• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

brown EL84, is this normal?

Lavane

Lavane

Lunatic Member
One of the el84's I pulled from a Maggie 9303 looks kind of nasty. The amp was working when I pulled it. It looks to me like its a bit leaky. Or is this normal for these tubes? All four are Magnavox branded and marked "made in great Britain".
 

Attachments

  • DSC00605.jpg
    DSC00605.jpg
    30.6 KB · Views: 109
  • DSC00604.jpg
    DSC00604.jpg
    96.5 KB · Views: 83
Register to hide this ad
Might be a bit gassy, or maybe it means nothing. Probably Mullard though. They tend to look fairly awful but they sound and work just fine.
 
I thought it looked a bit gassy. The mica inside lookes discolored compared to the others as well. They all look a bit uggly. :D Thanks gadget!
 
Gassy. However, I have one (smokey Mullard EL84) just like it that has been working fine for years (approximately 55, to be precise). I also have an Amperex Bugle Boy EL84 in the same state that works fine. As long as it isn't chalky on the inside, you should be fine.

-D
 
It looks as though it has been run very hard. Often, power tubes, like the 7591, can have most of the getter flashing consumed to where it simply looks like a little cola stain inside of the glass. It usually means lots of hard hours but ... doesn't mean it is ready for the bin. If it works well, biases well, and even tests fair to good, you are good to go. Whatever, don't throw it away.

However ... if it is gassy, caution is advised. A good Mutual Conductance tube tester will usually let you know the answer to that question.
 
derekva said:
Gassy. However, I have one (smokey Mullard EL84) just like it that has been working fine for years (approximately 55, to be precise). I also have an Amperex Bugle Boy EL84 in the same state that works fine. As long as it isn't chalky on the inside, you should be fine.

-D
Click to expand...

Thanks, good to know. :thmbsp:
 
kvflyer said:
It looks as though it has been run very hard. Often, power tubes, like the 7591, can have most of the getter flashing consumed to where it simply looks like a little cola stain inside of the glass. It usually means lots of hard hours but ... doesn't mean it is ready for the bin. If it works well, biases well, and even tests fair to good, you are good to go. Whatever, don't throw it away.

However ... if it is gassy, caution is advised. A good Mutual Conductance tube tester will usually let you know the answer to that question.
Click to expand...

When I'm done with the resto of the amp I'll probably get a new set of tubes. A tester is on my short list. So it will go into my box of tubes until I can test it. Thanks for the info. :yes:
 
It's amazing how awful Mullard EL84 can look (and measure!) and still work fine.

I've seen them nasty stained like this- even showing slight grid leakage (gas?)- but still work absolutely perfectly in circuit. Not just once, either!

I've learned to check them in the amp- in a cathode-biased amp, check the DC grid voltage. If it's within a few millivolts of zero volts (usually +20mv or less is safe), you don't have any problem. If you start to see climbing grid voltage, up to and beyond +100mv, then it's time for a replacement...

Regards,
Gordon.
 
GordonW nails it.

Look up smoky Mullard and you'll see it's quite common and sometimes a badge of excellence.

Look for the acid etched factory codes near the bottom. 3 or 4 character codes starting with a "B" are Blackburn production and highly sought.

Nice find!
 
You must log in or register to reply here.
Back
Top Bottom