 a sub to use for the 9-92, or did you HAVE to use the module the set came with? and Ron, I've got those modules so hollar if you have any problems repairing yours. Jamie

kx250rider
12-12-2005, 11:47 AM
The 9-147 is an update, to go in all sets that had/have the 9-92. It's a direct plug-in swap.

Charles

jblmar
12-12-2005, 03:58 PM
Hey Charles. Over the weekend, I'll check the voltage going to the board. When the set is first turned on, the bottom half of the screen is black. Not as black as the top, a shade lighter. As it warms up, it clears up. I need to find the source of that problem first. That may or may not be the board.
Ron

jblmar
12-19-2005, 12:33 PM
Had a look a the set toda and found the following,
Measured voltages to vertical board. All measured o.k.
With the back removed, the bottom of the screen remains black.
When I replaced the back panel, the picture clears up in about 15 minutes.
Remove the back and the problem is back!
Ajusted the vertical size (Vr 717). Screen size is now normal.

The problem is COLD related, not heat related. I'll ceck all the boards for cold solders.

Ron

andy
12-19-2005, 05:25 PM
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jblmar
12-19-2005, 10:39 PM
I tryed that, Andy. The problem is that the set cools faster that I can remove the back panel. With the back off, it never reaches the temperature for the problem to be visible on screen. I'll check all electrolytic caps on the video board.
Thanks for your input.
Ron

jstout66
12-19-2005, 10:46 PM
it has GOT to be the vertical module

andy
12-20-2005, 12:02 AM
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jblmar
12-20-2005, 11:31 AM
The screen area was smaller. The top and bottom were missing about 2". Voltages to the vertical board were correct, so I adjusted VR 717 (vertical size) and that corrected that problem. The remaining problem is that on set turn on from "cold" the bottom of the screem is black (about 1/5 of the screen), but you can see some picture through the black area. It takes about 15 minutes for the condition to clear up, slowly, the black area lowers until the screen is normal. Afterwards, the screen is full size and works fine. When the set cools after turn off, the problem returns.

jstout66, I cooled the vertical board with no return of the problem after the set heated up. That set is difficult to do that with since the ac plug needs to be pulled before removing the back. By that time, the set cooled enough for the problem to return.
Ron

jblmar
02-03-2006, 06:43 PM
Just an update. As of today, I haven't had the time to work on the set. Thanks to all who responded. I'll keep you posted.

Ron

kc8adu
02-04-2006, 07:13 AM
take the clip out of the cheater cord.then use a hairdryer to warm it up faster.

jblmar
02-04-2006, 12:02 PM
Thank's kc. The problem is when the set is cold, the botton 1/4 of the screen is black. When the set warms up after 10-15 minutes, the picture is fine. The opposite of a thermal intermittent.

Ron

andy
02-04-2006, 01:50 PM
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jblmar
02-04-2006, 09:30 PM
I agree. There are caps soldered to wires behind the chassis.

Ron

jblmar
07-11-2006, 04:15 PM
Hi all,
Here's an update. I haven't had a chance to look at the set for the past few months. The set now works! I was surprised when the problem occured while cold and functioned properly when warm. Intermittent problems are usually the opposite. I still believe that there is a bad electrolytic capacitor(s).
Thanks to all for helping out. I'll keep an eye out and report back.

Ron

jblmar
11-08-2006, 01:14 PM
Hi all,
Just a follow up on the set. Thanks to all for your input.
The problem has returned! I went through the PCB and found 2 capacitors that measured 0 mF. I replaced one on the output board. I need to get the other on the Raster Blanking board.
The voltage regulator (Q 201) checked out o.k on diode test and voltage test. Next step was the vertical output transistors for voltage.
A cold solder was found on the output board. Resoldering returned the proper bias voltage to Q707. All measurements on the board are now correct. On to the next board(s).
I'll replace C908 on the Raster board and post the results.
I need to go through all boards and wire soldered components in the set. If 2 caps are bad, there's more.
This set is very easy to work on. I can't setup the 'scope for lack of room to work. Have to do it the hard way.

Ron

holmesuser01
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! :thmbsp: :dammit:

jblmar
11-09-2006, 08:04 AM
Thanks Charles.
Repaired the problem last night. C908 measured 0 mF. That cap should ground the Vertical Blanking transistor to turn it on. The transistor wasn't conduction.
Thanks to all for your help and input.
A special thanks goes out to JSTOUT66 for his generious offers re replacement boards for this set. If anyone needs replacement boards, JSTOUT66 is the person to contact.:thmbsp:
Charles. The picture is fantastic. This is the 19EC45 25" Picture Tube. Cleaning of the tuner along with all pins on each PCB will result in a great picture.

A note on handling the Vertical Output PCB. It's very easy to touch the Vertical Centering or Size VR while handling the PCB for inspection. Upon completion of a repair/inspection, check to see that the picture is centered while observing a program containing CC pulses. Watch the TVs tuner, not a tape or disc. Most CC is either on the top or bottom of the screen, hidden behind the frame of the Picture Tube area. When I put the set back together last night, the CC pulses were visible. A slight 'touch-up' of the Vertical Centering control fixed the problem.

Ron