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    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Any audio use for ER21A?

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Giaime

Giaime

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Joined 2004
giaimeugliano.tk/
#1
Hello Folks!

I'm very proud of being a member of this forum, it's so full of friendly and helpful people (and very clever too) :angel:

So I have just found 2 of these tubes: I know there's nothing like a useless tube, but these might be the exception :smash:

So what can I do with them? I just found them in a box, don't know whether they've been used or not, but they look like new.

The only data I could find was: http://4tubes.com/All-Files/datasheets-tables/html/ER21A.html

ps in the same box I found 3 GE EL84, 1 Siemens EL84, and various 12A*7 Sylvania, GE, Siemens... and a GE EZ81, and an uknown RCA magic eye tube... and also 2 EF86 (oh those tubes look so nice).

Thanks in advance for the help!
 
#4
Netlist said:
Here's a bit more info: http://www.oneillselectronicmuseum.com/page10s.html

The ER21A seems to be ~equal to the GR16.

/Hugo
Click to expand...

Hello Hugo!

Thanks so much!

so if I understand well

There are gas filled tubes (Diodes) with an ignition electrode. Thyratrons. If a minimal voltage is applied to the ignition electrode (nanoA) then the tube ignites (the gas inside ionizes) allowing more current to flow. The ignition condition is indicated by glowing neon gas.
Click to expand...

Since I have no use for those two tubes, can I setup a circuit to just ignite them if they do make light? That would be a nice useless tubed thing!

Can someone show me how to properly use them? If I understand well, I have to apply a B+ voltage to the anode, and a small voltage to the "ignition electrode" to lit the tube.

On the first post there's a link to the pinout, sorry but I'm not able to understand...

Thanks in advance!
 
#7
It's all there in the spec sheet.
Apply some voltage (200V or so) through a resistor (maybe start with 100K) between the Anode (a) and Cathode (k) and then another higher value resistor to Trigger (t) and touch the unconnected end of the trigger resistor - If AC I think it should light just for the time you touch, if DC it should stay alight until you disconnect.

Be careful.:att'n:
 
#8
Thank you so much!!!

But I have some doubts: when you say to touch the unconnected end of the trigger resistor, you mean with my finger or with some positive voltage?

And by AC or DC you mean the anode voltage or the trigger voltage?

And what is the purpose of the pin marked "s"?

Sorry to seem so dumb, but I just don't know how those kind of tubes work! I'm not unexperienced in working with tubes, but this is the first time with non audio ones.

Thanks anyway!
 
#9
But I have some doubts: when you say to touch the unconnected end of the trigger resistor, you mean with my finger or with some positive voltage?
Click to expand...
Your finger or some voltage. A 500K or higher resistor cannot pass enough current to harm you from 220V mains, but you will feel a "tingle" if you complete a circuit by touching earth or neutral. It should not be necessary to form a circuit, your body "hum" should be enough.
You must have in Italy, small clear screwdrivers with a neon inside for testing mains voltage? This is the same principle. The resistor inside these is normally between 2.2M and 10M ohms.

And by AC or DC you mean the anode voltage or the trigger voltage?
Click to expand...
Either / both.

And what is the purpose of the pin marked "s"?
Click to expand...
I don't know either. Maybe shield?

What I described is what I would try. It will probably give a result, but it may not. This is sometimes the way to learn.😉
 
#10
Thank you so much John!!!!

So you think I could put a 100K 2W resistor from one of the mains leads to the anode, the other mains lead to the cathode, and try to ignite the tube with those methods?

Is 220V too much? I will test the thing with an isolation transformer (220V - > 110V) just for safety...

I'm so grateful to you!!!
 
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