I have an NOS quad of 6B4's but 3 of them have slightly loose bases.
Does anyone know how to fix this?
Can I dribble some super glue into the joint?
I searched the internet and this forum without happy results.
Thanks.
Does anyone know how to fix this?
Can I dribble some super glue into the joint?
I searched the internet and this forum without happy results.
Thanks.
I believe the original glue that was used in this application was phenol-formaldehyde, or 'recorcinal' adhesive. It's a brown powder into which a dark red catalyst is mixed. Dries slow, heat helps cure it, and it's pretty impervious to heat.
If I am in fact mistaken, it will be in lieu of another similar adhesive, urea formaldehyde, or 'plastic resin' glue. The original WeldWood. This is a light brown powder that is mixed with water. Very similar properties to recorcinal glue.
Aloha,
Poinz
AudioTropic
If I am in fact mistaken, it will be in lieu of another similar adhesive, urea formaldehyde, or 'plastic resin' glue. The original WeldWood. This is a light brown powder that is mixed with water. Very similar properties to recorcinal glue.
Aloha,
Poinz
AudioTropic
This recipe for RCA's basing cement, yielding about 200 pounds of material, was "standard for all bases.":
Coarse marble flour 170 lb.
Orange flake shellac 19-1/2 lb.
Durite phenolic resin LR275-2 7-1/2 lb.
Medium-color (grade G) rosin 3-1/4 lb.
Denatured alcohol 9 liters
Malachite Green aniline dye 10 g.
(Just for reference: the above recipe yielded enough cement to put bases on 23,000 Type 50 tubes
The AWA Journal - The Vacuum Tube
Never would have guessed, myself.
Coarse marble flour 170 lb.
Orange flake shellac 19-1/2 lb.
Durite phenolic resin LR275-2 7-1/2 lb.
Medium-color (grade G) rosin 3-1/4 lb.
Denatured alcohol 9 liters
Malachite Green aniline dye 10 g.
(Just for reference: the above recipe yielded enough cement to put bases on 23,000 Type 50 tubes
The AWA Journal - The Vacuum Tube
Never would have guessed, myself.
Yes. Or nail polish.
Loose Bases.
To re-cement the tube, use clear nail polish - paint a ring around the base, let the polish soak into the old cement, recoat, and let dry overnight. Polystyrene "coil dope" works as well, and can be used to refill the nail-polish bottle.
Solvent (acetone, etc.) are ineffective in softening the old base cement - the cement was baked hard in manufacture, and "nothing" dissolves it.
"Source : Tube Lore by Ludwell Sibley"
I've used superglue with some limited success.. Limited in the sense that the tubes were small signal triodes (UX4 base) that don't get very warm in operation, and they are tubes I didn't particularly care about.
In higher temperature applications I am not sure what would happen - perhaps it would work, perhaps the glue would quickly fail, or perhaps the stress on the envelope due to the glue (non matching coefficient of expansion) might cause the envelope to crack.
IMO Removing the base in order to use a diy mix of basing cement is a bad idea - no guarantee that you will get it apart & back together without damaging the tube, not the least of which is the leads have been trimmed back after soldering and it may hard to assure long term integrity of the solder joint if you are not good at soldering tube pins.
Generally when installing or removing octal tubes you should be grasping them by the base anyway.
In higher temperature applications I am not sure what would happen - perhaps it would work, perhaps the glue would quickly fail, or perhaps the stress on the envelope due to the glue (non matching coefficient of expansion) might cause the envelope to crack.
IMO Removing the base in order to use a diy mix of basing cement is a bad idea - no guarantee that you will get it apart & back together without damaging the tube, not the least of which is the leads have been trimmed back after soldering and it may hard to assure long term integrity of the solder joint if you are not good at soldering tube pins.
Generally when installing or removing octal tubes you should be grasping them by the base anyway.
Loose tube base
Thank you all for your input.
The RCA recipe is a most interesting but of historic trivia. Love it.
I'm thinking about the nail polish solution, but I will await further input.
By the way, I'm long past knowing not to use the glass to remove tubes.
These tubes arrived this way. Old Russian glue it seems.
Thank you all for your input.
The RCA recipe is a most interesting but of historic trivia. Love it.
I'm thinking about the nail polish solution, but I will await further input.
By the way, I'm long past knowing not to use the glass to remove tubes.
These tubes arrived this way. Old Russian glue it seems.
I've used clear fingernail polish on several small signal octal based tubes (6SL7GT, etc.) with good success. I've also used it on a couple larger tubes (6B4G, 6L6GC types, etc). So far, it seems to help hold the base tighter and no apparent ill effects to the tube.
I believe it's been spelled both ways, Stu. I couldn't decide, and picked one.
In woodworking applications, I hated the stuff.
Aloha,
P
In woodworking applications, I hated the stuff.
Aloha,
P
I have sucessfully used Weldwood Plastic Resin mixed to a paste with alcohol for faster drying. Use of a hair blow-dryer makes it faster still.
Repairing Octal Bases
I have two 6V6 tubes, a 1951 RCA and a 1959 RCA, that I successfully repaired using aquarium sealer. I use a small flat-tip screwdriver to force the silicone into the gap between base and envelope. I then clamped the tube together and let it sit. After a day, I took a razor blade and trimmed off the excess silicone.
These tubes tested great and I didn't want to toss them. The 1959 was so loose that when I had it in the tester it would die if I slightly twisted it. I marked the position where I had connection and reglued it in that position.
To my way of thinking, the silicone isolates the base from the envelope, possibly reducing vibrations from the chassis that might cause microphonics.
I have two 6V6 tubes, a 1951 RCA and a 1959 RCA, that I successfully repaired using aquarium sealer. I use a small flat-tip screwdriver to force the silicone into the gap between base and envelope. I then clamped the tube together and let it sit. After a day, I took a razor blade and trimmed off the excess silicone.
These tubes tested great and I didn't want to toss them. The 1959 was so loose that when I had it in the tester it would die if I slightly twisted it. I marked the position where I had connection and reglued it in that position.
To my way of thinking, the silicone isolates the base from the envelope, possibly reducing vibrations from the chassis that might cause microphonics.
I've used the JB weld epoxy, push into the joint and wipe clean prior to standing upright with book on top to weigh it down in place. I also used it for loose top plate connectors.
FYI - You never want to use silicone in anything electronic.
Because it migrates ends up in switchs, outlets, connectors, etc.
and starts screwing them up and you'll have all sorts of unidentified
problems down the road.
This bit of wisdom was handed down to me by the good folks at Lucent Technologies/Bell Labs/Western Electric from the old Dallas Work's
plant. A former world leader in power supply and design amoung others.
I picked up a lot of interesting knowledge from those folks.
I think he was probably referring to RTV, hopefully an electronic grade silicone adhesive. I've used this for +30yrs with no problems mostly to secure electrolytics and film caps to an underlying substrate. (chassis or insulator)
I've used cyanoacrylate on several tubes with success.
I've also disassembled and reassembled 6L6s that were loose. (remove solder and carefully pick the leads loose first) I used epoxy on the 6L6s.
I've also disassembled and reassembled 6L6s that were loose. (remove solder and carefully pick the leads loose first) I used epoxy on the 6L6s.
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