Why no love for this GE roundie ? - Page 16 - Videokarma.org TV - Video

DaveWM · #**226** 01-13-2015, 11:47 PM

check the schematic, see if its isolated by caps or tube elements, if so then you can check in circuit.

tvcollector · #**227** 01-16-2015, 02:11 AM

I just ordered up some resistors.. I did find that 2.2meg resistor like you said, that's isolated near the .1 cap.. It measured around 3.0meg cold.. I also tested the Shunt regulator tube.. The tube chart shows a 6EA4.. There is a 6EJ4 in there.. On the tester it tests into the lower good side, and needle falls while in the test mode.. During life test it drops into the "?".. Now would this tube be causing the issue with the HV maxing out only at 22kv?

DaveWM · #**228** 01-16-2015, 07:56 AM

tube testers are not much good in sweep circuits, subbing for known good ones is the way to go. 3.0 is a little high, but i seriously doubt its the problem.

tvcollector · #**229** 01-16-2015, 09:40 AM

Well there is another resistor that's slightly high, was thinking between the two is creating the vert problem.. Should I try and change them out, or what else would be the problem?

DaveWM · #**230** 01-16-2015, 10:24 AM

is the linearity set properly? they interact.

Electronic M · #**231** 01-16-2015, 11:10 AM

High is relative. I don't know if you know about tolerances, but if you don't here is the deal: The fourth band of a resistor represents the tolerance and is either gold (5%), Silver (10%), or absent (20%). Multiply the tolerance % by .01 then by the resistance of the resistor. This will give you a permissible deviation value. Subtract the permissible deviation from the part's labeled resistance to get the minimum allowable resistance value of the part, or add the deviation to the labeled to get the maximum allowable resistance....If the measured resistance is between the min and max allowable resistances you just calculated based on the label consider it to be a good part, but if it is outside those bounds (or inside and really close to the edge when trouble shooting a tough fault) declare it a bad part and replace it.

tvcollector · #**232** 01-16-2015, 03:44 PM

I'm able to set Linearity properly with the crosshatch pattern to were all squares are pretty even....

I know a bit about tolerances.. the 2.7 meg resistor measures around 30meg and even higher when hot.. It measure up to 38megs, so I would say that's a bit out of it tolerance..
The 2.2meg resistor measures at 3.0 cold, and even that is slightly out of the tolerance range, I believe..

None of them are one time, or double out of range.. I've measured pretty much every resistor on that board and in the HV section.. Most are within range, just a few that are slightly higher, and maybe even questionable.. But nothing I could find that's way out of spec.. There is a a 12 meg resistor (R141) on the bottom part of chassis that is apart of the shunt tube circuit and measures in circuit at 1.2meg.. I haven't tried measuring that out of circuit yet, and I don't see that being a problem with the vertical issue.

I take the meg and plus/minus the percentage.. Here's an example: 2.2meg plus 10% = 2.42 meg

Seems like 10% is most common, followed by 5%..

tvcollector · #**233** 01-20-2015, 05:47 PM

I changed the shunt tube with one that gives better emissions, and the HV did go up slighty, and now is at 24kv, still with the HV control maxed out...

The big green 7watt power resistor (in middle of image slightly upper right) that is 13k (R134) measures around 17k...

I did a digikey and mouser search for one.. And both don't have power resistors in this spec and wattage..

Now for the Vertical issue.. I replaced the 2.7meg resistor the other day, and it made the vertical slightly better, and now doesn't drift like it did.. Today I replaced the 2.2 meg resistor and another one that was a bit high in spec and also replaced the vert tube, and it didn't do much difference.. When I replaced all resistors today all i noticed that centering was off, and so I re positioned the centering control, and also when I replaced the tube, again all it did was throw off the centering a little bit to where I needed to position the control again.. I get full vertical.. And that's with the Vert height control at 100% maxed out.. But should I have more range? Shouldn't the vert control be around the middle for the maximum height instead of all the way up?

tvcollector · #**234** 01-20-2015, 06:06 PM

And why is the blue line in the service mode look like this? Should be a straight line across without it doubling.. It was straight before..

Electronic M · #**235** 01-20-2015, 06:50 PM

R134 needs to be changed. Look for a higher power rated unit if available. If worse comes to worse get a 10K and a 3K (3.3K might be more common) of sufficient wattage and put the two in series to make 13K.

tvcollector · #**236** 01-20-2015, 07:57 PM

Thanks for the input.. That resistor is in line with Grid 2 on the Horz output tube.. Wonder if this would help with the HV, and Vertical issues?

Digikey has a 13.5k 7watt one here:
http://www.digikey.com/scripts/DkSea...12702468193910

I think it's close enough...

The horz centering is slightly off.. Seeing how flyback was replaced.. There is no centering control that comes out of the side of the HV cage next to the HV output tube.. How would I go about centering?

Findm-Keepm · #**237** 01-20-2015, 08:29 PM

Quote:

Originally Posted by Electronic M

R134 needs to be changed. Look for a higher power rated unit if available. If worse comes to worse get a 10K and a 3K (3.3K might be more common) of sufficient wattage and put the two in series to make 13K.

And make sure it is a film type resistor. Those Corning film types are used to eliminate inductance that would be present with a wirewound. Corning FP (light blue) or Mallory MOL (green) resistors were used, but now, any Metal Oxide resistor of sufficient wattage will do.

Edit: Corning Glass Works is now part of Vishay - the Dale/Vishay FP10 series is the equivalent. Mallory no longer makes film resistors.

old_coot88 · #**238** 01-20-2015, 08:39 PM

I wouldn't worry about H centering as long as lin looks good and width fills out all the way, which appears to be the case.

tvcollector · #**239** 01-20-2015, 08:52 PM

I can't find anything that is film type.. Everything at Digikey is wirewound.. I've tried the different combinations too.. I'm able to find a 10k 7watt film resistor on mouser but 3k or 3.3, no luck.. Anyone of a source besides digikey and mouser that would have this?

dtvmcdonald · #**240** 01-20-2015, 09:26 PM

You don't have to use series combos. Parallel works fine too.
For example, use a 15k 10 watt film, readily available
cheap from Mouser (some are odd shape) in parallel with a
regular film 2 w 100k.

Or use three 56k 2 watt in parallel with one 47k or 51k 2w.
Or don't worry and use 5 68k 2 watt in parallel.

When paralleling, don't stick them right up against each
other, give them some cooling air.