Roundie left edge purple

[Tom_Ryan]

A bad flyback could be it. Some shorted turns or leakage could cause an impedance mismatch with the yoke resulting in ringing.

[DaveWM]

going to try adj the purity and see if I can move the yoke a bit more forward to increase the scan with out having to increase the drive.

Have not check the temp of the fly but will after the next test cycle.

[DaveWM]

the pot in the HV cage was a horz centering pot, so I adj that and re did the purity (rings and yoke placement).

I am getting pretty much a full raster now, I could get more by upping the horz bias, but as is its about 240ma with the CRT bias at min.

Still have a bit of center RG vert issues top and bottom that I can't seem to work out with the convergence board.

I am going to try replacing the Se 4pack with discreet diodes and check again.

I checked the Se pack and was getting AC on them (and DC) so my guess is they are leaking when reverse biased. I assume this is not good for convergence.

At least the purple line is gone.

[DaveWM]

while doing convergence I had some issues wiht the RG vertcenter topa nd bottom.

checked the Se 4 pack and one was bad. Also a bad resistor off the diode was 250 shb 56

[DaveWM]

got the diode pack replaced, replace a 4X out of spec resistor on the conv board. Just got to find my diddle stick to finish the convergence on the right side.

Fly it running pretty darn hot So maybe that is the issue with the lack of scan width.

I turned down the horz bias so the cathode current would be lower and got the purple line back. Oh well. Just have to use it for short periods of time I guess unless I can find a philco fly (assuming that is the problem).

I have a secore model SS105 sweep circuit trouble shooter, but I have no manual and have no idea if it would work with this set (has an octal plug, the set I have uses the 6KD6 which seems to new for this tester.

[DaveWM]

Next plan will be to check the "focus" adj. Its a coil that is tied into the horz winding of the yoke, you adj the focus by adj this coil. So the plan will be to check the cathode current and see if that coil has any effect. I will deal with the focus afterward. It uses a stick rectifier, so perhaps that could be an issue, that ady the focus coil is just overcoming, at the expense of excessive cathode current. Just speculating at this point. I need to check the drive waveforms and voltages in the horz drive circuits.

[marty59]

Maybe I missed it somewhere, but what make of set is this again?

[DaveWM]

its a philco roundie hybrid, has a SS tuner and IF, all the rest is tube.

there is no adj for horz width which seems to be the problem, the under scanning of the horz results in a raster that just fall short of full screen, with the green gun on the left falling short a bit more that the red and blue, resulting in the purple edge on the left.

I can adj the horz bias (there is a pot for that) enough in fill out the screen and get rid of the purple edge, but then the cathode current soars to over 300ma, and the KV is at 30kv.

I have to check the drive waveforms and peaks on the horz out tube grid, but its getting old. Its such a low parts count circuit, I am tempted to just shot gun the entire board.

I am going to be check the B+ more closely, starting with the current draw at the B+. Its a bit of a pain since the bridge diodes are directly soldered to the 1st filter cap (this is where the schematic wants you to check the current draw). So I will need ot un solder some very well wrapped diodes. I will prob just snip them out and replace with some 1n4007's.

[DaveWM]

http://www.videokarma.org/showthread.php?t=247179


this is the set

[old_tv_nut]

Did you try rotating in different HO and damper tubes? My CTC-5 had a width problem, turned out to be a HO tube that was OK on the tube checker but obviously not good enough in the set. Checking the H drive is also a good idea, as you said.

[DaveWM]

I did, but will try a few more. will also sub the driver tube a 6BL8

[miniman82]

Is this color 'fringing'? I just got a hold of a suplement from Mark (zenithfan) for my CTC-9 that mentions purple fringes being a result of unequal cathode potenials, so if 2 of your cathodes are tied together while the third is off a resistor by itself at the video amp tube it might be worthwhile to look at.

[old_tv_nut]

Originally Posted by miniman82

Is this color 'fringing'? I just got a hold of a suplement from Mark (zenithfan) for my CTC-9 that mentions purple fringes being a result of unequal cathode potenials, so if 2 of your cathodes are tied together while the third is off a resistor by itself at the video amp tube it might be worthwhile to look at.

Fringing due to unequal cathode potential would be expected on small bright highlights anywhere in the picture, I think - so don't go there until the scan problems (and possible edge convergence as well) are fixed.

[DaveWM]

swapped out some horz tubes (hot and driver) minor change. there were a couple out of spec resisotors the screen on the hot had a 47 that was 60+. it was in series with a 7 watt 4200ohm resistor. I am guessing the 47 was there to measure voltage drop to determine current since it gives a screen ma of 21 in the sams.

there was one cap that came off a winding from the fly that connected to the horz bias adj (which is a pot that goes to the HOT grid). I dont recall checking that cap.

there were a couple other 5% resistors that were out 20% again in the grid circuit of the HOT. the coupling cap from the horz osc to the HOT is a .0047 but its a disc so I really doubt its a problem, but again, I may just shot gun the parts in the horz circuit when I pull the chassis. I will leave the 5% caps (the clear tube ones) in the horz osc tank circuit since the horz freq seems fine. Will just replace the screen and cathode bypass caps.

there is a VDR in the bias circuit off the fly, but it has no specs so I cant check it. I assume this is used in the HV regulation, there is no shunt tube.

[DaveWM]

replaced a few out of spec resistors (not far but 20% on a 5% rated).

and a few disc caps in the horz osc circuit (mainly the coupling cap to the HOT). these disc tested "funny" on my cap tester, the eye would not open all the way and the edges were fuzzy, more so than what I have seen on other caps. I replaced with some good quality film caps, that were higher rated voltage.

There was a 23pf 1kv on the damper plate to ground, just since I had the chassis out I replaced that one as well.