[JKDJedi]

I have a WE 421a tube that seems to have stopped working in one channel (using a BHC). Has anyone experienced this before or have any tips on how to try to fix? I’ve tested at least 10 different power tubes and it is an issue with this one tube for sure.

I'd try zapping the pins with a sodder iron. What else could you do? Anything loose inside?

 

[raindownthunda]

I did give it a good smack and that seemed to temporarily restore both channels for one session but sadly didn't last. I'll try heating the pins with a soldering iron and report back. Thanks for the suggestion. I can definitely hear a rattling noise when I shake it, but nothing visible is loose in the glass part of the tube.

 

[JKDJedi]

I did give it a good smack and that seemed to temporarily restore both channels for one session but sadly didn't last. I'll try heating the pins with a soldering iron and report back. Thanks for the suggestion. I can definitely hear a rattling noise when I shake it, but nothing visible is loose in the glass part of the tube.

oh oh.. might be a loose contact underneath. No crackling or static?

 

[raindownthunda]

oh oh.. might be a loose contact underneath. No crackling or static?

Is a loose contact fixable? I’ve never taken apart a tube before. There’s no sound at all through one channel and sounds normal in the other. The one time it did come through both channels it sounded fantastic - no static, hisses, pops, etc

 

[JKDJedi]

Is a loose contact fixable? I’ve never taken apart a tube before. There’s no sound at all through one channel and sounds normal in the other. The one time it did come through both channels it sounded fantastic - no static, hisses, pops, etc

Haven't a clue. Hopefully someone can chime in here.

 

[mordy]

Does the tube make popping or loud crackling noises?
Or it it completely silent on one channel?
Did you clean the pins and check all connections ?

 

[JKDJedi]

Does the tube make popping or loud crackling noises?
Or it it completely silent on one channel?
Did you clean the pins and check all connections ?

He's saying completely silent on one channel, that all other tubes behavior is normal in that same slot

 

[raindownthunda]

Does the tube make popping or loud crackling noises?
Or it it completely silent on one channel?
Did you clean the pins and check all connections ?

I gave the pins a light sanding and cleaned them with 99% Iso. Success!! I have never cleaned pins before on any of my tubes. I am thinking now is a good time give each tube a good cleaning before each roll... Thanks for the help!

 

[mordy]

I gave the pins a light sanding and cleaned them with 99% Iso. Success!! I have never cleaned pins before on any of my tubes. I am thinking now is a good time give each tube a good cleaning before each roll... Thanks for the help!

Very happy to be of help! And it is always a good idea to look at the pins. Very often there is oxidation and or corrosion after being stored for several decades....

 

[leftside]

Here's a tube from yesterday I was cleaning up. Took me an hour to clean up four like this. The pins were so dirty that I thought that was their actual colour - until I started cleaning the pin on the left.

 

[raindownthunda]

Very happy to be of help! And it is always a good idea to look at the pins. Very often there is oxidation and or corrosion after being stored for several decades....

So the tube worked in both channels for one session. Next time I powered up the amp (without touching the tube at all let alone removing it) the left channel had completely cut out again... Tried the solder trick today with 30 seconds on each pin plus adding a bit of extra solder to the tip. No luck! Still only one channel. I took the tube out and gave it a dozen good whacks against my mouse pad. Tried it again and voila, both channels are working again! Very strange - I guess I'll just keep whacking it...

 

[JKDJedi]

So the tube worked in both channels for one session. Next time I powered up the amp (without touching the tube at all let alone removing it) the left channel had completely cut out again... Tried the solder trick today with 30 seconds on each pin plus adding a bit of extra solder to the tip. No luck! Still only one channel. I took the tube out and gave it a dozen good whacks against my mouse pad. Tried it again and voila, both channels are working again! Very strange - I guess I'll just keep whacking it...

I'd be going sideways if my Western Electric was going bonkers. I only bring mine out on special occasions. With that special bottle of red wine.

 

[mordy]

I am guessing now, but it could be an internal connection inside the tube construction that isn’t soldered or welded together.
Hopefully you will be able to get the pieces staying connected so that you don’t have to go through all the aggravation again.
Wonder if you can see the break by inspecting the tube carefully......

 

[fuzzroffe]

I recently built Pete Millett's low-mu preamp that's designed for a 7236 or alternatively 6AS7. I've used it with either a Winged C 6H13C or a Telefunken-branded GE 6080 (I think I prefer the 6080), but I'd really like to try a 5998 or 7236 in it for a little more gain. What would be a good choice here?

 

[JKDJedi]

I recently built Pete Millett's low-mu preamp that's designed for a 7236 or alternatively 6AS7. I've used it with either a Winged C 6H13C or a Telefunken-branded GE 6080 (I think I prefer the 6080), but I'd really like to try a 5998 or 7236 in it for a little more gain. What would be a good choice here?

5998 has more gain than the 7236