n2kbod9 - need to know Body, chapter 9

last updated 18 oct 97 - mjh

9) service

We service what we sell!

But then again, we don't sell anything :-)

While phrased as a joke, this is actually quite a serious issue. We don't sell products, so we don't make a profit. We obtain grant money *not* based on what (i.e. how many) we build, but based on our reputation for being able to build. And that means making them well, and/or keeping them that way.

9.1) testing

The testing specifications for a module are defined (if at all) by the designer. This information is most likely kept in the (2.2.5) 3 ring notebooks relevant for this design. If you find that the procedures need updating, add a page yourself!

9.2) repairing

If repair is required, you will need to do what needs to be done. Keep in mind that the device in front of you is important, and quite possibly the only one of its kind. It may be irreplaceable. Work with care.

9.2.1) desoldering

Of special concern in repairing boards is desoldering. Some of the boards are old. Some have thin copper. Some have lousy lamination, especially with the surface copper. It is really easy to rip up pads or burn the fiberglass while desoldering.

Don't fight with the board.

In replacing IC's, we typically cut the pins off, then desolder the pins individually. This may even require 3 steps: cut, heat+pull pins, *then* remove the solder, either with a vacuum pick-up or braid. We also have some high-tech resources, including hot-air, and Chip-Quick (metalurgical poison, which depresses the metaling point of PbSn solder to a nice, safe, low temperature.)

Don't try to rush. Don't try to be "efficient." The safety of the board is paramount; your time is expendable.

9.3) cleaning

We are currently "between solutions" with respect to board cleaning. We had a vapor-degreaser, but it used now-illegal chlorofluorocarbons, so it is no more. The current hope is to have our contract-assembler, or someone here in town, provide us with cleaning services.

If, on the other hand, you are so inclined, we do have some aqueous flux solder. This can be cleaned with 5% isopropanol in deionized water. Keep in mind, however, that aqueous flux "cures" as it dries, so you will need to wash your board(s) daily. If you solder all week, and plan to wash only Friday afternoon, you will be in for a disappointment!

There is also quite a bit of controversy as to whether boards should be cleaned at all. While residual flux looks nasty, it is not that much of a hazard, since its caustic nature is temperature sensitive. As long as it stays cool, it is not too bad, in the greater scheme of things. (Be prepared for debate on this). Small flecks of solder, on the other hand, are transient shorts waiting to happen.

9.4) calibration

Calibration specifications for a module, like testing, are defined (if at all) by the designer. This information is most likely kept in the (2.2.5) 3 ring notebook for this design. If you find that the procedures need updating, add a page yourself!

9.5) record keeping (especially phototube bases)

There are a few categories of items for which we make large quantities (100+) and which require individual histories. Phototubes are one of them. Talk to Todd about his phototube bookkeeping, and/or refer to the (2.2.5) 3 ring notebook defining the design.