Deflector Yoke and Motherboard Pairing

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Deflector Yoke and Motherboard Pairing

I have just picked up a project Macintosh Classic II. It came with a deflector yoke on a samsung CRT. The connector on the yoke is the clip style, but on the analog board has the connector style without a clip. Is it posible to swap the connector out , or will a diffrent CRT yoke need to be sourced?

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Not sure

I think the parameters of the yoke were changed, thus the different connector?

This should be covered in one or more of Larry Pina's Macintosh repair books.

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Ok, thank you. I will have to

Ok, thank you. I will have to take a look at that book. Would you happen to know if the yokes and CRT's are interchangable. Like if i found a yoke with the connector that matches the power supply will it still work with the Samsung tube?

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Yes

I am pretty sure that the yokes will fit over any 9" CRT.

The manufacturers changed, but the electrodynamic properties are identical (tube length, accelerating voltage, and screen dimensions). And the ring size of the tube neck is the same so they will fit on to it.

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Hm

According to Pina's "Mac Classic & SE Repair and Upgrade Secrets", the yoke connectors are incompatible between the Classic and Classic II.

I don't know if the yokes themselves are different (technical information at that level is amazingly difficult to find) but it seems likely.

 

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I have a non-working Classic

I have a non-working Classic II also...  Mine the CRT seems to be OK, but it just comes up with garbage on the screen when powered on.  No startup chime.  I'm guessing maybe bad memory or something.  Haven't had much time or inclination to look at it much.

 

 

 

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More notes

I verified the resistance of the yoke's horizontal coil (the upper two pins of J1) is 0.2 Ω, and the vertical coil (the lower two pins of J1) is 8 Ω on a Macintosh SE.

Since these are air coils the inductance is roughly proportional to the resistance and can be disregarded with respect to compatibility questions.

These measurements agree with the ones given in Thomas Lee's "Classic Mac Repair Notes" which is largely about the 128/512/Plus but has a few comments about the SE and Classic.

Some information I found does state that the Classic and Classic II use incompatible yokes to the earlier B&W models, although the author appears slightly confused on the subject: if you move an existing yoke to a replacement picture tube, the yoke is not replaced and no adjustments to the analog board would even make sense!

What I was not able to find are actual measurements of the electrical parameters of the earlier/later Classic & Classic II (with and without locking connector clip) yokes, which is what you most need to guide your project. Sorry!

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