ALC68 strip down & clean - Help please

[smogthemog]

Excellent, thanks for the praise and info.

Am I OK removing the end optics to clean the brewsters without re-baking the canisters? Will it be OK to remove and seal up the ends while I am doing it?

Thanks

Jim

[mixedgas]

Excellent, thanks for the praise and info.

Am I OK removing the end optics to clean the brewsters without re-baking the canisters? Will it be OK to remove and seal up the ends while I am doing it?

Thanks

Jim

the baked canisters have more then enough capacity to be open to the air for a few days or more. They are good for at least 5000 hours once sealed. Those Orings on the stems do leak air slowly during operation, so yes you can easily remove one mirror at a time and stick a cotton swab (wood stick, medical kind, no glue) in for a careful wipe as opposed to tearing it down and using a lens tissue in a hemostat. If your acetone or methanol is clean enough, you can usually get away with a simple quick wipe
down the stem cover. tape over the optics hole usually causes more problems then its worth
unless your in a "coal mine" type environment.

enjoy,
Steve

[smogthemog]

Thanks again Steve.

I have been mapping out the beam table today and sourcing and cleaning some nice bit's of Ally for heightening all the components.
What I have now decided to do is to mount two 650 reds, each mounted in Meredith LD mounts, firing into a combining PBS. Rob (Stanwax) has kindly offered to scource me sutiable analoge drivers for the LD's. This then beams into a 45 degree EO reflect red dichro and joins the main beam from the PCAOM. The mixed beam then goes on to the scanset.
Nothing is mounted as of yet but just the layout is below:

[smogthemog]

the baked canisters have more then enough capacity to be open to the air for a few days or more. They are good for at least 5000 hours once sealed. Those Orings on the stems do leak air slowly during operation, so yes you can easily remove one mirror at a time and stick a cotton swab (wood stick, medical kind, no glue) in for a careful wipe as opposed to tearing it down and using a lens tissue in a hemostat. If your acetone or methanol is clean enough, you can usually get away with a simple quick wipe
down the stem cover. tape over the optics hole usually causes more problems then its worth
unless your in a "coal mine" type environment.

enjoy,
Steve

I have cleaned the glowing brewster and re-aligned the optics and it made a huge difference to the visible output (I don't have a meter).

Thanks for that advice Steve.

----------------------------

Well done Jim! A fantastic job. Have you measured the output power yet? Also, what's the outlet air temperature?

I have an HGM5 with a 903 tube in it which is just slightly smaller than the 68B tube you have. I get about a watt (all lines) at 22-23 amps of tube current, and the outlet air temperature hovers around 145 degrees F. I can push the tube to a max of 29 amps, but I don't have a means to measure the power output at that level, and besides, I don't want to kill the tube!

Just curious what sort of numbers you're getting on that 68B... (In theory, you could get up to 3 watts at 32 amps of tube current for short periods, but you need to watch the temperature or you'll cook the thing.) I've been told that 170 degrees outlet temperature is a good number for redline.


Adam

I have just done a few tests reguarding the temps Adam and at 15A tube current (or so the meter on the front of the PSU tells me anyway), the exhaust temp is 165F. At 20A it rises to around 178F. Perhaps a little high?
Please bear in mind though that the input voltage to the PSU is still going through the transformer as I haven't had a chance to remove and re-plug all the connecting leads. The AC voltage at the PSU mains input terminals when running at 20A tube current is a little low.

Jim

[buffo]

at 15A tube current (or so the meter on the front of the PSU tells me anyway), the exhaust temp is 165F. At 20A it rises to around 178F. Perhaps a little high?

Sounds a little on the high side to me. I don't think I'd run it at over 18 amps until you get more air flow through the head. (Might want to get a larger blower.) High temp will kill it mighty quick.

Please bear in mind though that the input voltage to the PSU is still going through the transformer as I haven't had a chance to remove and re-plug all the connecting leads.

I'm not sure that's really relevent to the high head temperature... The situation you're describing might create some extra heat in the PSU, but that's separate from the head.

Adam

[smogthemog]

I have the separate red beam table now finished and am now preparing the ally mounts for this, the scan set and the 45 red dichro.

I am using 2x 16xDVD reds in Meredith mounts, a Rob (Stanwax) Laser-wave.co.uk PBS and a modified optical mount that I purchased in a job lot off of EBay. The bounce mirror was also from the job lot of EBay optics but had to be re-mounted to this mount.
The twin analogue driver for the reds again was built for me by Rob (Stanwax).
I will be running the reds at around the 300mA mark.

[allthatwhichis]

That's a nice lil red there. Interesting contrast betweent the two.

What is the output on that gas beast? Sounds like you could point the blue in a totaly different direction, use a waste beam off of a dichro and send that through the PCAOM to balance with that red. That blue does Watts correct?

[smogthemog]

Last night I finally had some white light out of it all. I was using just one of the red diodes as I don't quite think I have the AOM all set up correctly as of yet. Also, the red isn't quite on target either. The far field (20m) is OK but near field is a bit off. I need to raise the bed about 0.8mm to get the red spot on the dichro in the same place as the 68's colours.
The last photo is a white bit of paper suck in a bush at the end of our garden about 20M away. Can anyone tell me why I am getting the green and blue blobs above the white? It seems like a sort of echo or something? Could it be internal reflections off of the AOM/Dichro?
The red is also a bit wide there but that was a bit of dust on the dichro right where the red spot was aimed at.

[smogthemog]

This is the beam table now I have the AOM, dichro mount and red diode table all mounted and bolted down. This is how it was set up when I took the previous photo's.

[stanwax]

Looking Good Jim
One word of warning - those wires from the driver to the diodes need to be shorter - I would say make them as short as possible - you dont want them acting as antenna and picking up the 68 Start pulse - they wont last long then!

As for the blobs....where are you dumping the waste from the aom? You can sometimes get odd artefacts from the aom especially if it not blob on. But simplest is to follow the blobs back to the source to trace where they are emminating from.
As Im sure you know you need to get the beam scanning - even off a mirror on a motor to draw a circle - and this will allow you to get the far field bang on - though not worth a carrot if near field is off.

Great work pal! Keep the pix coming

Rob