On Thu, 6 Jul 2017 18:25:31 -0000 (UTC), frank
wrote:
Jeff Liebermann wrote:
On Thu, 6 Jul 2017 07:15:39 -0000 (UTC), frank
wrote:
I'll try to make a test setup with constant current on a GDT and try
to measure the frequency of the oscillation.
Frank
Could I trouble you to disclose the maker and model of the gas
discharge transient suppressor that you're testing, and the model
I don't know, I've pulled them out of a scrap PCB.
They are marked as 201M TM4M (on two separate lines).
201 might be the discharge voltage which is in good agreement on what I see
on the curve tracer.
I tried to identify the manufactory from the part numbers supplied.
Nothing. I would agree that 201 might mean 200V discharge voltage.
I found one in my junk box inscribed Joslyn M-3 2204-44. I also
couldn't find any specs on that device. I was going to try it on my
hi-v power supply, but ran into 2 problem. The power supply is dead
for no obvious reason. My workbench is currently being used to test
my latest Harbor Freight purchase, a 1x30" belt sander suitable for
sharpening all my dull kitchen knives. That's a priority project.
number of the Heathkit curve tracer? I don't have a curve tracer but
I do have a high voltage variable power supply that I can manually
sweep to see if there are any negative resistance regions.
it's IT-3121, connected to an HP-1801A/180AR as display.
Schematic and operating instructions at:
http://www.vintage-radio.info/download.php?id=225
On Pg 62 of the operations manual, it shows various display anomalies.
Some are loops which look something like your photo. They suggest
using the LOOP control to reduce the effect or lower the power supply
voltage. You've probably already tried this, but I thought I would
mention it anyway.
series resistor was already selected to limit the current peak value, it's
a knob on the curve tracer.
Yep. Resistor values from 0 to 1M. Aim towards the higher values
here.
I've tried going from 5K to 50K and oscillation remains, of course peak
current varies. Using 100K as series resistor doesn't make the tube ignite
at all. Max voltage value on this curve tracer is around 240V.
You might be too close to the conduction threshold on the tube. Hard
to tell without specifications. If the device appears to fail to fire
at high series resistances, it might have fired, dropped the voltage
to about 15v across the tube, and stayed there. Grab a DVM and
measure the voltage across the device. My guess(tm) is that it's
about 15v and holding.
For fun, put a capacitor (300v or high) across the tube with a high
series resistance and see if you can get it to oscillate as a
relaxation oscillator.
For additional entertainment, replace the tube with a common NE-2 neon
lamp and see if it does the same thing.
Do you mean I should add an external resistor? I believe it would just go
in series with the internal one.
No. I didn't realize that there was a series resistor in the curve
tracer. This switchable resistor should be sufficient.
Indeed these tubes are meant to adsorb transients, so once fired, their
impedance could become very low, that would explain what I'm seeing.
Yep. Good luck.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558