K7000 to G07 Yoke Swap

[WindDrake]

Going to keep this as short as I can.

G07's have serial-connected vertical yoke winding pairs, versus the K7000's parallel connected pairs.

I noticed that the G07 yoke came out to 54R, and the K7000 about 13.5.

If you work the math backwards, that means each winding should be 27 ohms. Meaning if we swap the yoke from parallel to serially connected, it should be able to stand in for the G07 yoke...

In theory. We also have this thing called INDUCTANCE to worry about. It also must match, or we could end up with amp sections pushing too hard and puking. This includes the horizontal section, as this affects B+ as well as X-Ray output at the tube.

So, I went through my pile of tubes and noticed that I've got a bunch of Matsushita tubes with K7000 compatible yokes, as well as some other stuff like Funai and Phillips.

Picking through them, I found that many K7000 compatible yokes already had serially connected vertical windings - can't use those. But I did find a Funai tube with a parallel pair - score!

Here's what I measured.

G07-CB0
Res H: Measured 2.4R, leads 0.3R
Res V: Measured 58R, leads 0.3R
Ind H: Measured 1.646mH, leads 0.002mH
Ind V: Measured 102.9mH, leads 0.002mH

19K7901
Res H: Measured 2.6R, leads 0.4R
Res V: Measured 13.5-13.6R, leads 0.4R
Ind H: Measured 1.682mH, leads 0.002mH
Ind V: Measured 29.5mH, leads 0.002mH

Random 3 (Parallel V!)
2.3R 1.88mH leads 0.4R 0.002mH
14.1R 28.6mH

Horizontal difference from G07 - 14% inductance 4% resistance.

After parallel to serial re-wire: 54.8R 114.6mH
Difference from the G07: Resistance 7% Inductance 11.3%

These measurements fall right in line with another set of specs I found someone else took, getting 54.5/2.6 H/V resistance and 1.673mH/108.4mH H/V.

That's the yoke I rewired, for measurement. I had to heat the posts and gently unwind the windings from them, then join one end of each in the middle. It's since been buttoned up, shrink tubed, etc.

And there's the picture of it working. Absolutely fantastic picture, and none of that absolute nonsense that is trying to re-converge those HORRIBLE G07 yokes.

So yes, you absolutely can re-wire a yoke for G07 use.

 

[LordOfDoubleDee]

This is fantastic - I love the look of the G07 chassis but have really been disappointed how difficult they are to tube swap because of convergence. This looks like a good solution. Thx!

 

[DeLuSioNaL29]

Nice write-up! I'm still trying to wrap my head around the serial vs parallel windings. (no pun intended).

I typically measure the resistance on tube yokes using the Ohm setting on a multimeter. I'm taking this as a opportunity to learn... What are the "R" measurements and what are you using to read them? Those calculations threw me off.

Thanks in advance and congrats on getting that to work!

Jason

 

[LordOfDoubleDee]

^^^^I am wondering about this as well.

I thought I might hit up the OP when I was ready to try this my first time but if were talking about it now, let's do it, curious as well.

 

[TimePiloteer]

Wish it was easier to find CR23 fat neck tubes in the k7000 yoke range. Most of the k7000 compatible tubes I find from TVs are 8 pin thin neck CR31 tubes, and wouldn't swap to a G07 neck board without some kind of adapter. But really cool proof of concept there.

 

[nerdygrrl]

Rep'd even though I only understood a fraction of this, but my takeaway is that we can now, more easily tube swap G07's.

 

[WindDrake]

Nice write-up! I'm still trying to wrap my head around the serial vs parallel windings. (no pun intended).

I typically measure the resistance on tube yokes using the Ohm setting on a multimeter. I'm taking this as a opportunity to learn... What are the "R" measurements and what are you using to read them? Those calculations threw me off.

Thanks in advance and congrats on getting that to work!

Jason

Only measuring the yoke with a DMM in resistance mode gives you an incomplete picture of compatibility. The yoke is an electromagnet, so matching inductance is also extremely important. You'll need either a DMM capable of inductance, or an LCR (Inductance, Capacitance, Resistance) meter to measure it properly.

I use this guy: https://www.amazon.com/gp/product/B071WNNYQT/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

Measurements where R is used, I'm just denoting resistance. 58R = 58 ohms, etc. mH is Millihenries, a measure of inductance. Where I denote "leads", I also recorded the measurable resistance and inductance of the leads on my meter, for accuracy's sake.

Re; Serial/Parallel yoke winding setup - All yokes have two horizontal and two vertical windings, some are set up serially, some are set up in parallel. In this case, we just got lucky that Electrohome was taking a common commodity yoke and setting it up for high impedance (serial connection) on the vertical, while leaving the horizontal low-impedance (parallel). The k7000 just so happened to have a low-impedance horizontal (serial, but still low impedance) and a low impedance, parallel-setup vertical that we can re-wire to high impedance by changing it to serial.

 

[behrmr]

Wish it was easier to find CR23 fat neck tubes in the k7000 yoke range. Most of the k7000 compatible tubes I find from TVs are 8 pin thin neck CR31 tubes, and wouldn't swap to a G07 neck board without some kind of adapter. But really cool proof of concept there.

I keep wishing someone would just make a socket adapter.

 

[jacklick]

Only measuring the yoke with a DMM in resistance mode gives you an incomplete picture of compatibility. The yoke is an electromagnet, so matching inductance is also extremely important. You'll need either a DMM capable of inductance, or an LCR (Inductance, Capacitance, Resistance) meter to measure it properly.

I use this guy: https://www.amazon.com/gp/product/B071WNNYQT/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

Measurements where R is used, I'm just denoting resistance. 58R = 58 ohms, etc. mH is Millihenries, a measure of inductance. Where I denote "leads", I also recorded the measurable resistance and inductance of the leads on my meter, for accuracy's sake.

Re; Serial/Parallel yoke winding setup - All yokes have two horizontal and two vertical windings, some are set up serially, some are set up in parallel. In this case, we just got lucky that Electrohome was taking a common commodity yoke and setting it up for high impedance (serial connection) on the vertical, while leaving the horizontal low-impedance (parallel). The k7000 just so happened to have a low-impedance horizontal (serial, but still low impedance) and a low impedance, parallel-setup vertical that we can re-wire to high impedance by changing it to serial.

? So it really doesn't matter that they are serial or parallel but rather what the inductance is, correct? it matters here because you were able to take a low impedance parallel yoke and make it high impedance by changing it to serial. << do I have this right?

I am curious about the difference between a 4900 yoke (later version) and g07 yoke. I have a theory they are similar enough to swap with each other but will need to get that LCR meter to do some additional measuring.

Also like how you measured the resistance of your test leads. many of the resistance measurements of yokes are off a few 10ths or so because of different meters etc.

 

[TimePiloteer]

I keep wishing someone would just make a socket adapter.

Dezbaz makes these, out of Australia. Surprised they haven't been more popular here, but maybe the shipping costs have something to do with it.

 

[jacklick]

I found another thread about this here and also picked up one of those proster meters so I can measure this going forward as well.

Was going to hijack thread with my 4600 tube swap but will start new thread on that.

Edit>>My thread on 4900 tube swap using same method that WindDrake used. Thanks for posting WindDrake as I would have never known about this series vs parallel yoke thing.
https://forums.arcade-museum.com/showthread.php?t=453789

 

[JoeB1355]

So I was totally psyked to try this I found a fat neck tube with 3.x H and 14.x V ohms

I went to unsolder the wires fro Y-G(BR in my case) only 1 on each pole and 2 in the middle.... seems it was already wired in series to get the 14, as both sides after under doing the middle and the sides -- were only 7.x ohms each.....

Damn..... guess I'll be doing a yoke swap now...