I just inherited an Aerotech stabilized HeNe laser, model100A, vintage
1996. The laser power supply is included (RED/BLU 12V input /Hi-V
output w/ white Alden connector),but there's no other power supply.
The stabilization "head" has two "connectored" twisted-pair leads (one
GRN/BRN and one RED/BLU) but there are no markings to indicate voltage
or current draw. There is also no LED in the hole marked "Stable/OT"
on the side of the stabilization head.

The laser runs fine with 12V into its RED/BLU leads, so my question is
about the stabilizer. Due to a tight strain-relief I wasn't able to
get the lid all the way off, but from what I can see the GRN/BRN pair
comes from the PC board contacts that would have been used for the
missing "Stable/OT" LED. So, it looks like they are for remotely
sensing the status.

Sam's very thorough Laser FAQ warns about overheating issues with this
stabilizer, so I'm nervous about fooling around with it until I know
what's what. I'm an optics guy without much electronics know-how, but
on Sam's reverse-engineered schematic I see +12, +Vin and +Vref - tho
I don't know enough to make use of that info. It's a good bet that
the RED/BLU is +12V.

I'm hoping someone can confirm this and also tell me (a) what I should
do with the GRN/BRN leads and (b) how to check/set the over-temp
threshold or whatever it takes to protect from overheating.

Thanks!

Peter writes:

I just inherited an Aerotech stabilized HeNe laser, model100A, vintage
1996. The laser power supply is included (RED/BLU 12V input /Hi-V
output w/ white Alden connector),but there's no other power supply.
The stabilization "head" has two "connectored" twisted-pair leads (one
GRN/BRN and one RED/BLU) but there are no markings to indicate voltage
or current draw. There is also no LED in the hole marked "Stable/OT"
on the side of the stabilization head.

The laser runs fine with 12V into its RED/BLU leads, so my question is
about the stabilizer. Due to a tight strain-relief I wasn't able to
get the lid all the way off, but from what I can see the GRN/BRN pair
comes from the PC board contacts that would have been used for the
missing "Stable/OT" LED. So, it looks like they are for remotely
sensing the status.

Sam's very thorough Laser FAQ warns about overheating issues with this
stabilizer, so I'm nervous about fooling around with it until I know
what's what. I'm an optics guy without much electronics know-how, but
on Sam's reverse-engineered schematic I see +12, +Vin and +Vref - tho
I don't know enough to make use of that info. It's a good bet that
the RED/BLU is +12V.

I'm hoping someone can confirm this and also tell me (a) what I should
do with the GRN/BRN leads and (b) how to check/set the over-temp
threshold or whatever it takes to protect from overheating.

It sounds like it has been modified. There should be a normal
coaxial power connector on the control head. The power input is Vin, needs
to be a couple volts higher than 12 VDC because of the regulator that's inside.
+12 and VRef are generated internally. The Aerotech wall adapters that
are normally used are rated 13 V, 1.3 A (but the actual voltage is higher
at low load).

So the only remaining unknown is polarity. The wire that shows continuity
with the case is the negative.

If the other twisted pair came from the PCB holes for the LED, replace them
with an LED or hang an LED off the end of the wires! I have a vague
recollection that some versions may have a dual color LED but put a normal
one in. If it doesn't light after the output stabilizes, reverse the polarity.

As far as overheating, monitor the operation through when it stabilizes and
make sure it's not too hot. It does run quite warm though. That's normal.
Just shouldn't start smelling bad. MG claims their version doesn't have
the overheating problem but I don't know if it was ever addressed in the
Aerotech version. Monitor the output on a graphing power meter. It should
lock quite quickly, then may lose lock a couple times over a half hour, but
then remain stable forever.

--
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