SDS200 Unauthorized modification to fix hum

allend

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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 gone for at least a month.
 

garys

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It's a nice fix and maybe Uniden will offer it or something similar in the future. I'm sure that there are people here who can do that, but that's not most of them.

I think the NMP200 was developed as a quick, easy to perform, update that would work for most people. I know that even though I wasn't bothered by the "hum", I was bothered by interference to my aftermarket stereo. The NMP200 certainly improved that.
 

Joe_Blough

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There is no fix to the hum, you should continue to use the term "mitigation"...soldering doesn't even eliminate the hum.
Compared to what Uniden has done it's a fix and the hum isn't going to keep coming back. I think the shorter the wire the better the results.
 

frazpo

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There are just a bunch of haters and nobody else has gone the distance to figure out the fix with soldering and taking the radio apart. Thanks for the hardwork and the pictures. I just need to get that X tool and then do the fix.
Good point. I like how the OP was corrected and advised what terminology to use. Geez.
 

tumegpc

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This might be the reason that some of us have the humming more than others. Look at the pictures and you will see that one of my ground wires which happens to be a very small 30AWG. If you look at the factory soldering job you can see that this wire has very few strands of wire. A couple of the strands are not even crimped in the connector and it looks like maybe only 2-3 strands are.
 

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SteveSimpkin

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How can the bcd996 have no noise at all while scanning but the 536 and 100 both have the hum is it the type of display the 996 had was not susceptible to creating hum over the audio? Or was it better grounding from factory?
Different model components, circuit trace layouts, component locations, component values, parts orientation, local shielding shapes, physical enclosure differences, proximity of digital/analog circuitry, etc. These are just some of the variables that can contribute to noise being added to the audio path on its way to the speaker. Analog and particularly mixed analog/digital circuit design and layout have to be carefully designed to minimize noise in the audio path. Every time a new design is created or even when an existing design is modified, these variables can contribute to increased audio noise. While there are guidelines, common design practice and layout tools to assist in reducing noise, the complexity is great enough that you can't guarantee the final result until you test a particular design and its circuit layout. I have even seen component manufacturers recommend making several circuit layouts with their part and picking the one that has the least amount of noise.

Given how even slight pressure on the top cover and/or mitigation part can make a big difference in the noise level, it is easy to see why some units have more noise than others. As has been shown, the best way to consistently reduce the noise to its minimum achievable level, in this design, is to use a soldered connection rather than one that relies on physical pressure that can change over time. I realize the mitigation part was a "practical" solution to units that were already shipped but it is not reliably working for everyone. I think Uniden should make a more permanent fix for production units and ones that have been shipped back for repair due to noise.
 

mikewazowski

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Gents, this thread is in the Tech Support forum so let's try and keep it technical. Some of us would like to resolve the hum issue on our scanners without having to wade through the back and forth non-stop debate.

If you want to discuss the warranty consequences of performing the mod or why Uniden doesn't recall these scanners to do the mod then please use the thread in the Tavern.

Thanks for your cooperation.
 
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mikewazowski

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This might be the reason that some of us have the humming more than others. Look at the pictures and you will see that one of my ground wires which happens to be a very small 30AWG. If you look at the factory soldering job you can see that this wire has very few strands of wire. A couple of the strands are not even crimped in the connector and it looks like maybe only 2-3 strands are.
Have you tried replacing that wire with something a little more substantial?
 

radio3353

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This might be the reason that some of us have the humming more than others. Look at the pictures and you will see that one of my ground wires which happens to be a very small 30AWG. If you look at the factory soldering job you can see that this wire has very few strands of wire. A couple of the strands are not even crimped in the connector and it looks like maybe only 2-3 strands are.
Coming from decades of electronic manufacturing, the first photo with the loose strands is very poor workmanship. Please let us know if you replace that wire as Mike suggested and the effect, if any. Thanks.
 

frazpo

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I haven't yet. Even though my initial modification mitigated most of the humming I still plan on replacing that ground over the weekend using an 18AWG copper strand wire.
I'd you do take it apart again
Could you post more photos of the screws that are removed for this repair.
 

tumegpc

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Here are the updated photos. Hope this helps.
 

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kruser

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Uniden has had their shot at resolving this issue and they have been unable to do so. They have even instructed owners how to make the modification that they have devised. So with Uniden allowing owners to make the modification, they would not be legally able to void a warranty on the basis that it was done by the owner and not Uniden. I am surprised that people continue to purchase this scanner with the foreknowledge of this issue. If sales of the SDS200 tanked, Uniden might be more proactive in resolving the issue. Consumers may have noticed that GRE/Whistler has not released a SDR scanner... They are waiting to see what Uniden does, which to date isn't worth the $700+ price tag.
After reading about this 'hum' problem for so long, I decided to purchase an SDS200 from HRO a couple weeks ago so I could experience it first hand.
Guess what, my radio has absolutely zero hum including when used with an amplified speaker.
I was so disappointed.

I did open the radio and found the so called 'mitigation' part had been factory installed but I removed it. It looked like a loose piece of metal just waiting to slip out and short something out. Even with the mitigation shield removed, my SDS200 is still totally hum free.
It also has none of the other odd issues I've read about here like display flicker or poor keypad backlighting.

I did inspect the factory installed ground straps (wires) and found them to be intact plus they looked to have been done properly unlike the poor job that tumegpc showed from his SDS200. I was almost tempted to lift the ground leads and see if I could detect any hum as that does look like it could be the problem but I decided to leave well enough alone.

I'm of the same opinion of several here that these 'problems' are rather rare compared to those owners that do not have one or more of these problems. By nature, people will complain about problems way more than people that will take the time to go online and say how well their SDS200 works with no hum.
 

mikewazowski

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Off-topic posts deleted.

Remember, this thread is for discussing the technical aspects of the grounding fix.

It is not for discussing where Uniden makes their scanners or their response to the issue. Please use the thread in the Tavern for that.

Thanks.
 

Anderegg

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What is your serial number?

I have 13 SDS200's, all hum/buzz to the exact same extent, and are from 3 different serial number batches.

Paul

After reading about this 'hum' problem for so long, I decided to purchase an SDS200 from HRO a couple weeks ago so I could experience it first hand.
Guess what, my radio has absolutely zero hum including when used with an amplified speaker.
I was so disappointed.

I did open the radio and found the so called 'mitigation' part had been factory installed but I removed it. It looked like a loose piece of metal just waiting to slip out and short something out. Even with the mitigation shield removed, my SDS200 is still totally hum free.
It also has none of the other odd issues I've read about here like display flicker or poor keypad backlighting.

I did inspect the factory installed ground straps (wires) and found them to be intact plus they looked to have been done properly unlike the poor job that tumegpc showed from his SDS200. I was almost tempted to lift the ground leads and see if I could detect any hum as that does look like it could be the problem but I decided to leave well enough alone.

I'm of the same opinion of several here that these 'problems' are rather rare compared to those owners that do not have one or more of these problems. By nature, people will complain about problems way more than people that will take the time to go online and say how well their SDS200 works with no hum.
 

kruser

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What is your serial number?

I have 13 SDS200's, all hum/buzz to the exact same extent, and are from 3 different serial number batches.

Paul
It's 38426098001xxx-xxx

Are some people simply more sensitive to this hum? That's possible.
I remember when digital cell phones were first hitting the market. I could not stand to use one nor would I use one because the delay introduced by the analog to digital and back again conversion just drove me nuts. For me, the delay seemed like an eternity in time but for others, they claimed they did not notice any delay at all.

I kept my old AMPS band phones until the day they shut the AMPS signals down here. By then, A/D technology was much better and I could live with the delay but to this day, I will not use a cell phone because of it if I have another option available. That's how noticeable the delay is for me with todays cell phones. Now that drives me crazy! If this hum is anything like that, I can definitely see how it would be a bother.
 
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Anderegg

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9 of mine are 01xxx also...

I bet if you jack your SDS200 speaker out into a PC (only using a ground loop isolaotor or you will need to spend $70 repairing the blown audio amp) and record us some audio, the hum/buzz will be present. Hum/buzz is not present if audio comes through the LAN via IP.

Paul
 
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kruser

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9 of mine are 01xxx also...

I bet if you jack your SDS200 speaker out into a PC (only using a ground loop isolaotor or you will need to spend $70 repairing the blown audio amp) and record us some audio, the hum/buzz will be present. Hum/buzz is not present if audio comes through the LAN via IP.

paul

Paul
That I do not do, pump audio into a computer. I do use Motorola amplified speakers though and they will usually highlight any hum or noise on the audio out of the radio but this 200 has been very clean sounding with or without any type of external speaker.
All my 536HPs on the other hand have all kinds of digital artifact noise when reading or writing the SD card while it's in the radio. That noise can be heard with just their internal speakers but not near as well as it can be heard using external amplified speakers. For those, I found different brand and different speed SD cards made a difference. I know that's different then the hum issue being discussed here however.

I do use 1:1 audio isolation transformers on all my x36HP and later models speaker level outputs so I don't ground either side of the BTL amp that Uniden is using in these models. They work well and give me nice and clear audio when I need it.

I can see a feed into a computer having issues. There's a lot of variables that come into play when doing that. Even with the use of so called ground loop isolator's, there can still be several different level ground potentials floating around on all the cables.
If I were to feed audio from a scanner, I'd convert it to a fiber signal first and then back again at the sound cards input. That can correct a lot of hum and noise issues as you are potentially taking some of the needed grounds away when using a beam of light.

Are most people having this hum problem when running live scanner feeds? If so, I missed that fact. I could see it being a problem for those that do want to run a feed though knowing how any noise on the input at the sound card will only be amplified along with the intended signal.
 
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