Dan Cordova <danny_cordov@...>
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The main symptom of the problem was that the neon lights do not light up, and the CRT doesn't display.
This all occurred because I removed all the tubes to clean up the curve tracer and didn't replace the 12AU7 tube (V804) in the CRT circuit. V804 sits back behind
So far, I've had to replace all the paper capacitors in the CRT circuit and am awaiting new neon lamps, hoping that that will take care of the problem.
Moral to the story is to read the manual where it tells you not to go muck with the river and remove the tubes to clean up some minor dirt and dust. I also learned that you should make sure you replace all the tubes, instead of wondering how a RCA clear top 12AU7 tube magically turned up on the workbench.
On Thursday, January 24, 2019, 11:36:04 AM PST, Harvey White <firstname.lastname@example.org> wrote:
On Thu, 24 Jan 2019 19:01:23 +0000 (UTC), you wrote:
While I appreciate the help, this talk about strike voltage confuses me.
I'm not sure what the two neon lamps that I broke the leads are B826 and B827, listed as NE-23, are used for strike voltage?
There are several other neon lamps in different circuits on this curve tracer. I thought they were there to show that voltage and current were running through that part of the circuit.
There's two ways of using a neon lamp. One is a simple indicator to
show that there is voltage or current. Typically, about 1.2 ma or so
goes through the lamp (120 volts/100K or so ohms). The NE2H varieties
take about twice the current and are brighter (H = high brightness).
The other way is to use it much like a zener, that is, to limit the
voltage differential between two points in a circuit. When the lamp
fires (the strike voltage), it starts to conduct, which causes current
to go through it, limiting the voltage to what's called the
"maintaining voltage". The maintaining voltage is lower than the
Supposedly, the temporary overvoltage condition goes away, voltage
across the lamp goes below the maintaining voltage, and the circuit is
A zener diode works just about the same way, but is more stable, and
has effectively tighter tolerances.
On Thursday, January 24, 2019, 8:45:48 AM PST, Dave Wise <email@example.com> wrote:
I investigated this when I was exploring repairs for my HP 141T A2V1 ZZ1000 voltage reference glow tube. Illuminating an NE-2 reduced the strike time much more than the strike voltage. I tried several lamps and all did the same.
Illuminating the VR tube did neither enough to be useful. I replaced it with a TL431/zener combo, see https://groups.io/g/HP-Agilent-Keysight-equipment/album?id=68333 .
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Chuck Harris <firstname.lastname@example.org>
Sent: Wednesday, January 23, 2019 7:07 PM
Subject: Re: [TekScopes] Tektronix Neon Light replacement parts?
I shouldn't think it would be all that difficult
to test the strike voltage in various ambient lighting
conditions, both with and without the blue led...
Harvey White wrote:
On Thu, 24 Jan 2019 01:09:54 +0000 (UTC), you wrote:
What about plain NE-2's and 1 or more blue led's shining on it?Not sure what this would do for accuracy of strike voltage. Ought to
lower it, though. No idea if it would stay constant, either.
(have a power strip with the usual flickering neons, UV light or blue
light and they go on....)
Leon Robinson K5JLR
Political Correctness is a Political Disease.
Politicians and Diapers should be changed
often and for the same reasons.
On Wednesday, January 23, 2019, 6:30:01 PM CST, Dan Cordova via Groups.Io <email@example.com> wrote:
Thank you for your prompt reply!
I found the lamps on the schematic and ordered some.
Once these are installed, the curve tracer should be back in working order. I found three paper caps that were bad and replaced them.
Speaking of radiation- I have a EG&G KN-2 tube that has Ni-63. It is a radioactive isotope of nickel, half life of 101 years, emits beta particles (when functioning). It was used for triggering a laser.
I'm retired from Sandia National Laboratories after 30+ years, don't glow at night, and haven't suffered any ill effects (yet) from soldering with Sn/Pb solder.
Thanks again for the info.
On Wednesday, January 23, 2019, 4:06:54 PM PST, David Holland <firstname.lastname@example.org> wrote:
They appear to be NE-23's.... Eg: NE2's + Radioactive gas (that's no
longer radioactive by now) :-)
I'd probably just go with bog standard A1A's, as I don't believe
they're particularly critical (though I did not look).
But if you want a little more radiation in your life, and be more
correct I gather they're called 5AB's now.
(No, I don't think there's any radiation danger, though I don't
recommend huffing a 5AB... :-P )
On Wed, Jan 23, 2019 at 4:08 PM Dan Cordova via Groups.Io
Hello- while replacing bad capacitors on my Tektronix 575 Curve Tracer, I literally touched a couple of the neon lights and broke the leads.
Is there a replacement part the group can recommend?
The neon lights are useful to show at a glance that the circuit has power, but can the lights be replaced with a wire, or would I need to put a resistor in place?