PTW repairmen: Be aware of electrostatic discharge (ESD)

[Styrak]

Originally Posted by stokes

Can I just do it naked?

Lol, that won't help. But whatever floats your boat I guess?

[mcguyver]

It's not an issue for me. My workbench is steel and bonded to ground. Any static will be shunted to ground as soon as I touch my bench. Any metal workbench with any electric devices on it (mounted worklights, receptacles, etc.) and manufactured to meet CSA standards must be bonded to ground. Even if you retrofit one yourself, it must meet CEC in Canada and be bonded to ground.

And grab any boards by their sides. There is never a need to touch the components or traces.

[stokes]

Originally Posted by Styrak

Lol, that won't help. But whatever floats your boat I guess?

I was just kidding :P!

[MadMax]

A very conductive top isn't the best situation either. If your board is charged to some potential, it will discharge quickly when it arcs to your grounded metal table. Also, a powered circuit can short through your table surface. Still a conductive table works well if you don't troubleshoot powered boards that can contact the table. Putting a PTW on a grounded steel top will bring it to ground before you dig around the circuits so if you rest your elbows on it you'll be at the same potential.

The best surface is mildly conductive (around 1megOhm/cm I think). Not conductive enough to short most ccts, conductive enough to gradually dissapate an ES buildup, resistive enough to provide a super easy grounding potential for a spark.

A good ESD mat runs around $40 online and a wrist strap under $10. Besides PTWs I do a lot of electronics rework so it was an easy decision to go with. Go with a rubber mat instead of a vinyl one as they resist melting better (hot solder splats).

Originally Posted by mcguyver

It's not an issue for me. My workbench is steel and bonded to ground. Any static will be shunted to ground as soon as I touch my bench. Any metal workbench with any electric devices on it (mounted worklights, receptacles, etc.) and manufactured to meet CSA standards must be bonded to ground. Even if you retrofit one yourself, it must meet CEC in Canada and be bonded to ground.

And grab any boards by their sides. There is never a need to touch the components or traces.

[mcguyver]

I have rubber mats if I need to power anything up to test. But realistically, there is virtually no PTW user or tinkerer that's going to need to remove all the boards from the gun to test them. Mostly all your testing can be done with the components in the gun. I'm not concerned one bit of stray voltage on a board discharging. Set the board itself on a mat.

Voltage present at switch board can be tested with the board on the bench, but it's in heatshrink anyways. This is mainly for assembly and disassembly. You know when to and when not power up a board, as do I. But usually the boards I have to power up don't cost a measly couple hundred dollars and don't rely on 12VDC or less.

You can make your own anti-static strap for basically nothing. Wrap some fine-strand wire around your wrist and bond yourself to your workbench, which itself should be bonded to ground.

[MadMax]

For those who do not have purpose built ESD protection, I suggest the following:

Connect alligator clips to one end of two 4' lowish gauge flexible wires (stranded 18GA or less). Bare the unclipped ends and screw them down to something that's grounded (say a handy computer case).

Clip one to your watch strap so the clip is touching your wrist. Touch the other to your PTW before you begin disassembling it. Try to hit some place in the mag well where there's a spot where your paint has worn off as you want to hit bare metal instead of a chunk of insulative coating.

This arrangement will continuously dissapate ES that you build up while you work and initially bring your PTW down to ground plane before you start digging around in it's brains.