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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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CT169 board :)
Hi Guys... Swallow your coffee or beer before you read this or you're gonna ruin your monitor... you've been warned Went for a walk Sunday morning... came upon a yard sale. Nice rca tv sitting there, sign said not working, not worth repair, for parts only. Ten bucks. Asked the fellow what was wrong with it, he said works for about 10 minutes, then it "squishes down to the middle" for a while, then back, ad nauseum. Said to myself, aha - a bit of solder and it's in business. Picked it up today, and runs beautifully, looks fantastic, sounds fantastic- but only for 10 minutes. Some percussive maintaince brings it back just fine. Now swallow. I can't get the board out of the case! I easily removed the board support, but now can't budge the board in its slot. Tight as a drum, can't budge it. Slip a screwdriver between the case and board and twist and it might budge a hair, but gonna break before it comes out. Any of you know of the secret? Shoulda mentioned, if there's a difference this one says home theater on it... external speaker terms on the back panel and so on. Now it's half apart on the dining room table Thanks, and take care. Ken |
#2
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Nothing holds the 169 in there only sticky dirt on the track..
kip "Ken Weitzel" wrote in message news:tWHte.1755411$6l.655817@pd7tw2no... Hi Guys... Swallow your coffee or beer before you read this or you're gonna ruin your monitor... you've been warned Went for a walk Sunday morning... came upon a yard sale. Nice rca tv sitting there, sign said not working, not worth repair, for parts only. Ten bucks. Asked the fellow what was wrong with it, he said works for about 10 minutes, then it "squishes down to the middle" for a while, then back, ad nauseum. Said to myself, aha - a bit of solder and it's in business. Picked it up today, and runs beautifully, looks fantastic, sounds fantastic- but only for 10 minutes. Some percussive maintaince brings it back just fine. Now swallow. I can't get the board out of the case! I easily removed the board support, but now can't budge the board in its slot. Tight as a drum, can't budge it. Slip a screwdriver between the case and board and twist and it might budge a hair, but gonna break before it comes out. Any of you know of the secret? Shoulda mentioned, if there's a difference this one says home theater on it... external speaker terms on the back panel and so on. Now it's half apart on the dining room table Thanks, and take care. Ken |
#3
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There's probably dirt holding it back.
The cause is usually from bad capacitors in the vertical deflection circuit. With age, they can become thermo sensitive. You can find these with a heat gun, cooling spray, and an ESR meter. Jerry G. ====== |
#4
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You've taken the three 1/4" screws off the back panel that holds it to
the frame and flexed the plastic holders on each side of the back panel outwards to release the chassis? That's all there is. Solder the bad connections after scraping any glue off the top of the chassis which is easier said than done, and you'll have a nice set. |
#5
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kip wrote: Nothing holds the 169 in there only sticky dirt on the track.. Hi Kip... Thanks! Naturally you're right. Perhaps this is the first time this one's been out... sprayed it with a little wd-40 just to wet it and it slowly but surely jerked out... inch by inch. Tough part is keeping it going straight. Anyway, appears to be old dry sticky left over flux on the edge of the board.. gonna gently sand it off in case it needs to come out again. Thanks again, and take care. Ken |
#6
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Jerry G. wrote: There's probably dirt holding it back. The cause is usually from bad capacitors in the vertical deflection circuit. With age, they can become thermo sensitive. You can find these with a heat gun, cooling spray, and an ESR meter. Hi Jerry... Thanks very much, appreciate it. Seemed to be extra dried up flux on the edges of the board. Hoping that just a reflow will do, given that I can turn it on and off with just a bit of a tap on the case, but if not I'll be sure looking at the caps Oh - one more thing... I retired before these things came out... wouldn't mind touching it up while I'm at it. Is there no longer a service switch (or jumper) to completely collapse vertical? Thanks again, and take care. Ken |
#7
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I'm a pro, and don't just mean I get paid. That back panel on the
CTC169 is to be removed for service. Others don't do this. There is a metal frame on the board and between that and other things you can keep the pressure even when you pull. This is impossible when the plastic is in place. Anything stickying up the wicket makes it all worse. Once I get my hands in the right place and pull, if it doesn't come I cut the rails. RCA is great with this mounting, you spill one drop of Coke into it and it's wrecked. I worked on a CTC140 one time that had the foils peeled off in those tracks. I always take the plastic shield off a CTC or PTK169 before anything. Now realize that I can troubleshoot any of these chassis' with a dead set symptom in about 2 minutes after that, if even that long. I have literally worked on hundreds of them. I am telling you, remove the plastic backshield from the chassis. Failure to do so can result in overstressing the SMD components at the very least. Then you get intermittents that can be very hard to solve. On your last point, none of us use, well to my knowledge, service switches, even if they exist. You use the G2 and bias to get color balance with the contrast all the way down and the brightness at factory default. The color is all the way down, you get a balance down there, and make SURE you don't have retrace lines, then you crank the contrast and the drives (on that chassis it is red/blue differential and green), are what balances the high brightness areas. Some find it a bit difficult to work with this setup, but not all. There is a master setup procedure for all sets. I'll tell you but not now. I must go. The old bed/worktomorrow cross. JURB |
#8
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Ken Weitzel wrote: Hi Jerry... Hoping that just a reflow will do, given that I can turn it on and off with just a bit of a tap on the case, but if not I'll be sure looking at the caps Ken, your instincts are correct, it's not caps. Occasionally, you'll find the vertical yoke coupling cap (high value) vented, but it won't intermitt. I've had several 169s that had bad connections causing vertical loss. Oh - one more thing... I retired before these things came out... wouldn't mind touching it up while I'm at it. Is there no longer a service switch (or jumper) to completely collapse vertical? I think the 169 has a software service switch. Try holding down the menu while plugging the TV in, or holding the menu when turning it on. Like Jeff says, the best gray scale tracking is usually achieved without a service switch. Older CRTS don't track perfectly, so setting up the base screens is best done with the contrast to zero, and the picture dim. This will give you a different setting than if you did the same using a service switch, which kills *all* video. You'll then find that when you adjust the drives for best whites, it's sometimes advantageous to fudge the screens again, then back to the drives again. John |
#9
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On 21 Jun 2005 04:53:13 -0700, "John-Del" wrote:
Ken Weitzel wrote: Hi Jerry... Hoping that just a reflow will do, given that I can turn it on and off with just a bit of a tap on the case, but if not I'll be sure looking at the caps Ken, your instincts are correct, it's not caps. Occasionally, you'll find the vertical yoke coupling cap (high value) vented, but it won't intermitt. I've had several 169s that had bad connections causing vertical loss. That's one strange thing I noticed in my 6 or so years in this business...the most typical, multi-manufacturer failure of all, the cap causes vertical IC to fail...was not typical at all of most of the larger TCE sets. Tom Oh - one more thing... I retired before these things came out... wouldn't mind touching it up while I'm at it. Is there no longer a service switch (or jumper) to completely collapse vertical? I think the 169 has a software service switch. Try holding down the menu while plugging the TV in, or holding the menu when turning it on. Like Jeff says, the best gray scale tracking is usually achieved without a service switch. Older CRTS don't track perfectly, so setting up the base screens is best done with the contrast to zero, and the picture dim. This will give you a different setting than if you did the same using a service switch, which kills *all* video. You'll then find that when you adjust the drives for best whites, it's sometimes advantageous to fudge the screens again, then back to the drives again. John |
#10
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On Tue, 21 Jun 2005 20:12:27 GMT, Tom MacIntyre
wrote: On 21 Jun 2005 04:53:13 -0700, "John-Del" wrote: Ken Weitzel wrote: Hi Jerry... Ken, your instincts are correct, it's not caps. Occasionally, you'll That's one strange thing I noticed in my 6 or so years in this business...the most typical, multi-manufacturer failure of all, the cap causes vertical IC to fail...was not typical at all of most of the larger TCE sets. Tom Tom, you're correct. Vertical failures is extremely rare in those. It had to do with the vertical design RCA has done to it made the vertical circuit failure tolerant so well. Cheers, Wizard |
#11
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Hah ! After 25 years, last week I saw my very first vertical failure on
a 169. They are very rare. This was a real one, last time it was the degaussing transistor, as it kills vertical during degauss. Technically that one wasn't really vertical failure. JURB |
#12
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#13
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#14
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On Tue, 21 Jun 2005 01:02:18 GMT, Ken Weitzel
wrote: kip wrote: Nothing holds the 169 in there only sticky dirt on the track.. Hi Kip... Thanks! Naturally you're right. Perhaps this is the first time this one's been out... sprayed it with a little wd-40 just to wet it and it slowly but surely jerked out... inch by inch. Tough part is keeping it going straight. Anyway, appears to be old dry sticky left over flux on the edge of the board.. gonna gently sand it off in case it needs to come out again. Thanks again, and take care. Ken I am pretty sure it was that chassis...I worked on one once, and it worked well when out of the tray, but not when inside. It turned out that the tray was pushing a blob of solder on the edge of the board down, causing a bridge. Tom |
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