At least you have the pads. If I did I would just drop one in.
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BCD436HP/BCD536HP: UHF Reception Issues due to Noise from Battery Compartment
- Thread starter bearcat
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From what I read today on decoupling .01 uF and .1 uF are common decoupling caps. .001 may not be enough to do the job.
Yea, I overlooked the part of the discussion about the fix being part of the clock repair boards so yes you are correct, it is a non clock repair board.
If somone could check continuity from each side of that cap and see where it goes it would be great. Obviously one side must go to that ground near the battery ground. I'm wondering if the other goes to that clock line. Using the digital microscope to try to see the paths it looks like all of those test pads go to that line of filter caps except that CLK one. It goes through a PTH to the other side of the board then makes a long run on the keypad side of the board winding between button pads. I wonder if it's what's radiating.
I might pick a middle value like the .01 and try tacking to that CLK pad then to ground.
k3fs
Member
Mancow, If you have not sent your radio in for the repair campaign, your board is V01.01.01. There is a sticker on the board with that info. On those boards, there is no way to place the capacitor on there. The interesting thing is that the board is marked for both the resistor and capacitor that were later added.
All radios that were repaired, that I have seen, and new production, have board V 01.09.02. In all cases the resistor has been there. In my case there is solder on the capacitors pads, but no capacitor. In some other cases there is nothing, but bare pad where the capacitor goes.
Radio with the capacitor, no noise. Radio without capacitor, and one added, noise disappears. I cannot take credit for that experiment. I chickened out in putting a capacitor in mine due to space concerns, and proximity to another component.
All radios that were repaired, that I have seen, and new production, have board V 01.09.02. In all cases the resistor has been there. In my case there is solder on the capacitors pads, but no capacitor. In some other cases there is nothing, but bare pad where the capacitor goes.
Radio with the capacitor, no noise. Radio without capacitor, and one added, noise disappears. I cannot take credit for that experiment. I chickened out in putting a capacitor in mine due to space concerns, and proximity to another component.
What value cap was used?
You are correct. It has the V01.01.01 sticker.
There's room to tack one from that pad to nearby ground. I have it powered up with just the two boards, no case and am sniffing around with an SDR looking for noise.
There's room to tack one from that pad to nearby ground. I have it powered up with just the two boards, no case and am sniffing around with an SDR looking for noise.
k3fs
Member
I didn't do the cap mod. Problem is we don't know the value of what should be there. So, really it is not anything I would suggest trying. Nor would I suggest a value, and have someone seriously damage a radio. Space is tight due to the battery compartment and metal shielding. A disc capacitor may fit. Surface mount is what is needed. Truthfully, Uniden needs to address the problem.
From what I'm seeing so far the noise is radiating from the JRC 2360A DC-DC converter down on the corner of the other board near the batteries.
It spans from 150 Mhz - 650 Mhz roughly, peaking around 250. The noise is wider but less intense at the higher frequencies. I am running off of external power though. The next test will be on battery only to see the difference, if any.
It spans from 150 Mhz - 650 Mhz roughly, peaking around 250. The noise is wider but less intense at the higher frequencies. I am running off of external power though. The next test will be on battery only to see the difference, if any.
Noise is still there on battery. This seems to be the culprit.
http://www.njr.com/semicon/PDF/NJM2360_E.pdf
http://www.njr.com/semicon/PDF/NJM2360_E.pdf
Putting a capacitor on an actual clock line is the worst possible thing you can do to a digital device. It will essentially short out the clock output and "freeze" whatever component(s) depend on the clock signal for operation.
You do have a C1 label on your board. It just doesn't have SMD pads, only the test point at the bottom of the row of 3. Is that what you are calling CLK? That's unlikely to be correct, for the reason I just mentioned.
Connect a 0.1 microfarad cap between that pad and the nearest ground. For decoupling, bigger capacitance values are better, until the capacitor becomes large enough that its inductance becomes a factor (think electrolytic caps with wrapped foil plates).
You do have a C1 label on your board. It just doesn't have SMD pads, only the test point at the bottom of the row of 3. Is that what you are calling CLK? That's unlikely to be correct, for the reason I just mentioned.
Connect a 0.1 microfarad cap between that pad and the nearest ground. For decoupling, bigger capacitance values are better, until the capacitor becomes large enough that its inductance becomes a factor (think electrolytic caps with wrapped foil plates).
I thought about that capacitor clock line issue. (if it's actually a clock)
Article about DC-DC noise. Sure looks the same as what I'm seeing. I still think it's the DC-DC converter. I wonder if they changed something in that area that we are unaware of.
The converter is making 20 v for whatever reason and is right next to the RF/tuning circuitry under that metal can. They should have put a can over it as well.
http://www.interpoint.com/product_documents/DC_DC_Converters_Output_Noise.pdf
Article about DC-DC noise. Sure looks the same as what I'm seeing. I still think it's the DC-DC converter. I wonder if they changed something in that area that we are unaware of.
The converter is making 20 v for whatever reason and is right next to the RF/tuning circuitry under that metal can. They should have put a can over it as well.
http://www.interpoint.com/product_documents/DC_DC_Converters_Output_Noise.pdf
Since you have a unit that has yet to be sent back for the repair. Maybe that would be your best bet. You may get a board with the cap if not at least you will have the pad to put it in. It is a totally free including the shipping.
So if my '436 has had the clock issue repaired at Uniden, I can / should remove the copper foil I put inside the battery cover?
Leave it to the cow to dig into the problem with a spectrum analyzer. I don't have a 436, otherwise I could help get to the bottom of the problem and find a good solution. Sounds like a switching power supply RFI problem to me and its possible Uniden may have left out a seemingly unneeded part to save 2c and it was actually needed.
prcguy
prcguy
No. Mine went back for the repair and it did not have the cap and I know of two more that do not have it after the repair. The only way to know is look at the board.
I coated that area in tape then encapsulated it with conductive adhesive copper foil tape. I then coupled as many points to area grounds as possible (just using the conductive adhesive, not solder yet). It reduced the overall noise by 10 db when I can pick it up but I have to be right on it to get a signal. I think it has reduced the overall noise considerably.
EDIT: I went back and put more on and it helped even more.
EDIT: I went back and put more on and it helped even more.
Picture?
I did not. I'm still on the fence if I'm going to try to send it in for repair. I'm not convinced that single cap is capable of defeating all that noise either. Especially since it's in a totally different place. I wonder if they added some to the input and output of that DC-DC converter.
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