I've had some 6F12P on my desk for some time. I got them for my CRT TV fooling-around, for the video amp.
Recently I looked up some curves and simmed some sims, and it seems it's a very good audio tube. I plan to build a balanced amp with four of these tubes: triodes (mu 100) as preamp, then source followers, and the pentodes triode strapped (mu 70) as finals.
If they'll behave nicely in an audio amp remains to be seen. But based on curves and sims the 6F12P could be a great 'spud amp' tube.
Recently I looked up some curves and simmed some sims, and it seems it's a very good audio tube. I plan to build a balanced amp with four of these tubes: triodes (mu 100) as preamp, then source followers, and the pentodes triode strapped (mu 70) as finals.
If they'll behave nicely in an audio amp remains to be seen. But based on curves and sims the 6F12P could be a great 'spud amp' tube.
Or like this: The uTracer, a miniature Tube Curve Tracer / Tester. (the EL3010, unobtanium...)
Scary very high gm 😱 ...
there are other sleeper tubes out there.......😉
@smoking-amp, ygpm...
i hope pete millet chimes in with his updates for the testing he did a few years back...http://www.pmillett.com/pentodes.htm
@smoking-amp, ygpm...
i hope pete millet chimes in with his updates for the testing he did a few years back...http://www.pmillett.com/pentodes.htm
Well, looks like there will be some fun and games with these "tubes from Hell" too (like 6HB6).
I curve traced a GE and a Realistic Lifetime tube. Both look exactly the same odd construction (grey plate does not fully wrap around on one edge), but one says made in Great Britain (GE), and the other says made in Japan. Both test with about 30% higher Mu in triode, and 30% higher gm in pentode, than the original Raytheon tube (grey plate). Growing a bit suspicious, I put a GE 12GN7 in the tracer, and it tests the same. (The 12GN7 however physically looks just like the Raytheon...?)
Then I tried another GE that looks like the conventional grey plate, like the Raytheon, and it tests with about 5% less Mu in triode and 5% less gm in pentode. Same excellent triode curves still.
Then I tried a Sylvania (black plate) and it tests with 15% less Mu in triode, and about the same gm in pentode. However it requires 132V on g2 versus 145V on g2 for the Raytheon. So the Sylvania g2 has about 10% stronger gm2. I guess that leaves about 5% of the 15% less Mu in triode then to lower gm1. Excellent triode curves still.
Then I tried an RCA (black plate) and it tests similar to the Sylvania. Maybe 20% less Mu than the Raytheon. 124V on g2 versus 145V on g2 for the Raytheon. About 10% less gm1 in pentode. Triode curves still look good, just 20% less Mu.
Then I tried a Westinghouse (grey plate) and it physically looks like the 1st GE and Realistic tubes. It tests the same too, just like a 12GN7. Good triode curves still, just 30% higher Mu than the Raytheon. Says Japan on it.
Then I tested a Zenith, and it does NOT look at all the same. It looks just like an 11HM7. It tests with the same gm1 in pentode however, using 166V on g2 versus 145V on g2 for the Raytheon. It starts thermally running away though. In triode it looks exactly the same as the Raytheon amazingly.
Then I tested a Magnavox tube, and it physically looks just like the 1st GE and Realistic tubes. It says Japan on it. It tests like a 12GN7 with 30% higher gm1 and Mu. It however requires 197V on g2 versus 145V on g2 for the Raytheon. Triode curves are OK, but not as good as the Raytheon.
Then I tested a Sylvania Philips ECG tube, and it physically looks like the Sylvania black plate. It has about 13% less Mu than the Raytheon. Has about 15% less gm1 in pentode. Triode curves look good like the Raytheon.
Then I tried a different Raytheon with a black plate this time. It shows 25% less Mu, and about the same gm1 in pentode. However it requires 119V on g2 versus 145V on g2 for the original grey plate Raytheon. Triode curves are not so hot.
Tried another RCA, and 10% less Mu and 10% less gm1, Vg2 same as 1st Raytheon. Good triode curves.
Tried an RCA from an older looking box and its got the 11HM7 guts like the Zenith. 10% more Mu, 15% more gm1, Vg2 121V instead of 145V for 1st Raytheon. Crummy triode curves.
Well, looks like there is going to be some substantial (maybe 20%) reject rate if you want genuine "made in Hell" tubes.
I curve traced a GE and a Realistic Lifetime tube. Both look exactly the same odd construction (grey plate does not fully wrap around on one edge), but one says made in Great Britain (GE), and the other says made in Japan. Both test with about 30% higher Mu in triode, and 30% higher gm in pentode, than the original Raytheon tube (grey plate). Growing a bit suspicious, I put a GE 12GN7 in the tracer, and it tests the same. (The 12GN7 however physically looks just like the Raytheon...?)
Then I tried another GE that looks like the conventional grey plate, like the Raytheon, and it tests with about 5% less Mu in triode and 5% less gm in pentode. Same excellent triode curves still.
Then I tried a Sylvania (black plate) and it tests with 15% less Mu in triode, and about the same gm in pentode. However it requires 132V on g2 versus 145V on g2 for the Raytheon. So the Sylvania g2 has about 10% stronger gm2. I guess that leaves about 5% of the 15% less Mu in triode then to lower gm1. Excellent triode curves still.
Then I tried an RCA (black plate) and it tests similar to the Sylvania. Maybe 20% less Mu than the Raytheon. 124V on g2 versus 145V on g2 for the Raytheon. About 10% less gm1 in pentode. Triode curves still look good, just 20% less Mu.
Then I tried a Westinghouse (grey plate) and it physically looks like the 1st GE and Realistic tubes. It tests the same too, just like a 12GN7. Good triode curves still, just 30% higher Mu than the Raytheon. Says Japan on it.
Then I tested a Zenith, and it does NOT look at all the same. It looks just like an 11HM7. It tests with the same gm1 in pentode however, using 166V on g2 versus 145V on g2 for the Raytheon. It starts thermally running away though. In triode it looks exactly the same as the Raytheon amazingly.
Then I tested a Magnavox tube, and it physically looks just like the 1st GE and Realistic tubes. It says Japan on it. It tests like a 12GN7 with 30% higher gm1 and Mu. It however requires 197V on g2 versus 145V on g2 for the Raytheon. Triode curves are OK, but not as good as the Raytheon.
Then I tested a Sylvania Philips ECG tube, and it physically looks like the Sylvania black plate. It has about 13% less Mu than the Raytheon. Has about 15% less gm1 in pentode. Triode curves look good like the Raytheon.
Then I tried a different Raytheon with a black plate this time. It shows 25% less Mu, and about the same gm1 in pentode. However it requires 119V on g2 versus 145V on g2 for the original grey plate Raytheon. Triode curves are not so hot.
Tried another RCA, and 10% less Mu and 10% less gm1, Vg2 same as 1st Raytheon. Good triode curves.
Tried an RCA from an older looking box and its got the 11HM7 guts like the Zenith. 10% more Mu, 15% more gm1, Vg2 121V instead of 145V for 1st Raytheon. Crummy triode curves.
Well, looks like there is going to be some substantial (maybe 20%) reject rate if you want genuine "made in Hell" tubes.
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Back in posts #49 and 50 we discussed some LED light sticks that I got at Walmart for illuminating my lab area.
I was in the Moundsville Walmart today and found a box full of sunshine. It is a "Lights of America" LED shop light. 40 watts from 120 LEDs that put out 4500 lumens of 5000K light. This sucker is BRIGHT. Don't look at it. It lights up one end of the basement like daylight. Model number 8140SE2-WH5, $44.
I was in the Moundsville Walmart today and found a box full of sunshine. It is a "Lights of America" LED shop light. 40 watts from 120 LEDs that put out 4500 lumens of 5000K light. This sucker is BRIGHT. Don't look at it. It lights up one end of the basement like daylight. Model number 8140SE2-WH5, $44.
Hi!
Many thanks for both PMs, the tube from Hell does indeed look very tempting
Still, I already have so many tubes and projects, that I may have to skip this one - but I will keep the secret to myself.
Regarding vacuumtubes.net: they also do have the quantity sales: 500 tubes at 0.35USD each. I think Tubelab got his 6HB6 frmo there? I got some nice, but boring, 6CL3 tubes 🙂
Erik
Many thanks for both PMs, the tube from Hell does indeed look very tempting
Still, I already have so many tubes and projects, that I may have to skip this one - but I will keep the secret to myself.
Regarding vacuumtubes.net: they also do have the quantity sales: 500 tubes at 0.35USD each. I think Tubelab got his 6HB6 frmo there? I got some nice, but boring, 6CL3 tubes 🙂
Erik
Yes, and 100 25DN6, and over 1000 tubes that day a few years ago. I have already melted a few 25DN6. For 50 cents each, why not?
Thanks for PM's!
But since I am in conditions similar to Erik deBest (full of projects, and tubes, too) probably if I were to buy will be only a few specimens for experimentation ...
And the secret is guaranteed.
But since I am in conditions similar to Erik deBest (full of projects, and tubes, too) probably if I were to buy will be only a few specimens for experimentation ...
And the secret is guaranteed.
Here are some pics of the "tube from Hell" and pretenders for identification purposes.
On the left are the GE from Great Britain followed by a Triad from Japan, these test as a 12GN7. Notice the odd plate edges.
Then the next two in the middle are the real thing, a black plate Raytheon and a grey plate GE. (the black plate Raytheon had poor triode curves, can't say yet if that is always the case, the grey plate Raytheon and a black plate Sylvania had excellent triode curves)
On the right is an RCA with 11HM7 guts. (these type are going to get tossed)
And across the top is a real GE 12GN7 for comparison. (identical in appearance to the tube from H, but at least labeled correctly)
The back side of the plates have two or three strips of metal crossing between the plates on all. Except the 11HM7 guts version has a solid shiny metal plate across (it's the exposed beam plate) which is then covered over by the getter flash on the glass. The 11HM7 guts only extent back 1/2 way across the tube diameter, so is considerable smaller. (test example started thermal runaway on 10 Watt test scale on the Curve Tracer.)
So most of the imposter tubes are 12GN7 type, maybe 10%, which are still useful tubes and so far can be readily identified. Maybe 5% are 11HM7 junk. A few Triad tubes turned out to be one of each type, and then one with a non frame grid. Can spot that by the smaller (and copper) grid1 support rods.
On the left are the GE from Great Britain followed by a Triad from Japan, these test as a 12GN7. Notice the odd plate edges.
Then the next two in the middle are the real thing, a black plate Raytheon and a grey plate GE. (the black plate Raytheon had poor triode curves, can't say yet if that is always the case, the grey plate Raytheon and a black plate Sylvania had excellent triode curves)
On the right is an RCA with 11HM7 guts. (these type are going to get tossed)
And across the top is a real GE 12GN7 for comparison. (identical in appearance to the tube from H, but at least labeled correctly)
The back side of the plates have two or three strips of metal crossing between the plates on all. Except the 11HM7 guts version has a solid shiny metal plate across (it's the exposed beam plate) which is then covered over by the getter flash on the glass. The 11HM7 guts only extent back 1/2 way across the tube diameter, so is considerable smaller. (test example started thermal runaway on 10 Watt test scale on the Curve Tracer.)
So most of the imposter tubes are 12GN7 type, maybe 10%, which are still useful tubes and so far can be readily identified. Maybe 5% are 11HM7 junk. A few Triad tubes turned out to be one of each type, and then one with a non frame grid. Can spot that by the smaller (and copper) grid1 support rods.
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Anybody order any "TFH" for $1? I am curious what brand they are, and if they are the real thing. I might be able to order some in the near future but $$ is kinda tight with me building the 6HJ5 amp. If I do order some I will be sure to send some off to you for your expert opinion and throw em on the curve tracer.
Speaking of the 6HJ5 amp I am kinda stuck. I was just clipping leads to the PC mount compactron sockets for testing but now I have to mount them somehow.
They are these type:
I was thinking of making two small PCB's in Eagle (help me practice my PCB making skills) and solder them to that and them mechanically mount the PCB boards to the chassis with nuts, bolts and standoffs like normal. I also have turret board which I like using but not sure how to do something with these sockets. Any ideas are appreciated.
I might just order some I can mount on the chassis if all fails.
Speaking of the 6HJ5 amp I am kinda stuck. I was just clipping leads to the PC mount compactron sockets for testing but now I have to mount them somehow.
They are these type:
I was thinking of making two small PCB's in Eagle (help me practice my PCB making skills) and solder them to that and them mechanically mount the PCB boards to the chassis with nuts, bolts and standoffs like normal. I also have turret board which I like using but not sure how to do something with these sockets. Any ideas are appreciated.
I might just order some I can mount on the chassis if all fails.
I Like that tubelab dude, he is not afraid to try something different even if it fries $4 worth of parts.
Great work Tubelab !!
Great work Tubelab !!
Seriously the man!
I picture him having his own reality show on the History Channel called "Tubelab" where he is always hot rodding amps and blowing $h!t up! The neighbors lights flickering and stuff. I would watch that in a heartbeat!
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