My SDS200 Hum Fix

[hiegtx]

Nicely summed up. I didn't see where using the Uniden part would make a difference. I think I'm gonna plan on doing the screw scrapes and forget the rest. So basically the board is coated with green lacquer, and sandwiched in between the board's surface and that lacquer is the copper that we don't want to grind off, just removing the green enough to show the shiny copper with enough of each surface area so that each screw head fully makes board contact without touching lacquer and that's it, correct?

That would be correct. Remove enough of the lacquer so that a solid connection can be made. I suspect that is one reason some have the hum, and some don't. Perhaps, in some cases, there was not as thick a layer of lacquer, or maybe it was assembled before the lacquer was completely dry, so possibly the parts were assembled soon enough that a connection was made. I have one of the original run SDS200s, and have never had the hum issue. If, for whatever reason it crops up, I'll use Status Discharge's fix.

 

[Ubbe]

Didn't Uniden add two black grounding wires to some units, that where sometimes done porly, that perhaps reduced the hum if it wasn't to severe, additional to that mitigation metal piece?

/Ubbe

 

[buddrousa]

Ubbe I saw 1 when I did my SDS200 I never heard the hum (I am old) I fixed it anyway.

 

[scnrfrq]

Just got an SDS 200. The only sound I hear is a slight whine if you put your ear close to it. And only with an external speaker - it's totally quiet with the internal speaker. This sound does not really bother me, but is that the same as the hum people complain about?

 

[darkness975]

Just got an SDS 200. The only sound I hear is a slight whine if you put your ear close to it. And only with an external speaker - it's totally quiet with the internal speaker. This sound does not really bother me, but is that the same as the hum people complain about?

Sounds right, although I can hear it with the internal speaker on mine but it's the same as in your case where I don't hear it unless it's quiet in the room and I'm within about 3 feet or closer to the unit.

 

[djeplett]

I bought my SDS200 about a month and a half ago and on the second night I had it I noticed a hum. I wouldn't call it a hum, though. More of a constant tone once the squelch closes. This was only noticeable in a very quiet bedroom with the door closed. Since placing it in my office with two PCs running nearby and a switching power supply for my digipeater I can't hear it at all. If it ever gets bad and I notice it over all the fan racket I'll attempt staticdischarge's fix. But until then, that $700+ case is staying closed.

 

[darkness975]

I bought my SDS200 about a month and a half ago and on the second night I had it I noticed a hum. I wouldn't call it a hum, though. More of a constant tone once the squelch closes. This was only noticeable in a very quiet bedroom with the door closed. Since placing it in my office with two PCs running nearby and a switching power supply for my digipeater I can't hear it at all. If it ever gets bad and I notice it over all the fan racket I'll attempt staticdischarge's fix. But until then, that $700+ case is staying closed.

That sounds like mine as well, can only hear that "tone" sound when it's dead quiet.

 

[Kaleier1]

So basically the board is coated with green lacquer, and sandwiched in between the board's surface and that lacquer is the copper that we don't want to grind off, just removing the green enough to show the shiny copper with enough of each surface area so that each screw head fully makes board contact without touching lacquer and that's it, correct?

Yes buit don't try to scrape off the lacquer in one shop like trying to chip off paint or you will gouge the copper underneath. Use a razor blade or exacto knife and scrap it off gradually in layers almost like using sand paper to gradually get through it to the copper. You will need a very small phillips screwdriver bit as the display board screws are quite small.

 

[srpawski]

Ok, one more question on the lacquer removal - I've seen mentioned in multiple places that instead of scraping the crud off the top to get to the copper, some have inserted star external tooth lock washers in between the screw head and the board to accomplish the lacquer removal. That said, by simply tightening the screw after inserting the washer, has that action alone been enough to cut through the lacquer to make contact, or does one need to loosen and tighten more than once to cut through the lacquer sufficiently to make enough contact? I am concerned about over-tightening or scraping away too much of the copper underneath the lacquer if using the washer heads instead of the scraping method.

 

[scnrfrq]

Just got an SDS 200. The only sound I hear is a slight whine if you put your ear close to it. And only with an external speaker - it's totally quiet with the internal speaker. This sound does not really bother me, but is that the same as the hum people complain about?

Tried a ground loop isolator with a Realistic speaker. Totally silent from that speaker, but I have to increase volume from 8 to 23. Is that normal? Also the isolator only works in one direction - normal too?

 

[Ubbe]

The ground loop isolators are supposed to be used with low level signals like the line in on a computer and the transformer in them are made for high impedance sources like 1Kohm and 10Kohm and don't work so well with 8-25 ohm amplifiers and speaker. The audio level will be very low and probably no bass tones at all when used with low impedance devices.

/Ubbe

 

[Kaleier1]

Ok, one more question on the lacquer removal - I've seen mentioned in multiple places that instead of scraping the crud off the top to get to the copper, some have inserted star external tooth lock washers in between the screw head and the board to accomplish the lacquer removal. That said, by simply tightening the screw after inserting the washer, has that action alone been enough to cut through the lacquer to make contact, or does one need to loosen and tighten more than once to cut through the lacquer sufficiently to make enough contact? I am concerned about over-tightening or scraping away too much of the copper underneath the lacquer if using the washer heads instead of the scraping method.

The screws are very small so it may be hard to find small star washers. Because the screws are small and you need something like a jewelers screwdriver, it will be hard to over tighten them. I'd be interested to see if star washers would be effective. There are 4 screws so even if you get one to touch the copper you will probably be good. In other words you have 4 chances (4 screws) to makes a ground connection between the screw and copper. Just don't try to chip the lacquer off in pieces. lightly scrape it off in layers like sanding a surface with sand paper and you will be good. It is so worth it to not have any him at all. I could hear teh hum in mine from 6 feet away.

 

[darkness975]

The screws are very small so it may be hard to find small star washers. Because the screws are small and you need something like a jewelers screwdriver, it will be hard to over tighten them. I'd be interested to see if star washers would be effective. There are 4 screws so even if you get one to touch the copper you will probably be good. In other words you have 4 chances (4 screws) to makes a ground connection between the screw and copper. Just don't try to chip the lacquer off in pieces. lightly scrape it off in layers like sanding a surface with sand paper and you will be good. It is so worth it to not have any him at all. I could hear teh hum in mine from 6 feet away.

Where are you located?

 

[N4DJC]

Takes time, patience, concise step by step instructions, and the right tools. It does fix the problem, renders the mitigation part unnecessary.