Need assistance with vertical troubles on my silvertone
 

This one I got about a year ago:
http://www.audiokarma.org/forums/sho...d.php?t=154960
http://www.audiokarma.org/forums/att...6&d=1205983389

I finally got around to recapping the chassis and bringing it up. Everything actually looks pretty good except for the vertical problem at the top.

Its not a foldover, but rather a compression at the top. The linearity control changes the bottom of the picture from acceptable to huge. The height control has little to no effect.

I'll be pulling the chassis again this weekend. It appears to be a CTC-15 chassis, not a 12 like I had thought. Any pointers before I dive too deeply in it?
http://www.audiokarma.org/forums/att...1&d=1243573093

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nice picture! looks like a really sharp crt.i had a similar issue with my ctc 15.there is a resistor off the linearity control that may solve this.mine was almost identical.also a cap in the vertical by the output tube.good luck and that is a good looking roundie.keep us posted on this.

All of the paper and orange drops have been replaced. I checked the 150k resistor on the vert lin control which is ok at 152k. There are a few out of tolerance resistors that I'll replace and then go back and check some voltages.

Check the vertical center control and the yoke. See if by chance you put in a wrong value cap when you replace the orange drops. I know I have seen this and I think it was a cap I replaced with the wrong value. Cool set and it does have a good picture.
Ed

Ding ding ding! We have a winner.

I double checked my work, and found that the decoupling cap from the plate of the vertical amplifier to ground was the incorrect value. It was supposed to be .001 and I had a .02 in there. Don't know how I managed that.

Going to change that out along with the few out of tolerance resistors and give it a go.

Good luck Jordan! That's a cool looking set!

ayup. The vertical is fixed now.

I notice the width is a bit short and the HV is low at startup. The HO tube is a bit tired and will get replaced. then I can continue with the rest of the setups.

Thanks for the pointers guys.

Nice set Jordan! Post a pic when your done so we can see the end result. Do you have any chassis pic's?
-Tony

I can get some pics later. You'll undoubtedly see a finished thread when It's done.

ok, well the vertical is kinda fixed. The distortion went away when I put the proper capacitor in, but there is still insufficient height - now with a supplementary problem. Intermittently I loose sweep for about a half a second. Tube swapping has no effect on the problem.

The low width / low hv problem also seems to actually be a power supply issue. I also loose brightness and the vertical is somewhat shrunken too. B+ is low while this symptom occurs and it too becomes more intermittent as the set warms. Perhaps its just a bad solder joint. I resoldered just about all the boards in this thing already!

Looks like its time to pull the chassis again.....

Several craft stores sell a nice foil paper that would work if you ever wanted to tackle the foil behind your knobs problem. Otherwise your roundie is near mint. The unfrosted faceplate gives this one a different but nice look. These roundie clones have a neat look to them and glad they're finally getting some recognition. My latest Truetone roundie purchase gave me a whole new respect for the clones and makes me want more.
-Tony

well, the top on this one is pretty beat up. It iwll need to be refinished at some point.

I do like the out of the ordinary roundies. Its the only reason why I haven't parted out my packard bell. I've had more trouble getting that set to work than anything else I've ever owned. It was a rain victim and had a bad power transformer. I get to that when I have absolutely nothing else to do :D

I just need to put my thinking cap on. With some effort and time I'll get this one right.

I dont blame you on the Packard Bell...its a nice set also. You'll get there...you always do!
-Tony

ok, so here is where it stands. The vertical oscillator and output tube is getting incorrect voltages. The result is lack of height and poor vertical lock. Here are the measurements taken with everything in circuit.
http://i49.photobucket.com/albums/f2...n/vertical.jpg

No bias on pin 9, supposed to be -20
low plate voltage at 22 volts, supposed to be 140. With the tube out of circuit its near 300v.
low grid voltage on the vertical amp section. 27v vs 65v Does not change with the tube out.
no cathode voltage. 1.5 where it should be 120v.
Height and linearity controls are fine. Neither have any effect on voltage.

You made mention of a power supply problem. Do you have 270 at test point c? Check r 505 and c 507. Try changing the tube again. Go through the board again and check for more bad connections and grounds.
Ed

the 270v supply is present at point C. R505 and 507 are 104 and 102k respectively. The 440v supply is present at the plate of the vert out (pin6)

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You guys called it. R136 is a dropping resistor that takes the 440v supply from the top of the vertical centering control and drops it to supply the vertical height and grid voltage through a voltage divider network. its supposed to be 150k - which it initially tested in circuit. However I was apparently measuring the total resistance of the circuit. When i pulled the resistor it turned out to be damn near 2 meg!

I discovered this when tracing back the voltage from the grids of the oscillator/output tube. when I got to R136 it had over 400 volts across it. If it were a 150k it would be on fire - so i figured it had gone way up in value. Pull it out of circuit - sure enough.....

I'll get a new resistor in there. Should take care of the problem.

Replaced the resistor and I've got my bias and control grid voltages back. Gonna pop the chassis back in and try to finish the setups.

Hopefully everything will work out.

Good luck! I hope she works for you.

Bad news: The vertical restored and the set played for awhile. Then SNAP SNAP SNAP SNAP. The screen went dark momentarily then the breaker tripped.

The flyback melted down from a short in the primary. It wasn't running hot, was holding steady at 195ma on the HO cathode current. It just died horribly. I think I'm gonna call it quits on this one. It seems as though I'm just running into more nasty failure each time I try and run the thing.

I would rather take the excellent CRT outa this one and use it in another more favorable working set that needs it then continue to sink time into this set.