7000DLEMKII Black Case Not Grounded

[n4lq]

Having experienced some odd ground loop problems I decided to check the continuity of the case.

Between the rear ground lug and other case parts i.e. top, bottom plate, front panel etc... There is around
2 megohms resistance! Nothing conducts!

The problem is due to the painted bolts and bolt holes.

For example, measure between the ground lug and bottom plate then scrape paint out of the bolt hole and substitute a bare metal screw. Do the same for one of the bottom bolts. Remeasure... Now you should have zero ohms.

The same problem goes for the rear 1/4" speaker jacks. They don't come in contact with the back panel due to all the paint under the washers. I found this out when I tried to use shielded cable on the speakers which were plagued with RFI.
Really, every bolt around the outside needs this treatment.

Good construction practices normally call for totally interconnected metal panels.
Am I missing something? Is there some technical reason for this?

[W1AEX]

You definitely have not missed anything regarding this. The thick-paint problem creating an issue with bonding between the case, front panel, rear panel, and internal shield has been around since the first ANAN showed up. There are some very good tips for easily correcting the problem here:

http://anan-100d.wikidot.com/100d-case

I used Chuck's (K1KW) suggestion and used a dremel tool to clean the paint underneath each of the six fasteners that mount the front panel and then installed internal tooth washers before screwing the fasteners back into the case. This modification takes about 15 minutes, can't be seen when it's done, and it bonds the panel perfectly. I did the same thing with the rear panel, and also on the inside surface, I cleaned around all the BNC ports, the PTT port, and the ground lug. I also ran a 4" strap from the ground lug to the metal shield that is positioned between the main board and the PA deck. All the panels now show good continuity with each other and I've never had any issues with RF ingress or egress with the case following that little project.

73, Rob W1AEX

[w-u-2-o]

This has always been a design deficiency in every model going back to the original ANAN-10.

My guess is that Apache simply didn't think the added cost of proper coating and masking in order to achieve good bonding of all components was worth any technical performance improvements it might bring.

Don't forget that any naked aluminum will instantly oxidize. If you really want to do it right, get a brush on Bonderite (aka Alodine) kit and coat any bare aluminum areas with that so that they do not oxidize, which will also play havoc with bonding.

[n4lq]

Wow. Thanks. I was beginning to wonder if I was seeing things!
To further complicate things, the SCREWS are painted!
Is this something new? I had to scrape paint off the underside of the screw and that's not easy.
Maybe a new set of stainless steel screws would be in order?

Anyway I thought everyone knew that case parts needed to be electrically common for RF protection.
Who's in charge of building this stuff ? Do they read this forum?
Seems odd to be scraping off paint on a new radio :*)

[Tony EI7BMB]

I agree the larger case is much better.

[n4lq]

Helmut:
That big case is beautiful!
It's even got real feet. I was shocked when I opened the shipping box to my black one and found 4 little stick on feet in a pack.
I went to stick them on and discovered there was no place for a foot in back corner where the fan is. So it was either live with 3 feet and limp or just stick it inward somewhere. Oh well...They are too short anyway. I propped it up with some door stops.
It would be great to have that removable cover... This black one is built like a ship in a bottle.
And look at those nice 1/4" jacks actually fastened to the front panel while the black one just uses tiny 1/8" jacks sticking through holes in the panel, relying on solder to hold them in place.
And and I see "Bootloader on-off" labels on the switch on the rear panel. The black one has it's switch on the bottom and it's not even labeled.
"progress".

[db8gk]

Oh wow, that is an interesting bug that I hadn't expected at this price point. I do like the black case for its compactness and robustness, will look into improving the ground connections. Thaks for pointing this out.