photomultipliers, and yes those magnetrons.
cant live without microwave ovens
I'm not an expert, but I was told that microwave ovens get their microwaves via some other device other than magnetrons (now). I know they were originally made with Magnetrons. We were discussing construction of death ray machines or something and the conversation of course turned to the more practical aspects like where to get parts.
Well I see that everyone has a story to tell about technical incompetence.
Part of the problem today is the Education sector - and all its new safety rules - wrapping the kids in cotton wool; as they say. It seems to be a world wide phenomena.
Back in 1974 our school class of 16 year olds ( Year 10 or Form 4 Technical School students ) made an AC-DC 6/12 volt battery charger for our Electrical class.
We made our own charger box in sheet metal class; wired up our own power lead and fabricated the heatsinks for the rectifier, and even wound and assembled our own power transformer from scratch; even making the bobbin from fibreglass board and glue, winding the wore and installing the terminations under the direction of the teacher who was a qualified Electrician.
Nowadays kids would carry such an assignment out on p-Spice or some other computer program with little practical in the whole process. WHY ? Because the students might get electrocuted and the school might get sued !
But in reality that's how we learnt - by making mistakes and possibly getting electrocuted in the process of building something.
Just look as how few people are making anything now. Since the late 1990's techs have retired and left the industry stopped making kits and projects and sat at home on the butts surfing the net. Even I have fallen into this habit.
The cost of building something for many is too expensive now, and scrounging this or that from the hard rubbish dumps is quite difficult for many items - plus in our area you get fined by the Council ( or Police ) if you take stuff off the hard rubbish - as its stealing their profits.
Strangely I am seen by many as weird because I have a personal interest in electronics and hoard items from the dump ( ie old microwaves and radio sets ) and playing with gadgets. Even computer buffs see me in the same light. Each one to his own !
Part of the problem today is the Education sector - and all its new safety rules - wrapping the kids in cotton wool; as they say. It seems to be a world wide phenomena.
Back in 1974 our school class of 16 year olds ( Year 10 or Form 4 Technical School students ) made an AC-DC 6/12 volt battery charger for our Electrical class.
We made our own charger box in sheet metal class; wired up our own power lead and fabricated the heatsinks for the rectifier, and even wound and assembled our own power transformer from scratch; even making the bobbin from fibreglass board and glue, winding the wore and installing the terminations under the direction of the teacher who was a qualified Electrician.
Nowadays kids would carry such an assignment out on p-Spice or some other computer program with little practical in the whole process. WHY ? Because the students might get electrocuted and the school might get sued !
But in reality that's how we learnt - by making mistakes and possibly getting electrocuted in the process of building something.
Just look as how few people are making anything now. Since the late 1990's techs have retired and left the industry stopped making kits and projects and sat at home on the butts surfing the net. Even I have fallen into this habit.
The cost of building something for many is too expensive now, and scrounging this or that from the hard rubbish dumps is quite difficult for many items - plus in our area you get fined by the Council ( or Police ) if you take stuff off the hard rubbish - as its stealing their profits.
Strangely I am seen by many as weird because I have a personal interest in electronics and hoard items from the dump ( ie old microwaves and radio sets ) and playing with gadgets. Even computer buffs see me in the same light. Each one to his own !
Well hello Kimbal, I may be a bit younger than you but I agree, nobody seems to learn something practical anymore.
I stopped bringing home broken microwave ovens from the street, but old MW parts taught me about spotwelding, and when i fixed my grill/oven/MW with garbage parts even my girlfriend didn't complain. Magnetrons appear to be interchangeable between brands. Don/t throw away, recycle,
I stopped bringing home broken microwave ovens from the street, but old MW parts taught me about spotwelding, and when i fixed my grill/oven/MW with garbage parts even my girlfriend didn't complain. Magnetrons appear to be interchangeable between brands. Don/t throw away, recycle,
Just on Microwave ovens - they seem to be the only thing left with a serious power transformer inside these days. Now they weld the Laminations making them quite useless for most rewinding; unlike old Black & White T.V Power Transformers which were much bigger and very useful. Now they are even replacing these transformers with inverter supplies. But if you can find a practical use for them go for it !
I've worked as an electronics technician for many years (starting with tube gear in the Navy FWIW) but got about 75% through an engineering degree, first ME and then changed to EE, passed the EIT exam, etc. I think a lot of the trouble comes from the fact that many engineering students took up the major because of good job prospects, a BS is enough, etc. and don't have a true fascination with the technology and the design process...only a handful of my fellow students did any tinkering on the side, tried to build anything original, etc.
I grew up around around engineering as my father was an ME (but also did some EE work too), had dozens of patents, etc. Many engineers of his generation were smart kids that built hod rods, radios, etc. and wanted to move on to designing them...I didn't see much of that when I studied engineering myself, not in the students or the instructors (some of whom had an appalling ignorance of real world technology i.e. a thermodynamics instructor who was convinced that a 4 stroke engine completes its cycle in one revolution, etc.)
They still use magnetrons,
It's the power supply that has changed. It used to be just a HV transformer, with a capacitor and rectifier.
Most all of them now using are using an inverter instead.
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The inverter allows them to vary the power level continuously. And they cost less to ship. And they charge more for them.
-----------------------
Here are some research results on TV sweeps for screen grid drive.
These are the vg1=0, vg2 =150 V, knee plate current levels in mA.
6LR6 1200
6LF6 1144
6KG6 1135
6LX6/6MB6/6KD6/6MH6/26HU5 1080
6LW6 1050
6KN6 1050
6LZ6 940
6LB6 825
6JE6 749
6JS6 749
6LG6 740
6LQ6 715
6DQ5 700
6ME6 700
6JF6/6JG6 660
6KM6 630
6HJ5 610
6JR6/6JU6 600
6HB5 560
12HE7 550
6KV6 488
6EX6 460
6CB5 440
6CD6 422
6GT5/6GJ5/6JT6/6GW6/6JB6 380
6GE5/6JN6/6GV5/6DQ6B/6FW5 330
6AV5/6BQ6 255
KT90 220
6550A 190
KT88 170
6L6GC 75
-----------------------
Here are some research results on TV sweeps for screen grid drive.
These are the vg1=0, vg2 =150 V, knee plate current levels in mA.
6LR6 1200
6LF6 1144
6KG6 1135
6LX6/6MB6/6KD6/6MH6/26HU5 1080
6LW6 1050
6KN6 1050
6LZ6 940
6LB6 825
6JE6 749
6JS6 749
6LG6 740
6LQ6 715
6DQ5 700
6ME6 700
6JF6/6JG6 660
6KM6 630
6HJ5 610
6JR6/6JU6 600
6HB5 560
12HE7 550
6KV6 488
6EX6 460
6CB5 440
6CD6 422
6GT5/6GJ5/6JT6/6GW6/6JB6 380
6GE5/6JN6/6GV5/6DQ6B/6FW5 330
6AV5/6BQ6 255
KT90 220
6550A 190
KT88 170
6L6GC 75
That's fine.
Some tube values I had to extrapolate from a nearest vg2 rating by using 3/2 power law. I used the curve data where available, versus printed switching ratings. And some tubes have somewhat conflicting data from their data sheets for the two. For example, 6KG6 has a printed rating that would lead to 908 mA instead of the 1135 from the curves. 6KN6 has a printed rating that would lead to 1052 mA instead of 942 mA from the curves.
6KV6 is apparently the same tube as a 6KM6 (except for pin-out), just re-rated for regulator service, which draws low screen current, so its plate wattage got up-rated to 28 Watt (4 Watts more plate diss. per 1 Watt less screen diss. is the rule). Since I don't have any curves for 6KV6, I used the printed rating, which leads to only 488 mA (at 150 V). But the 6KM6 curves give 630 mA (at 150 V)
Then of course there is inevitable variation from tube to tube, the datasheet only being average. Then I see large variation in gm between different manufacturers often too. And then there are outright construction differences, 6LR6 from Sylvania has a smaller plate than from GE for example.
Some 6KN6 tubes have two beam pentodes in parallel inside, and other (newer) ones have one big one (probably 6LR6 or 6LW6 guts instead). 6DQ6 /A/B are all over the map too.
So these are ball-park figures. Not hard and fast.
One probably should make a combined rating sheet with peak current rating, max DC rating, max Watts diss., and maybe some of the stats normalized per Watt somehow. Also, would be nice to have some figure for screen current too. The 6LX6 would seem to be the standout winner on that if you believe the GE short form handbook at 750 mA/4.2 mA, but thats a typo. The datasheet says 42 mA. And since the screen current depends heavily on the alignment of the two grids, I'm sure that figure is all over the place from the datasheet average too.
Some tube values I had to extrapolate from a nearest vg2 rating by using 3/2 power law. I used the curve data where available, versus printed switching ratings. And some tubes have somewhat conflicting data from their data sheets for the two. For example, 6KG6 has a printed rating that would lead to 908 mA instead of the 1135 from the curves. 6KN6 has a printed rating that would lead to 1052 mA instead of 942 mA from the curves.
6KV6 is apparently the same tube as a 6KM6 (except for pin-out), just re-rated for regulator service, which draws low screen current, so its plate wattage got up-rated to 28 Watt (4 Watts more plate diss. per 1 Watt less screen diss. is the rule). Since I don't have any curves for 6KV6, I used the printed rating, which leads to only 488 mA (at 150 V). But the 6KM6 curves give 630 mA (at 150 V)
Then of course there is inevitable variation from tube to tube, the datasheet only being average. Then I see large variation in gm between different manufacturers often too. And then there are outright construction differences, 6LR6 from Sylvania has a smaller plate than from GE for example.
Some 6KN6 tubes have two beam pentodes in parallel inside, and other (newer) ones have one big one (probably 6LR6 or 6LW6 guts instead). 6DQ6 /A/B are all over the map too.
So these are ball-park figures. Not hard and fast.
One probably should make a combined rating sheet with peak current rating, max DC rating, max Watts diss., and maybe some of the stats normalized per Watt somehow. Also, would be nice to have some figure for screen current too. The 6LX6 would seem to be the standout winner on that if you believe the GE short form handbook at 750 mA/4.2 mA, but thats a typo. The datasheet says 42 mA. And since the screen current depends heavily on the alignment of the two grids, I'm sure that figure is all over the place from the datasheet average too.
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OOPs,
6HF5 should have been listed with the 6JS6 at 749 mA (at 150 V). (same tube, different pin-out according to GE) The printed info for the Tungsol 6HF5 (570 mA at 125V) gives 749 mA at 150V. If you use the printed info for the 6JS6C: 600 mA at 125V, that would give 789 mA at 150 V. The C version got a little uprating. Similarly for the 6JE6C, C version uprated to (600 mA at 125 V) or 789 mA at 150 V. Hmm, looks like the original 6JE6 was rated 580 mA (not 570) at 125 V, so that would give 762 mA (not 749) at 150 V for the original 6JE6.
Missed 6GC6 too, 340 mA (at 150 V).
6HF5 should have been listed with the 6JS6 at 749 mA (at 150 V). (same tube, different pin-out according to GE) The printed info for the Tungsol 6HF5 (570 mA at 125V) gives 749 mA at 150V. If you use the printed info for the 6JS6C: 600 mA at 125V, that would give 789 mA at 150 V. The C version got a little uprating. Similarly for the 6JE6C, C version uprated to (600 mA at 125 V) or 789 mA at 150 V. Hmm, looks like the original 6JE6 was rated 580 mA (not 570) at 125 V, so that would give 762 mA (not 749) at 150 V for the original 6JE6.
Missed 6GC6 too, 340 mA (at 150 V).
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Updated Listing: Plate knee currents for TV sweeps at 150 V on g2 (0 V on g1)
6LR6 1200
6LF6 1144
6KG6 1135
6LX6/6MB6/6KD6/6MH6/26HU5 1080
6LW6 1050
6KN6 1050
6LZ6 940
6LB6 825
6JE6C/6JS6C 789
6JE6 762
6JS6/6HF5 749
6LG6 740
6LQ6 715
6DQ5 700
6ME6 700
6JF6/6JG6 660
6KM6 630
6HJ5 610
6JR6/6JU6 600
6JZ6/21HB5A 560
12HE7 550
6KV6 488 (630?)
6HB5/6GY5/6KE6/16KA6/21JV6 475
6EX6 460
6CB5 440
6CD6 422
6GT5/6GJ5/6JT6/6GW6/6JB6 380
6GE5 350
6GF5 345
6JN6/6FW5/6GC6 340
6DQ6B/6GV5 330
6DQ6A 280
6JA5/10JA5 276
6LU8 265
6AV5GA/6BQ6GA 255
KT90 220
6550A 190
KT88 170
6GK6 84
6JC5 80
6L6GC 75
6HB6 70
6LR6 1200
6LF6 1144
6KG6 1135
6LX6/6MB6/6KD6/6MH6/26HU5 1080
6LW6 1050
6KN6 1050
6LZ6 940
6LB6 825
6JE6C/6JS6C 789
6JE6 762
6JS6/6HF5 749
6LG6 740
6LQ6 715
6DQ5 700
6ME6 700
6JF6/6JG6 660
6KM6 630
6HJ5 610
6JR6/6JU6 600
6JZ6/21HB5A 560
12HE7 550
6KV6 488 (630?)
6HB5/6GY5/6KE6/16KA6/21JV6 475
6EX6 460
6CB5 440
6CD6 422
6GT5/6GJ5/6JT6/6GW6/6JB6 380
6GE5 350
6GF5 345
6JN6/6FW5/6GC6 340
6DQ6B/6GV5 330
6DQ6A 280
6JA5/10JA5 276
6LU8 265
6AV5GA/6BQ6GA 255
KT90 220
6550A 190
KT88 170
6GK6 84
6JC5 80
6L6GC 75
6HB6 70
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More complete data now.
Watt dissipation now included. And since one would expect plate knee current to inherently increase with Watts, the last number gives a figure of merit: mA/Watt diss. (a row of *** after the best ones, 24 and above)
Tube: Plate current knee in mA for 150 V on g2 and 0 V on g1: then plate Watt diss.: then mA/W figure of merit
6LR6 1200 30W 40 ********************
6LF6 1144 40W 28.6 ***************
6KG6/EL509 1135 34W 33.4 ***************
13E1 1120 90W 12.4
6MH6 1100 38.5W 28.6 ***************
6MB6 1080 35W 30.9 ***************
6LX6/6KD6/6MC6/26HU5 1080 30W 36 ****************
6LW6 1050 40W 26.3 ****** high W *****
6KN6 1050 30W 35 *******************
6LZ6 940 30W 31 ******************
6LB6 825 30W 27.5 *****************
6JE6C/6JS6C/6MJ6 789 30W 26.3 **************
6JE6 762 24W 32 *****************
6JS6/6HF5 749 28W 27 ***************
6LG6 740 28W 26.4 ***************
6LQ6 715 30W 24 *********
6DQ5 700 24W 29 *****************
6ME6 700 30W 23.3 ********
6JF6/6JG6 660 17W 39 ******************
6KM6 630 20W 31.5 *****************
6HJ5 610 24W 25.4 ***********
6JR6/6JU6 600 17W 35.3 ****************
6JZ6/21HB5A 560 18W 31 ****************
12HE7 550 10-15W 55-37 ****************
6GB5/29KQ6/EL500 500 17W 29.4 ***************
6KV6 488 (630?) 20-28W 24.4-31.5 ***************
6HB5/6GY5/6KE6/16KA6/21JV6 475 18W 26.4 ***************
6EX6 460 22W 21
6CB5/A 440 23/26W 17
6CD6/GA 422 15/20W 21
6GT5/6GJ5/6JT6/6GW6/6JB6 380 17.5W 21.7
6GE5 350 17.5W 20
6GF5 345 9W 38.3 ****(ONLY 9W)
6JM6/6JN6/6FW5/6GC6 340 17.5/18W 19.4
6DQ6B/6GV5 330 17.5/18W 18.3
6DQ6A 280 18W 15.5
6JA5/10JA5 276 19W 14.5
6LU8/6LR8/6MY8 265 14/16W 19
6AV5GA/6BQ6GA 255 11W 23
KT120 221 60W 3.7
KT90 220 50W 4.4
6550A 190 35W 5.4
KT88 170 35W 4.9
6GK6 84 13.2W 6.4
6JC5 80 19W 4.2
6L6GC 75 30W 2.5
6HB6 70 10W 7
6V6GA 45 14W 3
Watt dissipation now included. And since one would expect plate knee current to inherently increase with Watts, the last number gives a figure of merit: mA/Watt diss. (a row of *** after the best ones, 24 and above)
Tube: Plate current knee in mA for 150 V on g2 and 0 V on g1: then plate Watt diss.: then mA/W figure of merit
6LR6 1200 30W 40 ********************
6LF6 1144 40W 28.6 ***************
6KG6/EL509 1135 34W 33.4 ***************
13E1 1120 90W 12.4
6MH6 1100 38.5W 28.6 ***************
6MB6 1080 35W 30.9 ***************
6LX6/6KD6/6MC6/26HU5 1080 30W 36 ****************
6LW6 1050 40W 26.3 ****** high W *****
6KN6 1050 30W 35 *******************
6LZ6 940 30W 31 ******************
6LB6 825 30W 27.5 *****************
6JE6C/6JS6C/6MJ6 789 30W 26.3 **************
6JE6 762 24W 32 *****************
6JS6/6HF5 749 28W 27 ***************
6LG6 740 28W 26.4 ***************
6LQ6 715 30W 24 *********
6DQ5 700 24W 29 *****************
6ME6 700 30W 23.3 ********
6JF6/6JG6 660 17W 39 ******************
6KM6 630 20W 31.5 *****************
6HJ5 610 24W 25.4 ***********
6JR6/6JU6 600 17W 35.3 ****************
6JZ6/21HB5A 560 18W 31 ****************
12HE7 550 10-15W 55-37 ****************
6GB5/29KQ6/EL500 500 17W 29.4 ***************
6KV6 488 (630?) 20-28W 24.4-31.5 ***************
6HB5/6GY5/6KE6/16KA6/21JV6 475 18W 26.4 ***************
6EX6 460 22W 21
6CB5/A 440 23/26W 17
6CD6/GA 422 15/20W 21
6GT5/6GJ5/6JT6/6GW6/6JB6 380 17.5W 21.7
6GE5 350 17.5W 20
6GF5 345 9W 38.3 ****(ONLY 9W)
6JM6/6JN6/6FW5/6GC6 340 17.5/18W 19.4
6DQ6B/6GV5 330 17.5/18W 18.3
6DQ6A 280 18W 15.5
6JA5/10JA5 276 19W 14.5
6LU8/6LR8/6MY8 265 14/16W 19
6AV5GA/6BQ6GA 255 11W 23
KT120 221 60W 3.7
KT90 220 50W 4.4
6550A 190 35W 5.4
KT88 170 35W 4.9
6GK6 84 13.2W 6.4
6JC5 80 19W 4.2
6L6GC 75 30W 2.5
6HB6 70 10W 7
6V6GA 45 14W 3
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Don,
Do you have anything for 6CM5/EL36.
These are what I would probably use for screen drive here in Oz (availability).
In fact I am doing some scribbles considering screen driving a 6CM5 to drive an 845.
I know some guys are using 6AV5 to drive 845 but not screen driven (at least I don't think so).
Getting a nice clean 300V pk-pk swing for the 845 grid is non-trivial. Not trying to go into 845 A2 territory.
Cheers,
Ian
Do you have anything for 6CM5/EL36.
These are what I would probably use for screen drive here in Oz (availability).
In fact I am doing some scribbles considering screen driving a 6CM5 to drive an 845.
I know some guys are using 6AV5 to drive 845 but not screen driven (at least I don't think so).
Getting a nice clean 300V pk-pk swing for the 845 grid is non-trivial. Not trying to go into 845 A2 territory.
Cheers,
Ian
Yep,
Using the Philips data here, page 4:
http://frank.pocnet.net/sheets/030/e/EL36.pdf
Its got data for Vg2 at 170 V (555 mA) and at 100 V (260 mA).
To get a 150 V figure: [555]*(150/170)^1.5 => 460 mA
or [260]*(150/100)^1.5 => 477 mA
so average is 468.5 mA for 150 V
6CM5/EL36 468.5 12W 39 ************************
Edit:
I just noticed that the Philips page 4 chart gives data for Va = Vg2, so is a little boosted above the knee. On page 5 is another chart with actual plate curve knees but with Vg1 at -1 V. Curves given for 140 V and 160 V. With a Mu of 5.5, the -1V would need an extra +5.5 V on the screen to compensate, so 155.5V is the curve to compute. Which looks like it would be around:
[420]*(155.5/160)^1.5 => 402.4
so:
6CM5/EL36 402.4 12W 33.5 ***********************
A good tube for screen drive!
Using the Philips data here, page 4:
http://frank.pocnet.net/sheets/030/e/EL36.pdf
Its got data for Vg2 at 170 V (555 mA) and at 100 V (260 mA).
To get a 150 V figure: [555]*(150/170)^1.5 => 460 mA
or [260]*(150/100)^1.5 => 477 mA
so average is 468.5 mA for 150 V
6CM5/EL36 468.5 12W 39 ************************
Edit:
I just noticed that the Philips page 4 chart gives data for Va = Vg2, so is a little boosted above the knee. On page 5 is another chart with actual plate curve knees but with Vg1 at -1 V. Curves given for 140 V and 160 V. With a Mu of 5.5, the -1V would need an extra +5.5 V on the screen to compensate, so 155.5V is the curve to compute. Which looks like it would be around:
[420]*(155.5/160)^1.5 => 402.4
so:
6CM5/EL36 402.4 12W 33.5 ***********************
A good tube for screen drive!
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