Pro 2006 crackling noise on UHF

Hi everyone,

I was just wondering if anyone else has run into the issue of a crackling noise along with the audio on conventional UHF frequencies on a Pro 2006. VHF and 800 Mhz frequencies are clear. It almost sounds like a little audio RFI getting into the mixer from a strong FM broadcast signal.

I've ruled out the antenna system by hooking up my handhelds to the discone the 2006 is connected to. The handhelds with their own antennas also don't have the same issue as the 2006. Lastly, I tried using the t 2006 telescoping antenna, but the interference was still there.

Any ideas would be appreciated.

TNX & 73,

-Larry KG6EJT, AKA: Engine 104

Is it all your UHF or just one Agency/Frequency ? It could be on their end.

If it was all frequencies, then the 2004/2005/2006 tend to get dust in the Volume control that need to be flushed out with cleaner

Engine104 said:

Hi everyone,

I was just wondering if anyone else has run into the issue of a crackling noise along with the audio on conventional UHF frequencies on a Pro 2006. VHF and 800 Mhz frequencies are clear. It almost sounds like a little audio RFI getting into the mixer from a strong FM broadcast signal.

I've ruled out the antenna system by hooking up my handhelds to the discone the 2006 is connected to. The handhelds with their own antennas also don't have the same issue as the 2006. Lastly, I tried using the t 2006 telescoping antenna, but the interference was still there.

Any ideas would be appreciated.

TNX & 73,

-Larry KG6EJT, AKA: Engine 104

Click to expand...

Hi Bill,

Thanks.. It is multi-agencies (LACoFD and LASD in the 470 Mhz range, as well as 440 ham). I opened the case yesterday and sprayed the volume knob with contact cleaner just in case, but it didn't help. I'm thinking this is somewhere in the UHF circuitry. VHF, 800 Mhz and air are clear. Also my handhelds don't exhibit the same problem, even when connected to the discone that I use for the 2006.

Sound like the radio is finally fading, unless..there is something near-by causing interference.

Have you tried using the 12v power on the rear to rule out the Power Supply ?

Engine104 said:

Hi Bill,

Thanks.. It is multi-agencies (LACoFD and LASD in the 470 Mhz range, as well as 440 ham). I opened the case yesterday and sprayed the volume knob with contact cleaner just in case, but it didn't help. I'm thinking this is somewhere in the UHF circuitry. VHF, 800 Mhz and air are clear. Also my handhelds don't exhibit the same problem, even when connected to the discone that I use for the 2006.

Click to expand...

That could be.. I bought it new in 1992!

Yes, I tried a 12v wall cube on it, but no change.

One final suggestion, take it mobile (12v plug) and see, just to ensure
the noise is not coming from appliances in the house (Microwave, routers, alarms, tv, cable box etc)

Engine104 said:

That could be.. I bought it new in 1992!

Yes, I tried a 12v wall cube on it, but no change.

Click to expand...

ecps92 said:

One final suggestion, take it mobile (12v plug) and see, just to ensure
the noise is not coming from appliances in the house (Microwave, routers, alarms, tv, cable box etc)

Click to expand...

That's a good idea. I was thinking of bringing it to work with me and see if the same thing happens here.

Just an update/bump on this... I finally was able to bring the radio to my office, which is about 20 miles from my home. I am still getting the crackling background noise on UHF transmissions, so the issue is probably in the radio. Any ideas on what to check or repair?

I need to check mine for this now. Have had it since 1994. Great receiver, and glad it has not worn out the backlight. I always leave it set to the low brightness setting. Other than a few tumbles from the bench, it has been babied.

Engine104 said:

Just an update/bump on this... I finally was able to bring the radio to my office, which is about 20 miles from my home. I am still getting the crackling background noise on UHF transmissions, so the issue is probably in the radio. Any ideas on what to check or repair?

Click to expand...

I know the 2004's had issues with thru-holes failing and a good soldering job by inserting and soldering some small gauge bare wire through the thru holes would often fix them back up.
I don't know if that problem was fixed with the 2005 and 2006 models.

I own one of each and they still all function probably as well as they did when new.
Of course all three have had the stupid backlight strip replaced by me more than once but at least it was an easy fix.

I've also had simple poor solder joints in at least the 2004 model but it has usually been in an area that affected all bands.
I've ran mine almost entirely from an external linear power supply since buying them new so that may have helped some in my case.

You should be able to find a schematic online and be able to trace out the UHF section and its related band switching components and see if you can narrow it down to a single component or area of the board.

I've had dried up electrolytic caps in all of mine but they were usually in the audio stage and affected all bands.
I'm also thinking the 2004 model may have had some trimmer caps that failed in the UHF section. I kind of recall that aligning the UHF section was hard to get perfect due to bad trimmer caps.
My bet is on a poor solder joint or thru hole though as I know they did have those problems as they aged. I think the thru holes were the most common problem as the copper plating in the hole was not solid so soldering in a wire from front to back would restore the connection.

The trimmer cap problem may have been in some of Electra's earlier programmable models like the BC-250 and not even existed in the GRE made 2004's.
I've worked on so many radios over the years that it is hard to remember which models had specific common problems!

I think Bob Parnass or Bill Cheek may have written a paper about the common issues the 2004/5/6 models developed over time. If you can find that, it may give you some ideas where to start looking.

They were great radios in the day and still are great for digital decoding with a discriminator tap. That is how I still use mine to this day.
I also still monitor railroad radio with them all and low band VHF.

Dear Kruser,

Thanks so much for your reply. Lots of good things to try there. My guess is a dried up cap, but it could be a bad solder joint/copper plating on the board issue. I've heard of that with the 2004s. It is a possibility, though and worth checking. I'll also check for a paper by Parnass or Cheek. I have a photocopy of the service manual. I'll look for the schematic in there.

Yeah, I've had to do the EL panel replacement twice.. Mine can use it again. I'm not sure where to get the panels, though. I tried G&G a while back, but he was out of them.

Even if I can't fix the UHF issue, the radio still works great on 800 MHz, VHF and Air, so I'll keep it for that and use my handhelds for general scanning.

Thanks again... Much appreciated.

Engine104 said:

Dear Kruser,

Thanks so much for your reply. Lots of good things to try there. My guess is a dried up cap, but it could be a bad solder joint/copper plating on the board issue. I've heard of that with the 2004s. It is a possibility, though and worth checking. I'll also check for a paper by Parnass or Cheek. I have a photocopy of the service manual. I'll look for the schematic in there.

Yeah, I've had to do the EL panel replacement twice.. Mine can use it again. I'm not sure where to get the panels, though. I tried G&G a while back, but he was out of them.

Even if I can't fix the UHF issue, the radio still works great on 800 MHz, VHF and Air, so I'll keep it for that and use my handhelds for general scanning.

Thanks again... Much appreciated.

Click to expand...

Good Luck getting it going. It probably is something stupid and easy once found!
Hopefully you can find it easily by tapping the components with a non conductive probe or alignment tool of some type while the radio is tuned to a noisy frequency. If tapping and probing does not find it, you can try a can of component cooler or freeze spray which may find it if it is a transistor that has become noisy. The same spray can also find cold solder joints if probing and tapping does not find anything.
I'd probably first try tapping around on components and the board when the noise is present and hope you hit an area that really makes it go crazy. That may get you close to the problem source.

Hi Kruser,

Thanks again for your help.

I'll give tapping another try. I wasn't able to isolate anything the first time, but it wouldn't hurt anything to try again. I've always been a little scared of trying freeze spray.

I really appreciate your help.