Removing valve caps

[Gabe001]

I'm not sure if I'm using the correct nomenclature, apologies for this.

I need to remove the 2 caps marked in the photo from the valves so that I can give everything in my filthy set, from a smoker's home, a good clean (the photo isn't from my set).

I tried pulling one off gently, and off came the valve top cap with it. I'm now left with a wire sticking out of the top of the glass of the valve (6k7g)- I'll try to stick it back on with epoxy and resolder the wire as described elsewhere.

Am I doing something wrong? I need to remove the second one and I'm a bit wary now.

Thanks
Gabriel

[Herald1360]

Since those metal top covers make any access problematic all you can do is be careful. A bit of Plus Gas (clean it off afterwards) or switch cleaner sprayed in and left for a while might help.

At least you've still got the piece of wire left and haven't let the vacuum out!

[OldTechFan96]

Could you not remove the valve from its socket, turn it upside down and trickle some switch cleaner between the cap and valve?

[Gabe001]

Thanks both. I'll try squirting some servisol and see.

My (nicotine coated) valve didn't go white yet so fingers crossed it's still serviceable!

Gabriel

[snowman_al]

It happens with top cap valves. You at least have a bit of wire to work with and do not have to file the glass pinch...
Make sure it is absolutely clean and shiny before soldering a loop round it, some times the wire 'repels' new solder if not spotless.
Fortunately 6K7 and 6K8 etc. are fairly plentiful still.

[high_vacuum_house]

I think the best way to remove them is with a gentle pull straight upwards. No wiggling or twisting which would break the cement glue between the top cap and glass. Cleaning the cap of old solder and ensuring there is a small hole for the wire to pass through, then Soldering a new length of wire to the stub before soldering the cap back into place. Something like araldite in the cap first to make a good mechanical joint between the glass and cap first before soldering.

Christopher Capener

[Kentode]

This is what they look like underneath Gabriel. If you can get a screwdriver into the slot arrowed, the valve will just fall out!

[Gabe001]

Thanks Alan, will do

[Gabe001]

Originally Posted by Kentode

This is what they look like underneath Gabriel. If you can get a screwdriver into the slot arrowed, the valve will just fall out!

Thanks Ken. I've still got the valve cap wedged in there so I'll use the screwdriver method you described to pop it out

[Gabe001]

Originally Posted by high_vacuum_house

I think the best way to remove them is with a gentle pull straight upwards. No wiggling or twisting which would break the cement glue between the top cap and glass. Cleaning the cap of old solder and ensuring there is a small hole for the wire to pass through, then Soldering a new length of wire to the stub before soldering the cap back into place. Something like araldite in the cap first to make a good mechanical joint between the glass and cap first before soldering.

Christopher Capener

Thanks Chris. That's the plan. I think the wire may be long enough, but we wiill see. I'll give it a go this weekend, swmbo permitting.

[crackle]

It is not always the end of the world if the top cap wire sheers off.
I have successfully reattached a wire to the top pip of a valve even when the original wire had sheered off altogether.
I used a dremel type tool with a fine cutting disk and carefully and slowly ground away a little of the top of the glass pip being careful to not grind into the copper wire.
eventually about 1.5mm of wire was exposed and I scraped this clean with a knife blade.
Once the new exposed wire is tinned you can make a small loop in a new length of copper wire and solder the loop over the tip of the exposed wire.
Leave spare wire in the top cap and then solder it on, prior to glueing it to the valve.

Mike

[Sideband]

When gluing the top cap (or a loose base for that matter), it is better to use an impact adhesive like Evo-Stik or similar since these remain slightly flexible once set. This allows for expansion as the valve heats up. Using superglue or Araldite might cause the valve to crack as it heats up since they set hard and don't expand in the same way.

[Gabe001]

Thanks both. I've just ordered some impact adhesive.
Gabriel

[Gabe001]

Just a little update. Wire extended and valve cap glued in place with impact adhesive. Once it sets I will solder the wire to the valve cap where it exits the hole and cut it flush. It wasn't too bad to be honest

[PJL]

Araldite remains pliable and even more so at higher temperatures so it should be OK for top cap fixing, superglue is the one to avoid.

[Gabe001]

Originally Posted by PJL

Araldite remains pliable and even more so at higher temperatures so it should be OK for top cap fixing, superglue is the one to avoid.

Yes I was going to use araldite initially, but bought impact adhesive as recommended above. I'm sure araldite would have been fine too

[David G4EBT]

I've removed 3/8" top caps and replaced them with 1/2" top caps as well as replacing the side contact valve bases with octal bases to convert EBL1 valves to EBL31 to enable then to fit horizontally in Ekco A22 radios. Also, have re-fixed quite a lot of loose top caps and bases, and replaced cracked bases. I've found that Plastic Padding 2-part epoxy 'Super Steel' to be far and away the best product for that purpose, and for other applications in vintage radio restoration. It sets rock hard in minutes, withstands high temperatures, and can be filed and sanded. (Despite its name, it isn't electrically conductive).

https://www.google.com/search?q=supe...hrome&ie=UTF-8

[McMurdo]

I've always used araldite on radio valves, although it might burn and soften if used at the temperatures of say a guitar amp output or TV LOP valve.