Two Way Hourglass Bends on My KCS47

[old_tv_nut]

Originally Posted by Chris K

I wonder if there's anything proactive that one can do to prevent winding insulation failures in yokes, power transformers etc. If you took a transformer core and submerged it in a varnish or shellac filled container for a period of time, could the insulation be beefed up to extend the life of the component? All these things will fail one of these days.

Don't know the answer in terms of a detailed procedure, but I do recall cases where the item being potted is put in a vacuum chamber to expell any air bubbles caught in the item - dunking may not be sufficient.

[Kevin Kuehn]

Originally Posted by old_tv_nut

Don't know the answer in terms of a detailed procedure, but I do recall cases where the item being potted is put in a vacuum chamber to expell any air bubbles caught in the item - dunking not be sufficient.

Over on the ARF there's a couple Australian engineers that swear on cooking transformer windings in mineral spirits to dissolve any wax. And while it's still hot dunk in marine grade polyurethane varnish. The theory goes the hot mineral spirits draw the vanish inside and replace the solvent as it evaporates. There's a write up of the process.

[jhalphen]

Hi to all,
Hi @Kevin Kuehn,

the ARF thread on saving/restoring flyback transformers is here :
illustrated by many photos.

https://antiqueradios.com/forums/viewtopic.php?t=444436

See also the flyback restoration section (pages 2 to 4) in a Bush TV22 UK TV restoration article by ACORNVALVE of Australia.
38 page pdf, color photos :

https://worldphaco.com/uploads/BUSH_TV22.pdf

Best Regards
jhalphen
Paris/France

[Chris K]

Originally Posted by Kevin Kuehn

Over on the ARF there's a couple Australian engineers that swear on cooking transformer windings in mineral spirits to dissolve any wax. And while it's still hot dunk in marine grade polyurethane varnish. The theory goes the hot mineral spirits draw the vanish inside and replace the solvent as it evaporates. There's a write up of the process.

Last comment from me as I feel the "SEPARATE SUBJECT REQUIRED!" wrist slap is on its way!

I read several of them and they are fascinating. In addition, I'm a little apprehensive about the health and longevity of my TVs with a flyback winding exposed by cracking and/or melted wax. I have several Philco restorations that have that era of flyback and I have a designer, special edition Hallicrafters 7" that exhibits the heat related fading brightness symptom. I think I should probably get to them with some corona dope sooner rather than later.

I suppose the most efficient way to drag varnish into the windings is to match the base solvents as closely as possible.

[Kevin Kuehn]

Originally Posted by Chris K

Last comment from me as I feel the "SEPARATE SUBJECT REQUIRED!" wrist slap is on its way!

I read several of them and they are fascinating. In addition, I'm a little apprehensive about the health and longevity of my TVs with a flyback winding exposed by cracking and/or melted wax. I have several Philco restorations that have that era of flyback and I have a designer, special edition Hallicrafters 7" that exhibits the heat related fading brightness symptom. I think I should probably get to them with some corona dope sooner rather than later.

I suppose the most efficient way to drag varnish into the windings is to match the base solvents as closely as possible.

My advise is try not to go crazy obsessing over the longevity of any vintage electronics. Try as we may these things aren't going to last forever, and will require ongoing maintenance to keep them working in the midterm. But our lives are relatively short, so enjoy them while you can. This is my fatherly advise for the day.

[Chris K]

Originally Posted by Kevin Kuehn

My advise is try not to go crazy obsessing over the longevity of any vintage electronics. Try as we may these things aren't going to last forever, and will require ongoing maintenance to keep them working in the midterm. But our lives are relatively short, so enjoy them while you can. This is my fatherly advise for the day.

Now that’s funny 😄 Actually I still have my dad rattling around at 96 telling his 65 year old son the same thing!

[Electronic M]

Originally Posted by Chris K

Last comment from me as I feel the "SEPARATE SUBJECT REQUIRED!" wrist slap is on its way!

I read several of them and they are fascinating. In addition, I'm a little apprehensive about the health and longevity of my TVs with a flyback winding exposed by cracking and/or melted wax. I have several Philco restorations that have that era of flyback and I have a designer, special edition Hallicrafters 7" that exhibits the heat related fading brightness symptom. I think I should probably get to them with some corona dope sooner rather than later.

I suppose the most efficient way to drag varnish into the windings is to match the base solvents as closely as possible.

Nobody has had any luck with fixing the original HV osc transformers in 7" halicrafters. Easiest thing is to find a Motorola TS-4 or TS-18 chassis set (the most common electrostatic TV) with a dead CRT or cabinet beyond restoration and steal the HV transformer from it. Copy the Motorola HV osc circuit but use a 8BQ5 instead of a 25L6. Replace the 6C4 heater with a resistor. The Hallicrafters has a split heater string that converges at the 6X5s hot heater pin (it's other heater pin goes to ground). Ungrounf the 6X5s grounded heater pin and insert the 8BQ5 heater between that and ground. I did this modification on my Hallicrafters and it's been solid ever since.

[Chris K]

Originally Posted by Electronic M

Nobody has had any luck with fixing the original HV osc transformers in 7" halicrafters. Easiest thing is to find a Motorola TS-4 or TS-18 chassis set (the most common electrostatic TV) with a dead CRT or cabinet beyond restoration and steal the HV transformer from it. Copy the Motorola HV osc circuit but use a 8BQ5 instead of a 25L6. Replace the 6C4 heater with a resistor. The Hallicrafters has a split heater string that converges at the 6X5s hot heater pin (it's other heater pin goes to ground). Ungrounf the 6X5s grounded heater pin and insert the 8BQ5 heater between that and ground. I did this modification on my Hallicrafters and it's been solid ever since.

Thanks Tom. I’ll have to get that set out of storage and give it some CPR. I thought it was a not working for parts sale on eBay but someone before the flipper who sold it to me restored everything. All caps, all resistors…absolutely everything so I haven’t done too much to it except put it on a shelf

[Penthode]

Did you fix the hourglass issue? It is not the yoke.

[Chris K]

Originally Posted by Penthode

Did you fix the hourglass issue? It is not the yoke.

No my friend, it's not fixed. The temporary viewing Band-Aid is to increase the image zoom using a Zenith converter box so the letterbox borders are off screen but, you can still see the bends in any sort of straight horizontal or straight vertical images. I had the TV show "Concentration" on where there's a crosshatch letterbox game board and you can see it there.

Just a quick edit of this post. The bending was reduced when I pushed the yoke forward and the zoom made it watchable, so I was happy with it and that's why I sorta put it to rest but yes P'thode, the problem still exists although it's far less noticeable. It has always struck me that this is probably a voltage issue with the B+ being low...at least the B+ going to the yoke. To be honest, I've not checked the DC level on the TV but there's a NOS 5U4 in it so my confidence stemmed from that.