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14th Jan 2020, 10:52 pm | #1 |
Triode
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
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Valve testing a 4212
I have recently acquired a very large valve - a 4212H, I believe.
Is it possible to test one of these huge valves ? It is undoubtedly beyond me ! I have ascertained the filament has continuity and thats me done! Is this a service that is provided by anyone ? Many thanks |
14th Jan 2020, 11:59 pm | #2 |
Dekatron
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Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,637
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Re: Valve testing a 4212
One of these: https://vintage-radio.net/forum/showthread.php?t=40716
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15th Jan 2020, 8:52 am | #3 |
Dekatron
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Location: Newcastle upon Tyne, Tyne & Wear, UK.
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Re: Valve testing a 4212
Hi Tinker, you should be able to run the filament supply up and then connect a voltmeter between cathode and grid. If the valve has emission you should get a small voltage reading.
Then you can think about other power supplies to try it in anger. Ed |
15th Jan 2020, 9:04 am | #4 |
Triode
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
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Re: Valve testing a 4212
Yes - thats the one.
Well - I have a voltmeter so thats a step in the right direction - but as to connecting up the filament I would have no idea what kind of voltage to apply and would be terrified of doing the wrong thing - I am led to believe this valve has a fair value, so it might well end upon ebay... |
15th Jan 2020, 4:05 pm | #5 | |
Triode
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
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Re: Valve testing a 4212
Quote:
If I apply that to the filament with a variac and connect a voltmeter to the other two pins I should get a reading ..... Am I on the right track ? I shan't do anything just yet .......!! Thanks for the help |
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15th Jan 2020, 5:10 pm | #6 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,838
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Re: Valve testing a 4212
There was a similar thread to this a few weeks before Christmas. See "Search". Also, I actually tested one a couple or so years ago, using a bespoke DC Rig, plus produced a Ia/Vg Graph which I could compare with an actual STC graph. Sourcing a high current heater voltage is the awkward bit.
Regards, David |
15th Jan 2020, 8:23 pm | #7 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
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Re: Valve testing a 4212
14V @ 6A would be the easy part for me.
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15th Jan 2020, 9:10 pm | #8 |
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Re: Valve testing a 4212
Car battery? With ln line fuses of course! Not quite 14V, but should suffice for testing.
CB radio PSU?
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
15th Jan 2020, 9:39 pm | #9 |
Triode
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
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Re: Valve testing a 4212
Wow thanks Station X -
Car battery - I have several of those hanging about. So connect that to the filament terminals and measure the other 2 with the voltmeter to see if there's any voltage ..... That's tomorrows project sorted |
15th Jan 2020, 10:14 pm | #10 |
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Re: Valve testing a 4212
Don't forget the fuses or you could find yourself doing some involuntary arc welding.
An alternative would be to connect to a car's cigarette lighter/accessory socket which will be fused within the vehicle.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
15th Jan 2020, 10:57 pm | #11 |
Triode
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
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Re: Valve testing a 4212
Ok - fuses at the ready !
I will report back tomorrow |
16th Jan 2020, 10:25 am | #12 |
Heptode
Join Date: Jun 2017
Location: Southport, Merseyside, UK.
Posts: 645
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Re: Valve testing a 4212
The National Valve Museum website for 4212 gives a PDF data sheet link
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16th Jan 2020, 12:08 pm | #13 |
Nonode
Join Date: Mar 2008
Location: Aberdeen, UK.
Posts: 2,838
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Re: Valve testing a 4212
Aye Tinker, you'll be needing hefty Va & Vg supplies plus being able to measure in the region of 160mA Ia. Way beyond the VCM's & Valve Testers we all know. Plus you'll need to make a bespoke valve holder with sturdy valve pin connections. Don't be tempted to use cheapo crock-clip leads.
Jesus, was it all that long ago - 7th Oct.2015 was my "Testing the STC 4212D Triode" Thread. My 4212D drew 6.3A at 14V Vh. And with 500V Va drew 160mA at -5Vg, but I started out gently at -50Vg. If you look at the STC family of Gm curves, you'll see that these fearsome valves were happy working in the 1KV Va region. Running Vh at 12V off a battery might do just to see the thing glow, but 14V would be needed to get comparisons with STC's data. Caution - if your valve is a decent NOS one, it could be worth a few hundred quid, so don't phook it. Regards, David |
16th Jan 2020, 12:25 pm | #14 |
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Re: Valve testing a 4212
If this were mine and I wanted to sell it, all I'd do would be to test the heater for continuity and state that it had continuity in my eBay listing or W.H.Y.
That's what I did with a load of 4CX250B's a few years back.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
16th Jan 2020, 12:56 pm | #15 |
Triode
Join Date: Nov 2014
Location: Leominster, Herefordshire, UK.
Posts: 25
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Re: Valve testing a 4212
Thanks everyone for the advice - I have already tested for continuity of the filament and it is good.
I think on balance I shall leave it there and sell it as is. |
16th Jan 2020, 1:03 pm | #16 | |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
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Re: Valve testing a 4212
Quote:
I'm just wondering how low a voltage you could use, and see some current and diode effect on a multimeter? Would a 9V battery be too low? Would -9v from a second battery be expected to cut the valve off or at least reduce the current? More a classroom demo than meaningful testing, but it would prove there was some vacuum and emission. (posts crossed)
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16th Jan 2020, 1:30 pm | #17 |
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Re: Valve testing a 4212
The OP was referring to the advice in post #3. ie measure the cathode to grid voltage.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
16th Jan 2020, 5:39 pm | #18 |
Dekatron
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Re: Valve testing a 4212
That's interesting, I don't suppose you could detect the space charge with an AVO 8 though...
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21st Jan 2020, 3:15 pm | #19 |
Dekatron
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Re: Valve testing a 4212
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