D9400 - preventive maintenance?

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Hackcell
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D9400 - preventive maintenance?

Post by Hackcell »

Hello,

I read somewhere around here that D9400s are prone to failure due to the external coating used in Thomson tubes made in Mexico, which may end up on a broken neck. I was wondering of there is a way to prevent this to happen.... idk, like cleaning the neck of any residual material or even (if possible) to replace the external coating.

Any idea or suggestion on a preventive maintenance routine/fixup?

Thanks in advance.
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grantspain
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Re: D9400 - preventive maintenance?

Post by grantspain »

the paint flakes off and then rots through the windings of the yoke causing deflection failure and whole load of shorted components, the issue with the tubes fracturing is more down to manufacture quality in my opinion
Hackcell
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Re: D9400 - preventive maintenance?

Post by Hackcell »

grantspain wrote: March 12th, 2021, 5:46 pm the paint flakes off and then rots through the windings of the yoke causing deflection failure and whole load of shorted components, the issue with the tubes fracturing is more down to manufacture quality in my opinion
So making sure the yoke is clean would be a preventive measure (at least for the electronics). Correct?
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grantspain
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Re: D9400 - preventive maintenance?

Post by grantspain »

removing the flaky paint from the tube would help, not sure what you replace it with though
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PrincessPrinPrin
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Re: D9400 - preventive maintenance?

Post by PrincessPrinPrin »

Thomson's bigger tubes had many design flaws and their resistive coating was particularly weak compared to that of other manufacturers like Philips or Panasonic. It would be highly impractical to apply a new one for several reasons not least of which the fragility of the yoke which breaks easily if you try to remove it. On the few tubes of this type that I decided to keep I scraped off all the coating with a toothpick and then washed the whole thing to make sure it all went away.

This is Thomson's patent for the coating if you want to know the details:

https://patentimages.storage.googleapis ... 300856.pdf
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Hackcell
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Re: D9400 - preventive maintenance?

Post by Hackcell »

This is the tube. I don't see that many coating paint as in the already shared examples. Not sure if I should ger rid of the small area of coating arond the nack.
Side note... the tube is not made in Mexico as the ones that I've seen with the ton of coating paint.

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