[Bradley Rush]

As a test I have painted some tube shields Black. Strictly non LAB conditions measured the temp. The Black painted Tube Shields did read a higher in TEMP.

But is it worth the trouble for what lil you might gain?

[morzh]

What is it exactly that you were trying to gain?

[jerryhawthorne]

+1 for Morzh, Why? Not original and in most radios would not look right.
Jerry

[murf]

I agree.
Let us know how long they stay black.
I will bet the heat will destroy the paint.
But then, we all have different tastes.
murf

[morzh]

Well, for heat destroying paint I can tell that I painted the ballast tube from Stromberg Carlson after I removed the rust by naval jelly.

However. I used the enamel I got with my gas range for taking care of nicks and chips of the cooktop panel (right now it is in a condition that makes any nick look anemic - I cook a lot and do not necessarily wipe right away, so the enamel goes to other uses).
It stands well to heat, but then it was designed for this exact purpose.

Now as for black color, a material that is black radiates better, hence anodizing heatsinks and such, but then anodization does not detract from heat conductivity serving as heat insulator, which paint might do.

This said, I have an impression our friend here read somewhere various things about improvements, such as sequencing voltages and painting shields. I even think there may be websites with people who might believe those are all great things to do.
To me these theories hold as much truth as the theories of Monster Cables which for the price of $200 - $1000 a set will greatly improve your sound. I am sure they will. I will let other people test those theories though.

[klondike98]

I thought the shields on tubes were for mitigating electrical interference and preventing unwanted oscillations in circuits?

[morzh]

Well... our women are there to mitigate ...whatever it is they mitigate, and to prevent unwanted oscillations (of us) but does that mean they cannot look good too? And paint is a major part of looking good.

[keithw]

If you want to find if the painted heat shield improves heat transfer you should measure the tube inside rather than the heat shield. Isn't the purpose of a heat shield to keep the heat in and be cooler on the outside?

So, how does a heat shield work? The heat from the tube is primarily radiated as IR with some visible light. That energy strikes the inside of the heat shield. Some is reflected back toward the tube and some is absorbed and heats the shield. If the inside is shiny then more will be reflected and less absorbed. If flat black then more will be absorbed and less reflected. The absorbed heat will warm the heat shield. That heat will be reradiated from the inside and outside evenly if the surface is the same and perhaps unevenly if the surfaces are different. So, the heat radiated by the outside of the heat shield is the heat put out by the tube minus the amount reflected back toward the tube minus the amount reradiated back toward the tube. On top of this some heat is conducted to the chasis and some is removed by convection of the air.

It is actually a bit more complicated than that but thermodynamics are really not my thing.

keithw

[Bradley Rush]

They are no longer black. Iwas trying to see if they work better after reading several articles on line. So I did paint some just on the inside as well. They got hotter than the non paint.

Is the sheild only for interferance or does in also help not to heat up other tubes near by as well? I thought that:
1. Shield protects tube from outside interferance
2. Protects surrounding tubes for getting heat generated form sheild tube.
3. Look good and hide the pretty filaments

[keithw]

The tube shield is to block electrical interference. The functions of containing heat, retaining tubes, etc. are secondary. Some of the foreign tubes, Italian and I recall, had the shielding material painted onto the tube.

Recently worked on a GE I think it was that was just being a pain to allign. Then I noticed that one of the tubes had a shield base and no shield. After intalling a shield things went much better.

keithw

[morzh]

The sole function of the shield is EMI (el. mag. interference) rejection/containment.
If anything, it will keep the tube hotter as it impedes the natural air circulation.
If your shields are clean, leave them alone.
If rusty, apply anti-rust agent, clean, rinse, dry and then leave them alone.
If used to be chrome plated (this is strictly aesthetic) - clean, plate, leave alone.

Do not paint.

And, one more thing, when you go to some questionable website and read some questionable articles, do yourself a favor, at least ask for opinions other people with experience, like the folks here - many of the got tons of experience and will gladly help.
This will save you time.
Time is money.
Money is more radios in your collection.

And remember, you are a radio restorer, not a painter.

[Bradley Rush]

Thx all

Just want to Say THX you all. Your Help on all my projects has been Great. That's why I will continue to come here and get help.