Those russian tubes look very well made. The anode material is much thicker than whit western tubes(good against red spots). The glass is thicker and higher temperature? So they ought to be able to be driven harder.
I'm in the process of trying o kill a trioded PL504. Its a hard one. The Philips specimen on my bench has been eating 200 volts at around 400mA for quite some time now. 15 minutes.
What strikes me is that the current hardly changes. The supply indicates 380-420 mA.
I initially had some trouble whit oscillations. I put grid stoppers and ferrite beads in place.
I know that its not oscillating now (I'm watching the anode/G2 supply whit a scope). I put around 10 ferrite beads in series whit the anode. And 1K carbon+ 10 beads in series whit the wire feeding G1 whit a negative voltage.
Edit.
Impressive. I held the anode dissipation constant at 120 watts for 3 minutes. then proceeded to 160 watts which caused the glass to melt and bulge inwards. After observing the phenomenon I went back to 100 watts dissipation, to make sure the glass wouldn't shatter due to a temp shock.
I'm in the process of trying o kill a trioded PL504. Its a hard one. The Philips specimen on my bench has been eating 200 volts at around 400mA for quite some time now. 15 minutes.
What strikes me is that the current hardly changes. The supply indicates 380-420 mA.
I initially had some trouble whit oscillations. I put grid stoppers and ferrite beads in place.
I know that its not oscillating now (I'm watching the anode/G2 supply whit a scope). I put around 10 ferrite beads in series whit the anode. And 1K carbon+ 10 beads in series whit the wire feeding G1 whit a negative voltage.
Edit.
Impressive. I held the anode dissipation constant at 120 watts for 3 minutes. then proceeded to 160 watts which caused the glass to melt and bulge inwards. After observing the phenomenon I went back to 100 watts dissipation, to make sure the glass wouldn't shatter due to a temp shock.
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The PL504 seem to be pretty consistent if you have philips manufactured examples. Onset of internal glow is at about 40 watts. So 25-30 watts seems like a reasonable operating point.
One observation I made that if you massively overload the tube briefly, it will tolerate this. However under prolonged overload conditions, the beam forming plates will heat up the cathode material and degrade the emissive layer.
Disection of a tube that was killed at a peak dissipation of 180 watts showed a blackened cathode. Under these conditions the screen grid finally gave way and shorted to g1, this caused my Switchmode power supply to dump a lot of current into the little tube. Vaporizing the cathode lead
At 60% efficiency 2*30/40 *100 =150 watts output. This seems to coincide whit George's observations quite nicely.
One observation I made that if you massively overload the tube briefly, it will tolerate this. However under prolonged overload conditions, the beam forming plates will heat up the cathode material and degrade the emissive layer.
Disection of a tube that was killed at a peak dissipation of 180 watts showed a blackened cathode. Under these conditions the screen grid finally gave way and shorted to g1, this caused my Switchmode power supply to dump a lot of current into the little tube. Vaporizing the cathode lead
At 60% efficiency 2*30/40 *100 =150 watts output. This seems to coincide whit George's observations quite nicely.
v4lve lover wrote:
This is the schematic of the 6P36S SE amp...it's a straightforward circuit and it sounds pretty good. If you have any suggestions to improve it, I would like to hear them.
An externally hosted image should be here but it was not working when we last tested it.
This is the schematic of the 6P36S SE amp...it's a straightforward circuit and it sounds pretty good. If you have any suggestions to improve it, I would like to hear them.
Pete's Red Board using 13GB5's mounted directly on the board. I drilled new holes right into the board to install the chassis mount 13GB5 sockets.
Getting 45 wpc with 320 plate volts and 170 screen volts with a 2k4 output transformer.
--edited to add pics but can't seem to load them right now...
Getting 45 wpc with 320 plate volts and 170 screen volts with a 2k4 output transformer.
--edited to add pics but can't seem to load them right now...
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I was going to etch a new PCB, the first one is built up and running with the 17JT6 output tubes, in pentode mode. I have 60 of them, perhaps a life's supply. Also is dependend on the heater tap on the PT.
I'm using 6.6KRaa outputs for a larger class A operation, with minimal feedback. I'm running 89db speakers. @ 4 ohms, using 4ohm tap.
The PL504 seem to be pretty consistent if you have philips manufactured examples. Onset of internal glow is at about 40 watts. So 25-30 watts seems like a reasonable operating point.
One observation I made that if you massively overload the tube briefly, it will tolerate this. However under prolonged overload conditions, the beam forming plates will heat up the cathode material and degrade the emissive layer.
Disection of a tube that was killed at a peak dissipation of 180 watts showed a blackened cathode. Under these conditions the screen grid finally gave way and shorted to g1, this caused my Switchmode power supply to dump a lot of current into the little tube. Vaporizing the cathode lead
At 60% efficiency 2*30/40 *100 =150 watts output. This seems to coincide whit George's observations quite nicely.
hello , it's possible up power to EL/PL 504 to me build SE ?
because , me use to me build , EL / PL 504 to possible upgrad to EL / PL 502 / 511 for up power to 20 W !
so me no up power max 17 W , i possible use curent to up power EL 504 to EL 502 ?
many thank
Now running 1k9 output transformers for an honest 60wpc rms both channels driven using 50 cent 13GB5 aka PL504 tubes.
Can you say D-Y-N-A-M-I-C-S this amp's got it! The transformers, Hammond 1650T's, are idling along, but they sure seem a good impedance match for the 13gb5's.
310 volts on the plates, 170 on the screens. 70 mA idle bias current.
These things have no right to sound as good as they do! Thanks to Pete for a great board!
I need to add a touch of global feedback and mount this stuff on a decent chassis.
Can you say D-Y-N-A-M-I-C-S this amp's got it! The transformers, Hammond 1650T's, are idling along, but they sure seem a good impedance match for the 13gb5's.
310 volts on the plates, 170 on the screens. 70 mA idle bias current.
These things have no right to sound as good as they do! Thanks to Pete for a great board!
I need to add a touch of global feedback and mount this stuff on a decent chassis.
Attachments
I have a couple of 25DN6 and what surprises me, is the vast amount of heater power they require; 0.6A @ 25V = 15W which is twice the heater power of a 25BQ6, PL504, 25GC6 etc which are all in the same power class for similar b/w tv service but only 7.5W heaters.
I mean 15W is more than a PL519 (!) (12.5W) which - being intended for color tv - is in a totally different class (45W plate dissipation vs. 15W plate, datasheet that is).
So why is the 25DN6 the odd man out when it comes to heater power vs. plate dissipation ?
It's not the peak current either, because the DN6 is in the same 700mA category whereas the 519 is at least twice that.
I mean 15W is more than a PL519 (!) (12.5W) which - being intended for color tv - is in a totally different class (45W plate dissipation vs. 15W plate, datasheet that is).
So why is the 25DN6 the odd man out when it comes to heater power vs. plate dissipation ?
It's not the peak current either, because the DN6 is in the same 700mA category whereas the 519 is at least twice that.
Series string 600 mA TV sets, yes, compactrons, no. In fact the most likely driver (horizontal oscillator) for a 25DN6 was a 6SN7 or 6FQ7. The 6DN6 and 25DN6 are from 1954 long before compactrons were dreamed up. They were early generation big sweep tubes. Other sweep tubes of a similar size like the 6CD6 and the 6DQ5 also need a 15 watt heater. The only anomaly is the specified dissipation rating of 15 watts. Trust me it isn't real
There are a few different constructions of 25DN6 but most of the ones I have contain the same plate structure as the 22 to 24 watt tubes. I got a big box full for 50 cents each. A pair will crank out 100 watts without glowing.
The 6SN7 was used quite a bit in TV sets. I have seen old B&W designs that used it as the vertical oscillator and output tube. That is why the dissipation and voltage capability was upgraded. As TV's got bigger and shallower, the 6SN7 wasn't enough, so the 6BL7 and 6BX7 were designed with the same pinout.
Yes, probably that's the point!
But have a look at the 25E5/PL36 tube: The same power class, same maximum cathode current, same octal base, roughly the same aera of it's development - but only half the heater power, as compared with the 25DN6!
Best regards!
and it can't be the 0.6V heater string argumentation either, because there is also the 12GC6 which has 7.4W heaters @ 0.6A and similar plate power characteristics and octal, too;
so what makes an "old design" sweep tube inferior ?
poor cathode emission efficiency - inferior cathode construction / materials ?
I made some pulsed peak plate current measurements, too.
same setup for each tube.
results in absolute amps and --> peak milliamps per heater watt
------------------------------------
25DN6 : 1.05A (15W heater) --> 70
------------------------------------
25BG6GT : 0.7A (7.5W heater) --> 93
PL36 : 0.7A (7.5W heater) --> 93
12GC6 : 0.8A (7.38W heater) --> 108
------------------------------------
PL500 : 1.1A (8.1W heater) --> 136
PL509 : 1.7A (12.5W heater) --> 136
21KQ6 : 1.5A (9.45W heater) --> 159
so what makes an "old design" sweep tube inferior ?
poor cathode emission efficiency - inferior cathode construction / materials ?
I made some pulsed peak plate current measurements, too.
same setup for each tube.
results in absolute amps and --> peak milliamps per heater watt
------------------------------------
25DN6 : 1.05A (15W heater) --> 70
------------------------------------
25BG6GT : 0.7A (7.5W heater) --> 93
PL36 : 0.7A (7.5W heater) --> 93
12GC6 : 0.8A (7.38W heater) --> 108
------------------------------------
PL500 : 1.1A (8.1W heater) --> 136
PL509 : 1.7A (12.5W heater) --> 136
21KQ6 : 1.5A (9.45W heater) --> 159
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Well, 12GC6 appears to date from 1960, so it is a later design than the 25DN6 (1954 or so)
Oxide cathode material composition/emission efficiency steadily improved over time. Different manufacturers (ie, tube designer) may have introduced improved material at somewhat different times on various tubes. 25DN6 was probably an early comer to the race for higher current in sweep tubes.
Oxide cathode material composition/emission efficiency steadily improved over time. Different manufacturers (ie, tube designer) may have introduced improved material at somewhat different times on various tubes. 25DN6 was probably an early comer to the race for higher current in sweep tubes.