SDS 200 Noise Mitigation

[kruser]

There are a few reasons including the fact that most units do not have the issue, and the metal tab solves most that do.

The user-added part was cost effective and issue-effective in most cases.

I was not part of that original discussion.

I too am disappointed that the solution I proposed was not done sooner, but complaining about it fixes nothing. I can only surmise that Paul was not aware of that or he believed that the tab was all that was necessary. I'm not going to speculate about what he knew or didn't know, or his motives.

Perhaps we do need to take early production units apart to check for issues like this. I'm sure management is not going to like me taking one apart, but if it finds an issue (unlikely from here forward) then maybe it is worth it.

I will address this with management again to see if there is a better solution to catch future production errors.

I swear there was a post here in the past few months where someone either had their SDS200 repaired by Uniden or it was a brand new purchase. I forget which but I think it was a new purchase.
Either way, that person opened up the radio to do the StaticDischarge mod and found that Uniden had added a new ground wire soldered to the visible side of the front board that ran to a case screw ground similar to the other ground wires.
I remember this as the OP had needed to do the mod on his older SDS200 but was surprised when he found the new ground wire that had been added in his new 200.

I never saw a reply post showing the point on the back of the front board where this new ground wire was attached so who knows. It sounded like this new ground wire provided the needed ground to the front board to eliminate that hum though.
What I don't know is if this was a Uniden fix or newly added ground wire or if he received a 200 that was really not new and had been modified by someone else that returned it.

The point was that the display board could be ground by adding a new ground strap wire to a ground point on the solder side of the board which could be done without removing anything but the covers to gain access to the back of the board.
It sounded good (and easy) if true but the OP never replied with any pictures to my knowledge so I never followed up on it any further. I'd already grounded my display board but found this info interesting.

I wish I could find that post about this. I guess it could have been a post on a groups.io message board also but I'm fairly certain it was here at RR.

 

[RandyKuff]

kruser.... Are you thinking of of the way "tumegpc" did his...

Check the pictures in the bottom row last two on the right...

Unauthorized modification to fix hum

For me I would rather take on a challenge and see how its done and take on a project and do it and WOW myself once I fixed it. This is all about learning and growing in-stead of being scared and worrying about some warranty issue. Plus the cost of shipping the radio and the time the radio is...

forums.radioreference.com

 

[kruser]

kruser.... Are you thinking of of the way "tumegpc" did his...

Check the pictures in the bottom row last two on the right...

No, the post I read was a very simple fix. A simple ground strap soldered to a point on the solder (visible) side of the display board without any disassembly needed other than removing the outer case half so you can see the main board component side and rear of the display board.
No front panel removal needed at all.

The OP of that post claimed Uniden had added a ground wire that was simply soldered to a point on the solder side of the display board and ran to a ring terminal which was under one of the chassis screws that the other ground wires use.
I can't recall if the OP just explained what he found or included a picture that was not close up enough see where this new ground wire was soldered on his display board.
It had nothing to do with what tumegpc did with soldering a ground to the displays frame which required a lot of disassembly.

I know the OP said it was a new factory wire added in the radio he was posting about and he'd never seen it in any of the other 200's he'd worked on. Now if it was really a new factory ground wire added by Uniden or not is unknown. I just remember reading the post.
It was probably in one of the larger "hum" related threads where I'd read it but I never could find it.
I was surprised it was never commented on further but it may have went unnoticed if it was in a large thread. I don't recall if I'd replied asking for a closer photo of the solder point or if I forgot and never did reply.

 

[JoeBearcat]

I remember this as the OP had needed to do the mod on his older SDS200 but was surprised when he found the new ground wire that had been added in his new 200.

I never saw a reply post showing the point on the back of the front board where this new ground wire was attached so who knows. It sounded like this new ground wire provided the needed ground to the front board to eliminate that hum though.
What I don't know is if this was a Uniden fix or newly added ground wire or if he received a 200 that was really not new and had been modified by someone else that returned it.

That is the repair that service is performing to address the issue. I pushed for the SD mod, but that was rejected due to the additional time required and the fact that the wire is said to work about the same. I do not know offhand if they are performing that mod on all units that are serviced. That may well be the case as a preventative measure.

 

[N7OLQ]

In hindsight, a better user fix would have been something similar to the little plate where it connects to the head unit, but about half the current size, connected to a ground strap or strip of metal that could be wrapped around the metal frame.
The problem with the current home-solution is that the plate makes poor/incidental contact with the scanner frame because there isn't proper alignment (it isn't perfectly parallel to the frame). When I soldered the plate to the frame, my hum went away 100%. Prior to soldering, it was about a 50% solution. A better way to make electrical contact with the frame is needed (without soldering).

 

[kruser]

That is the repair that service is performing to address the issue. I pushed for the SD mod, but that was rejected due to the additional time required and the fact that the wire is said to work about the same. I do not know offhand if they are performing that mod on all units that are serviced. That may well be the case as a preventative measure.

Thanks for that info.
Now I know I'm was not imagining that thread and what I remembered it saying. I can't say how well it works compared to the SD mod but it has to be better than nothing.

 

[N2IXX]

I got tired of listening to the Noise/Hum and when I opened it up Uniden had already added the plate. I noticed it did not touch the back rail very well so I remove and reinserted it with same issue. I could push down on the plate to make it touch the rail. I took a piece of tinfoil folded it up and inserted/wrapped it around the rail under the plate to take up the gap. Noise/Hum is now gone. This could be a quick fix for people who do not want to or do not have the ability to take it all apart. I may do that next time if the noise/hum shows up again.

 

[jonwienke]

The only potential issue with that is oxidation from dissimilar metals contacting. It may work for a while, but the noise may gradually return. Copper foil is less likely to have that problem.

 

[N2IXX]

The only potential issue with that is oxidation from dissimilar metals contacting. It may work for a while, but the noise may gradually return. Copper foil is less likely to have that problem.

I agree but one works with what one has on hand and everyone has Tinfoil in the house but not copper foil.

 

[wallyp]

I will be installing the Uniden part soon, when installed do I replace the black tape I took off ?
Later Wally

 

[JoeBearcat]

I will be installing the Uniden part soon, when installed do I replace the black tape I took off ?
Later Wally

No.

 

[trentbob]

The only potential issue with that is oxidation from dissimilar metals contacting. It may work for a while, but the noise may gradually return. Copper foil is less likely to have that problem.

Jon...as the problem is well identified and more spread than said, and can permanently, on the production line, be fixed... is it worth it for the average consumer who is not comfortable with the StaticDischarge intrusive surgery, that may or may not void his warranty arbitrarily at the discretion of Uniden on his brand new radio, is it worth it for them to wrap the mitigation device in copper foil or will the oxidation occur anyway?

 

[jonwienke]

Aluminum oxide is hard and abrasive (it's the most common ingredient in sandpaper), and non-conductive. Aluminum alloys for electrical devices are specially formulated, because normally aluminum electrical contacts oxidize and fail, and the increased resistance due to the oxidation caused numerous electrical fires before the use of specific alloys was mandated. Household aluminum foil is not made from the electrical alloy, so contact failure isn't a question of if, but when.

 

[Anderegg]

Joe, is it TRUE that some SDS200 do not have this hum problem whatsoever...not "they can'rt hear it", but they litterally do not have any hum that could be detected by NASA sensors if tested so?

Paul

 

[jonwienke]

Yes. It's not really hum, but RFI getting into the audio due to inadequate grounding. If the affected circuit board gets grounded properly, the problem goes away.

 

[StaticDischarge]

I guess I could have mentioned this a long time ago but whatever...
Anyway has anybody other than me even thought of trying dielectric grease on the "mitigation part"?
This, if applied as a thin coating to all contact areas, may very well eliminate the oxidation issue.

Oh and way before some of you start spewing off your nonsense that dielectric grease is an insulator (which it actually is) and "won't work" I have to ask you to simply look it up and find out for yourself why it is that you are wrong in your assumption that this "won't work" in this scenario... Specifically speaking of large TV manufacturers (RCA, Motorola, and Magnavox) and their TV tuners that contain multiple, light pressure, thin metal contacts that carry very small signals back in the day that were plagued with oxidation issues... Oh and every connector in your car say brake light, turn signal and backup bulbs/sockets have the stuff in them... Go figure!!!
And if this doesn't work for you then it is YOU, not the dielectric grease!!! Well I guess it could be the grease, depending on it's quality, but that would still be a factor of YOU trying to save money (or lack of knowledge) and buying the cheap generic stuff...
Also the way YOU install the part can also make you think that this "won't work" when misaligned or not enough contact pressure...

Yeah and OMGosh, you're gonna say something like "It will melt and drip all over my precious electronics and ruin them" Crap! simply Crap! It (the good stuff mind you) has a higher melting point than lets say Vaseline. So by using a "thin coating" won't hurt a dang thing simply because it is an "insulator" and the fact that the SDS200 should NOT get that hot and if it does, YOU have bigger issues and will probably need loads of professional help...
Just sayin'....

 

[sfb88]

I have been curious about this. Does dielectric grease work in this instance because it, in effect, forms a mini-capacitor which blocks DC signals but permits AC signals to go to ground? Also, does this mean that you could not use dielectric grease to prevent galling on something like the threads of a Mag-light?

 

[StaticDischarge]

Does dielectric grease work in this instance because it, in effect, forms a mini-capacitor which blocks DC signals but permits AC signals to go to ground?

It's purpose is to keep moisture and oxygen away from the contact surfaces to prevent them from being able to form oxidation and corrosion.

Also, does this mean that you could not use dielectric grease to prevent galling on something like the threads of a Mag-light?

Yes, it can be used to prevent galling as it is silicone based which can be used as a lubricant, but... the professional side of me will say that you should only use dielectric grease in this scenario if you do not have the appropriate compound (Anti-Seize) available which in turn is the product specifically designed to prevent galling. Which, by the way, is considered a lubricant too...

 

[kruser]

I guess I could have mentioned this a long time ago but whatever...
Anyway has anybody other than me even thought of trying dielectric grease on the "mitigation part"?
This, if applied as a thin coating to all contact areas, may very well eliminate the oxidation issue.

I've used a dielectric grease coating on many old dirty pots that I've restored over the years in older radios and test equipment.
In almost all cases it stopped the controls from ever becoming scratchy or dirty again.
I even used it in the rotary encoder in one of my 536HP's were the rotary control was about useless. It has worked for about two months now so far with no rotary control contact bouncing. Opening the rotary control to get the grease in was a chore though plus I was afraid I'd break the retainer tabs when I closed it back up but it survived the surgery. I doubt the retainer tabs would hold up to another disassembly and reassembly if it ever fails again though.

I can't speak for dielectric greasing helping the mitigation part hold up longer as I also went straight to a better electrical ground like your mod does in my SDS200 but I do like your idea for those that can't perform the proper mod for one reason or another. As you said, it would only need a very thin layer of quality dielectric grease between the different metals.