BCD436HP: Missing "C1" capacitor

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KevinC

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Somewhere other than home :(
I wonder if Uniden will install the missing C1 capacitor in my 436...for free? I have the solder pads for it but no cap.

Mine was one of the first ones for the repair campaign so it received one of the early revised boards (with pads, but no cap).

My gut feeling is no, but maybe they will do it as a "Goodwill" gesture.
 

Markscan

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Mine was also sent in for the repair, and came back without it too. The pads are there.


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RFI-EMI-GUY

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Maybe C1 does nothing at all, just a way for UPMAN to know who is tinkering inside their in warranty radios?

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jonwienke

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No. Every time I have installed C1 it dramatically reduces RFI in the 350-500MHz range coming from the battery compartment area.

And newer serials have it from the factory.
 

jonwienke

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Here's an extract from my mod records:

Manufacturer Model Serial Comments
Uniden BCD436HP 376z38000725 Install GMOUSE G28U7FTTL GPS, front panel 3mm status LED, install C1.
Uniden BCD436HP 376Z38000758 Install GMOUSE G28U7FTTL GPS, GPS power switch, front panel 3mm status LED, install C1.
Uniden BCD436HP 376Z38000820 Install Ladybird PA6, switch, & indicator light.
Uniden BCD436HP 376Z48001044 Install GMOUSE G28U7FTTL GPS, GPS power switch, front panel 3mm status LED, install C1.
Uniden BCD436HP 376Z48004863 Install GMOUSE VK16E GPS, front panel 3mm status LED
Uniden BCD436HP 376Z48006329 Install GMOUSE G28U7FTTL GPS, GPS power switch, front panel 3mm status LED.
Uniden BCD436HP 376z58003562 Install GMOUSE VK16E GPS, front panel 3mm status LED, install C1, remove faceplate.
Uniden BCD436HP 376Z58003643 Install GMOUSE G28U7FTTL GPS, GPS power switch, front panel 3mm status LED, install C1.
Uniden BCD436HP 376Z58006630 Install GMOUSE VK16E GPS, GPS power switch, front panel 3mm status LED
Uniden BCD436HP 376Z78001129 Install GMOUSE G28U7FTTL GPS, front panel 3mm status LED.

Some of the older serials that had C1 (and therefore I didn't install it) didn't appear to have been installed at the factory--the solder joints appeared to have been done by hand rather than machine. The pattern isn't clear enough to define a cutoff serial number where one can confidently say that higher SNs have C1, and lower SNs don't. Perhaps once more data is collected, the pattern or a cutoff point will become clearer.
 

k3fs

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Problem is the C1 capacitor was omitted from the earlier boards used in the repair campaign and production. C1 capacitor does not show up until sometime in 2016 production (Z68#####) models, and does not show up in the repair campaign swap out until about the same time.

Serial numbers on units before 2016 (Z68#####) will not have the capacitor unless sent in for the repair campaign late in 2016. Earlier 2016 is a crap shoot. Units made late 2016 may have it, but determining that cut off is difficult.

Copper tape helps significantly for UHF.

0.01uf capacitor installed showed significant improvement in VHF and UHF. It eliminated a broader spectrum of noise.

https://forums.radioreference.com/u...ion-issues-due-noise-battery-compartment.html

Has more information on this, including a lot of the information in tracking down the problem.

When there is a problem, admit it as soon as possible.

Customers are not stupid. Ignoring or denying a legitimate problem is not the way to handle it.
 

RFI-EMI-GUY

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Problem is the C1 capacitor was omitted from the earlier boards used in the repair campaign and production. C1 capacitor does not show up until sometime in 2016 production (Z68#####) models, and does not show up in the repair campaign swap out until about the same time.

Serial numbers on units before 2016 (Z68#####) will not have the capacitor unless sent in for the repair campaign late in 2016. Earlier 2016 is a crap shoot. Units made late 2016 may have it, but determining that cut off is difficult.

Copper tape helps significantly for UHF.

0.01uf capacitor installed showed significant improvement in VHF and UHF. It eliminated a broader spectrum of noise.

https://forums.radioreference.com/u...ion-issues-due-noise-battery-compartment.html

Has more information on this, including a lot of the information in tracking down the problem.

When there is a problem, admit it as soon as possible.

Customers are not stupid. Ignoring or denying a legitimate problem is not the way to handle it.
Have you looked up the FCC certification for the radio? Often there will be photos taken inside a radio and you can spot any parts that might be missing in production radios. Schematics are usually kept secret however.
 

pro92b

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Have you looked up the FCC certification for the radio? Often there will be photos taken inside a radio and you can spot any parts that might be missing in production radios. Schematics are usually kept secret however.
Evidently you didn't follow your own advice. There are no internal photos, nor have there been for any recently released Uniden scanner.
 

k3fs

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There are pictures of the different boards on the above thread. Post 654 is a board with no C1. Post 661 is a picture of the original board. No solder pads for C1, but it is marked on the board. Post 727 is a picture of a newer board with C1 installed. The original board was marked as V1.01.01 the boards with C1 missing or installed are V1.09.02 or other version.

Unless testing is done by using an antenna mounted on the radio, and the signal is not directly fed by other means. You will likely not see the noise hindering reception.

When there is a problem, admit it as soon as possible.

Customers are not stupid. Ignoring or denying a legitimate problem is not the way to handle it.
 

mancow

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Unless I missed it I never saw any photos or better yet any continuity test that definitely show where each side of C1 connects in circuit (what other component it connects to). I recall one side going to battery ground possibly but not where the other went.
 

RFI-EMI-GUY

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Evidently you didn't follow your own advice. There are no internal photos, nor have there been for any recently released Uniden scanner.
sorry I put you to all that extra work. I will accept your humble apology. Good Day sir.
 

k3fs

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Unless I missed it I never saw any photos or better yet any continuity test that definitely show where each side of C1 connects in circuit (what other component it connects to). I recall one side going to battery ground possibly but not where the other went.
Is there a particular point or points you suggest to look at?
 

jonwienke

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Unless I missed it I never saw any photos or better yet any continuity test that definitely show where each side of C1 connects in circuit (what other component it connects to). I recall one side going to battery ground possibly but not where the other went.
Somebody in the huge UHF noise thread traced the C1 pads as going to ground and one of the voltage regulator ICs. The IC generates UHF noise if the capacitor isn't connected. I'm not sure how they did the trace; the board is actually a 6-layer sandwich with connections and traces between each layer. It's impossible to trace connections visually between the layers.
 

lou9155

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im getting ready to pull the trigger on the bcd436. has anyone recently bought one and is this stll an issue.... @jonwienke you recommended the diamond rh77ca ,should i order the bnc version or sma i recall a post you said the sma to bnc adapter helped reception because of spacing
 

mancow

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Somebody in the huge UHF noise thread traced the C1 pads as going to ground and one of the voltage regulator ICs. The IC generates UHF noise if the capacitor isn't connected. I'm not sure how they did the trace; the board is actually a 6-layer sandwich with connections and traces between each layer. It's impossible to trace connections visually between the layers.
Ok, I need to go read that again I suppose.

Maybe I'll just start dropping caps on all those DC converters anyway. There are several in there.
 

jonwienke

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No point going through all that if your board already has the pads for C1.
 

jonwienke

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jonwienke you recommended the diamond rh77ca ,should i order the bnc version or sma i recall a post you said the sma to bnc adapter helped reception because of spacing
I recommend the BNC version for three reasons:

1. It makes swapping antennas easy, so you can switch from using the scanners as base to mobile to handheld with a minimum of fuss.

2. If your unit is missing C1, the additional standoff space provided by the BNC connector moves the antenna farther from the UHF noise, such that it has minimal effect on reception.

3. The SMA-BNC adapter takes the wear of antenna swaps. The SMA connector only sees wear if you change adapters, so if you swap the unit from the car to the house to your belt frequently, it puts less wear on the scanner itself.
 
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