Admiral Yoke

[Gregb]

I am working on an Admiral 17" Bakelite set and it had a bad yoke, original part number 94C 51-1. The center tap was open and I was not able to find the break
I purchased an NOS Thordarson Y-10 that was listed as a replacement and the set works but has bad ringing on the left half of the screen. I have tried changed the value of the cap on the yoke with little to no change.

The set has been completely re-capped and most resistors changed as well.

Does anyone have any suggestions?

Thx

Greg b

[Kevin Kuehn]

Damper tube is generally associated with left side ringing. If you can provide us with the model or chassis number that would be helpful.

[Gregb]

It is chassis number 19B1. I have tried a couple different NOS damper tubes with no change.

Greg b

[Kevin Kuehn]

I would try taking the filter network out of the original yoke and replace that for what came in the Y10. Looking at Riders schematic they show a 47pf cap in series with 1000 ohms. My Thordarson catalog shows only a 56pf cap there. Also make sure you don't have the yoke leads reversed. Ordinarily you'd catch a reversal because the picture would be mirrored, but it could be overlooked if you're focusing on other issues.

[edit] The filter network should be across the coil connecting the damper cathode.

[Gregb]

Sorry Kevin for the delay, the wife has side tracked me to another project. I will give your suggestion a try tomorrow.

Greg b

[bandersen]

I recall having ringing issues with an Admiral a few years back and ended up adding a filter.

I'll try to dig up my old project thread.

Sources of ringing and possible cures are discussed in this excellent book.
https://worldradiohistory.com/BOOKSH...-Darr-1963.pdf

[bandersen]

Haven't found it, but here's another discussion on the topic with some component values: https://www.antiqueradios.com/forums...c.php?t=108670

[Kevin Kuehn]

Originally Posted by bandersen

I recall having ringing issues with an Admiral a few years back and ended up adding a filter.

I'll try to dig up my old project thread.

Sources of ringing and possible cures are discussed in this excellent book.
https://worldradiohistory.com/BOOKSH...-Darr-1963.pdf

Seems like your latest GE restore was ringing too?

I finally got through reading the book you linked to, very good read.

The whole horizontal scan sequence is more complicated than I'd previously envisioned. Basically designed to resonate at the 4th harmonic of the scan frequency to accommodate the retrace staying within the horizontal blanking period. So this ringing we often encounter is really an inherent design feature, more less working more efficiently than it needs to. The damper tube is suppose to dampen the harmonic oscillation during retrace, but it doesn't always do it's job so well, and so we end up with several oscillations when the horizontal output starts tracing back across the screen.

[bandersen]

Yes, it sure was. That's what led me to that excellent book. I went through a dozen horizontal output and damper tubes to nearly eliminate ringing in the GE. If that hadn't worked, a filter was the next step.

I also experimented with a solid state damper and it reduced the ringing as well.

[old_tv_nut]

Originally Posted by bandersen

...
I also experimented with a solid state damper and it reduced the ringing as well.

Thanks for that comment - I never thought about that difference between tube and SS damper diodes.

[Gregb]

Sorry been really busy. I ended up putting the 47pf cap and 1K resistor in the new yoke and it did improve it but it is not gone. I am going to call it good for now as I have a bunch of other projects I need to get to and the picture on this set is pretty good as is. Maybe I am being to picky on this 69 year old set.

Greg b