Tuesday, April 14, 2009

Another Day, Part 7

Just now, I'd rather listen to Jon than follow my own thoughts to the dead end about how a stranger ended up dead on the hull in a stolen pressure suit. Four and a half minutes later, Jon is wrapping up, "...So there's a huge flash, half the lights go out and Steve is standing there, holding onto just the fiberglass handles of his cutters. The cutter part is plain gone! He looks at that and he says, 'Doggone it!' and he--"

"Throws them so hard they make that dent in the wall?"


"Yep, right over there!"

"Steve's my hero, Jon." Except when he's the Don't Be That Guy guy, that is, which he was for much of his stint aboard. "Ready light's on, it's time." "Okay..."

I step up to the rig and push BEAM ON and the ka-THUNK! sound of the vacuum contactor, followed by the quiet, emphatic Tick! of the step-start dropping out, slaps the room and the POWER OUT meter quivers and leaps up to 95%. I've stepped back -- it makes me nervous, starting the finals up and Jon turns to me, happy, "Fixed!"

"Fixed? We know whats not wrong and it's back on, Jon, but there was no reason for it to have shut down. Something's not right. I'm thinking the lower limit for Back Heater OK's set too high; we'll set it a step lower."

"Isn't that inside?"

"In the HV section, you betcha. We'll let 'er run a bit, then shut down, open up and have a look."

#

After a half hour and another of Jon's tales, it was time to have a look inside the rig -- this yarn was a rehash of the time the Lupine and sister ship Vulpine caught first sight of the Far Edge mothership SeeYa! (if radar and fuzzy optics count as "sight") since her abrupt and unannounced departure from what was supposed to have been the U.S. Space Force missile base on the Moon (and didn't that take some fast talking to smooth over with the Russians, not to mention our NATO allies). "Sight" was all it was, a distant, fading contact in the Linden system, where they'd once again had radio contact with a burgeoning settlement. By that point, the fleeing Far Edge revolutionaries? Refuseniks? had a very nearly reliable squirt-booster system, but the USSF was still having to do brute-force de-orbits, flaming ballistic re-entries ending in parachute landings with their handful of shuttle craft and were having a good day when half of them landed relaunch-ready without needing extensive repair. Jon had been on the second lander down, which darn near augered in; last I heard, the wreck was still in the Star City museum. The story's a little different every time he tells it but even discounting the wilder bits, it's some adventure.

But all good things come to an end, or in this case get cut short in the middle of his amazing hard-way discovery that basic homebrew vodka has no discernible taste. I dropped the final into OFF, Jon swore yet again that after having launched with a hangover in a lander cobbled together from the best parts of three others, nothing would ever bother his digestion again. Meanwhile the Stardrive cycled down, high-speed blower howling to silence followed by the OFF tally lighting up, it and LIQUID COOLING OK the only two indicators on the Christmas Tree still lit.

Walked around to the back of the cabinet, popped the Control Power switch which frees the mechanical interlock to the big rotary HV-shorting switch and flipped that switch while turned away: it's behind a clear window so you can be sure it's made contact, five places, and there can still be a little charge in the power filters. If so, there will be what Tweed terms "a small flash." Yeah, right, _small_ -- last time it happened, I had sunburn on the backs of my fingers. Stepped back to the Power Control cabinet where the contactors live (the High Voltage Supply proper, in its bath of hot oil, is in vacuum in a blister on the hull and even though that means it takes a pressure suit to work in it, I'm good with that, something about not wanting to be sprayed with transformer oil heated to its flash point) and snapped all three — Main, Control, Beam -- to off and engaged the lockout. No need to tag it ("Under Repair, leave your mitts off! Signed --") unless we have to leave it. Next step, pull the back panels and Tweed figured they shouldn't make it easy, lest we try it while the power's on: 16 screws per panel, three panels, and that still leaves the top quarter of the thing behind the cabinet-purge fans and the big shorting switch. Jon and I take a panel each and go to it, electric screwdrivers growling, the handy-dandy toe rail a danger to knees as we work our way down, stashing the screws in plastic bags as we go. Only need two panels off for where we're after, which doesn't take too long. Jon stows the panels in clips between the Power Control while I unclip the shorting hook and poke around at the bits that had better not be live. They're not.

Stuck my head in and unlatched (thanks, Tweed. For once) the cover over the Isolated Supplies Board, lifted it off and dead center on the circuit board thus revealed are two rows of jumper pins, labelled "HI LIMIT" and "LO LIMIT," with voltages indicated next to each pin. "LO" is on -- wait for it, wait for it -- the lowest setting. Of course.

It's not that complicated a thing to diagnose; a component has drifted in value. The ones we can check with power off, not so much, which leaves the exotic and wonderful compared-to-what reference, a two-lead component the civvy version of which you can buy at your neighborhood electronic emporium* and the 'Drive-field hardened version of which I have right... Riiight... Um. Not here. Not there. And after checking the database, we haven't stashed any with Stores & Cargo, either. The Chief will have Comments. They will be short, pithy and will not employ any words you could not say to Girl Scouts but it's gonna remove my hide in strips nonetheless. Oh, happy day.
_____________________________
* What, you don't have one? The homeworld gets stranger and stranger to me with every year.

(TO BE CONTINUED)

4 comments:

Hank Morgan said...

What, no percussive maintenance?

I always carried a can of liquid air to cool down components at board level, so you could isolate the drifter. Pitiably, you can't stick your head in an operational drive to do that.

Do you have a set of extension connectors/cables you can use to relocate the component in question "out" of the cabinet where it can be tested? Can you make said test cables? Or is it one of the cards that cannot be but a specific distance from the drive?

When I started doing this work, I got a strip torn out of my hide on such a regular basis I felt like a zebra. So long as they know who has their asses covered, and pay accordingly, I can grin and bear the occasional outburst of someone else's inability to understand that I cannot actually move heaven and earth.

One way or the nother, be careful.

You Know said...

Hank, you guys at The Edge are way ahead of us: this is one of those cards that even for testing, runs at 3kV -- and Tweed has made no provision to extend it. The trick is to open it up and hang a meter where it can be read through the shorting-swicth window, but i's sloooow.

Hank Morgan said...

Crap. How about simulating operation so you know what component is drifting? can you make a test bench to do that?

Alternately, if the back heat is OK, why not look at the projector itself? Maybe it's providing the right (or even low) output but the projector/emitter is failing? (yes, I know. Not all components can as easily be changed)

farmist said...

re: electronics emporium What, you don't have one?

Unfortunately, we have RadioShack which is just a shadow of itself in my youth. "BestBuy lite" as it were.