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Old 08-22-2018, 05:00 PM
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Zenith Chromacolor II - chassis 17EC45

Hi all,

I recently picked up this oldie/goodie and I figured I would get some input from the fine folks here.

I noticed when I have my NES hooked up the picture is vertically off (I'm at work but I think it was too high up, I'll check again when I get home and update the post). I was wondering if this is a voltage regulation issue, if I need to adjust the deflection yoke, or if there might be a pot I'm not seeing that could do the trick.

This guy has a ton of external pots, which is really nice, but nothing like "vertical position" that I see inside or out. I wasn't able to find much info or any schematics. Any info about this set is appreciated! (Sorry for picture quality and dust)

Pictures - https://imgur.com/a/DzRQARZ
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Old 08-22-2018, 05:28 PM
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The control would probably be called vert centering...That set may lack such a control...I'd have to dig out the schematic for a look.
You may also be able to improve it with the height/linearity controls...You'll want to have a crosshatch test pattern on the screen or end credits to a movie with evenly spaced text lines...Adjust for minimum vertical overscan AND even spacing of the lines from top to bottom (don't want everyone to become coneheads).
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Old 08-23-2018, 02:18 AM
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I used to have a set with this chassis, and I loved that set. It had the best picture I had seen on a shadow mask TV. It could look good sitting next to a Trinitron. One thing to look out for on these is the big run capacitor. If it hasn't already been replaced, it will certainly fail in very short order. An A/C supply house will have it. Also sometimes the picture can look a little bit grainy, if it isn't crystal clear, you can tweak the AGC delay and it should clear up. I'm pretty certain this set has vertical height and centering controls.
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Old 08-23-2018, 07:45 AM
zeno zeno is offline
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Vert size & centering are on the vert module. Either a
9-92 or newer & better 9-147.
You should also be sure the 4-lead cap was updated. Its
mounted on the horz output heat sink. If orange its OK.
If white it MUST be changed. Early runs did not have one. They
use IIRC 5 white caps marked 22-5001. White ones should be
changed but its not as critical.

73 Zeno
LFOD !
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Old 08-23-2018, 11:20 AM
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Quote:
Originally Posted by TUD1 View Post
I used to have a set with this chassis, and I loved that set. It had the best picture I had seen on a shadow mask TV. It could look good sitting next to a Trinitron. One thing to look out for on these is the big run capacitor. If it hasn't already been replaced, it will certainly fail in very short order. An A/C supply house will have it. Also sometimes the picture can look a little bit grainy, if it isn't crystal clear, you can tweak the AGC delay and it should clear up. I'm pretty certain this set has vertical height and centering controls.
Think you just had bad luck. Of the 5 original CCII sets I've had 0 have needed that cap changed...
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Old 08-23-2018, 03:43 PM
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That's a nice set, good to know it's in good hands.
Quote:
Originally Posted by Electronic M View Post
Think you just had bad luck. Of the 5 original CCII sets I've had 0 have needed that cap changed...
No kidding, my 1976 Electrohome used a Zenith-supplied run capacitor which I ended up changing needlessly in an attempt to remedy random brightness fluctuations. I thought it might be going bad because it was getting quite warm, but that will happen to anything mounted on a plate on top of the VRT, doi. I chased that problem around most of the time that set has been in service, finding the cause only a few days ago by accident. It had been holding up well for quite some time, then I tried to get a Sylvania remote tuner to work in there but no dice. I had been using a temporary tuner while the original awaits repairs, it's just sitting in there. Once I reconnected that the brightness started dropping out again. I finally traced the problem to a poorly grounded IF cable; I bent the tabs slightly inward on both ends, shoved the connectors back on and presto, normal brightness.
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Old 08-23-2018, 06:44 PM
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Quote:
Originally Posted by TUD1 View Post
I used to have a set with this chassis, and I loved that set. It had the best picture I had seen on a shadow mask TV. It could look good sitting next to a Trinitron. One thing to look out for on these is the big run capacitor. If it hasn't already been replaced, it will certainly fail in very short order. An A/C supply house will have it. Also sometimes the picture can look a little bit grainy, if it isn't crystal clear, you can tweak the AGC delay and it should clear up. I'm pretty certain this set has vertical height and centering controls.
I'd be happy to replace that cap but I'm not really sure what to look for. Do you think this is the replacement? This is behind the heatsink on the top right.



I just went down the Automatic Gain Control rabbit hole, I love learning about this stuff but much of it is over my head. Also I'm not sure I would be able to tell if the image is too grainy, most things are pretty grainy over RF.

If you have some direction as to where I should look let me know. There are lots of pots and I'm a little nervous to just start poking around.
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Old 08-23-2018, 06:51 PM
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Quote:
Originally Posted by zeno View Post
Vert size & centering are on the vert module. Either a
9-92 or newer & better 9-147.
You should also be sure the 4-lead cap was updated. Its
mounted on the horz output heat sink. If orange its OK.
If white it MUST be changed. Early runs did not have one. They
use IIRC 5 white caps marked 22-5001. White ones should be
changed but its not as critical.

73 Zeno
LFOD !
Thanks! I suspected it would be there but I wasn't sure. I gave it a try and it worked! The top pot is vertical size and bottom is centering.



Shot of the screen - https://imgur.com/usdLbFP
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Old 08-23-2018, 10:06 PM
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Quote:
Originally Posted by starstuff View Post
I'd be happy to replace that cap but I'm not really sure what to look for. Do you think this is the replacement? This is behind the heatsink on the top right.



I just went down the Automatic Gain Control rabbit hole, I love learning about this stuff but much of it is over my head. Also I'm not sure I would be able to tell if the image is too grainy, most things are pretty grainy over RF.

If you have some direction as to where I should look let me know. There are lots of pots and I'm a little nervous to just start poking around.
Your picture shows what looks like an Orange Drop replacement for the 22-5001 white safety capacitor. This is good news, but it's not the big run capacitor I'm talking about. This picture shows the capacitor that FAILED in my 1976 Zenith CCII 17" set similar to yours, 17GC4x chassis. It may fail, it may not, but I've had four of them go bad just in the past two years.
Attached Images
File Type: jpg IMG_5329.jpg (93.1 KB, 12 views)
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Old 08-23-2018, 10:38 PM
zeno zeno is offline
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Looks like you have the early version under run 401.
IIRC one cap behind the h out ( shown), one or 2 on the
flyback transformer & 2 or 3 on the bottom chassis. If they
are all orange no worries. The white ones open. When they do
the HV goes up apx 1.5 KV for each one opened. If it had the
4 lead cap it would be wire tied to the heat sink & is much
bigger than the 22-5001. These caps cost Zenith millions.
They had to recall about a year of sets. Thats about 20% of
17, 19, 23 & 25 inch sets sold in the US.

73 Zeno
LFOD !
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