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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Vince
Vielhaber
Sent: Saturday, January 02, 2021 6:24 PM
To: [email protected]
Subject: Re: [TekScopes] Slightly OT: How can I dissolve Potting Compound?

A heat gun is often the method for removing the potting, but care must be
taken since some of the potting compounds get very toxic with heat.

Is there a model number on the dead supply?

Vince.

On 01/02/2021 09:18 PM, Dennis Tillman W7pF wrote:

I need to dissolve the black HV potting compound of a 12VDC powered
Helium-Neon laser inverter power supply I have that stopped working. I
would appreciate any suggestions on what works to do this. I’m
guessing it may be epoxy. I stuck the tip of a hot soldering iron in
it for a few seconds without much effect.

When it was working it turned out to be perfect for powering gas
filled Spectrum Tubes. These spectrum tubes (smaller versions of neon
signs) filled with a variety of gasses are an excellent source of
spectral lines for the
7J20 / J20 Rapid Scan (Optical) Spectrometer to measure.

Spectrum tubes require an initial high voltage (1,000V to 1,500V for
example) to break down the gas and start it conducting. Once the gas
in the spectrum tube conducts the voltage across the gas drops (250V
to 450V for
example) and unless you limit the current (to a few mA) it will
destroy the tube. Can anyone can point me to a source of information
on how to determine the proper voltage and current I need to power
these spectrum tubes? Is there a web site or group devoted to Spectrum

Tubes?

Something happened to the inverter and it stopped working. The input
is now open. The inverter is a black potted brick 3” x 1?” x 1”. The
ballast resistor has continuity so that is not the problem. The
original label on the inverter is partially destroyed so I can’t tell
what its initial high voltage output was or what it current limits at.
All I do know is that it was made by Laser Drive Inc.
5465 Wm. Flynn Hwy. Gibsonia, PA 15044
Model: 1150-6330, S/N: 610574
The input was +12VDC at 0.35A.

I wrote to the company that took over the company that took over Laser
Drive Inc. asking if they could tell me the output voltage and
limiting current but I didn’t receive a reply.

At this point I am hoping if I can remove the potting compound I can
figure out what went wrong with it.

I have a different, bigger Laser Drive Inc. potted inverter which is
powered by 115VAC. It puts out 2350VDC at 6.5mA. This causes the
Spectrum Tubes to flicker. They do not run continuously. I am guessing
that this because 6.5mA is more current than the tube can conduct. The
amount of current the tube draws increases in proportion to the inside
diameter of the tube but I don’t know much about this matching the
power supply to the tube. All I do know is the one that went bad seems
to be an ideal match for the spectrum tubes I have.

Battery operated (DC input) inverters are much more desirable than AC
input inverters for this application because the AC rectification and
poor filtering shows up on the output DC as significant ripple causing
the amplitude of each spectral line to be blurred.

Dennis Tillman W7pF

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K8ZW







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Dennis Tillman W7pF
TekScopes Moderator