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Old 2nd August 2011, 11:34 AM   #1
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Default Some tube info that I hope is helpful

Good morning everyone,
I hope this tube info is helpful. I found it on a ham radio website.

Ray
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File Type: pdf By Plate Dissipation.pdf (41.1 KB, 112 views)
File Type: pdf By Tube Number.pdf (41.0 KB, 86 views)
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Old 2nd August 2011, 07:40 PM   #2
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Thanks for the info. These appear to be conservative ratings based on the datasheet info. (Not TubeLab ratings!) What is the PP/PC in the last column? Interesting to see the rather larger output power ratings for the "Sweeps" in comparison to similar plate diss. rated audio tubes. Some of this uprating would be due to the lower plate saturation voltages possible with the lower screen voltage used for the Sweeps. And some uprating from the different rating standards for Sweeps versus audio service.

Some adjustments might be in order on some tubes, like 6KV6A for example. It is the same as the 6KM6 but re-rated differently for HV regulator service, with a skimpy 2 Watt screen dissipation (since the plate voltage stays well above the screen V in this service). At the usual 4 Watt plate diss. per 1 Watt screen diss. tradeoff ratio, this would translate back to 22 Watts at 3.5 Watts screen diss. (like the 6KM6 screen rating). Dropping the power output rating down to about 80 Watts in P-P (from the listed 105 Watts).

The 6HJ5 is rated 24 Watts plate diss. and a hefty 6 Watts screen diss. If we drop the screen diss. down to a more typical 5 Watts, then the plate diss. would rise to 28 Watts. (giving about 95 Watts output rating in P-P, and it is after all a slightly bigger tube than the 6KV6A) Seem to recall George getting 125 Watts with these in P-P, but that would be with some spec busting. For comparison, the 6HF5 tube is the same size as the 6HJ5, but with a bigger grid heatsink. It lists at 28 Watt plate diss. and 5.5 W screen diss. and lists at 120 Watt output in the table.
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Old 2nd August 2011, 09:39 PM   #3
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Quote:
These appear to be conservative ratings based on the datasheet info. (Not TubeLab ratings!)
Since the info was gathered from a ham radio website the power output numbers are probably for RF amplifier service. Most are likely Class AB linear amplifiers but some could have been class C plate modulated ratings. Both types of service were used in the tube days of ham radio. SSB requires a linear amp usually run in class AB. The distortion criteria are far less than audio service. Further back in time hams used AM which was usually a class C saturated RF amp with plate modulation.

Quote:
Seem to recall George getting 125 Watts with these in P-P
I have a red board running 6HJ5's at 125 WPC. The tubes idle at about 20 watts dissipation per tube and see about 25 watts at full power. It is not uncommon for a class AB audio amp to dissipate the most power somewhere between those extremes, which I have not checked. For typical music the average dissipation is within limits. You can't be near it at full power since I have 96db speakers with 15 inch woofers.
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Old 2nd August 2011, 10:08 PM   #4
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I was unfamiliar with 8236. Looks perfect for screen drive.
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Old 3rd August 2011, 03:04 AM   #5
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The 8236 is a 6DQ5 with 50w plate dissipation. Nice tube, hard to come by. I had 4 in 1995 but got sold with the divorce.
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Old 3rd August 2011, 03:46 AM   #6
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I sold almost all sweep tubes on epay for cheap after found that GU-50 stock from military warehouses from Asia to Eastern Europe is big enough, also their current Chinese copy FU-50 are good enough.
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Old 3rd August 2011, 05:57 AM   #7
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Quote:
Originally Posted by smoking-amp View Post
What is the PP/PC in the last column?
It looks to me like Plate Connection: Plate Cap (PC) or Plate Pin (PP).

Another curiosity. According to my datasheets (my memory), a 6DQ6B is identical to a Compactron 6JM6, except in octal base. But the specs here are quite different. I'll have to double-check that.

..Todd
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Old 3rd August 2011, 04:22 PM   #8
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Plate Cap (PC) / Plate Pin (PP) Thanks!

I think you are right on the 6DQ6B as the same (GE datasheets at least). Possibly the 6DQ6B was rated using a higher screen voltage, which would increase the saturation voltage (and lower efficiency), no reason for that though. I don't have the GE manual handy, but some of the A/B/C tube variants I've seen in it seem to have an occasional carry-over typo from earlier tube versions (ie, the GE manual does not agree with the datasheets on one parameter).

6FW5 is another odd one. It seems to occur in the different 6DQ6 -/A/B variants, but without any indication on the tube.
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AVEI in the tables appears to be the Max DC mA spec. This gives an indication of the cathode emission capability. It should be possible to use this to determine a ballpark OT primary load impedance for a similar type tube in similar class operation. If you know an optimum primary load Z at some B+ for one tube, then you should be able to scale that Zpri to another tube by accounting for the 1/AVEI ratio, 1/Sqrt(Watts) ratio, and (B+ -Vsat) ratio between them. (edit: Oops, 1/Sqrt(Watts) ratio may be redundant, already accounted for in the other ratios, have to check this) Or just plot a loadline...
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Last edited by smoking-amp; 3rd August 2011 at 04:50 PM.
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