The AM Forum

  I have a 1625 that was removed from an ART-13 I got the other day, the plate cap came off. Looks like I can re solder it back but the what would be a good product to glue it back to the tube? I'm not sure that standard epoxy or glue will take the heat well.



                                                Tom W6TOM

Ive used what is close to the original since being told in the 50's. Many modern glues have different expansion characteristics that can crack the glass

Ordinary old fashioned Furnace Cement is a close match to the original or other hard to find products. The silicate based variety may be stronger but hard to find in the nanny states.

Pick out the loose cement in the cap and lightly scrape any loose residue on the glass, perfection not required. Make sure there is a clear path for the wire to pass thru; clean the wire and re-tin.

Clean the glass area to be covered, lightly moisten and apply the cement. Wipe off excess with a damp cloth. It helps to use heat to cure; I place the tube in an operating radio with a modest weight to keep pressure on the cap. Dont disturb for 12-24 hours depending on the cement instructions. On a large tube apply just filament voltage, while some smaller ones can run in a tube tester.

Ive repaired transmitting and receiving tubes that way and havent had one come loose yet.

If you live in an area that doesnt use furnaces in homes try an industrial supplier.

Carl

For years I have used Dow 3140 flowable silicone RTV.

It sticks to everything like crazy, and adds just a tiny bit of 'give' that hard glues like super-glue and epoxy don't have.

Besides, those come loose with heat, something you expect from a tube.

Use a tiny bit in a throw-away syringe, and run it into the cap (inverted) or base depending.  Set aside for a day and you will be impressed with the hold.  So far, I have not needed to unsolder things to get it in, as it is thin enough to wick in.

If a bit is excess, trim it with an Exacto-knife or blade after set.

It ain't cheap, but 90 ml will do a LOT of tubes:

http://www.ellsworth.com/dow-corning-3140-rtv-silicone-conformal-coating-90ml-tube/?gclid=CMfZ396dkbUCFQ_hQgodgFIAqQ

73DG

Wasn't the original tube cap type of stuff called glyptol cement?  I'll have to look it up. Brownish/Tanish and powderish upon drying.   ...and all the little ish's.

Glyptol was a chemical division of GE and was spun off in the 80's.  They made a number of products but we use to call the liquid you used to stop corona around TV high voltage Glyptol as I remember. It probably had a real name and we called it by the company or division name.

Search- "How do you re-glue a plate cap" in this forum for more answers

I've seen a number of people say that JB Weld epoxy works great.

Thaaaaat was funny. I did it.  ;D

http://amfone.net/Amforum/index.php?topic=25780.0

Should have referred to it this way.

I referred back to the old thread and I looked at the Lowes site and found the following products.

http://www.lowes.com/pd_15879-138-35515_0__

http://www.lowes.com/pd_316174-76554-B13287_4294765325__?productId=3455644&Ns=p_product_avg_rating|1&pl=1&currentURL=%3FNs%3Dp_product_avg_rating|1&facetInfo=

http://www.lowes.com/pd_64843-85334-GA0188_0__

Would any of these products be suitable for plate cap bonding?

If not does anyone have a specific product that might be available locally?

Forget all the dark and dirty glues. Go to any auto store and buy a tube of Permatex rear view mirror glue for gluing rear view mirrors back on the glass windshield. Drys colourless. Very strong. Designed SPECIFICALLY (pay attention here) for gluing metal to glass. I use it and nothing else not only for caps but also for regluing loose tubes back in the base.
Don VE3LYX

All in all, it is a lot of friggin' work for a $3 NOS tube... :P

73DG

Well in my case its a 572B but in reality it is not a lot of work once you get the right material. It shouldn't take more than 10 minutes to do. If the tube is good its worth saving.

Dennis, I'd love to know where I can get NOS 1625's for $3!

How many would you like?

PM me.

73DG

10 would be nice.

I just bought 10 off ebay paid $39. Cost almost as much to ship them. So I am in about $6 each but I have some ARC5 stuff so jumped at the chance since I already needed one. My tube not only had a loose cap but the glass underneath had also been broken so I didnt have the oppourtunity you do to repair it.
Don VE3LYX.