|
Zenith 19L25 Chassis Restoration - Advice?
I think I'll be getting started on my Zenith L1846R sometime soon, so I've been sorting out the parts list I'll need to put together. I already have a good list of all the capacitors that are gonna have to go, but while I was at it, I went ahead and checked around on the resistors, too. Among other things...
Here's one thing that I decided to get out of the way early: http://img830.imageshack.us/img830/7654/img0166at.jpg The original plastic cover over the yoke had deteriorated and created a mess of black shards that I'm still finding all over the place. Testing those resistors was getting pretty boring, so one night I decided to make a cover myself. It's just a bunch of thin card-stock type paper from a folder rolled up, cut, trimmed, and coated in duct and electrical tape. It holds my magnetic rings nicely, but I'll want to go back and seal this thing over with something heat-resistant. Plastic coat and engine paint should work. A fellow told me that he remembered these sets having faulty screen resistors near the horizontal output tube. I found a bunch of resistors going from pin to pin that aren't listed in my schematics: http://img831.imageshack.us/img831/1228/img0171q.jpg I found one resistor in the parts list that was called a "screen resistor." It was a 200 ohm resistor. It's way over by the tuner stuff, though. There's another near the horizontal output tube that looks similar but I haven't figured it out yet: http://img836.imageshack.us/img836/6324/img0168i.jpg Both those read very little resistance. Here's something else I haven't seen before: http://img825.imageshack.us/img825/3006/img0173c.jpg Schematic calls it an "integrator." Looks just like a ceramic cap with three leads. I also noticed that the getter on my horizontal output tube looks a little hazy... http://img839.imageshack.us/img839/6708/img0180u.jpg And now, something I really need some advice on: My flyback! http://img835.imageshack.us/img835/2546/img0181l.jpg Looks kinda grody. Doesn't help much that it was right in the path of those falling chunks of plastic from the yoke cover. This is the first time I've popped the cover off the top of the high-voltage cage. I only managed to clean up around the 1B3 before because I could reach it from the back and it was covered in smut. But, the flyback itself is surrounded in filth and seems to have a coat of wax peeling off, which you can see there in the picture. I've read that getting dirty and falling apart like that can lead to serious problems. I hope there's something I can do to clean it up and keep it in one piece! |
That resistor with the coil around it will check really low, you are measuring the coil mostly and not the resistor.
The black things with the color bands are capacitors, Black Beauties, Bumblebees, whatever you call them, they need to be replaced. I wouldn't worry about the integrator or the resistors at this point, I would recap first then check resistors if you have any issues. The flyback needs to be re coated with something, most Zenith Flys seem to be cracking and flaking even when they work OK. I'd probably clean off that old wax and then coat it with Low Acid Silicone Rubber. You have to be very careful not to break off any of the very fine wires while you're doing it of course. This stuff here works good for insulating too: http://www.aervoe.com/paints_coating...y-Coating.html |
Thanks for the advice on the flyback! Yeah, I need to figure out how to get this out of there safely so I can clean it up. It's only got two screws that hold this assembly under the chassis, but past that there's just the wires leading to it. They go through some tight rubber fittings and have to be pulled through partway just to get the flyback loose from underneath but it only comes out so far. I'm not sure of a good way to undo those wires other than unsoldering them from the flyback, which seems iffy since I'd have to get a soldering iron so close to all that wax.
I'll find a way to get to this so I can clean it up and coat it. I presume this flyback was fine. I was able to get a perfectly squared image that filled up the screen before, but there was no sync any which way. Also no sound. But yeah, I just was poking around through these resistors in the meantime because I knew I'd have to place another order again later if any were bad so I wanted to see if there was anything that stuck out to me in advance. So far, only two that seem to be out of spec. I did find an annoying number of bumblebee's in there. In total, I think I have about 37 caps to replace. |
2 Questions!
First, as I go about ordering the electrolytic caps, I noticed that a few of the value's I need for this set are out of stock. I can order the same value of the next available higher voltage rating, or exceed the value without having to go up and thus save a bit on price. I've read that it's safe to exceed the capacitance value in radios, so is that still fair game in a television set like this?
Also, where do I find a power cord? Simple issue; replace cord. But, I really, seriously, have no idea where to get one for my television. It's a simple brown cord, non-polarized blades, and the end that goes to the set has a plastic piece with two female ends ( like what some call a figure-8 ) and it has tabs with holes as if to use screws or rivets on either side. My cord wasn't screwed or revetted, but simply flopping around in an interlock. Don't like it. http://img838.imageshack.us/img838/2773/img0194v.jpg It's stuck in there, so I guess I'll have to drill the rivets that hold the interlock together to the back cover, but I still don't know where to find a proper cord. I've tried searching for it online, but I don't know what I'm looking for? Not too keen on power cords... |
If the cord is in otherwise good condition, don't be concerned about it. It should "float" in it's mounting to help facilitate the installation of the back, and the alignment of all the back's screws while at the same time confirming the mating of the cord to the chassis.
Hopefully, you should have some spare (loose) cords for troubleshooting, otherwise known in the trade as "cheater cords". If you do need one maybe Moyers or Mock Electronics for starters will have some NOS ones. I've got quite a stash of 'em so I really haven't given it much thought as to where to purchase them anymore... |
In the late 50's-early 60's Remington electric razor cords made perfect cheater cords for many TV brands.
|
The original cord is partially cut in half. I had it patched up just to test it before, but I need a correct replacement, or at least a brown cord that's compatible. I have cords that will work crudely for testing, but I don't want to be stuck with any of those as a final solution. So, I'm just keeping my eyes out for a NOS or at least something close. I'm not picky about originality, just appearance. The old cord didn't even say "Zenith" on it. Just "Phalo, USA" whoever that was.
|
Quote:
Phil Nelson |
Alrighty. Well, I couldn't find a 40uF in a voltage rating I needed, so I went up to a 47uF in those cases. Oddly enough, I found a 4uF rated at 550v in my parts list, but in the schematics, the circuit legend, and in the television itself on the cans, the corresponding filter cap was actually labeled as 4uF at 350v. I guess it was a typo. It made the difference between a $1 cap versus a $4 one, so I'm glad I noticed it.
|
I started recapping the set yesterday and I got a good bit more done today. Nothing but a couple bumblebee's and the electrolytics left. I noticed that one of these 47uF's I've got will replace a 40uF that appears to be first in line to the 5U4G low voltage rectifier. I recall hearing that exceeding the original capacitance rating of filter capacitors closest to the rectifier could overdraw the rectifier during the start-up surge. The 47uF's are all I could find, and it's only 15% off. Cause for concern? Just thought I'd get a second opinion on this.
|
It won't matter. You'd have to be off by a huge amount. 15% is still smaller than the normal tolerance of electrolytics.
John |
Ah, well that's good. I had figured as much, but I thought I'd make sure. I've replaced about 26 capacitors so far, so I've got less than a dozen left. It's getting close to that time... about to find out if she glows or blows. :D
UPDATE: http://img810.imageshack.us/img810/2470/img0324b.jpg Almost there... 5 more electrolytics and a couple hard-to-reach capacitors still left to go. |
New problem...
I finished recapping my Zenith tonight and was ready to test it out with the new CRT, but I now have reason to suspect that the rebuilt CRT I bought awhile back isn't really a 17LP4. While it does look nearly identical to the original, I'm having problems getting it to fit in the cabinet properly. I've managed to get it inside, but it looks "different" once you get it in there. I can see the edge of the black frame that supports the CRT more than before, and it looks higher up with more of a gap at the bottom. Worse still, is the fact that the shafts of the switches don't stick out as far as before, and I can't even get my power/volume knob on far enough to keep it in place.
I don't know what to do, honestly. I've been working on this all night, and I'm exhausted. I've pulled that chassis out 3 times so far, and I still can't get it right. Guess I'll try and figure it out tomorrow... http://img821.imageshack.us/img821/7025/img0332hb.jpg http://img837.imageshack.us/img837/6609/img0335w.jpg |
It's possible that your rebuild started life as a different tube #. These early square crts went through a few changes in geometry as they went through various manufacturing changes.
I know my 17" Sentinel is a real pain to get back in the cabinet, showing the exact same symptoms you describe. I just really have to mess with it to get the mask to line up right, or else the controls won't stick out far enough. Right now, though, I would just focus on seeing that your tv is working before fussing over this setback. |
Yeah, I was putting off my initial testing due to the fact that I was too tired to fool with it, and I was hoping to tuck the chassis back in the cabinet to clear up some of the clutter I've accumulated working on all of this. I'm excited to see how it's gonna work, but I never did even test fit this new CRT when I got it so I wanted to make sure it would work out. Looking back into it today, I should have no problem. Even putting the old CRT back in renders the same symptoms so I know it's probably a minor adjustment that I've overlooked. If the tube is in fact that much longer, the yoke can be adjusted from front to back about a half of an inch. So, I'll keep that in mind.
|
First power up after recap...
Alright, here's what the tentative end result of my recap looks like: I say tentative because there's a couple more I could replace if need be.
http://img299.imageshack.us/img299/2653/img0329j.jpg Hey leadlike, I remember asking you about that 2 x .01 ceramic and I do have two .01's to replace it but I haven't yet, because it didn't seem to be open or shorted and it was pretty hard to get to. I still may replace it anyway, though. There was also a .001 ceramic? that I couldn't find. Either way, my sound isn't working, just as I figured would happen. ( But I'll explain that later ) First off, I did get it to fit in the cabinet. I scooted the yoke back just a hair and that helped somewhat: http://img33.imageshack.us/img33/8466/img0334wk.jpg http://img46.imageshack.us/img46/7352/img0343f.jpg Haven't gotten around to painting that control panel gold yet, but it should look nice when it's done. Anyways, I finally fired it up with the new CRT and all the new capacitors and was treated to some static and pops from the speaker. I had the volume all the way down, but the noise cracked in and out for about 15 seconds or so and finally went away completely. I thought maybe the volume switch had an issue, but I fear it's actually the audio output transformer. There's a small burn on it that I had noticed before. Keep in mind, I haven't changed any tubes, either and I'm pretty sure that's going to be next on my agenda. As for the picture... well, I've got something! http://img830.imageshack.us/img830/3712/img0340a.jpg No need to worry about ion burn. Looks like it's already got one on the center of the screen. Very small and faint, though. http://img243.imageshack.us/img243/3378/img0341h.jpg I recall bandersen having issues with dark vertical lines on the Motorola he's been restoring, which I believe had something to do with the flyback? I seem to have very faint vertical lines, but brighter rather than darker. Huh... no concern, there. I can't get the vertical and horizontal to sync up into a watchable image, but I haven't had very long to play with it so. I'm not familiar with the proper technique for adjusting these things from scratch. I'm willing to bet there's a couple tubes that could use replacing, too. Using a VCR as input, I can tell from the changes in brightness that it's getting the signal at least. So, no sound, bright raster, nothing watchable. But... it feels like progress. |
Definitely progress :)
I have a burn like that on a couple sets. I think it's from the bright dot that forms when the set is turned off. I recall someone came up with a circuit to cut the beam off immediately. If you have a horizontal drive control, adjusting that may reduce those lines. It certainly helped with the Motorola although doing so reduced the overall brightness. |
You know, I thought the same thing about the tiny ion burn. Since my old CRT was so weak, the few times I tried it out, I never saw that little tiny white dot after I turned the set off. This time, I did. It was off-center, down and to the left of the old burn. I think I need to turn my yoke slightly counter-clockwise and maybe fiddle with the centering magnets.
I'll try that "hor drive" control later and see how it changes things. Mine is on the back, along with a fringe lock and buzz control. There's also a bulls-eye adjustment but that had something to do with the tuner. I remember you saying once how unnerving that first power-up can be after doing major work, and boy was I feeling it today! I've only replaced capacitors in two old radios so far, and I'm still pretty new to it. In the case of this Zenith, I've replaced almost 40 components so far, including all of the electrolytics. Since I had already ordered axial caps, I decided I wouldn't attempt to re-stuff the old cans and instead simply install the capacitors under the chassis. Figuring out how and where to position these capacitors made my brain hurt, but I'm pleased with the result. I feel that the resulting layout doesn't look too shabby, and thankfully... nothing popped, crackled, or smoked. Maybe I'm getting better at this. :scratch2: |
Hey! Almost there. I don't think you'll notice the burn once you get a picture.
Good work. John |
that is VERY encouraging! Take some measurements on your audio output transformer to confirm it is toast. I should have a spare one I could pull from a junker chassis for you.
But for now, hook up a video source and see what kind of picture you get.... |
Thanks for the encouragement, guys! I've been using a VCR as input and I thought I'd get something on channel 3 or 4, but 4 goes black the moment I turn on the VCR. I was getting something to happen on channel 6, so I went with that...? :dunno:
I had Rio Bravo playing on the VCR and finally got this: http://img802.imageshack.us/img802/4545/img0348.jpg http://img512.imageshack.us/img512/2642/img0350k.jpg Wow, John Wayne and Dean Martin are actually recognizable through that mess! I couldn't get the picture to stop overlapping from top to bottom. I did finally get the horizontal to lock and the vertical to more or less stay in place. Horizontally it would jiggle just slightly here and there, and vertically it would roll here and there and sometimes it would go dark and flip out and I'd have to readjust a few things again. I can't get it too bright without being washed out. By the way, here's what that audio output transformer looks like: http://img18.imageshack.us/img18/2507/img0314pg.jpg I took this picture while I was recapping. You can see the burn mark pretty clearly. The schematic has readings for this transformer but they're printed really small. I think it says .5 Ohms on the "out" side and either 380 or 580 Ohms on the other side. I did check for the .5 Ohms and I got more like .004 or something, shorted I guess. I'll have to take a closer look at it next time I pull out the chassis. I wonder why it crackled for a bit and gave up. Arching inside the windings? It did this the first time I ever turned on this tv, but to a much lesser degree. This time it actually sputtered quite a bit before it gave up. Hasn't made a sound since. |
VCRs are just about the worst video source-I had a tv set that was giving me vertical troubles last week, only to find that it was just the tape I was playing. Once I changed tapes, the problem stopped. VCRs can also create weird smearing effects at the top of the picture and all sorts of other fun things. Before you do anything else, get a DVD player or use your cablebox for a video source. Not sure what to tell you about the signal coming through on channel 6, though...
If your picture is locking on vertical that way, with a "stable" double image, something is making your oscillator run off frequency. It is a pretty common problem, so some voltage checks from the sync separator to yourt vertical output will hopefully find the problem. The burnt output transformer might have been caused by running the set with bad caps, or maybe something got miswired-definitely check for that possiblity before putting a new one in. |
How about this AOT?
I did a little more tinkering with the set this morning and found that I could get a surprisingly stable picture despite the overlapping image which I'm still looking into. The contrast and brightness isn't too impressive, either. Turning the contrast, brightest, and screen register all seem to do the same thing. They just wash out the image. In any case, I only ordered two resistors that I was pretty sure needed to be replaced from looking over it before, but these were mainly in the horizontal section. There appears to be a couple of 10% resistors that are out of spec, especially a 680k that measures more like 40k if even that. Unfortunately, I ordered only what I thought I needed and I have no replacements on hand. If "Sync Clip" and "sync separator" mean the same thing, I think I'm looking in the right places.
I've been meaning to take some voltage readings in this area, but I wanted to ask about leaving the high voltage out of it. I don't think I need to run the CRT at HV to take those measurements, and I was hoping it would be safe to pull the 1B3 or something to that affect. I just wanted to make sure first. Discharging the CRT seems to be no challenge at least. It doesn't spark near as much as I'd feared. Now here's something I found: http://img821.imageshack.us/img821/1278/img0363d.jpg On the left, the original audio output transformer and to the right is one I pulled from a derelict RCA radio chassis ( Model 8R74 ). The schematics for my set say that the AOT should measure 580 ohms across the "in" side, and .5 ohms on the "out" side. The one I pulled out measures (?) million ohms across the "in" and .8 across the "out" and is clearly burnt. I can't find any faults in the wiring. It was burnt when I got it, judging by pictures I took then, so I'd say it was the bad capacitors. Now this other AOT worked in the other radio and measures .5 "out" and has 3 wires on the "in" side. There's a green, a striped red and white, and a red. Green to striped, it's 582, green to red it's 595, striped to red is 14. As best I can tell, that striped wire went to the rectifier of the radio. What I'm wondering is since the resistances seem to coincide closely enough. could I use this transformer and omit the extra wire somehow or another? |
The resistance isn't as important as the turns ratio. However having said that, it'll probably work well enough. I'd use green to red and leave out striped one disconnected.
John |
That worked... kinda.
Well, I had to do some serious work to get it installed, but it's finally in. I left out the striped wire and went with the green and red. It was a pain to install, mainly because the bracket around the AOT had to be swapped with the other in order to fit properly and even then, the holes in the bracket had to be drilled out a bit in order for the screw holes to line up. It's because the bracket was forced into being a bit wider than before, fitting around a transformer that is literally less than a millimeter larger in width.
I put everything back together and fixed my pilot light while I was at it. Someone had a #47 in there but the bulb was too long to line up with the "window" it had to shine through in order to project the number. I swapped it for a #44 and it now works great! As for the sound... It works but it's VERY buzzy. All of the cable channels come through with a lot of loud buzz and distortion that overpowers everything. The buzz gets louder when the picture gets brighter. The VCR fairs a little better, but the buzz is still obnoxious. Plenty of volume... the tone control works nicely... but the noise is horrible. I tried adjusting the "buzz control" on the back and it only made it louder. :thumbsdn: UPDATE: I can get the buzz to go away with the VCR playing by turning the screen register up and tweaking the fine tuning and buzz control. This only works with the VCR, though. The cable channels still sound distorted beyond belief. I guess it's something about the raw cable signal. I don't have a converter box, just the VCR. I'd try the DVD but the only DVD player I have uses the red, white, and yellow connectors. This tv came with a coaxial adapter so I've been using anything that plugs in that way. |
Quote:
So there may be a weak tube, bad resistor or such in the IF strip. The audio amp is likely not a fault. But sometimes some TVs used the audio output circuit as an IF strip voltage source, they'd place the audio output circuit in series with the bank of tubes in the IF strip. But your TV probably doesn't do that, else you would have gotten no reception with the open primary of the audio output transformer. |
I see what you're saying. That's interesting... I'd always wondered what it was about bright images that would make that little buzz come through the speaker on some of televisions I've watched over the years. I'd never heard it this bad before, though! My dad even told me that he remembered a lot of televisions that buzzed back then.
I'm poking around in the IF section and checking resistors. For many of them, it's hard to say if they're good or bad since they have both ends going to ground or a coil so that they read shorted. So far, most of the one's I can get a reading on appear to be good. As for the tubes themselves, it uses 3 6CB6's. Of them, one is a red-lettered Zenith brand and likely original to the set. It looks a little cloudy in the upper half unlike the other two, so getting a few NOS 6CB6's wouldn't hurt. I'd love to be able to plug these tubes into a tester and get a simple "good" or "bad" but I can't get ahold of a tube tester to save my life. I watch them on Ebay all the time. Even old, untested emissions testers are selling for far more than they're worth, in my opinion. In regards to my overlapping vertical troubles, I did find a 680k resistor coming off the 6BE6 (sync clip) that read's more like 40k or less. There's a couple others than are "iffy" but likely not a problem. They're on the borderline of their listed tolerance. I also found out why I was getting the VCR on channel 6. When I took the tuner out before, I had turned the turret and when I put it back, it was naturally in disagreement with the controls. I took care of that easily enough. |
Quote:
The hard to find parts look to be working fine, and it's likely just a matter of finding a few bad caps or resistors. |
Resistors to the rescue...
After replacing several resistors between the sync clipper and vertical oscillator, I found that leadlike's appraisal of my vertical troubles was spot on! That helped ALOT!
http://img204.imageshack.us/img204/6448/img0369hh.jpg I still need to do some tweaking, but it's starting to look nice! I don't know if you can tell from that picture, but I've been getting a "curve" in the image towards the top of the screen. Everything starts bend off to the right in the top few inches of the picture. I also found some other horizontal jitters... http://img299.imageshack.us/img299/2497/img0372d.jpg This is from a Tweety Bird cartoon, btw. Still need to get an RF converter so I can plug in the DVD, which I'd imagine will look better than this. Still, I get the impression there's at least something amiss in my horizontal section. My sound's still buzzy, of course. I've got some new IF tubes on the way that will hopefully help that. My contrast is still pretty weak, too. Any chance that my video amp tube might need replacing? It's a 12BY7. |
The bending is probably related to the horizontal sync, so probably fixing one will solve the other. Dig around in that area for bad resistors/weak tubes.
Your screen shots look really dark-does the picture look pretty good as far as brightness and contrast go? |
Quote:
Phil Nelson |
I found that the bending a the top of the screen doesn't occur on the cable channels, so I'm thinking it's definitely the VCR. Also, that double horizontal image only happened with those cartoon tapes. Later I turned the set back on to show a friend, and I didn't get that problem then, either.
As for the brightness and contrast, I can get the screen to become fairly bright by cranking up the brightness... but increasing the contrast virtually does the same thing. It just becomes brighter until everything is barely recognizable. Turning up the screen register does the same, and I've tried various combinations with only a few rather poor compromises. The only way I could get decent contrast was to turn the screen register way down and then turn up the brightness, and the contrast would improve somewhat. However, turning the screen register down increases the buzz so badly that the image begins to jitter horizontally. So, the pictures I took appear fairly dark because I have the picture set to the best compromise between picture and sound. I have three NOS 6CB6 tubes on the way for the IF section ( GE brand for $1 a piece ) and I'm hoping that might help the buzz at least. I had just read somewhere that a washed-out, low-contrast image was sometimes the result of a bad video amp tube. So, unless there's no truth to this, I might consider picking up another 12BY7. |
Still buzzy...
The picture has improved significantly...
http://img339.imageshack.us/img339/6796/img0374wc.jpg The bad news is that the new IF amp tubes didn't help. Actually, it seems that when I change channels, the horizontal goes nuts and all the sound goes away, then after about 30 seconds or so, it eventually all suddenly comes back. All the audio is really distorted depending on the channel, and the buzz is still prevalent. I guess I'll get back to hunting through resistors and ceramic caps. |
I believe poor alignment can lead to that symptom-where it takes a minute for the picture to sync when you change channels. Your set is really turning out like the first 21" I restored-an RCA tabletop. For the longest time, I just had this faint washed-out picture, but as I replaced more and more bits, it came together.
|
If you totally ignore the audio (turn it down) and adjust for best picture, is there a combination of picture controls that gives you a nice image? Good contrast, brightness, focus?
Phil Nelson |
zenith
Also check for open peaking coils. they will give you a washed out picture.
|
Well, one thing I noticed is that the control I was calling the "screen register" is actually the A.G.C. delay. The A.G.C. isn't labeled on the control panel and it's right next to the screen control, which is unused. It's just an empty hole?
So yeah, I can get better contrast by bringing the A.G.C. delay down ( darker but more contrast ) and turning then turning the brightness up. However, the lower the A.G.C. goes, the louder the buzz, and to a certain point, the horizontal starts to jitter really bad. Last night, I figured out how to auto-program the VCR and use it as a cable box. The television's tuner may be out of alignment, but at least I can get channel 3 cleanly enough to flip through the channels on the VCR without much trouble. Many channels still need a bit of a tweaking to get the buzz to a moderate level ( fine tuning, buzz control, etc ) to where it's not perfect, but certainly watchable. Where would these peaking coils be located, if I do indeed have one that's potentially open? |
I would also double check the capacitors in the video output circuit for correct value and wiring...it looks to me as if you get a decent black at the edges of a transition to a black area but it does not last, as if there is a cap somewhere in the circuit is too small a value. Does this set have DC restore circuit?
jr |
Here's something I was wondering about ever since I recapped my set...
http://img813.imageshack.us/img813/240/img0389.jpg To mount these two filter capacitors I used the lugs of two of the vertical output tube's unused pin sockets. It was convenient this way because I could still arrange that 470 ohm resistor between them and send them both to a common ground, which is also being shared with a 47uf from the audio output tube. The big 80uF filters from the low voltage rectifier, and the 30uF filters pin 8 of the audio-out. I just thought I'd mention this in case there's a chance that there might be a problem with this arrangement. It concerned me that there might be something about the close proximity of these unrelated tubes/circuits that could cause any of the problems I've had. None of the capacitors I replaced are of the wrong values. A couple of the 40uF have been replaced with 47uF, which should be fine. If I'm reading this right, however, this .002 should be a .001? http://img691.imageshack.us/img691/4079/img0393q.jpg Oh, unless this was the .001 I was looking for...? http://img180.imageshack.us/img180/5678/img0395q.jpg There's three red "domino" caps in this set. Never dealt with them before. Anyways, I was able to watch some tv on my set last night and today with some buzz here and there. If I played old movies from the DVD player, it worked fine. But if I put in something more modern, there were sudden scenes of bright to dark and everything got buzzy. I just pulled the chassis back out again and I found a 100k resistor between the contrast control and the video amp tube that was reading about 40% out of spec, so I replaced that. I'll let you guys know if I find anything else. Oh, and I'm not sure about the DC restore circuit. I can scan some of the schematics if it would be of any help. |
YouTube video of my set playing...
Here's a clip I recorded earlier today after making some adjustments to the yoke and centering rings. I still don't have the contrast I want, and the buzz is still there on some DVD's and the cable channels, but I can certainly tune it out well enough to play these black and white movies!
http://www.youtube.com/watch?v=ofUCT57sfRM |
| All times are GMT -5. The time now is 03:02 AM. |
Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2026, Jelsoft Enterprises Ltd.
©Copyright 2012 VideoKarma.org, All rights reserved.