The 6DQ5 "impostor" lineup.
Looking back at the curves etc, some tubes can be eliminated from consideration. 6EX6, 6CD6, 6CB5, 6CL5, 6JS6A all have the old kinky style curves and old style plates. 6HJ5 might fit the curves, but doesn't have the right type of plate. 17KV6A and 21HB5A have the right type of plates and similar curves, but require 140V and 150V respectively on grid 2 to get to the same level of plate current.
We are left with 21L6A and 6JE6C/6LQ6, and also (after some checking on
Ebay) the 6JS6C (the C version does have the plate boxlets and winglets). (unfortunately I don't have one to curve trace, but should have similar curves with the boxlets there.)
One surprising thing did show up in the Ebay pics for the 6JS6C, a Sylvania model with a gray plate, boxlets, and black winglets! Just like the winged 6DQ5 tubes. Bingo!
So, the lineup pics:
21LGA pentode
21LG6A triode
6JE6A/C pentode
6JE6A/C triode
6JS6C Sylvania picture with black winglets
6DQ5 winged pentode (102)
6DQ5 winged triode (102)
Late edit:
UH-OH!
I just went and pulled out some Sylvania 21LG6A and Sylvania 24JE6A/24LQ6 tubes, and some of them have the gray plate with black winglets too! Looks like all three tubes are in a tight race here for contention as the "rogue impostor" winged 6DQ5.
Maybe they are all the same tube....
Looking back at the curves etc, some tubes can be eliminated from consideration. 6EX6, 6CD6, 6CB5, 6CL5, 6JS6A all have the old kinky style curves and old style plates. 6HJ5 might fit the curves, but doesn't have the right type of plate. 17KV6A and 21HB5A have the right type of plates and similar curves, but require 140V and 150V respectively on grid 2 to get to the same level of plate current.
We are left with 21L6A and 6JE6C/6LQ6, and also (after some checking on
Ebay) the 6JS6C (the C version does have the plate boxlets and winglets). (unfortunately I don't have one to curve trace, but should have similar curves with the boxlets there.)
One surprising thing did show up in the Ebay pics for the 6JS6C, a Sylvania model with a gray plate, boxlets, and black winglets! Just like the winged 6DQ5 tubes. Bingo!
So, the lineup pics:
21LGA pentode
21LG6A triode
6JE6A/C pentode
6JE6A/C triode
6JS6C Sylvania picture with black winglets
6DQ5 winged pentode (102)
6DQ5 winged triode (102)
Late edit:
UH-OH!
I just went and pulled out some Sylvania 21LG6A and Sylvania 24JE6A/24LQ6 tubes, and some of them have the gray plate with black winglets too! Looks like all three tubes are in a tight race here for contention as the "rogue impostor" winged 6DQ5.
Maybe they are all the same tube....
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Well, I just pulled the GE datasheet for 6JS6C and compared it with the GE datasheet for 6JE6C. The EXACT same curves!
Then I looked at the GE datasheet for the 6LG6A and this one does have quite similar curves, but distinctively sharper knees.
I don't see much difference on the curve traced GE 21LG6A however. All of these are within the typical variation seen between different tubes of the same type.
So maybe we now call these winged 6DQ5 tubes:
6DQ5A = 6LG6A = 6JE6C = 6JS6C = 6LQ6 = 6ME6 = 6MJ6
Then I looked at the GE datasheet for the 6LG6A and this one does have quite similar curves, but distinctively sharper knees.
I don't see much difference on the curve traced GE 21LG6A however. All of these are within the typical variation seen between different tubes of the same type.
So maybe we now call these winged 6DQ5 tubes:
6DQ5A = 6LG6A = 6JE6C = 6JS6C = 6LQ6 = 6ME6 = 6MJ6
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6HJ5 should probably be included in the above 6DQ5A.... equivalence group too. Not the same plate construction, but fairly similar plate curves (below).
Re: Tony
I don't have any KT120 or KT150 tubes here to trace. Can send one over if you want it traced, a bit $$$ tubes though.
Re: Tony
I don't have any KT120 or KT150 tubes here to trace. Can send one over if you want it traced, a bit $$$ tubes though.
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Just by comparing the datasheet plate curves, I'd say the 6KG6/EL509 family of tubes does also belong to this row. They usually don't have these plate winglets, though.
Best regards!
The 6KG6/EL509 curve sets do look quite similar also. (below)
The reason I didn't add them to the "finalist" list was that the plates are obviously larger, and the lower grid 2 V I used to get the same approx. 1/2 Ampere curve sets (76V and 81V for the 40KG6s I traced, versus approx. 100V for grid 2 for the other finalists) 6KG6/EL509 is just plainly a bigger tube.
The above finalist tubes could literally be subbed for each other (other than sockets and Htr V).
The reason I didn't add them to the "finalist" list was that the plates are obviously larger, and the lower grid 2 V I used to get the same approx. 1/2 Ampere curve sets (76V and 81V for the 40KG6s I traced, versus approx. 100V for grid 2 for the other finalists) 6KG6/EL509 is just plainly a bigger tube.
The above finalist tubes could literally be subbed for each other (other than sockets and Htr V).
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Just saw this interesting implementation for PL509 / 40KG6:
Gold mine of DI¥ audio tubes schematics from Japan
Looks like some kind of twin drive g1+g2 similar to crazy drive.
Best regards
Philipp
Gold mine of DI¥ audio tubes schematics from Japan
Looks like some kind of twin drive g1+g2 similar to crazy drive.
Best regards
Philipp
Here are some curve tracings for the two 6P41S tubes Davorin sent. The tubes were numbered 66 and 67 so I have used those annotations here.
All: 50mA/div Vert., 50V/div Horiz.
a) 66 pentode -2.5V steps, 190V on grid 2
b) 66 in triode -5V steps
c) 66 pentode with positive g2 stepping up to 170V from 0V, grid 1 at 0V
d) 67 pentode -2.5V steps, 190V on grid 2
e) 67 in triode -5V steps
f) 67 pentode with positive g2 stepping up to 170V from 0V, grid 1 at 0V
g) the earlier 6P41S from here in pentode -2V steps, 170V grid 2
h) the earlier 6P41S from here in triode -4V steps
All: 50mA/div Vert., 50V/div Horiz.
a) 66 pentode -2.5V steps, 190V on grid 2
b) 66 in triode -5V steps
c) 66 pentode with positive g2 stepping up to 170V from 0V, grid 1 at 0V
d) 67 pentode -2.5V steps, 190V on grid 2
e) 67 in triode -5V steps
f) 67 pentode with positive g2 stepping up to 170V from 0V, grid 1 at 0V
g) the earlier 6P41S from here in pentode -2V steps, 170V grid 2
h) the earlier 6P41S from here in triode -4V steps
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Interesting. This is quite similar to the earliest 4D32 version we saw from MJ magazine. I think Tony found it. Even has the CFB part. No way to readily determine by inspection if it is set up for constant gm operation like Crazy Drive. The 10K resistor from grid 1 to grid 2 seems rather on the high side for Crazy drive. In any case, I don't think the CFB will make a lot of difference in drive for a HV grid 2 drive. At least I do have a 40KG6 tube here. Maybe I could rig something up to test on the curve tracer.
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i have the crazy drive 4D32 as a work in progress, all irons are complete, but i am replacing the power traffo to give a tad more B+.....
An externally hosted image should be here but it was not working when we last tested it.
Looks a bit like something I did 11 years ago. Post #30 here:
G1=G2/mu Scaled Drive Strawman Design
I'm wondering what a 4D32 would do in UNSET / CED mode?
Symbols 66 and 67 for 6P41S tubes indicate plate currents measured according to the manufacturer's instructions for static measurement where Ia = 66mA represents a 100% new tube (+/- 10mA).
Davorin:
I haven't forgotten about your tubes here. I plan to do some Crazy Drive curves and "new" series Schade (UnSet, CED) curves for 6P41S and the odd "6DQ5A" soon. (the "Boss" here is demanding I get some real work done around the house lately, curve tracer off limits for a while)
However, I did just find this unusual tube picture on Ebay (right side of pic). A Magnavox "6DQ5A" box. An "A" version!
Unfortunately, the tube they show with the box is a conventional RCA 6DQ5 which looks used. Probably is what got pulled when someone installed the Magnavox 6DQ5A. Anyway, might be worth keeping an eye out for Magnavox 6DQ5A tubes.
I haven't forgotten about your tubes here. I plan to do some Crazy Drive curves and "new" series Schade (UnSet, CED) curves for 6P41S and the odd "6DQ5A" soon. (the "Boss" here is demanding I get some real work done around the house lately, curve tracer off limits for a while)
However, I did just find this unusual tube picture on Ebay (right side of pic). A Magnavox "6DQ5A" box. An "A" version!
Unfortunately, the tube they show with the box is a conventional RCA 6DQ5 which looks used. Probably is what got pulled when someone installed the Magnavox 6DQ5A. Anyway, might be worth keeping an eye out for Magnavox 6DQ5A tubes.
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Here is the Ebay link to that pic.
The 6BK4C they show there was released in 1970. The 6JB6A (Syl 1972) they show has a later looking plate, but no obvious "winglets". These tubes may have been late aftermarket replacement tubes, with the Magnavox name. The 6DQ5A box looks old and worn. I have a Magnavox 6KM6 tube like what is in the pic, the tube is a GE with white print Magnavox on it.
6DQ5A might have just been a controlled warm up heater version, which went into most all tubes around that time, but never got a JEDEC update specifically for the 6DQ5. ( maybe Magnavox updated boxes anyway) Or it could be a 6JE6C on an octal base. Can't tell without seeing the Magnavox tube.
The JEDEC release sheet for the 6DQ5 (RCA 1957) shows an update in 1959 which increased the max DC cathode current from 285 mA to 315mA. The 6JE6A (RCA 1964/65 ) went from 315mA to 350 mA DC max. Then 6LQ6 (RCA 1967) had 350 mA DC max.
Magnavox Electronic Vacuum Tube 6DQ5 6BK4C 6KM6 6JB6A 6EN4 Lot of 5 | eBay
The 6BK4C they show there was released in 1970. The 6JB6A (Syl 1972) they show has a later looking plate, but no obvious "winglets". These tubes may have been late aftermarket replacement tubes, with the Magnavox name. The 6DQ5A box looks old and worn. I have a Magnavox 6KM6 tube like what is in the pic, the tube is a GE with white print Magnavox on it.
6DQ5A might have just been a controlled warm up heater version, which went into most all tubes around that time, but never got a JEDEC update specifically for the 6DQ5. ( maybe Magnavox updated boxes anyway) Or it could be a 6JE6C on an octal base. Can't tell without seeing the Magnavox tube.
The JEDEC release sheet for the 6DQ5 (RCA 1957) shows an update in 1959 which increased the max DC cathode current from 285 mA to 315mA. The 6JE6A (RCA 1964/65 ) went from 315mA to 350 mA DC max. Then 6LQ6 (RCA 1967) had 350 mA DC max.
Magnavox Electronic Vacuum Tube 6DQ5 6BK4C 6KM6 6JB6A 6EN4 Lot of 5 | eBay
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“Priced into orbit” is why you use the 26DQ5. When making your own power transformers, what’s another winding?
That row across the back are going to be the 26DQ5’s. In the other pic you can see the original donor transformer, and the custom wind job for the project. Lots and lots of wires coming out of it.
That row across the back are going to be the 26DQ5’s. In the other pic you can see the original donor transformer, and the custom wind job for the project. Lots and lots of wires coming out of it.
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