grounding strap

[bloodyviking77]

Hi there all

Maybe I'm just a tad stoopid, but after Mamefan and dhausen's very informative posts about the guts of monitors below (in thread called "whooooo mama"), I've got a question:

With my grounding strap, I've located the relevant neckboard connector for the strap. My question now is: do I just need to ensure that the braid is in contact with the "conductive paint" on the tube somewhere? Is there a particular part of the tube the strap needs to cross?

I pulled apart a crapped out vga pc monitor I had lying around to check out how that was wired, (though I didn't want to mess around too much with the anode still hooked up and tube not discharged) - and it seemed that the grounding strap was connected to two "corners" of the monitor (at the mounting holes), and ran diagonally across the tube about in the middle.

Is this the right sort of idea?

Anyone able to post a pic of an arcade tube's strap so I can  compare notes?

Cheers - and thanks for all the help!

bviking

[MameFan]

You are correct.

The ground wire is usually in the form of a grounding strap (sometimes covered on the ends with yellow plastic) or somtimes braided bare silver-colored wire, or sometimes a small circumference(sp?) but long spring.

The intent of this is to touch *as much* of the aqua-dag (the black graphite paint on the sides and bottom rear of the tube) as possible, for the best contact.

Theoretically, as long as a 1 centimeter square part is touch, that's all that's needed , but the more that is touching, the better.  It also is done across the bottom of the tube to prevent any possible arcing if placed near the anode wire (and why the anode wire is usally suspended by a plastic piece from laying against the tube.

Generally, most thin grounding strips/straps, are attached like so: (forgive the ascii art)

 1o__________o2
    |         Q        |
    |          .        |
    |                   |
 3o----------------o4

1o..4o are the 4 corner mounting pieces of metal attached by the metal band.  Q is the anode cap (grey cap, red wire), . is the tube neck.


Attach the strip at corner mount 1, run it flat along the tube down bewteen 3o and the neck '.', then back up between the neck and 4o and attach again at o2.. Should form a wide "U" shape and basically touch ALL of the aqua-dag.


Another pattern I have seen is if there is a spring used instead, and an internal purity shield (the thin brown colored metal piece around the tube but mounted to the frame), is that the spring is attached to 2 holes on either side of the frame, somewhere between 3o and the neck, and 4o and the neck, running horizontally between them under the neck.


And finally, with the banded wires, I usually see them in the shape of 2 U's...  The first matches the banding strip pattern above...1o to under the neck to 2o again for the upright "U", and then crimped to this, another wire from 3o to meet to the top U left of the neck, then across and then down to 4o, creating an upside down "U".


The key is:
- Touch as much aquadag as possible
- Keep it as taunt as possible--without damaging the tube.
- Keep it away from the grey cap/red anode wire
- Keep it over the aquadag mainly, avoiding the bare glass
- Keep it away from the more fragile center neck


Finally: Ensure you connect it to the GROUND (usually labelled "E") pin on the neck board.  Don't guess, there may be test pins that provide power/etc and you could fry the chassis if connected to the wrong pin.  Follow the traces on the back if unsure, and the ground should have a large amount of connected "trace" since many components will connet to it. It should not be a fine trace leading up to the pin from some other far point.

[bloodyviking77]

Thanks mamefan!

I think Im ok - now I've just got to build a bracket to hold the chassis and plug the lot in (very carefully of course).

I'll post some progress as it happens