Finally joined the club! (CTC-9 content) - Page 3 - Videokarma.org TV - Video

*zenithfan1* · #31 07-07-2010, 06:39 PM

I'll bring over a B&K NTSC generator that's fun to play with. After the convergence, we can use the color functions and dial that thing in perfect (or as close as possible). Plus, the color bars make great screen shots.

Lemme know when I can stop by.....

miniman82 · #32 07-07-2010, 07:07 PM

This Friday? Bring the truck, so you can clear out my garage. lol

*zenithfan1* · #33 07-07-2010, 07:45 PM

We'll see about clearing the garage, mine needs a bit of clearing as well. I did like that Admiral and Zenith though, that should help somewhat

. See you Friday.........

miniman82 · #34 07-07-2010, 08:38 PM

This might be a dangerous precedent, but I'll help rearrange your garage if it help you fit stuff...

miniman82 · #35 07-16-2010, 04:29 PM

More progress to report!

Late last night, I finished replacing the last electrolytic caps in the power supply. I was only able to restuff the cap that has a paper cover though (C1 in Sams), since the replacement caps I bought (Illinois brand) were too large to fit inside the metal can of the multisection ones. That's probably because they didn't have exact replacement values available at Antique Electronics Supply, so everything that went in was double original capacity.

That being the case, I populated the remaining caps close to their respective circuits. I was able to use spare terminal board points in most cases, it almost looks like they belong where I put them. Naturally, I left the original caps in place on the chassis for the sake of appearances. I also found the AGC pot ground had worked loose, so I soldered it back down.

Today that led to a nice afternoon of slight tweaks, and a good 30 minute session of Fox News and a bowl of ice cream treat myself.

It was short lived, however.

After I shut the set down, I looked over the chassis to make sure none of the work I had done caused any problems. I saw nothing out of the ordinary, but I did smell something odd. Immediately I suspected a hot flyback (smelly old wax), so I popped the HV cage off. Sure enough, melted wax was all over the place and the HV coil had started to sag downward. Right now what I'm going to do is clean up the fly, and replace the silicone since it's old and nasty. Once that's done setting, I will check the horizontal output tube's cathode current to make sure it's OK.

Sams gives a nominal value for the 6DQ5's cathode measurement as 160ma, if it's high I need some suggestions on what to check. Right now I don't think the flyback is bad (it's a low hour set), but I will replace it if I have to.

miniman82 · #36 07-18-2010, 12:42 PM

Just checked HOT cathode current, it's sitting at around 190ma. That's about 30ma high, but not really alarming to me. Anybody think the 6BK4 could be causing too much load on the HV supply? I'd like to adjust it, but I have no idea what the anode is currently at. Being that most of the pots in this chassis have drifter by quite a bit, it wouldn't suprise me at all if the anode voltage needs checking/correcting.

EDIT: forgot to mention that I replaced the old silicone on the flyback, and installed all new wiring for the HV rectifier filaments and HV reg.

*zenithfan1* · #37 07-18-2010, 01:31 PM

I also have a Sencore yoke and flyback ringer tester with HV probe if you want to borrow that too. Let me know......

miniman82 · #38 07-18-2010, 01:52 PM

Will it read anode voltage, while the set is running the flyback?

I'm not going to attempt to converge this until I'm certain I have a handle on the HV section, so I might just take you up on that.

*zenithfan1* · #39 07-18-2010, 03:35 PM

Yes, it reads the HV with the set running.

miniman82 · #40 07-18-2010, 05:18 PM

Nice, you'll have to bring that thing by sometime.

miniman82 · #41 07-18-2010, 08:03 PM

Did some tweaking, and after the set ran for a while the 6DQ5 cathode dropped to around 183ma. I think I could still get it lower though, 183 is still 23 high. Flyback is not quite so hot anymore, so the wiring I replaced was probably arcing or something.

old_tv_nut · #42 07-19-2010, 12:54 PM

Pretty bars - bet they look even better without the window light.

miniman82 · #43 07-19-2010, 04:03 PM

They are!

I shot in the light partly because I wanted to show how bright the tube really is, it's not necessary to be in a dark room to see a great picture with this set. I think black level could still be better, though. As you know, that's another odyssey.

I'm thinking the only way I'll be able to get cathode current back into spec will be to add a horiz drive control to the circuit, what do you think?

miniman82 · #44 07-21-2010, 07:06 AM

Well I tried lowering the drive signal to the 6DQ5 unsuccessfully, lowest I was able to get it was 179ma and that's after trying some of the things outlined in Sams on adjustment of the horizontal section. Tweaking the horizontal linearity coil got me a drop of a few ma, but I can't check anode voltage just yet to finish the proceedure. Basically what you do is monitor cathode current on the horiz output tube and HV reg, turn the focus and HV pots all the way down, then adjust the horiz waveform coil for equal peaks, adjust horiz lin for 'lowest reading' on the output cathode, then tweak the HV pot to read .8ma on the 6BK4 cathode.

That reminds me, does anyone in Chi Town have a scope they'd let me borrow, so I can tweak the waveform coil?

*zenithfan1* · #45 07-21-2010, 03:52 PM

Too bad mine needs recapping at the moment or you could borrow that too

Those color bars look great on that 21CYP22! That generator is fun to play with huh? The thing is great for doing purity, just press the red button