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#1
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Hey All!, now that i've had this set for a while i have noticed a little problem. after about 15 mins or so, the tuner drifts ever so slightly off of channel. first thing i notice is the image goes to B&w instead of color. I've reseated the chroma board, so i think it is a tuner prob. if i switch channels then back to ch 3 "which is what my converter output is" the color comes back no problem and will look good for 20 mins or longer. The chassis is a 23lc45z1 if that helps. any ideas?
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#2
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I was worried about that, and was watching this thread to see if a tuner issue cropped up. Those electronic tuners could be a pain in the ass, and were showing problems by the late 80's. It's Electronic, so there is no cleaning.
Start with the obvious... turn the AFC off, tune it in to the strongest signal/pix/ turn the AFC back ON. If it still has the problem, the tuner is a module, and you'll need to replace. If that's the case, let us know which one. It's listed on the schematic. |
#3
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The AFC switches get noisy. So do the pots in the selector.
IIRC it has 2 tuners & a tuner control board. Check the board for cold joints especially under the connectors. Some tuners had connectors on them, same deal. After that its an AFC problem which I doubt........ 73 Zeno LFOD ! |
#4
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Quote:
as far as the tuner module number i could only find 2 numbers in reference to the tuner, first is 175-5074-01 plant 12 on a sticker on the tuner and 3439626 stamped in red ink on the tuner itself. The diagram on the inside of the cabinet only list the modules on the vertical chassis. I know it says on the module to not use contact cleaner on the tuner but what is the failure mode on these tuners, corosion? can they be repaired? I used to collect and repair watches as a hobby, i think i could dismantle the tuner if i knew what to look for. |
#5
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What happens if you just leave AFC off? If you're feeding it through a modulator on channel 3, AFC shouldn't be necessary anyway.
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Audiokarma |
#6
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By the book
Turn AFC off Tune all channels for color pix without "worms" Turn AFC back on. Should be good for years now. Even with AFC off the set should work for years OK. Selector module has only the following IIRC AFC switch Channel switch 18 tuning pots AFC defeat switch ( defeats AFC during channel change ) Trouble shooting: We did change some for erratic ops IIRC. Try tuning ch3 on another slot (2 or 4) Try tapping selector, VHF tuner, TNR control board & 150-190-01 IF module. Defeat AFC by grounding the blue/white wire at tuner. Monitor the tuning voltage at tuner. Dont remember color but its NOT red, yellow or blue/white. CHECK FOR COLD JOINTS ! CU later Zeno LFOD ! |
#7
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well last night after trying the text book method that failed on channel 3, i switched the converter output and tv set to ch 4 and tuned in the set, it would detune a couple more times that evening, I fell asleep in my chair watching Svengoolie but as i awoke the next morning the set was still showing a great picture after being on all night. I think i will keep my eyes open for a 175-5074 tuner control "module and the tuner module "is this on the backside of the chassis or is it the long metal box or the left side of the chassis?" and have spares ready if i want to clean/repair these parts. Thanks everyone for their help and suggestions.
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#8
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It's the one that the tuning knob attaches to.
It's been years since I changed one, but it's basically "plug n play", If it works on CH 4, and stays that way, I wouldn't worry, but if you come across a module I would snag for a spare. The tuner is totally electronic, so there is nothing to corrode. I can't remember what the specific part failed on them, but it was common. Doug Harland would be the one to explain how that works. |
#9
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Hey everyone!, Sorry for resurrecting a long dead post but i have a new development: over the Holiday week i had a chance to install a new part. On ePay i found a new tuner control... module... selector whatever it is called. My set uses a 175-5074 module and i found a 175-5073 for cheap. The difference is the connectors and the angle of the base plate, It is used to connect it to the cabinet and tuner module which is a 175-2026 module. Well long story short, i found that the mechanical parts "variable resistor boards" are the same. this unit uses printed circuits on a ceramic substrate and are connected via a socket(s)????. I dismantled both units and swapped the new substrates for old and now the set has rock stable channels and has no de-tuning after a few days. Just thought i'd update my latest work with it's outcome. Logan
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#10
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Well done !
For future reference there are 2 major varactor tuner set-ups in Zenith CC2 sets. Early sets used separate UHF & VHF tuners ( 175- ### ) a tuner control board ( 9-###) & a selector assy ( S-##### ). Later sets used a big combo U/V tuner ( 175-#### ) & the selector assy. If you have more drift resolder the connectors on the big tuner or if it has a control board on that. If that dont do it pull the tuner & look for cold joints especially at the shield points. BTW Selectors were known to drift but I dont know why. We just swapped out the unit, it was faster & cheaper than troubleshooting it. 73 Zeno LFOD ! |
Audiokarma |
#11
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I was servicing those sets when they were relatively new. The 175-5074 and 175-5082 "tuner packages" were troublesome, and eventually Zenith started selling just the selector switch assembly as a replacement part.
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#12
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I don't suppose you might remember the zenith part number for the selector switch assembly? I'd like to find a few spares on ePay just in case.
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#13
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Also, those models had a neon lamp probably a NE-2 bulb illuminating the channel display. Set looks nice.
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Sony Trinitron is my favorite brand. My wish list: Sony KV-7010U Sony KV-1220U |
#14
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I've always been curious, did these last model 23v CRTs have the delta gun/dot phosphor CRT or were they inline? I've never seen one up close, but cant imagine why they would tool up for an inline 23v style crt with readily available onlive 25v styles.
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Honey, turn on the tv.. I'm cold! |
#15
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Zenith made CCII deltagun 23 and 25" into 1978... inline became an option on CCIIs in 76 IIRC. I believe the system 3 was all inline.
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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 |
Audiokarma |
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