1949? Motorola 10VT24R, TS-14B chassis - Page 2 - Videokarma.org TV - Video

***Eric H*** · #16 08-10-2015, 11:27 PM

Did you try turning down the brightness at line voltage? What may be happening is when the brightness comes on turned up full it may be pulling the high voltage down which in turn, kills the brightness.

There's a bit of keystone in that raster, possibly a sign of a bad yoke but more likely something wonky in the vertical circuit.

The horizontal squealing is caused by it running way off frequency, you may need to adjust the frequency coil, or possibly you have a cap that's the wrong value in the horiz oscillator circuit (which could also bring down the high voltage and brightness).

Electronic M · #17 08-10-2015, 11:36 PM

On the vertical circuit make sure the tube is good, the resistors are in tolerance, the pots are clean/not open, and check voltages on the vertical tubes.

If that fails connect the yoke or primary of the vertical output transformer to a variac (make sure it is disconnected from the set before connecting to the variac) and slowly turn it up while watching for more deflection. If you don't get more deflection from that then your yoke or vert transformer is bad (which one can be determined by the connection point).

To add to Eric's point if the H osc. is out of tune it can cause poor HV regulation and even cause the HV to drop out. If you have a scope, connect it to a video source (like a DVD player), and measure the horizontal period by looking for the synch pulse, then with the horizontal settings of the scope unchanged connect the scope to the set's H osc. and tune the osc till the width of the osc wave form is as close as you can get it to the one you measured on the composite video....I've done this on sets with pure unobtanium flys before plugging the output tube in as a safety precaution, and it has worked.

ZackN920 · #18 08-10-2015, 11:40 PM

In responce to Eric's post. My computer is being very slow tonight.

I did not turn it down. I left it alone durring. I havn't had it set at max though. I don't want to take the chance of burning the crt.

I know that yoke is stuck on the crt. When I tried pulling the crt off, it wouldnt let it move far.... I didn't want to push my limits so i just tightened everything back up and left it together. I also dont think that thingamajig behind the yoke is original. Looks different than the images on the manuals

ZackN920 · #19 08-11-2015, 12:00 AM

in responce to Electronic M...damn slow ass computer

Tubes are good, pins are clean, I cleaned all the pots but still have yet to check them. I still need to check resistors and voltage too.

That sounds like an interesting test...

Unfortunatly I dont have a scope....or much of any actual test equipment other than my analog multi meter and my tube tester.

Zenith26kc20 · #20 08-11-2015, 08:17 AM

If the yoke is an "iron wire" type, the iron wire making up the core will make the windings shrink and get stuck to the neck of the picture tube. I fought with my Admiral and ended up losing the vacuum in the CRT when I accidently pulled the CRT socket off when I tried to put the yoke over it. I got a replacement that had an iron wire yoke (stuck also) and unwound the wire and got it off. I also had to get a replacement yoke for the admiral. Be careful and if you don't have to, leave the CRT/yoke alone for now. If the variac test shows the yoke bad, you'll have to take it apart to get it off.
The resistors were around 22 ohm 5 watt. Check the B+ after you install them. It looks like you have a good number of bad capacitors in the set. I completely recapped mine before I started to troubleshoot.

ZackN920 · #21 08-12-2015, 07:19 PM

Good thing I never pulled it off then. I wanted to for the recap. Oh and yes, it's fully recapped. I really hope it didn't look THAT bad to ya...to make ya think I've done nothing in regard to recapping. Thanks for giving me a value to look for in my resistor stash.

While poking around it last night, I noticed that there are 2 oddball looking resistors under the yoke with the wires. It looked like they were supposed to be connected to each other on one side (and go in) I couldn't see where the leads led to on the other end. Well the one had broke off on one side.(where they were connected to each other). I'm going to resolder that connection together and see what it does.

Also, anymore tips on testing the yoke/vert transformer? If I test the yoke, do I hook the wires to the +&- of the variac? Or just the positive and other side of the yoke's vert. to a ground? Idk. If I test the vert. output trans I hook the primary to the + of the variav but where do I go with the neg? Honestly I don't know much about this test, still learning as I go with these TV's...Well even with the radio's!

Zenith26kc20 · #22 08-13-2015, 10:23 AM

You can use an old line cord to plug into the variac. I put alligator clips on the wire ends. If you remove the B+ from the vertical transformer (usually the red wire coming from the power supply) and connect the variac from the transformer wire going to the tube socket (plate of the tube) with the set powered up, go from zero volts on the variac up slowly. You should get deflection as you increase the voltage from the variac. If the keystone still exists, the yoke is probably bad. This set has a "hot" chassis, be very careful with the variac connections. Do not let them contact the chassis. It looks like it has a power transformer but the transformer is filament only. The B+ comes from a voltage doubler.

Zenith26kc20 · #23 08-13-2015, 10:26 AM

according to the schematic, the vertical windings of the yoke have 100 ohm resistors across each winding. If the transformer has never been changed, the wires you would put the variac across are red and blue.

wa2ise · #24 08-13-2015, 03:59 PM

Quote:

Originally Posted by ZackN920

Thanks guy's for the info about the diodes. I didn't realize that when used as rectifiers that ya essentially swap there polarities. ...

It may be easier to visualize when you compare the diode to a vacuum tube rectifier. The end of the diode with the band is the cathode, the other end is the "plate". The cathode of the vacuum tube rectifier is the side that B+ comes from. As seen from the AC source, the power transformer secondary, there are two cathodes in series. One of those cathodes is the rectifier, the other is one or more cathodes of the various tubes doing the audio amps, IF amps, vertical or horiz outputs, and such.

Confusingly, some selenium rectifiers had "+" symbols next to their cathodes. As if to say "Connect this side to your B+ filter caps".

ZackN920 · #25 08-13-2015, 10:36 PM

Well, who's got an extra yoke they want to sell....

Thanks for "spelling out" that test procedure for me Zenith26kc20. I appreciate that.

Well I wired in the resistors on the diodes and also disconnect that vert. out. transformer, and hooked it to the variac. I powered the set up, slowly turned the brightness up till I could see a line, then flipped on the variac. Well, when I started applying voltage I noticed the wierd line on the right popped on the screen and(I didn't know how high I should go) I eventually went up to 90 volts with it only growing to about the same size it always has. I didn't want to burn the trans up so I stopped at that 90 and just shut down.

ZackN920 · #26 08-13-2015, 10:42 PM

Oh- some good news that I forgot to mention a little while back.
It seems the tuner's at least fine and signal gets where it should. I hooked an old videogame to it just to see what it'd do, and got good sound, and video in what I do have for a picture!

ZackN920 · #27 08-17-2015, 07:44 PM

Well, what do y'all think? Did I go high enough with the variac, not high enough?... Where can I get another yoke that would match or just work correctly? Would it be hard to rewind the windings on the yoke? (I've never done anything like that before). Where should I go from here?... Should I just put it back together and just say "the hell with it"?
IDK........

ZackN920 · #28 08-28-2015, 11:49 PM

UPDATE!!!

I got a new yoke for it. I had to murder the old one to get it off. That thing was also pretty rusty inside as well... Now its extra scrap metal.

Got the new yoke on and put it all back together. Figured out how to hook it up correctly, and got that all done and wholla! I've got a full size rastor.

Now... I noticed that it seems to have video sync issues. I'm going to need some help with figuring this out. Other than that, all seems well with it, nice and stable.

I've got the set attached to my SNES in the pic.

Electronic M · #29 08-29-2015, 12:50 PM

Can you get the horizontal bar to roll both ways (up and down) with the vertical hold control? Can you get the horizontal to sync even for a moment by with the horizontal hold control? If the answer to either of those is not then the circuit associated with the control needs more work and or adjustment. If the answer to both is yes go after the AGC and synch seperator stages....Try adjusting the AGC if it synchs with good contrast your good if all it does is change the video level leave it at a setting that gives reasonable video and move on to the synch sep (check it's resistors).

The vertical will need to have it's resistors checked if it can't be rolled both ways with the hold control. If the horizontal can't be flopped both ways first try adjusting the slugs of the osc. transformer (assuming it is a synchroguide circuit)....Get it in synch, and then use a scope to get the peak and hump of the waveform roughly the same height (crucial for stability).....If the osc. can't be adjusted for sync. then check all the resistors in the horizontal.

ZackN920 · #30 08-29-2015, 04:41 PM

I can get it to roll either way, and stabalize with the vert.hold control. What you see in the pic though, is the best the horizontal will sync. It'll stay like that,(won't bounce around) but I can't get it to adjust into 1 full image. and I cannot mess with the hh control much, because it'll squeel like crazy if turned more that 1/4 counterclockwize. I always slam it back to the safe range, then because I don't know if that sound equals harm or if it's just emitting the sound... I'll have to check some stuff around there like you suggest.

I dont think my set has AGC...I'll check around the sync seperator some. Honestly I havn't done much 'checking of resistor's.

Should I mess with the osc. trans. if I don't have a scope?