77 sylvania - Videokarma.org TV - Video

DaveWM · #1 10-26-2010, 09:09 AM

I can't find the chassis number unless its the real long one E4000....

anyway assy in mexico,has the 3 main boards, does NOT use the loose coupled power tranny and big motor run cap, instead has a SS regulator (I presume, its next to the HOT).

Two issues

vert kind of unstable, will colapse for a fraction of a second at times (I dont leave it alone and will not use it until i resolve as I do not want to burn the 25vdmp22.

second, looks like a yellow stain on parts of the screen (pls no jokes), I assume its a purity issue as when I went to set it up I did not get perfect red. in the same area.

However I was at a loss on how to set it up for purity. It seems like the horz yoke is not designed to be moved fore and aft and has no provisions for tilting etc. to adj. the purity rings are hard to adj since they are right up against the convergence board. they are current both set at 12:00. I did try moving them but was not able to get it any better, but I was limited in what I could do since I was fighting the conv board placement.

this one is in a very simple cabinet, with twist on legs. Clean by 1970's standards, I am guessing a low end set (cabinet wise).

DaveWM · #2 10-26-2010, 06:54 PM

pics,

the vert is still jumpy, I pulled the deflection board, reflowed some iffy looking solder (really not bad) including the socket for the yoke plug.

tested a few e caps since I had it off, one was a bit weak (power factor of about 35, again not bad but since I had it out to test I replaced it). reflowed some solder around the ground points (4 corners of pcb) cleaned the chassis at those points as well.

put it all back and it still is jumpy. intermittant jumpy that is, it will be fine for a while then kinda jump up from the bottom, not roll just shrink from the bottom a bit, then snap back.

I did reset all the transistors (sockets), but left the IC's alone, they where in real tight and I did not want to break anything.

guess I will pull it again and try checking some more caps. or maybe try some freeze mist to see what is going on.

Findm-Keepm · #3 10-26-2010, 08:43 PM

Quote:

Originally Posted by DaveWM

pics,

tested a few e caps since I had it off, one was a bit weak (power factor of about 35, again not bad but since I had it out to test I replaced it.

Dave,

What is the "power factor" you refer to - and how do you test it?

I've heard of value, ESR, leakage, and dielectric absorption tests for e caps, but this is the first I've heard of power factor.

Cheers,

sampson159 · #4 10-26-2010, 09:17 PM

that is an e 40 chassis.decent set,not quite as good as the 41,45,48.still pretty good.you have to loosen collar around yoke and move convergence board also to get purity.very easy.may have to degauss first.my mother bought a new set just like this.9 years later,she sold and bought a new xl100.worstset she ever had.dim picture,many service issues.i got her a e-45.she used it until i bought her the first 36 inch flat crt toshiba.that 45 is in her bedroom as a spare.still playing and still looking sharp!

DaveWM · #5 10-27-2010, 06:40 AM

Quote:

Originally Posted by Findm-Keepm

Dave,

What is the "power factor" you refer to - and how do you test it?

I've heard of value, ESR, leakage, and dielectric absorption tests for e caps, but this is the first I've heard of power factor.

Cheers,

I use an old heatkit condenser check (uses an eye tube, and a balanced bridge cirsuit for check caps) good of vintage gear esp leakage test at rated voltage, but can not check caps in circuit. there is a "power factor" adjustment, you turn to null the eye tube, which I think is about the same as ESR.

Findm-Keepm · #6 10-27-2010, 11:27 PM

Quote:

Originally Posted by DaveWM

I use an old heatkit condenser check (uses an eye tube, and a balanced bridge cirsuit for check caps) good of vintage gear esp leakage test at rated voltage, but can not check caps in circuit. there is a "power factor" adjustment, you turn to null the eye tube, which I think is about the same as ESR.

Aw geez, now I gotta buy anudder piece of equipment. Jes' when you think you have everything.....

Thanks! I've got some old Heath stuff - I'll have to see what I've got stashed away. I may have one of them varmits. Probably similar to my Sprague tester's eye tube checks - some kind of reactance vs value check.

Cheers,

DaveWM · #7 10-28-2010, 07:41 AM

I think I may have found the vert prob, after going thru every cap (all good) I finally did a swap on one of the vert out transistors, but now the stupid converter box is on the fritiz so I cant get a signal to check it out on. I cant believe what pure junk these DTV boxes are, this is the second one that went out, less than a year old. I have other video RF sources, but it will have to wait for a bit.

I did a quick check last nite and it looked fixed, so I was going to check again this am.

AUdubon5425 · #8 10-26-2010, 08:12 PM

E40 sounds right for the time - Sams 1620.

Reece · #9 10-28-2010, 03:14 PM

Those sweep transistors give trouble from heat, I've used more heat sink grease between them and their sink and added more homemade aluminum fins with good results. Also crimped their leads a little like bobby pins to get more grip inside the sockets.

DaveWM · #10 10-28-2010, 03:31 PM

I have a spare board that donated the transistor from, there was also one on that board that was not orig, it was a different color body and had been bolted to the sink, rather than rely on the spring clip that held it on.

holmesuser01 · #11 10-28-2010, 03:48 PM

Well, good. This one's done. Now, come on up to NC and help me get this DuMont, Magnavox, and the other Magnavox going!!!

Bruce

DaveWM · #12 10-28-2010, 05:11 PM

would love to, but got a few more still to go.

DaveWM · #13 02-04-2011, 07:16 PM

the vert nonsence reared its ugly head again, slight fold over on the bottom and shaking pic. Pulled the board, both output transistors checked ok, so I replaced the 2500uf coupling cap from the collector of the output transistor to the yoke. I only had a 1500uf handing so I ran down to the shack and got a 1000uf. the 1500 went in from the top, the 1000uf was attached to the bottom (using the wires from the top cap as stakes to pig tail too). Seems to have resolved it, will watch Jimmy and Angle later and see how it hold up.

I should have replace that cap orig, I figure its got to see lots of hard use.

bgadow · #14 02-04-2011, 10:18 PM

I have a mid-70s Sylvania that also suffers from some vertical jitter. I'll remember this thread the next time I dig into it. One thing I found, and it might be worth checking if you haven't already: the service switch is sorta cheap and not well mounted to the board. It is real easy, when installing the back, to not have the button lined up with the hole. On mine a couple of the posts had been pulled loose from the board due to this, and the intermittent contact was causing both a video and vertical problem. As I write this, I recall that it was mostly video (raster would go dark/negative) but worth checking if you are in there already.

DaveWM · #15 02-04-2011, 11:10 PM

the cap did the trick, rock solid. My cap tester only goes to 1000uf so I could only test it for leakage. I figure it may have been an ESR issue rather than a leakage issue. I had noticed before the jitters started to happen that the pic was shrinking up from the bottom a bit more than normal. At 1st I attributed it to just the way a thermistor in a yoke may have been behaving, but now I think it may have been the cap. I know ESR goes down with heat, and the cap sits right next to the heat sink from the defection transistors. I am pretty sure I checked on that switch when I 1st started trouble shooting the vert (that was a problem from the get go).