#16
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Nice, tidy work on those caps. What did you use on the chassis?
Phil |
#17
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First I tried to wipe the crud off with solvent and a rag, which didn't get me anywhere. Then I grabbed a piece of 0000 steel wool, which removed the crap and polished the surface at the same time. You have to be gentle with it though, or it will leave scratches.
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Evolution... |
#18
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First Signs Of Life!!!!
Time for another update!
This weekend began much like the last, lots of hunting and not a single sign of any deer whatsoever. In fact, the only deer we ever saw was an already dead one in the back of a fellow hunter's truckbed. All that freezing for nothing, I guess. Fast forward a few hours, and I went on down to the basement to get more work done to the chassis. I finished restuffing the last power supply capacitors, so they all have brand new caps living inside the original paper tubes now. I made sure to use plenty of adhesive, to keep them from bouncing around and possibly shorting. As soon as the glue had set enough to reposition the chassis, I flipped it up, double checked all my work by bouncing it off the schematic, and cautiously applied power for the first time through a heavy 20 ohm resistor in case the PTX was bad (variac is currently OOC). Nothing happened at first- was the PTX actually bad? No, both fuses were blown. I replaced them with their rated values and tried again. Success this time! I got B+ (380) and B++ (285), within 20 VDC of the values given in schematic. -20 VDC also looked good, if a few volts high. All tube filaments lit up, so that tells me the PTX is 100% good to go. Just for kicks, I scoped the horizontal oscillator to see if anything besides the power supply was alive at this point. I was pleasently surprised to find a perfect waveform at the grid terminal of the HOT! Picture of the waveform is below. All in all, not a bad day!
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Evolution... |
#19
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More!
I was not content to stop at having a waveform, as the next day dawned. Something about finding life in a 56 year old chassis gets me going, call me crazy. So after finding the horizontal oscillator working, I decided to pump as many new caps as I could find into critical circuits to see what else I could get. I ended up doing everything on the 2 PCB's, everything in the vertical oscillator, everything in the horizontal oscillator, and a few other random caps just to exhaust my supply. I'm now totally out of .047's, .022's, .01's, and the 'lytic bin took a good hit as well.
Turns out the vertical section is just fine as well, though the 6AQ5 running the show tests barely into the green scale on the tube tester. I'll have to get a fresh one before attempting to run a CRT. As you can see in the first 2 pics, I did a whole lot of recapping. Took me the better part of the day to get to this point, my back is killing me. I'm way ahead of the power curve as a result though, I figure there's only about 2 more days of recapping to the matrix section (3rd pic), and the chassis will be 100% free of PIO's. Tidbit: every single paper cap in this chassis was made by Dumont...strange? Most were MicaMold labeled made by Dumont, a few were were Aerovox and 'MicoMould'. I left the ElMenco micas in place, as every one I tested was within tolerance. I'll probably get to those at a later date, when I'm not so tired of capacitors. The one bad part I found so far was a video peaking coil that had split it's case all the way around. The wires inside were eaten by corrosion, so it's toast. If I can't get another one, I'll have to wind one with the help of my brother.
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Evolution... |
#20
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Bad Tubes!
Last day of work to the CTC-4 for this weekend. I decided that after the success of getting both oscillators up and running, I should go for broke and see if I couldn't get some HV flowing.
I wired some 10-meg power resistors from the HV tower to ground as a load, and let 'er rip..... Nothing. Not only did I not have any HV, but the previously observed waveform at the HOT grid was mysteriously gone. I couldn't find anything at all wrong with the horizontal oscillator, then I pulled the HOT and damper out. Come to find, the HOT had a short which shunted the grid to ground, which explained the loss of a drive signal. I don't have any spare 6CB5's around, so I subbed in a 6CD6 for testing (not same ratings, I know!). Still nothing. Tested the 6AU4 damper next, and it had 0 emission. I was beginning to think the HV transformer was bad at this point, since both tubes that run it had gone bad...dramatically, as it turns out. In the pic, you can see what's left of the 6CB5 HOT. It burned a hole right through the plate on both sides! Cathode was done for too, and the grids were melted. But my fears were proved wrong about the HV transformer. I put a new 6AU4 in along with the 6CD6, and while the 6CD6 did not like being put in the position of having it's ratings exceeded, it did drive the HV transformer for long enough to let me know HV was working. I saw the normal blue glow from the 3A3 rectifier as HV came up strong, and the power resistors got nice and toasty after a short run. I'd call this a very productive weekend, all in all. So to 'recap' recent events (pardon the pun!): I now have a redone power supply, 2 good oscillators, good HV, and all that remains is the matrix recapping before I can take this thing on it's maiden voyage with a real picture tube! Nothing but excitement on my end!
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Evolution... |
Audiokarma |
#21
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I hate to tell you, but you also let the vacuum out of that 6CB5
Really, great progress! Keep us informed. |
#22
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miniman82-
Do you have a color TV test jig? If you do, and you need the details of how to hook up your CTC-4 chassis to it, let me know.
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Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
#23
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Chris,
I have the Sylvania check-a-color with a butt ton of adapters, but nothing for 70* picture tubes or early RCA chassis. I suppose I should cannibalize the NOS brightener I got off Ebay and make my own harness, but I just figured I bring a spare 21CYP22 with me next time I head home for tetsting purposes. Do you have wiring diagrams on how to hook up the check-a-color?
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Evolution... |
#24
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Quote:
http://videokarma.org/attachment.php...5&d=1290924895 Bill(oc) |
#25
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Quote:
Phil Nelson |
Audiokarma |
#26
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I haven't had a problem yet, I just blow off the chassis with compressed air and that gets the whiskers out.
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Evolution... |
#27
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I'd be worried about tiny metal whiskers getting inside wafer tube sockets and such. So I'd avoid steel wool. I even hate to have to drill holes in metal chassises for fear of the chips getting into somewhere.
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#28
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I'm not superstitious, it'll be fine. :p
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Evolution... |
#29
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Quote:
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Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
#30
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OK, thanks for that!
Meantime, Allied Electronics dropped off an early Christmas present today for the '4. Plenty of new caps, the new horizontal centering pot (2-watt wire wound), various 'lytics and so forth. Still on the way is a pair of 6CB5A's, a pair of 6AU4GTA's, a 6AQ5 and a 3A3 rectifier. Those are coming from Antique Electronics Supply, should be here Friday or Saturday.
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Evolution... |
Audiokarma |
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