6P14-K not good audio tubes

Carbsandcaps

Carbsandcaps

Super Member
I ordered 3 sets of 6p14p-k (K is the inportant part here) tubes and have had nothing but problems with each set. In a fixed bias amp the were pulsing blue inside the tube (not arching just pulsing) and the bias was jumping all over the place this would happen when there was no audio signal only. In a cathode bias magnavox build, bias would hold for about a minute then slowly start to rise from 6.4v up to 12v on the cathode resistor and not stop until I turned the amp off. Even with the coupling cap disconnected I had 10v on the grid. I finally found 2 tubes of the set that would hold bias. It seems like anything that disturbs them like unplugging the rca inputs or even just moving the tubes drives them crazy.

I’m not sure exactly what’s causing it but I’ve read that the K version are not good audio tubes but they are for pulse applications. I’m starting to believe it. Anyone have any experiences like this with the K version?
 
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Have stoppers on the grids? Maybe add them to the anodes as well. What is the grid resistor value? 10v on the grid sounds like grid current. Might try burning them with just the filaments heated for a few hours.
 
I've been using the 6P14P-K's in two amps. A Magnavox 9303 PP amp, and a DG1 single ended amp without issue. I did make the mistake of ordering one quad from a seller I hadn't used before and two red plated right away. The one matched quad I bought from the seller I trust and have never gotten a bad tube from have been rock solid. Most of these "K's" are used. Something about being used in submarines? The seller I use tests with a Russian military tube tester that tests at high voltage. All the various tubes I've bought from him have been matched very close.
What amp did you try them in? The K's are a ruggedized version of the 6P14P. The EV's and EB's are a longer lasting ruggedized version.
I haven't read anything yet that the K's are different than th we others other than the rated hours they are supposed to last.
Do you have a link to where the K's are said to be used for pulse applications?
 
nerdorama said:
Have stoppers on the grids? Maybe add them to the anodes as well. What is the grid resistor value? 10v on the grid sounds like grid current. Might try burning them with just the filaments heated for a few hours.
Click to expand...

I was using a grid stopper on the first project pp but not on the second se.
 
Lavane said:
I've been using the 6P14P-K's in two amps. A Magnavox 9303 PP amp, and a DG1 single ended amp without issue. I did make the mistake of ordering one quad from a seller I hadn't used before and two red plated right away. The one matched quad I bought from the seller I trust and have never gotten a bad tube from have been rock solid. Most of these "K's" are used. Something about being used in submarines? The seller I use tests with a Russian military tube tester that tests at high voltage. All the various tubes I've bought from him have been matched very close.
What amp did you try them in? The K's are a ruggedized version of the 6P14P. The EV's and EB's are a longer lasting ruggedized version.
I haven't read anything yet that the K's are different than th we others other than the rated hours they are supposed to last.
Do you have a link to where the K's are said to be used for pulse applications?
Click to expand...

Here is the site. I could she just gotten a few duds. They were inexpensive enough to try them out.
vacuum-tubes.com

ᐉ 6P14P Tube: Datasheet, Equivalents, and Comparisons with EL84 & 6BQ5

Learn everything about the 6P14P tube, including its datasheet, pinout, equivalents, and comparisons with EL84, 6BQ5, 6P14P-EV, and 6P14P-K. Discover its unique specifications, max plate voltage, and performance differences.
vacuum-tubes.com vacuum-tubes.com
 
It could just be another “it’s on the internet it’s got to be true” things but finding any info on these Russian tubes is difficult and may never be proven.
 
Carbsandcaps said:
Here is the site. I could she just gotten a few duds. They were inexpensive enough to try them out.
vacuum-tubes.com

ᐉ 6P14P Tube: Datasheet, Equivalents, and Comparisons with EL84 & 6BQ5

Learn everything about the 6P14P tube, including its datasheet, pinout, equivalents, and comparisons with EL84, 6BQ5, 6P14P-EV, and 6P14P-K. Discover its unique specifications, max plate voltage, and performance differences.
vacuum-tubes.com vacuum-tubes.com
Click to expand...
There is only one seller I use on ebay. And that's for Russian tubes.
As I posted, I tried another seller that had quads for half the price and got burned.
Lessson learned for me! The seller I use ships from Romania and it does take about 4 weeks or so to get them, but not a bad tube yet.
 
You might be interested to try the 6p15p. It is similar to EL84 but not exactly. The suppressor is pinned out separately and a fellow on DIYaudio has figured out that with some positive voltage of +25 to 30VDC relative to cathode it squares up the corners and reduces screen current so it works much more like the 6p14p/EL84. It has higher voltage ratings of 330VDC for plate and screen as well. Still cheap and cheerful.

Using 6P15P in triode at 300V - suggestions?

There's some confusion about the G2 rating of this 6P15P. Some data indicates 330V for both anode and G2, while other comments suggests the G2 is "fragile" and should be de-rated, maybe down to 160V like the EL83. So for those wanting to use this in triode e.g. in a PSE amp, how to proceed? A...
www.diyaudio.com www.diyaudio.com
 
I also tried the K's in my ST-35. They worked just fine. I put the Sovtek
EL-84M's back in that amp. They're supposed to be the same as the
6P14P-EV's. They sound good too.
I'll add that the two K's that red plated tested good and strong in my Hickok
Tube tester. But it doesn't test at higher voltages. So the seller you used may have put them in a tube tester set for 7189, or EL84 and they tested good like the two I had did. :dunno:
 
Well these 2 K’s have been running for 2 hours not and haven’t budged on bias. Maybe I did get duds they all tested good but maybe like gadget said they are gassy.
 

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The burn-in that I mentioned above might help. I've also heard of putting tubes in the oven at some temp to help reinvigorate the getter and absorb residual gases. I've never done it so can't say from experience.
 
Carbsandcaps said:
I ordered 3 sets of 6p14p-k (K is the inportant part here) tubes and have had nothing but problems with each set. In a fixed bias amp the were pulsing blue inside the tube (not arching just pulsing) and the bias was jumping all over the place this would happen when there was no audio signal only. In a cathode bias magnavox build, bias would hold for about a minute then slowly start to rise from 6.4v up to 12v on the cathode resistor and not stop until I turned the amp off. Even with the coupling cap disconnected I had 10v on the grid. I finally found 2 tubes of the set that would hold bias. It seems like anything that disturbs them like unplugging the rca inputs or even just moving the tubes drives them crazy.

I’m not sure exactly what’s causing it but I’ve read that the K version are not good audio tubes but they are for pulse applications. I’m starting to believe it. Anyone have any experiences like this with the K version?
Click to expand...
They sound like a bad set of tubes. Did the seller claim to test and burn them in before selling?

I'd go with a known good 6P14P-EV from a reputable dealer with a return policy. :thumbsup:

Thanks!
 
nerdorama said:
You might be interested to try the 6p15p. It is similar to EL84 but not exactly. The suppressor is pinned out separately and a fellow on DIYaudio has figured out that with some positive voltage of +25 to 30VDC relative to cathode it squares up the corners and reduces screen current so it works much more like the 6p14p/EL84. It has higher voltage ratings of 330VDC for plate and screen as well. Still cheap and cheerful.
Click to expand...
I have an amp that I use these in, but its set up so it can run these or a regular EL84/6bq5. Works quite well. Its running about 275v across the tube and with EFB it's happy point is 11ma of cathode current per-tube so they are used super gently. Its brighter sounding than an EL84 but not a bad thing in an amp with somewhat limited bandwidth transformers. I'll have to try giving the suppressor a little extra voltage and see what that does for it.
 
Do you get about the same bias settings for EL84 and the 6p15? Or readjustment required?

I have a large carton of new 6p15's but have only used them as driver pentodes in a SE plate-to-plate feedback amp with GU50 finals.
 
Needs a re-adjust, but I couldn't tell you what the actual voltage difference is to do it. Its within range of the 10k pot I'm using for bias though. Pretty sure the 6P15P needs the grid less-negative for the same current flow.

Possible with some positive G3 voltage it will be different though. It should flow more current at a given grid voltage if G3 is a little positive.
 
Carbsandcaps said:
I ordered 3 sets of 6p14p-k (K is the inportant part here) tubes and have had nothing but problems with each set. In a fixed bias amp the were pulsing blue inside the tube (not arching just pulsing) and the bias was jumping all over the place this would happen when there was no audio signal only. In a cathode bias magnavox build, bias would hold for about a minute then slowly start to rise from 6.4v up to 12v on the cathode resistor and not stop until I turned the amp off. Even with the coupling cap disconnected I had 10v on the grid. I finally found 2 tubes of the set that would hold bias. It seems like anything that disturbs them like unplugging the rca inputs or even just moving the tubes drives them crazy.

I’m not sure exactly what’s causing it but I’ve read that the K version are not good audio tubes but they are for pulse applications. I’m starting to believe it. Anyone have any experiences like this with the K version?
Click to expand...
ooh thats no good.
well, K means shock/vibration resistant: none of this should disturb the tubes in the slightest.
 
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