Motorola 19k14wa Possible Arcing?
 

Hey guys, I powered her up tonight and noticed a funny hissing noise as well as some horizontal waviness which went away after a while, and the set seemed fine. I turned it off and waited a while, then with the back and HV cage off I watched it power up in the dark and didn't see anything funny. it did hiss a bit but the picture looked okay upon warmup. All tubes test okay (at least around the video/horiz/vert section) but I haven't tested the HV rectifier.

Only other thing I noticed was a blue glow in the damper diode (12AF3), but that shouldn't be a concern right?

http://i263.photobucket.com/albums/i...psegk9dzgp.jpg

The Photobucket image...


http://www.videokarma.org/attachment...1&d=1500010320

IIRC that blue glow is fluorescence of the glass, not uncommon in power tubes and nothing to worry about

Blue glow in power tubes is common.
To find arc do it on a very humid day in the dark.
Also check the HV rect socket for corrosion, a white or
greenish color usually or sometimes rust.

73 Zeno:smoke:
LFOD !

How are you rescuing photobucket images/bypassing photobuckets' new policy of requiring money for external hosting to work? I can't even view pictures bigger than the gallery thumbnails in bucket accounts.

I had pretty intense arcing out from the CRT connector on a similar Motorola when I first started messing with TV over 40 years ago. Optimal time of year for that nonsense! I had to clean the CRT and then the connector suction cup rubber with silicone to get rid of all the tracking. The HV rectifier was a 3A3, like what a color TV used, so I know the HV was higher than normal BW sets.

What is the chassis number? Mine was CDTS581YA totally all-gray metal 19" cabinet, like my avatar.

I didn't bypass the PB requirement, I just accessed the image with their link, saved the image, and then uploaded it directly to VK.

I right click on the PB update image in the post and either hit open image in new tab or open link in new tab. (I am using Google Chrome.) That gets me to the PB page, which again shows the PB update image. Then I right click on that PB update image and open the image in a new tab, which then displays the real image. I then save the image to my computer, and upload it to VK through the Manage Attachments feature, and then use the VK assigned link for the image within the IMG and /IMG tags to display it in the thread.

The old images are not difficult to access this way, just very time consuming. I fear that anyone who closes their PB account will be eliminating this access path, so I advise everyone to leave their PB accounts idle rather than closing them.

I think everyone involved in this fiasco get a class action suit going against PB to force them to grandfather in all old images to be usable as hot-linked 3rd party hosting, as that is what the policy was when they were placed on PB in the first place. The recent changes are a violation of trust against all who used PB.

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I figured the blue glow was nothing, the power tubes in my home stereo have a blue glow, but I'm kinda a noob to TVs......

I fired her up tonight and found some arcing in the HV rectifier socket, though it looked like it was happening inside the tube. Time to pull it out for a good clean!

I couldn't figure out the chassis number, but its in a floor standing wood Danish modern style console. I attached the picture this time to avoid the PB blues

http://www.videokarma.org/attachment...2&d=1500086543

So this TV has been playing well, I replaced the HV lead, cleaned the cage, replaced the tubes in the tuner. I also cleaned the "noise gate" pot, it was scratchy and made the picture go wavy/buzzy intermittently.

only quirk I have now is some buzz in the audio which can sometimes be minimized with adjustment of the fine tuning. Perhaps I have a dirty tuner? or could it be alignment related?

Sometimes this is just a fact of life with old TVs, especially when digitally generated text is shown. Alignment can definitely help, especially if the best picture and sound appear at different parts in the fine tuning range.

Really nice TV!

If your using a cheap consumer grade modulator it can be the modulators fault. Some units use a single carrier osc. that gets AM and FM modulated...If the AM video modulation exceeds %100 it will also affect the FM sound...As noise that repeats at 60Hz and varies with video content.

Thanks! I'll keep that in mind.

I'm using a DTV converter box, so that might be the issue. Getting a BT modulator is on my list, as I have some Watchmans that need some use.

Buzz in audio could be AGC, optimizer or noise gate settings,
which ever you have.
You could also touch up the quad coil but there are reasons not to.
Live with it if you can. If not come back for more.
BTW you will need a manual.

73 Zeno:smoke:
LFOD !

Gotta different problem today. washed out picture, barely stable horizontal, hard to lock vertical. Tubes test okay, I re did a bunch of bad looking solder joints with no improvement.

https://farm2.staticflickr.com/1851/...0c44a9ac_c.jpg

maybe it's time to do the power resistors near the horizontal? Goodall film capacitors maybe not so good?

Looks like either you've lost gain between the ant terminals and the vid detector*, or your AGC circuit is misadjusted or defective.

*Check signal source, clean tuner, check tuner and IF tubes, wiggle said tubes in case bad socket contacts.

When you develop weak sync in both deflection axes that is a sync separator problem...If the picture has far too little contrast ()along with the synch issue the signal feeding the synch separator (usually picked off just past the video detector) is too weak for the separator to process correctly (even if the separator is functioning correctly which it probably is) due to reasons mentioned in the first sentence.

Thanks M :thmbsp:

something's goofy in the IF as I wiggled all the IF tubes and the picture came back, I'll check the solder joints and clean the sockets tomorrow, but it's playing fine now.......

Yaargh! this TV is frustrating...... it seems the vert/horiz is locking but the washed out contrast look goes in and out, but can sometimes be "fixed" temporarily by jiggling the channel selector.

I might try injecting video past the detector diode and rule out any problems there. I'm still thinking the tuner might be troublesome, but the card edge connectors at the back of the PC board might be problematic, but I've cleaned those several times. I have cleaned the tuner, but I've been gentle (maybe too gentile) trying not to screw it up.

When I clean a tuner I use De-Ox-Id and a white rubber eraser...The De-ox loosens the crud and the eraser gently scrubs it off and polishes the surface...Hasn't failed me yet. There is something nice about seeing a black terminal become completely shiny metal once more.

Well I feel dumb. I found another 3BU8 (agc keying/sync sep/noise limiter) in my tube stash and swapped it in and the picture is back. I woulda tried this earlier but I hate throwing tubes at a TV set.

The tube tested ok in my tester, but it was slow to get into the green zone :scratch2:

Sometimes tube substitution is a better approach than testing...I had a CTC-15 clone that had low HV and sweep issues. That set I tested all the tubes, nearly drove myself nuts checking all the passive parts a couple of times, then had it spring to life when I subbed all the sweep tubes from another working CTC-15 clone. Once I narrowed it down I retested the tube and found it still tested good...Buuut if I held down the test button for nearly a full minute it would slump into the bad end of the scale.:thumbsdn:

If you look at the pin-out of the tube in a tube manual, you'll see it's a rather unique design with a few common elements. I don't think it can be checked properly with a tube checker. Best is substitution.
IIRC, the circuit is a Zenith design, as they used it first. :scratch2:

Working on tvs/radios...etc since the early 70, s in my basement shop for a large part of my career (made more working for myself)(tough to keep new stocked tubes) i used pretested in tvs or whatever used tubes i knew were good in a set.saved me a LOT of trouble.i would recommend that any tube set every member has in this forum,stock used tubes tested on a tube tester AND tested in your known workining (or once you got it working sets. A lot easier. Maybe this should be a stiicky post. RonL

Well the sync went funny again. So I pulled the board and found a crack in the ground plane trace around the edge of the board (near the horizontal output tube - high stress area), solder bridged it back and got sync again :banana:

The sync circuit must have been dropping the ground there intermittently.

Now the horizontal linearity is a bit off, but I screwed up the noise gate (sync stability) pot so now to fix that.....

That PC board job wasn't one of Motorola's better efforts. They made a few years of those and then went back to the hand wired chassis. The tuners were also trouble prone. Yours is probably the last year of that chassis.

This ol' ball of wax again.

I'm having problems with the horizontal, barely able to hold a steady picture, and I have determined the voltage is too low on the horizontal oscillator tube due to out of spec resistors in the horizontal sweep couplate. I have built simple couplates in the past using perf board, but these are some stacked up monstrosities with 12 pins. Anybody here attempt to make one of these? I'll likely try to build the new ones similar to how the old ones are made.....

Aah, the mil spec couplates (there is a YouTube video of their manufacture out there), I've never changed one, but I've seen them in gear once or twice, and have a couple nos specimens....it probably has fewer parts than legs which might simplify construction of the replacement.

Here's a schematic of the two of 'em in this TV. The bad one is the horizontal but I'm going to redo both of them.

Have you attempted to replace the horizontal phase detector diodes? Those are easier to change, and could possibly also cause this issue. It looks original in that photo.

+1.

Definitely replace the dual diode if you got horz sync issues that subbing the tube don't fix.

Would silicon rectifier diodes work there? I have some of those laying around......

Fast acting shotkey diodes are best but standard silicon 1N4007s will work in most sets (h locking range may be smaller than designed with normal silicon.