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What's wrong with those porcelain plate grips?

Discussion in 'Amplitude Modulation - AM Fans' started by K5UJ, Sep 7, 2017.

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  1. K5UJ

    K5UJ Ham Member QRZ Page

    TR1_busted_811A.jpg

    Here's why they suck. Actually the question should be: Why do hams think these $%^&ing things are so WUNDERFUL?

    Dennis, if you could shoot me three of your spring grips if you can spare them that would be awesome. I need to cut off those porcelain POS and **** can them so they don't do any more damage here or anywhere else. yes I'm kind of pissed off.

    I'll cover postage, etc. just let me know & tnx

    Rob
     
    WA3VJB and N6YW like this.
  2. W7TFO

    W7TFO Subscriber QRZ Page

    Will do, Rob.

    You can tame them a bit with a rotary stone in a Dremel tool to remove some of the little tits inside that grip too much.

    73DG
     
    N6YW likes this.
  3. K5UJ

    K5UJ Ham Member QRZ Page

    Thanks D; much appreciated.
     
  4. WB2GCR

    WB2GCR Ham Member QRZ Page

    Don't think I've seen an 811a(??) with ceramic up top around the plate cap!

    That's cement failure, something that happens pretty regularly with old tubes.

    As far as popular? Don't think popular so much as available. And they are insulated.

    I spent some time researching "lamp cement", which is what is used to hold tubes together.
    Apparently you can get some of the newer white compound that is often found holding halogen
    bulbs together. Although I have not acquired any, and it's still not easy to source in small quantities.

    They also made a spring type plate clip, squeeze to open up several turns of spring steel, but they're not insulated.
     
  5. WA3VJB

    WA3VJB Ham Member QRZ Page

    I lost a nice JAN-4D32 to one of those "pretty" ceramic caps, that I had converted from the stock spring clip because it looked nicer. OK, cut me some slack, I was still a Novice and didn't know any better. But it's true, the damn things need a lot of twist to remove, and that torque can easily crack the old cement, which otherwise would have been fine had a spring clip been used.

    As for insulation, the merit of that is lost in most instances since who would be fishing around in an energized area anyway. And if other components were in close proximity, insulate THEM rather than risk the physical integrity of the tube with those ceramics.
     
  6. K5UJ

    K5UJ Ham Member QRZ Page

    Steel's no good for RF however it might be okay on modulator tubes. Thanks for reminding me--I was going to ask about high temp. glue for the plate caps and forgot to. What I have done is simply re-solder the plate caps back on, but then they have to be used with spring clips because the only thing holding them is the solder and anode wire.

    The older versions of a lot of higher v. top anode tubes had the ceramic ring. It went away when things got cheap. I have 866As with it and later ones without it.

    Yes, it seems like only the porcelain caps are to be found mostly, and the spring clips are unobtainium, probably due to the nanny state and liability FUDs. Who in their right mind is going to stick their body parts into an area with live h.v. on the anodes (or anywhere else)?
     
  7. N2DTS

    N2DTS Ham Member QRZ Page

    I have not lost a tube to the spring clips and do use them.
    Better is the heat sink type plate cap with the set screw.

    I only have so many of those....

    On a side not, the Russian tubes have a smaller plate cap (metric?) that the normal caps dont fit, they are too loose which is good since the glue used on those tubes lasts until you use the tube...
     
  8. K9STH

    K9STH Ham Member QRZ Page

    The Ameritron AL-811 and AL-811H often come with the ceramic plate caps that are, basically, impossible to remove without breaking the 811A tubes. These are new tubes and the adhesive, that holds the plate connector in place, definitely does it job. The glass envelope breaks instead of the connector coming loose.

    Glen, K9STH
     
    N5DMC likes this.
  9. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    IMHO...
    One scenario would be to etch the glass in a manner that wouldn't compromise structural integrity,
    thus giving whatever cement/bonding compound a chance at "digging in" without breaking off.
    Perhaps there are Silicone adhesive products that can do the job and handle the heat, but getting
    it to stay put is another matter.
    Here's a thought. Solder an insulated flying lead to the plate cap and make the connection directly to the
    plate choke by any means needed. The plate caps on many tubes are soldered on anyway, like the 811A.
    I have repaired many in this manner and it works just fine, thus negating the need for the clumsy
    porcelain thingy.
     
  10. K4KYV

    K4KYV Subscriber QRZ Page

    The easiest way would be to never use those p.o.s. insulated caps in the first place. I always toss mine after smashing them with a hammer so no-one will ever ruin another tube with the damned things. The problem is that over time, humidity and air pollution may cause a reaction between the metal in the caps and the metal in the clips, so that they freeze in place. With the spring clips, it's easy to insert a thin blade like a knife or miniature screwdriver between the cap and the clip, and gently pry them loose without stressing the tube cap. Sometimes a tiny drop of WD-40 helps release them.

    Whenever I encounter a piece of equipment with those insulated caps, if a gentle tug (not a twist) doesn't remove them, I disconnect the wire or cut it off right at the clip, then carefully hold the tube in place while engaging the insulated part in the jaws of a vice, and tighten the vice until the ceramic cracks and falls away. Then the remaining part of the clip can be pried off without pulling the cap off the tube. I then replace the caps with spring clip ones, even if the insulated clips did easily come off the tube; no guarantee they will come off so easily next time. If no spring clips are available, a piece of copper or brass strip can be used, wrapped round the plate or grid cap and tightened in place with brass 4-40 nuts and screws.

    I grab every spring clip I can find at hamfests and flea markets. I have been known to dumpser-dive or pull from a box under a hamfest table, an otherwise worthless piece of junk just to salvage spring clips I spotted dangling from wire leads.
     

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