Hi Wavebourn
Are you trying to get enough evidence to prove your prior statements?
http://www.diyaudio.com/forums/showthread.php?s=&threadid=94949&highlight=
I am curious as well as how this physical comparison of 6P14P and 6P15P turns out: I have quite a stash of the latter ones (the EV version).
Erik
Are you trying to get enough evidence to prove your prior statements?
http://www.diyaudio.com/forums/showthread.php?s=&threadid=94949&highlight=
I am curious as well as how this physical comparison of 6P14P and 6P15P turns out: I have quite a stash of the latter ones (the EV version).
Erik
The screen is rated for a totally believable 1.5W.
Current * Voltage = Watts. Easily controlled by
the properly selected resistor and/or whatever
proportion of plate feedback or drive you might
or might not choose to feed it.
Its wattage that melts a screen, not volts...
In the context of a real circuit that may not
resemble one used to create the paper spec.
Can't see purpose putting an absolute limit on
screen voltage, unless expecting poor vacuum.
If its arcing at 150 or 200, thats just ridiculous.
I personally believe the limit implies headroom
for the plate to swing (without dipping into the
screen) , when characterized for a very specific
type of circuit.
An XRay won't tell you which screen (each more
identical than the last!) melts first. Only a Viking
funeral of several dozen warriors at sea will set
your tea leaves in motion.
Current * Voltage = Watts. Easily controlled by
the properly selected resistor and/or whatever
proportion of plate feedback or drive you might
or might not choose to feed it.
Its wattage that melts a screen, not volts...
In the context of a real circuit that may not
resemble one used to create the paper spec.
Can't see purpose putting an absolute limit on
screen voltage, unless expecting poor vacuum.
If its arcing at 150 or 200, thats just ridiculous.
I personally believe the limit implies headroom
for the plate to swing (without dipping into the
screen) , when characterized for a very specific
type of circuit.
An XRay won't tell you which screen (each more
identical than the last!) melts first. Only a Viking
funeral of several dozen warriors at sea will set
your tea leaves in motion.
ErikdeBest said:Hi Wavebourn
Are you trying to get enough evidence to prove your prior statements?
http://www.diyaudio.com/forums/showthread.php?s=&threadid=94949&highlight=
I am curious as well as how this physical comparison of 6P14P and 6P15P turns out: I have quite a stash of the latter ones (the EV version).
Erik
My prior statemen was the result of observations of screens visible through holes, and of reasoning about intended usage. 6P15P was developed for more linear applications than 6P14P, so knowing how R/D themes were going in former USSR I suspect that the team that developed the tube just took already well organized technology, changed construction a bit (stricter alignment, 3'rd grid out, more mechanically stable construction), rated the tube for better linearity, and got the job done. I am not a beginner with tubes so know well how screen grid voltage reflects on overal linearity of a pentode through anode voltage variations, so I believe that if to keep screen grid of 6P14P on lower stable voltage results will be similar, but less reproductable due to less rigid construction.
In my previous flagman design (Pyramid) I used paralleled 6P3S tubes with stiff lowered screen grid voltages, they worked very linearly, unlike 6L6GC in guitar amps. However, late I've found that using different tubes I can get better results for a buck, like GU-50 with 800V on plates and 270V on screens, or 25L6 with 120 volts on screens and 170V on plates plus MOSFET steroids, but anyway a 2'nd grid is a control element that helps to vary tube's parameters a lot in order to achieve desired transfer function.
The different story is 6J52P: the tube was designed very differently, though have parameters similar to 6P15P. It has much smaller area of anode so max power dissipation is smaller, but transconductance is huge. It is very different tube, while 6P15P looks suspicially similar to 6P14P.
Hi Anatoliy
Thanks for the explanation on the 6P15P, specially to its linearity. In fact you already mentioned the linearity issue before, so I bought them with that in mind. My plans are to build a transconductance amplifier to drive my OB. I will use the 6P15P as pentodes and not apply any feedback to get a high output impedance (but still 'linear'). I now have a bunch of the 6P15P's, but still not good enough iron to go on with the experiments.
In the meanwhile I also bought a couple of the GU50's and the 6J52P's. The first I only used triode wired in a SE amp: not really your cup of tea, I know while the latter are still resting.
Erik
Thanks for the explanation on the 6P15P, specially to its linearity. In fact you already mentioned the linearity issue before, so I bought them with that in mind. My plans are to build a transconductance amplifier to drive my OB. I will use the 6P15P as pentodes and not apply any feedback to get a high output impedance (but still 'linear'). I now have a bunch of the 6P15P's, but still not good enough iron to go on with the experiments.
In the meanwhile I also bought a couple of the GU50's and the 6J52P's. The first I only used triode wired in a SE amp: not really your cup of tea, I know
while the latter are still resting.Erik
I now have a Fisher X100 with 7189's, mix of Fisher and Sylvania
branded. Once I get inside and verify the "unused" socket pins
aren't gonna cause an immediate short, I'll be testing some of
the "lesser" spec'd tubes. Put some of these mysteries to rest.
Needless to say, the 7189's will be going under the Ray here
in a day or two... Just to make sure the higher screen rating
isn't attributable to an actual physical difference. And give my
"new" B&K 747 mutual conductance tester a workout.
I'll probably fuse the X100 a bit low, just incase... I'll also have
one hand ready to kill the switch on the power strip if anything
don't look or sound to be working exactly the way as expected.
I also need to figure out where the bias is measured...
The real 7189's glow a tiny bit blue inside, more so when cold.
Plates slowly brightening to an even distributed dark orange.
One tube seems to warm up a lot slower than the other three.
But again, these are well used tubes of no particular match.
I am with you on the theory there may be no difference at all.
But perhaps only how the spec sheets were characterized?
Or the level of assurance testing as they left the factory.
branded. Once I get inside and verify the "unused" socket pins
aren't gonna cause an immediate short, I'll be testing some of
the "lesser" spec'd tubes. Put some of these mysteries to rest.
Needless to say, the 7189's will be going under the Ray here
in a day or two... Just to make sure the higher screen rating
isn't attributable to an actual physical difference. And give my
"new" B&K 747 mutual conductance tester a workout.
I'll probably fuse the X100 a bit low, just incase... I'll also have
one hand ready to kill the switch on the power strip if anything
don't look or sound to be working exactly the way as expected.
I also need to figure out where the bias is measured...
The real 7189's glow a tiny bit blue inside, more so when cold.
Plates slowly brightening to an even distributed dark orange.
One tube seems to warm up a lot slower than the other three.
But again, these are well used tubes of no particular match.
I am with you on the theory there may be no difference at all.
But perhaps only how the spec sheets were characterized?
Or the level of assurance testing as they left the factory.
I think, but am not sure, that the first 6bq5 may have been a soviet/russian tube. Maybe an IEC or Richardson relabel. I seem to recall that most US tubes did not use the platter getter, could be wrong. Sure it's not a 6p14p-ev? They also happen to have the same basing as a 7189A I believe. My sylvanias are halo getter, my EHs are platter getter. Mullards are halo getter too, at least the ones I have.
My 1st 6BQ5, beam tube, came from my Father's stash. And is
much much older than the iron curtain came down. If its fake
based on 6AQ5 guts or something, its a domestic one.
What markings survive and the few visible construction details
look most like a photo of an RCA 6BQ5. Of course, the one in the
photo I compare it to, might also be a fake of the same vintage.
much much older than the iron curtain came down. If its fake
based on 6AQ5 guts or something, its a domestic one.
What markings survive and the few visible construction details
look most like a photo of an RCA 6BQ5. Of course, the one in the
photo I compare it to, might also be a fake of the same vintage.
Sylvania 6BQ5 and 7189 -- same?
Greetings from FixitLand!
Exactly! I have two Sylvania 7189s and two Sylvania 6BQ5/EL84s; all are black-plate and all are identical in every visible way other than the type numbers. It would appear that (a) these 7189s are uplabeled 6BQ5/EL84s that passed the higher standard, or (b) the 6BQ5/EL84s are 7189s that didn't make that standard...or did they??????
Would love to see X-rays of specimens of these two tubes!
Take care,
--
J. E. Knox "The Victor Freak"
Greetings from FixitLand!
I've seen Sylvania 7189 that look a lot like my Sylvania 6BQ5 (the two on the left).
Exactly! I have two Sylvania 7189s and two Sylvania 6BQ5/EL84s; all are black-plate and all are identical in every visible way other than the type numbers. It would appear that (a) these 7189s are uplabeled 6BQ5/EL84s that passed the higher standard, or (b) the 6BQ5/EL84s are 7189s that didn't make that standard...or did they??????
Would love to see X-rays of specimens of these two tubes!
Take care,
--
J. E. Knox "The Victor Freak"
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.