Faulty 5881 tube ?

Emmanuel K · 15th March 2010, 12:12 PM

Hi, I received today my Onix SP3 and I have a question regarding a 5881 valve.
As you can see on the first picture, the upper "part" seems to be bent

Can I switch on the amplifier or the valve has to be changed

Thanks

OneyedK · 15th March 2010, 12:38 PM

The upper part is called the getter.

Getter - Wikipedia, the free encyclopedia

After construction of the tube, it has no influence on the working of the tube.

Rod Coleman · 15th March 2010, 07:13 PM

Yes, that's the getter mounting structure, and it does look badly built.

I have seen Chinese EL34s built like this. when one got too hot, the getter arm softened and fell into the 'flags' (grid heatsinks). The getter arm is connected to the anode, so the result was a spectacular BANG!

O, look, I found the photo of it! see how the top getter is shorted to grid1

Buy a Russian 5881. They're cheap, reliable, and sound great.

Emmanuel K · 15th March 2010, 09:44 PM

Thanks for your replies, link and picture

I just switched it on 10 minutes to see if the amplifier works well, but you are right, I won't use it before changing the 5881 tetrodes.

Which russian 5881 ? 6P3S-E ?

Someone told me that the SED winged "C" 6L6GC is a very good tube, well built, reliable and sound great.

cogsncogs · 16th March 2010, 07:09 AM

Actually the weld on the first tube looks better than the second one. Getters don't have to be perfectly straight. In Rod's pic the getter is so close to the grid fins that any expansion of the copper grid support rod could have caused grid cooling fin to getter contact. IMHO you should be fine but if the weld doesn't look good to you, as you are much closer than I, or if it makes you feel better, then by all means you should replace the tube(s)!

I've read that JJ's are good, they do sound good albeit a little forward sounding, but my experience with their E34L's left a bad taste in my mouth. Four tubes with bad welds, one unstable, out of 8 tubes. Went with Svetlana "Winged C" EL34's, going on five years now and no problems so far. I'm very happy with them.

Rod Coleman · 16th March 2010, 08:20 AM

For the money, the Sovtek 5881WGC (or -WXT) is really hard to beat. Yes, this is the Saratov/Рефлектор 6П3С-Е/6P3S-E. I believe these to be the best made 5881/6L6 equivalents, although I haven't tried any of the fancy reissue variants.

They will sound better than roughly made 5881s, anyway.

The sound will depend on the amp as much as anything, but I would use the Sovtek or 6П3С-Е as reference for judging other valves. The SED is popular with guitarists, but that's a different thing, and I would say the extra money is better spent improving the amp's capacitors, for instance.

OneyedK · 16th March 2010, 09:20 AM

Before you run off to ebay to buy hard to find tubes,
check
Freeqi Audio Design
and
TAD Online Store

Both chose to profile themselves as musical instrument amplifier/parts shops, but they have the equipment to match pairs and quads the proper way.
Save yourself some dissapoinments and buy from them.

tubesteve · 16th March 2010, 10:21 AM

the shown 2 tubes are 5881 made by shuguang factory, china and then custom branded. They are a bit sloppy manufactured and their getter is always "thin" and a bit transparent. I abiused them with higher screen grid and plate voltages, about 10% higher that rated, but worked fine.but their life, due to little getter and maybe vacuum problems may not be very long.

MellowTone · 16th March 2010, 12:29 PM

Quote:

Originally Posted by Emmanuel K

Thanks for your replies, link and picture

I just switched it on 10 minutes to see if the amplifier works well, but you are right, I won't use it before changing the 5881 tetrodes.

Which russian 5881 ? 6P3S-E ?

Someone told me that the SED winged "C" 6L6GC is a very good tube, well built, reliable and sound great.

Personally, I love the Russian 6P3S-E. It sounds great (to me) and they're cheap. You can usually pick up lots of 8 for US$60, which works out to be &.50 a tube.

Emmanuel K · 16th March 2010, 09:14 PM

Thanks all for your inputs.

Correct me if I am wrong but when I see "6P3S-E = 6L6GC = 5881" and specs (anode voltage) between 5881 and 6P3S-E here:
TDSL Tube data [5881WXT]
6P3S, 6P3S-E

Is the 6P3S-E really a direct 5881 replacement ? 5881 seems to accept more voltage (360V) than 6P3S-E (250V), right ?

16th March 2010, 10:21 AM	#8
tubesteve diyAudio Member Join Date: May 2009 Location: since 1998 in China as an electronic consulting design and testing engineer	5881 faulty the shown 2 tubes are 5881 made by shuguang factory, china and then custom branded. They are a bit sloppy manufactured and their getter is always "thin" and a bit transparent. I abiused them with higher screen grid and plate voltages, about 10% higher that rated, but worked fine.but their life, due to little getter and maybe vacuum problems may not be very long. __________________ The amount of humans is increasing, but the amount of available intelligence remains a constant.

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15th March 2010, 12:38 PM	#2
OneyedK diyAudio Member Join Date: Oct 2007	The upper part is called the getter. Getter - Wikipedia, the free encyclopedia After construction of the tube, it has no influence on the working of the tube.

15th March 2010, 09:44 PM	#4
Emmanuel K diyAudio Member Join Date: Apr 2009	Thanks for your replies, link and picture I just switched it on 10 minutes to see if the amplifier works well, but you are right, I won't use it before changing the 5881 tetrodes. Which russian 5881 ? 6P3S-E ? Someone told me that the SED winged "C" 6L6GC is a very good tube, well built, reliable and sound great.

16th March 2010, 07:09 AM	#5
cogsncogs diyAudio Member Join Date: Jul 2003 Location: Wayne, West Virginia	Actually the weld on the first tube looks better than the second one. Getters don't have to be perfectly straight. In Rod's pic the getter is so close to the grid fins that any expansion of the copper grid support rod could have caused grid cooling fin to getter contact. IMHO you should be fine but if the weld doesn't look good to you, as you are much closer than I, or if it makes you feel better, then by all means you should replace the tube(s)! I've read that JJ's are good, they do sound good albeit a little forward sounding, but my experience with their E34L's left a bad taste in my mouth. Four tubes with bad welds, one unstable, out of 8 tubes. Went with Svetlana "Winged C" EL34's, going on five years now and no problems so far. I'm very happy with them.

16th March 2010, 08:20 AM	#6
Rod Coleman работник diyAudio Member Join Date: Jul 2004 Location: Warwickshire UK	For the money, the Sovtek 5881WGC (or -WXT) is really hard to beat. Yes, this is the Saratov/Рефлектор 6П3С-Е/6P3S-E. I believe these to be the best made 5881/6L6 equivalents, although I haven't tried any of the fancy reissue variants. They will sound better than roughly made 5881s, anyway. The sound will depend on the amp as much as anything, but I would use the Sovtek or 6П3С-Е as reference for judging other valves. The SED is popular with guitarists, but that's a different thing, and I would say the extra money is better spent improving the amp's capacitors, for instance.

16th March 2010, 09:20 AM	#7
OneyedK diyAudio Member Join Date: Oct 2007	Before you run off to ebay to buy hard to find tubes, check Freeqi Audio Design and TAD Online Store Both chose to profile themselves as musical instrument amplifier/parts shops, but they have the equipment to match pairs and quads the proper way. Save yourself some dissapoinments and buy from them.

16th March 2010, 09:14 PM	#10
Emmanuel K diyAudio Member Join Date: Apr 2009	Thanks all for your inputs. Correct me if I am wrong but when I see "6P3S-E = 6L6GC = 5881" and specs (anode voltage) between 5881 and 6P3S-E here: TDSL Tube data [5881WXT] 6P3S, 6P3S-E Is the 6P3S-E really a direct 5881 replacement ? 5881 seems to accept more voltage (360V) than 6P3S-E (250V), right ?

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