Help! - Measuring Vertical Winding Impedance - or, "Ken Layton, where are you?!

[RetroJames]

If you saw my other post you know I am pressed for time, hence the noob cry for help.  From the 8-liners website: http://www.genao.com/datatech/monitor.html

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For 13, 19, 20 and 21 inch TV's:

Find a TV.  The TV could be a broken one since you are only going to use the CRT with the yoke.  The connector for the neck board must be of a specific type and most TV's have this type (see picture below).  Measure the ohms of the vertical winding on the yoke (usually Green and Yellow! Red and Blue are horizontal deflection).

The measurements should be between 11 to 17 ohms (Low Impedance) or more than 37 ohms. (High Impedance). You must also note what type of neck board you need: 8 pins or 10 pins.

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My question, "For a 19" tv, how exactly do I measure the imedance of the vertical windings?"  Please explain as if I were 2.  You guys rock, thanks!  

James

[menace]

on the tube there should be a wire harness coming out with 4 colored wires, red, blue, green, yellow, Stick an ohm meter between the yellow and green leads and that should be your vertical windings.

[Ken Layton]

I've been gone part of the day on an emergency service call to a local theater and will back there part of tomorrow to finish the job.

Get a digital multimeter and set it for resistance measuring (ohms) on it's lowest scale. Stick the leads in the yellow and green wire holes in the yoke connector (with the monitor power off!). If the resistance is less than 11 ohms then you can't use an 8liners chassis with that yoke.

[MonitorGuru]

To be techincally correct.. You can use ones with lower than 11 ohm DC resistance however you won't be happy with the results (and it could stress the chassis of course)

If you look in the WHOO MAMA thread and look at my tests posted to OSCAR'S site, you will see that the use of a yoke rated at about 8.6 ohms IIRC produces a horrible pincushion on the 8liners chassis due to the impedence being off.

Finding one closer to 15 ohms is the key. Lower and you'll have more pincushion it seems.

However, remember this: Measuring DC resistance is ONLY AN ESTIMATION of the real impedence of the yoke. Impedence is AC resistance that varies at each frequencey, ala your home stereo speakers.  Two yokes both measuring 15 ohms may produce significantly different results, especially on vertical linearity as well as possible beam bending at the corners due to differences in Impedence.  That's why finding an "exact match" for ANY chassis hard, and why many people who keep old arcade chassis also keep the yokes from dead tubes around for a later swap.

And though not mentioned.. horizontal impedence also affects the picture in similar (but 90 degree rotated) ways. The reason it's not discussed when talking about things is that most every yoke has about the same resistance.. somewhere around 2.3 ohms on the horizontal yoke. Therefore you dont need to pay attention to that when finding a tube (but always should doublecheck). But the impedence will be different on every yoke even on horizontal.  

Good luck with your search!   If you try multiple tubes, post the tube numbers, where they came from and pictures and I could whip up a web page and see if Oscar would host more examples for the 8liners chassis along with my reviews.