Apache Labs Community Forum

Greetings all-

This post is to address issues with the 7000DLE III which could cause you to have RF feedback.

Situation:
The case on the 7000DLE II (MK II is Black) has ground bonding issues.
The case front and rear covers are not electrically connected to the main case shell. The paint
insulates all the points of contact that would normally insure a unified ground.
None of the antenna connectors ground or other I/O ground is connected to the rear cover plate.
This means that the actual ground post on the radio is not connected to the case of the radio.
As well, the main speaker output's outer connector sleeves are not grounded. The entire circuit board
connected to the rear case shell is "floating". The icing on the cake is that the speaker outputs
are also not RF bypassed. These are balanced (bridged) outputs. The typically "Stereo" two hot pins
on the phono 1/4" plug's tip - are the speaker connections. Shorting either of these to ground -shorts out one of the audio amp's
output rails and could blow the chip. There is a center shield plate inside between the two sections of the radio. There is also the
bottom slide-in plate/cover on the enclosure. These rely on physical contact in the slot.

Remedy:
Grounding has to be insured between all the case parts. The speaker outputs need their shield/sleeve to be bonded to ground.
As well, the speaker outputs should have RF bypass caps. Luckily, this can all be accomplished in an hour's work.

1. First, remove all the case screws front and back. Take a drill bit that is slightly smaller than the conical countersink hole and
with your hand rotate the bit to take off the black paint in the hole. Some aluminum may come off too..it's OK. Go slow.
2. Take each screw and use >150 sandpaper to remove the paint on the underside of the screw head. Watch those threads!
3. Optional: Get some non-ox paste to add a tiny amount when re-assembling. It can help conductivity.
4. Wait: There is work to do inside!
5. Add a short piece of 1/4" braid or 16ga or better stranded wire between under one of the front handle's mounting screw to a small hole you can drill through the central shield panel near it in the radio. There is plenty of room on the shield panel to add the hole for a screw/nut to hold one side of the wire. (sorry no pix) Wire should be 3-4" so you can remove the front panel and lay it over when opening.
6. Speaker out treatment: See the picture below. I added two .01uf caps as RF bypasses . One from each hot lead of the balanced audio output to ground. then I took the connector shell lead from both outputs and bonded them together. That lead then went into the radio and I connected it under the closest nut on one of the fan mounts. I used a lug on the fan side wire connection. This picture was before I added the connection wire that goes to the fan nut. Make it 4-5 " so you can get the panel off easily later. Solder it to either green wire.
[img][/img]

That's it! Now you can use two conductor shielded speaker wire with the two hot pins (Ring & Tip) going to the speaker and the outer ground connection from the sleeve protecting the leads from RF intrusion. And RF that does get in will be grounded by the Bypass caps.

Hope this helps!

Bob-AB5N

Excellent work, Bob, and clearly the bonding/grounding/shielding of the design could be better, but so far you are the only person I know who has had a problem specific to the powered speaker outputs.

Bare aluminum definitely needs something like NO-OX-ID or, my preference, Bonderite (nee Alodine) conversion coating to keep the bare aluminum from oxidizing. Also, another option for sanding screws is to simply replace the hardware with stainless steel equivalents.

Bob:

Paint insulating otherwise good grounding is not new to some ANAN products back panel. Recently I discovered my 200D(Blue Case) had no ground to PTT out RCA jack. Removed all back panel connectors and sanded/ground paint off as needed around most all back panel holes including screw holes. That fixed missing PTT issue and probably other unseen grounding issues. Quality looking work on what you did.

Tom
KA1GXR

I received my 7000DLE MKII Black back in April. When I checked the connectors in the rear I found all of them finger tight, at best. One was really loose. I tightened all of them and checked all to ground and found that they all were showing good ground except the two speaker nuts. I don't use them so didn't look any further into that and have not had any RF issues with anything related to the new unit.

Today, based on the this topic, I decided to look again. I found all connectors still showing zero ohms to ground, including all case parts and all front connectors too including the Ethernet shell, MIC, Headphone and key and front panel screws. I tested all of this to the rear ground lug so I don't seem to have the problems reported above other than the speaker jacks. Speaking of them, I get NO reading at all; not even a few megohms from them which makes me believe they were designed to be floating. Not sure about that but if they weren't, I should read something from them to ground but don't. Balanced outputs don't need ground so this assumption sounds reasonable to me.

Joe W4WT

It's a shame they didn't continue using the brushed aluminum cabinets that were used on the early 7000 mk2 and the 8000.

I don't mind the black case. I do like that mine is very cool-running. I've never detected the slightest hint of heat coming from the case or the vent holes in the rear panel. I can feel airflow coming out of the holes but the air is cold. It's as though the radio isn't even running, just the fan.

I think Abhi confirmed in a post on a different thread that the connector shells for the speaker outputs are "no connect" ie by design they are floating. It is only the other two connections on the 3.5mm jack that have connections. And I like the solution that decouples the "balanced" signals to ground using the capacitors.