The story so far.

We are busily re-rehabilitating a 4MeV VanDeGraff particle accelerator. The energies are too low to do any interesting work in nuclear or particle physics, but perfect for irradiating crystals or semiconductors to see what happens.

I'm coming in partway through the project, and the initial baselines readings on our samples have been taken and analyzed. Now, we have to bombard then with 1MeV protons. Which means we need to have a source of said protons, and thus the accelerator.

This machine was built in the mid 1970s and last brought into operation in the mid-90s; there is a spring that flows into the basement where the two-story tall beast lives so the humidity is rather high; someone actually sabotaged it at one point in a number of subtle and difficult to find ways. Last week, we'd managed to get some function from it, but the moment we tried to switch the voltage stabilizer on, it went haywire and started pulling a huge current off the accelerator plates. We shut it down and dug the manual out, and there was this maintenance procedure for the control circuitry that we resolved to get into on Monday.

Monday: The procedure pretty much consists of iterations of: Ground a few circuits; Connect a meter to this other spot; Adjust a trim-pot until it reads zero. We start the first adjustment and we read about -9.5V, and can't adjust it more than a quarter volt away from that, and it needs to read zero. Problem!!! Easiest thing to do was replace the socketed op-amp, but no luck. We traced the thing back and the only thing we could find was that the power supply was all norky. We locate another power supply that seems to be the right sort, but it's in another device and has solder all over the pins. Desoldering wick is located, but there isn't an iron to be found. We decide to pick it up the next morning and I'll bring my kit in.

Tuesday: Solder removed, power supply module in place and... its only 10V not 15. Still, the op-amp adjustment is in the right range and I can zero it, so it looks like the theory was sound. We had another supply, so we pulled it out, had to solder on new leads and... right voltage but not enough power to drive the circuits.

Today: We bring in an adjustable power supply down from one of the labs and start working our way through the procedure and we locate a bad amp. Thankfully we have a spare and are able to finish everything up to the point where the adjustments require a beam. We're ordering a new supply and should have it when we get back into it on Tuesday.

I suspect we'll need to go in and re-tune everything with the new supply but it should go fast. Hopefully we can fire the beast up and start in on beam profile characterization.