#16
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On my first attempts I was using a small pair of wire cutters to pry the edge up. It was pretty easy that way, but left ugly marks on the outside of the wider ring at the bottom of the can. With the right small jewelers flat blade screw driver I can force up the edge and then wedge it in, applying pressure along the circumference and then pry up a very short bit at a time. It gives a nice result but is tiring on the hands.
Dave |
#17
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Quote:
__________________
Vacuum tubes are used in Wisconsin to help heat your house. New Web Site under developement ME http://AntiqueTvGuy.com |
#18
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Re-stuffed the last electrolytic after the parts came in. This one is the 1000uF 3V non-polarized cap. Here are some pictures of before, cover un-crimped, the parts, back together, and back in the set. I did this for the other little electrolytics except for three that I did not have the original caps to re-stuff. I wet the paper cover before I uncrimp the end to try to keep the paper from crumbling.
Last edited by Zenith6S321; 04-20-2013 at 10:44 AM. |
#19
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My selenium rectifiers had been replaced by the time I bought the set. They had been replaced with the 5A 600PIV silicon rectifiers as shown in the first picture. The original(?) soldered-in-fuses were blown and snap on fuse holders with replacement fuses were used. This mess is kinda hidden by the rectifier cover. The plug-in dropping power resistors still measured ok, but I decided to replaced them with chassis mount power resistors. I also wanted to add the recommended 7.5 ohm dropping resistor to match the drop from the selenium rectifiers. And I wanted to put in chassis mount fuse holders. So I rewired it all. Here are pictures before and after all the changes.
Last edited by Zenith6S321; 04-20-2013 at 10:46 AM. |
#20
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I wanted to test the power supply rewiring and cap re-stuffing. The power cord was intermittent, the chassis mounted cheater socket removed, and the cheater cord cut and soldered in. So I removed the kludge and replaced the chassis mounted cheater socket. Its now back to factory configuration. I removed all of the fuses expect for the main 4.5A 400VAC supply fuse. I brought the power up on a variac with a dim-bulb while measuring the 400VDC supply rail across the 80uF 450VDC cap. At about 300VDC I saw the dim-bulb flicker brighter, heard a "pfffft" sound from under the chassis and smelled smoke!
I cut power and turned the chassis upside down. After not finding anything really wrong, I brought the power back up and saw the source of the smoke. The phenolic insulator of one of the voltage doubler capacitors had carbonized and was heating/burning/smoking intermitantly. The voltage on that capacitors' case is at 200VDC, so there is 200VDC across the phenloic insulator. I guess that's why I removed that cap from the set so many years ago. So I removed the re-stuffed caps' ground wire from the can ground lug to remove the 200VDC across the carbonized insulator and then wired the re-stuffed caps' ground directly to the other voltage doubler capacitor. Here are some pictures. Its all better now. Now to start the long process of replacing all the paper caps and out-of-tolerance resistors.... Last edited by Zenith6S321; 04-20-2013 at 10:50 AM. |
Audiokarma |
#21
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Yep, carbon tracking can cause a lot of heartache. I once had a Philco 17MT80 roundie with intermittent reds, which I traced back to a carbon track going to ground from the plate of the red output tube. I was able to grind out the carbon from the PCB with a Dremel, then fill it in with epoxy. Whole PCB would have been a loss if I hadn't been able to fix it.
__________________
Evolution... |
#22
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I've been working on measuring and replacing out-of-spec resistors and all the paper capacitors. I found that the vertical blocking oscillator transformer secondary is open. I melted it out of its tar hoping to find a simple loose connection. No such luck, the open is deep inside somewhere. I was able to find a replacement from oldradioparts.com. Here is a picture of the old and NOS part. It has a -2 where the original has a -1, but its resistance measurements match the Sams. I also have found that some of my sets resistor values match the Sams values where they differ from the RCA schematic values. And also some in my set differ from both schematics. Here is a picture of the HO screen resistor which Sams and RCA (R269) list as 11K but my set has a 10K. Its soldering looked original, but I could be wrong. I guess they are production run changes. Is it best to start with my sets original values and see if I need to change from there?
I have also found all but one of my sets white peaking coils are open. I got some replacements from oldradioparts.com but had to get some from digikey. Can modern coils of the same inductance be used as peaking coils? I think the old ones as Pi-wound, no clue on the modern ones. |
#23
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11k sounds picky - 10 k should be good.
New peaking coils should be OK unless they have so much stray C that they self-resonate in the video band. Try them, they probably work. |
#24
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Meh, people told me not to use the ferrite cored ones from Digikey, but they work just fine in my CTC-2 and 2B.
__________________
Evolution... |
#25
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Cool, thanks for the information guys. I'm eager to fire it up, but I still have to rework the HV cage. Any good way to remove corona dope?
Dave |
Audiokarma |
#26
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I replaced all the bad peaking coils and then compared all of the wiring and component values against the schematics. Then I installed the F104 300mA fuse ... and ... another carbon tracked part let out some smoke. Here is a picture of the burst amp transformer with a carbon track. I used a dremel tool to remove the carbon and trim that area away from the case and re-installed it.
I then turned my attention to the HV cage that needed to be completely rebuilt. I decided to remove it from the chassis to try to clean out the goo left from the original doorknob cap meltdown. Here is a picture of the mostly empty cage. I noticed my flyback had an opening right under it, but the cage did not. So I added an opening for better cooling. Then decided to add a fan. Here is a picture after the cage cutout. Here is a picture of the rebuilt cage with all new HV doorknobs. And picture from the bottom of the rebuilt chassis. |
#27
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Next I installed all the tubes except for the V and H output tubes as did what voltage checks I could without them. I found that my audio output transformer primary was open. I will have to search for a proper replacement, but in the mean time I am using a 120V/12.3CT power transformer. Yeah, I know, power transformers are not designed for this, but its only temporary and it does make noise you could call sounds.
Before I could test the rebuilt V and H sections, I needed to replace the remains of the yoke cover. Here is a picture of the yoke with whats left of the original plastic yoke cover. And another picture of a Home Depot paint can cover taking its place. Then I installed the V and H output tubes and actually got good, adjustable HV. I found that the H lin. inductor core was frozen in place and had to remove it to use lacquer thinner carefully dripped into the core to free it. I re-installed it and went through the horizontal adjustments. I monitored the current through the F101 450mA fuse and got a minimum of about 210mA. So that means what is next is.. try the chassis with the 30yr dormant 21AXP22A.. Here is a picture of the first light after 30yrs. After a quick V lin/size adjustment I got full deflection. Then I drove it with a VA62 channel 3 crosshatch pattern as shown in the next picture. After wiggling the not-glowing 6BQ7 tuner tube I got a signal. It only had chroma noise in the shape of the test pattern. After wiggling the 2nd video tube I got luminance and the crosshatch in this last picture. |
#28
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I actually said, "Wow!" when I read the latest post...
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#29
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Great news, she lives again!
Now let's see some color damit! lol
__________________
Evolution... |
#30
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I have not done any convergence yet but here is a picture of the VA62 multiburst video response test pattern. And lastly a black and white picture of some video. Color does not yet work, and IIRC, that was the main problem I had intermitantly 30yrs ago.
I checked and found the 3.58MHz oscillator is not working. I tried the one other crystal I have and that made no difference. I guess I will start changing what parts I can in that circuit. Is it right that I can disconnect the reactance tube plate coupling capacitor (just to isolate and simplify the circuit) while I get the oscillator working? |
Audiokarma |
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