[R-390] Re: [R-390]IERC shields (was New owner with...)

Tue, 22 Apr 2003 21:11:26 -0400

Hi,

More weird stuff:

Black - reflects heat poorly, radiates heat well (carbon black does a good
job)

Shiny - reflects heat well, radiates heat poorly. (pure gold is really good
...)

Why ? Well one way to look at it - if a black object radiated heat poorly
and absorbed it well it's temperature would go up and up if you put a chunk
of it inside a vacuum jar and shined a light on it. It would be a cool
effect, but tube plates would not be black ....

This is simply what people who make iron stoves have observed long before IR
ever got discovered. Black stoves make the room warmer .....

    Take Care!

        Bob Camp
        KB8TQ

----- Original Message -----
From: "Todd Bigelow - PS" <[email protected]>
To: "blw" <[email protected]>
Cc: "R-390 List" <[email protected]>
Sent: Tuesday, April 22, 2003 1:39 PM
Subject: [R-390] Re: [R-390]IERC shields (was New owner with...)

> blw wrote:
>
> >Found that older reference to tube shields. This was a long thread in
1999
> >and 2000. Maybe someone has the info on the pros/cons of cutting on the
tube
> >shields??? Wasn't that about berylium, or some other nasty metal?  I need
> >more coffee before I finish beating horses.
> >
> >Barry
> >
> >
> Barry and group -
>
> To the best of my knowledge, the nasty part is the insert itself, not
> the shield. Don't hold me to that though, because I didn't build 'em!
> The thinking on shiney shields is that they weren't really intended as
> shields so much as holders to keep the tube in place for gear used in
> harsh environments (like on a battleship with 16 in guns firing). Makes
> sense when you look at the bayonet base and spring in the top to keep
> downward pressure on the tube. Whatever the case, it sure doesn't look
> like removing heat was a consideration.
>
> Here's my view of cutting them (IERC): Don't. They are designed a
> certain way to perform a certain way. Altering the shape could
> potentially mess this mechanism up and defeat the purpose. Now, having
> said that, here are some other thoughts:
>
> -Use the correct size shield for the correct tube size. Or, don't use a
> shield designed for a short 9-pin on a 6U8A (slightly taller,
> medium-height 9-pin). I've seen this recently on an SP-600 listed via
> ePay. If you look at the tubes, you'll see that the shorter shield is
> snug to the top of the tube. This defeats the chimney or convection of
> heat being sinked away from the tube and passing up and out of the
> shield. You get the false security of having an IERC shield 'protecting'
> your tube, yet in reality it's just keeping heat in. Looks fancy, but
> doesn't work. One exception would be the later IERC types with the open
> sides. I've never seen these in the shorter 9-pin configuration, though.
> Still, the inner fingers have to align properly with the tube. If you
> tried using a tall 7-pin on a stubby 6AL5 for example, it wouldn't work
> worth a damn. Best thing to do is to take the different sizes and
> inspect them side-by-each. You'll quickly see the difference.
>
> -WPM sockets work well also, just not as well as the IERC types. WPM are
> more along the lines of the ELCO/EBY/CINCH bayonet-base shiney shield,
> except they are black with inserts. I have a bunch of these in older
> equipment, I'm thinking of enlarging the top opening just a bit with a
> reamer to allow better airflow up through the inserts. There's a reason
> the IERCs have a wider mouth at the top.
>
> -Some of the shiney shields actually have great inserts in them. I've
> always wondered how a shield with a shiney exterior and black interior
> with an insert would fair. Shiney exterior = reflects external heat
> floating around inside the radio instead of absorbing it. I have to
> guess that the engineers who came up with the IERC designs knew what
> they were doing, so I've never pursued it.
>
> - Heatsinks/inserts for bases are important also. Somewhere between the
> shiney shields and the IERC types, these were used to pull heat away
> from the pin bases were too much heat can cause the seals to fail
> accompanied by loss of vacuum and the associated darkness within the
> tube. I've seen only a few IERC bases made to work with the IERC
> shields, and therefore conclude that the more standard IERCs were
> perhaps made to replace older types (or work with existing designs) and
> offer an improvement in cooling.
>
> - Prices are only as bad as you're willing to pay. Sure, they appear on
> ePay for big $$ and if you want the convenience of not having to look
> around and can afford the price, it's a deal made for you. If your
> budget won't permit or you're a packrat at heart though, there are
> always the usual sources: old avionics, defunct test equipment, etc
> often yeild these nice, black tube shields. It involves being patient as
> well as looking around at surplus outlets, under tables at hamfests, or
> even dumpster diving. Where do you think the dealers who sell them
> online are getting them? Just remember when cannabilizing an old piece
> of gear to also retreive the little 'band of fingers' from the tube
> socket bases, if they're in the unit. Always check!
>
> Now, a couple years back a few of us put together a deal on here which
> yeilded a lot of these shields. I'm fairly well set myself for now,
> although I could use a few of the taller 9-pin types. IIRC, there where
> 3 of us - Bill Cotter, myself, and one other person whose identity
> escapes me. We mainly traded with other list members, with trading being
> the preferred method, selling being the second choice (Bill sold a
> bunch, though). If there's enough interest and enough people have at
> least some amount of surplus they'd like to trade for sizes they need,
> we could try it again. Sizes are(from memory, don't yell if I'm wrong):
>
> 5015 - short 7-pin (6AL5/5654 etc)
> 5020 - medium 7-pin (6BA6)
> 5025 - tall 7-pin (6AQ5 etc)
>
> 6015 - short 9-pin (6AK6?)
> 6020 - medium 9-pin (6U8A, 12AX7 etc)
> 6025 - tall 9-pin (12BA7, 3TF7, etc)
>
> So....any interest?
>
> de Todd/'Boomer'  KA1KAQ
>
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