StaticDischarge
Member
- Joined
- Mar 30, 2019
- Messages
- 295
Unauthorized modification to fix hum
- Thread starter tumegpc
- Start date
- Status
Great! Good thing is if it should start you'll know what to do.
I did all 4. With an exact knife. I just showed one to illustrate before and after.
seth21w
Member
Did anyone contact uniden and let them know so they can adjust there manufacture process?
ColdnFrosty
Member
Even with the small part supplied by Uniden, I was still getting a noticeable hum. So I performed the "enamel scrape" mod that StaticDischarge suggested (thanks). I used photos that Tumegpc provided as a reference (thanks). The hum disappeared completely!
I can confirm that this modification does work well. I purchased my SDS200 new and it already had the noise mitigation metal plate installed when I received it. My unit still had a fair amount of processor noise. It was tolerable but at quiet times I could hear it very well.
I grounded the display with a wire to the chassis and I also scratched some epoxy from around the display board screws. I can't say which did the most to fix the problem but I figured while it was open, I want to be sure its resolved.
I was able to remove the metal noise mitigation plate and as far as I can tell there is no noise coming from the speaker now. I use an external Motorola speaker most of the time. Even if I plug earbuds in to the headphone jack I didn't hear any noise.
Thank you for sharing the modifications.
I grounded the display with a wire to the chassis and I also scratched some epoxy from around the display board screws. I can't say which did the most to fix the problem but I figured while it was open, I want to be sure its resolved.
I was able to remove the metal noise mitigation plate and as far as I can tell there is no noise coming from the speaker now. I use an external Motorola speaker most of the time. Even if I plug earbuds in to the headphone jack I didn't hear any noise.
Thank you for sharing the modifications.
Performing both the chassis wire mod along with the display board grounding screw mod is not a bad thing.
I don't really call them mods but rather call them fixes that should have been found and corrected during manufacture.
Proper grounding in a radio is a basic step that should always be done. It can really help stop a fair amount of problems.
Some things can't simply be grounded to a chassis ground. For those, they often use decoupling capacitors to bleed off stray RF or voltage.
I don't really call them mods but rather call them fixes that should have been found and corrected during manufacture.
Proper grounding in a radio is a basic step that should always be done. It can really help stop a fair amount of problems.
Some things can't simply be grounded to a chassis ground. For those, they often use decoupling capacitors to bleed off stray RF or voltage.
Youd think uniden would have figured it out by now and miracle there wasn't a class action. If so this fixes it using the dremel around the screw grounds then they need to test a factory unit wity a PCB eity the proper grounded area for the screws and then mass produce the solution. They also need to give a new free scanner to those who went beyond their engineering team to resolve
.. or did they not care and said fix it next model.
.. or did they not care and said fix it next model.
You at once both understand, and didn't understand uniden on this issue. Yes, they know there is a problem, but if they were to fully "resolve" the problem and start putting new design into the current SDS200 line, they would be admitting a design flaw and would be liable to replace or repair every SDS200 sold to date. By continuing to ship flawed units, they are not liable for bringing old units up to spec to changes they have not made...the piece of tin was the cheapest lawyer solution they culd come up with.
Paul
I don't know if they will fix this in newer models. I do know the problem existed in older models like the x36HP series.
With the x36HP models, one could often hear data sounds from the speaker as the radio booted and was reading from the SD card.
If you used recording, you could hear the sounds during scanning if you had the volume turned down. And like the hum in the SDS200, volume settings did not change the data sounds.
After the SDS200 grounding problem was found, I opened up an 536HP and found the small board that the SD card socket was mounted too had no good ground. I grounded it in my test 536 and it did eliminate the data noise.
The data noise was hard to hear for most but if you used an external amplified speaker, the data noise was very noticeable.
Uniden seems to have issues with proper grounding. I know in their earlier days that they used nice braided ground straps from the chassis to the front panel boards. In several models, this ground strap was soldered at both ends proving a proper ground.
I guess someone forgot about that in the newer models.
How true that statement is. I'm sure they don't want another recall program to address the hum like they did for the dimming backlights and RTC failures in the x36HP line!
Ubbe
Member
But Uniden did change the BCD436 circuit board to add the soldering pads for an interference surpressing capacitor, but didn't install it until in later batches. Would that then make all 436 owners of the older versions eligible for a free hardware upgrade of their scanners?
/Ubbe
Ubbe
Member
Manufacturers tries to reduce cost, even during a products life time. They remove components and skips time consuming work in their prototypes and beta versions if the end result aren't too bad. Uniden probably tested to remove several manufacturing steps and thought it was good enough for it's user base. Designers and engineers are often voted down by management, that focus on short time quarterly profit and not as much at reputation and quality, and their creations doesn't end up as good as they looked on the drawing board.
/Ubbe
Could anyone please point me to the thread (with any photos?) of exactly how to remove the faceplate to get at the screws that need to be better grounded? I've searched and only find one mention of how to actually disassemble everything, but not the thread itself if it still exists
So far, the exterior black case is off, top metal plate is off, knobs are removed and all three spanners nuts are off. I really don't want to mess this up and while not an electronics tech by profession (obviously) I can follow detailed instructions. Any help, please? TIA. (Off list replies are very welcome if no one wants to reference this on the forum itself.)
So far, the exterior black case is off, top metal plate is off, knobs are removed and all three spanners nuts are off. I really don't want to mess this up and while not an electronics tech by profession (obviously) I can follow detailed instructions. Any help, please? TIA. (Off list replies are very welcome if no one wants to reference this on the forum itself.)
This thread... Page 2... Post 33...
If thats what your looking for...
If thats what your looking for...
In addition to the thread RandyKuff linked, look at post 7 in this thread: SDS200 Hum > External Speaker
It has a picture of the front board showing where the lacquer was removed down to bare copper for the four screws so a good ground can be made. This is what makes this fix work the best.
It has a picture of the front board showing where the lacquer was removed down to bare copper for the four screws so a good ground can be made. This is what makes this fix work the best.
Couple of things I encountered doing the mod.
I have two sets of small screwdrivers, all screwdrivers about the same length and just a tad too long to sit inside the radio at a 90 degree angle to the screws retaining the front panel assembly. However one set of screwdrivers have a slot at the back of each, allowing a blade screwdriver to drive the smaller screwdriver to undo the screws. I also needed to remove the bottom metal plate to get at one of the screws.
The spanner nuts were loosened and came off from the two smaller knobs OK, but I could not shake out the one for the large knob and the white plastic moulding with it. Until that moulding came out, I didn't know if it would or if instead it was part of the front panel. However gently maneuvering the front panel caused the spanner nut and the moulding to release and the panel to be completely removed.
I have two sets of small screwdrivers, all screwdrivers about the same length and just a tad too long to sit inside the radio at a 90 degree angle to the screws retaining the front panel assembly. However one set of screwdrivers have a slot at the back of each, allowing a blade screwdriver to drive the smaller screwdriver to undo the screws. I also needed to remove the bottom metal plate to get at one of the screws.
The spanner nuts were loosened and came off from the two smaller knobs OK, but I could not shake out the one for the large knob and the white plastic moulding with it. Until that moulding came out, I didn't know if it would or if instead it was part of the front panel. However gently maneuvering the front panel caused the spanner nut and the moulding to release and the panel to be completely removed.
It was a positive learning experience for me. I built circuit boards and modded radios, I had not been inside a radio in 25 years. Take your time and stop if you're not sure what to do next, refer to the photos,. It was a bit tedious but I felt like I had accomplished something.
Thanks for the several suggestions and references to the photos. Folks on a Facebook SDS100/200 page pointed me in the same direction.
I finished the modification(s) this morning using a flat diamond-tipped Dremel bit to gently take the lacquer off around the 4 screws holding the circuit board in place. It all worked out fine. In that FB group, I also posted before and after audio clips of the sound. Conservatively, the noise decreased by at least 90%.
Truth is, I wasn't terribly troubled by the sound, but decided I'd do the 'fix' anyway. The absence of sound is now deafening, so to speak. Happy camper. Thanks all.
- Status
