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Good work ! Comments:.
63-9895 subs to 63-9896 also Only $6 back then ! Use the 4.7meg to center F & check the HV. Check CRT socket. Look & smell. Most get damaged. I dont see jail bars Arcing. Sit behind it with lights out to spot the flash. Around the anode they would sizzle from to much HV & leave carbon tracks. Clean up real good with 91% isopropyl. The 2 hole anode cap also. IIRC P## is 15-276-01 for the two holer. Chromatic ON switches to a 2nd set of controls for bright, contrast, color & tint. They are accessed through the hollow control shafts. I always ran it in off pos. |
#2
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On my 1971 Zenith hybrid I think I added 10-20M in series with the ground as it drifted over a couple of years in the early part of using it as a daily driver over a decade ago. Interestingly it stopped drifting and has been stable for years now.
If the focus divider is off the HV and has a path to ground then it will automatically discharge the HV after a few seconds...A splendid feature of that circuit.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#3
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Thank you all for your generous help! Certainly would not have gotten to this point without it.
I will make a list of items to work on a knock them off the list when I can. I think cleaning the contacts on the duramodules will also go a long way. There is definitely some carbon tracks on the socket (I believe visible in one of my early photos of the set) so that will get the cleaning treatment and possibly a replacement if its too bad. I found the source of the snap. Its my fault. There voltage divider kit I used had too short of cable for the focus and ground wires. I spliced it with the wires from the old divider (solder) then filled around the solder with silicon and heatshrinked it. Apparently it wasn't thick enough and its arcing from the solder joint to ground (about a millimeter arc). Is there a more suitable way to lengthen high voltage cables besides finding the right kit? |
#4
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It looks like the ECG or NTE HiDIV4 which is also a SK3871/DIV-4 is a nice part to have for this application. Multiple mounting options and long leads for every need. Not to confuse things but you still have the option of going to a Tripler with an internal divider. I will try to post a scan from Sams 1375 tomorrow that indicates the Late Production 25DC56 and 25DC58Z went to a 212-141 Tripler. Which was "Preferred to CR224 and R361" If you plan on watching this set, which is a really nice TV, the best advice would be to use the right part in the end, whichever direction you go with the focus divider. What you have now was useful for troubleshooting. Interesting, the Avanti series are still sought after. One of the few sets you could sell and get your money back out of it...... you would not want to quit your day job... In your previous pictures the greenish tint on the back of the CRT socket is an ominous sign. Don't forget the Degaussing thermistor from your earlier post. I can't tell from the picture if it is cracked or the lead broke off or not.
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Todd |
#5
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These are the changes documented in Sams for the 25DC56 Late Production. I haven't had any luck finding a copy of the Zenith manual. Interesting they added the spark gap as well.
__________________
Todd |
Audiokarma |
#6
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Quote:
I've got a saved search should a 212-141 show its face, but so far no luck. Unless the focus divider I am using just doesn't work out, it will probably stay as I also have a NOS 212-130 universal tripler ready for use. I agree on the socket, that will be taken apart and cleaned. Hopefully it doesn't require a replacement. I have also ordered a replacement thermistor per the service manual (surprisingly still available). The old one is cracked in half. Apparently it is common for these to just crumble away over the years. Last edited by ThePlague; 03-10-2023 at 09:56 AM. |
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Corona Dope - GC 10-5002 is the good stuff. Dod specified it for connections above 40KV on airborne radars, followed by Humidseal. We used it with the AWG-9 (Tomcat) radar. Let it dry well before shrinking the heat shrink to prevent cracking (from uncured layers within...) Double-wall heatshrink - NTE Part No: 47-23248-R (red) - 3;1 shrink ration, 3/16" and 1/4" cover 90% of electronics needs for HV insulation. Our bench test jig HV connection was jury-rigged - we used a plastic squeeze bottle like they use for ketchup in restaurants. It kept the connection from arcing - and only one hole needed drilling.
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Brian USN RET (Avionics / Cal) CET- Consumer Repair and Avionics ('88) "Capacitor Cosmetologist since '79" When fuses go to work, they quit! |
#8
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I'll be waiting for a warm day to do this outside. Thank you for the recommendations! |
#9
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Finally had a nice warm day. I was able to correctly extend the divider wires with the red-x corona and double wall shrink tubing. So far no arching!
I opened up the picture tube socket and it was pretty clean. I removed any light dirt/traces and buttoned it back up. The degaussing circuit thermistor was replaced with an equivalent IAW the service manual. I also replaced the divider resistor with the one including in the kit (I forget the ohms off the top of my head). It helped with the focus, but what you see in the pictures is maxed out. For good luck, I cleaned all of the dura-module pins and re-seated each one. Long story short, we have some real life now! I gave it a quick pass with the deguass wand and that sorted out most of the impurities. However, it is in dire need of a convergence alignment. I'm hoping that this will help with focus as I am still not impressed with it. The picture is currently wider than it out to be (need to find the horizontal adjustment) and there is some vertical linearity issues that the adjustment couldn't quite sort out. Next up is to de-oxit the control pots and work on going through the service manual for calibration. Is there anything that I should replace on the dura-modules before continuing? This TV will be a daily driver once fully up and running. Of note, I got a nasty shock when I touched the metal frame around the picture tube on the front of the TV after powering it up for the first time. It did not occur again. Not quite sure what was the cause of that. |
#10
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On the 9-57 hoz board check for a 330 ohm IIRC. go to a
1 watt film. Clean the service switch ( rear ) & normal - align sw ( top ). Semis on modules if they plug in should be cleaned. If they go int remove the socket. The sockets were more trouble than the parts. Remember when doing the conv. the center is ONLY the center. Ignore T, B, & sides. Brite & contrast should be about 1/2 turn so as not to drive it too hard. 73 Zeno |
Audiokarma |
#11
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If the set is focusing such that you can defocus by rotating the control either direction from optimum, turn down the brightness some and adjust the focus again as well as the fine tuning...If the pot is at one extreme adding something 2M resistance to the end the end it's butting up against may help.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
#12
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Hello all,
Sorry for the hiatus again. I've had time to spend a solid day working on this set. Items replaced before starting: S-84384 coil (my slug broke inside) 212-72 rectifier (mine was cracked and falling apart) I was able to replace all but the Chroma Duramodule with NOS modules that I happened upon. I added another 2M ohm to the focus pot such that I can get to either side of out of focus and then center it. Personally I think its still blurry but that is either my expectations are a little high for the set. I also noticed that the image is shifted to the right. I cannot find any horizontal position adjustments however. Following the manual and advice I just cannot seem to get this set to align properly. My left and right sides are always out of alignment against the blue no matter what is tried. Convergence strips needed maybe? Below is the best I could get after about 4 hours. Given the age of the set, what level of compromise should I expect? Last edited by ThePlague; 04-29-2023 at 06:21 PM. |
#13
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Is the vertical linearity as bad as it looks in the photo, or is it just the angle of your camera? Bad vertical linearity can affect convergence.
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#14
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The angle of the photo skews it. Its not perfect, but its not to that degree. I am going to try adjusting the purity tomorrow and see if that helps any moving forward.
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#15
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The pix is not up to how they looked. I think the CRT is a little weak.
That will make it hard to set up. Cant tell for sure from up here in NH. ! Check a few things. Boost, 1K resistor on focus pin if CRT, be sure instant on is working. Also for laffs check the CRT date codes & EIA ## to see if its OEM. Check diodes on convergence panel. 73 Zeno LFOD ! |
Audiokarma |
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