10HE Portacolor problem

[legenbass77]

Ok back on the 10he with some voltage updates. I found, and bought the sams! Now the voltages I have checked: 665v boost off pin 3 of the flyback. I'm getting 7.4 ohms across pins 3-6. Checking voltages on the blue, green, red triple pot test point "1" B+ on the sams I have 273v. On test point "42" boost I have .02 volts, so looks like my boost is disappearing. I cut the .1 mfd @ 1000v out of the circuit, and subbed a new one with no change in operation. I also checked voltages on the 11bt11 according to the sams pin 2 should be 80v, I have 89v. Pin 11 -5v, I have -205. Pin 10 125v, I have 145v. I have the tv in direct sunlight, and can see tin whiskers around the pots. I guess taking them apart, and cleaning may help?

[DaveWM]

I would suggest you do some continuity checks from the output from the fly to the boost side of the pot. look for continuity from thru the circuit and look for shorts to ground. something does not make since since 0v at point 42 would tend to indicate a short which should kill the boost a the fly (assuming you have continuity from the 0v test point back to the 670v boost point.

[legenbass77]

I decided to finally get back on the Portacolor this week. I replaced the .039mfd @125v capacitor with a safety capacitor, which I believe now to be the original failure. I did see where the smoke was let out. Also the .1mfd @ 1000v, and the .047mfd @ 630v. Still no go, now no high voltage at all, and the horizontal output tube was red plating. Finally I noticed the high voltage adjustment pot was laying down on the chassis, so gently stood it back up, powered on once more and it actually came back to life! Must have bumped into the pot while checking voltages earlier in the year. I've been running it for about 3 hours, and it's settling down nicely!

[user181]

Originally Posted by legenbass77

I decided to finally get back on the Portacolor this week. I replaced the .039mfd @125v capacitor with a safety capacitor, which I believe now to be the original failure. I did see where the smoke was let out. Also the .1mfd @ 1000v, and the .047mfd @ 630v. Still no go, now no high voltage at all, and the horizontal output tube was red plating. Finally I noticed the high voltage adjustment pot was laying down on the chassis, so gently stood it back up, powered on once more and it actually came back to life! Must have bumped into the pot while checking voltages earlier in the year. I've been running it for about 3 hours, and it's settling down nicely!

I'm glad to hear your good news. My PortaColor has almost the identical problem. What are the reference designators of the capacitors you replaced? Did you have to replace anything else, or was the cure just those caps?

[legenbass77]

Originally Posted by user181

I'm glad to hear your good news. My PortaColor has almost the identical problem. What are the reference designators of the capacitors you replaced? Did you have to replace anything else, or was the cure just those caps?

Thanks! I'm happy to have this going again. The .039 @125 volt cap on the power supply board was burned open. I'm positive that was my original problem. The three replaced were C401 .039mfd@ 600 volts according to the Sams, while the set had .039 mfd@125 volt. I replaced with a safety cap .047mfd @275 volt, closest value I could find and it's working fine. C212 .047 mfd@ 400volt, and I replaced with a .047mfd @630volt. C268 .1mfd @ 1000volt, and I replaced with exactly the same value. The set in the Sams is laid out a bit different than my set, like it shows C268 down by the flyback, mine is under the power supply board on a terminal strip. My second problem was the high voltage pot (R273) shorting on the chassis. I must have bumped into it, and laid it down while checking voltage on the flyback back when the failure occurred around the first of the year. I walked away from it for a few months, and finally decided to give it another try. So the three caps, and bending the high voltage pot upright got mine going, nothing else had to be done! I got the caps from Just Radios while I was ordering for my Admiral 19A11.

[user181]

Thanks for the information, and especially the annotated photos! My set has an H4 chassis and I believe predates the HE. There are some board and component layout differences, so perhaps the later chassis made some improvements. I still like to know the details of your repair, and can compare it to mine.

Until my set failed this past November, it was in regular use, decked out with a DTV converter, DVD, VHS, and a Roku.