Uniden UHF radio help/component needed

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SteelRat
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Uniden UHF radio help/component needed

Post by SteelRat » 15 November 04 8:46 pm

A couple or so years back I bought a pair of Uniden UH-040XRs. They have been great little units with nary a problem :D . Till now :evil: . The other day the one on my belt decided the 'monitor' function needed to be permanently on. This means there is a constant background static hiss, very loud :?. Everything else works fine, just can't get the damned thing back to normal 'quiet' mode. Uniden Australia offered to look at it, starting at $88, but that cost more than the unit :shock: . I pulled it apart (naturally :lol: ) and have decided that the entire main circuit board with the LCD display needs replacing (as everything is so bloody tiny and soldered in place and looks fine to my untrained eye). Putting in the circuit board component should just be plug-n-play stuff. Anyone know where I can get one? (Uniden don't sell such things apparently, and I like the unit as it uses AA batteries like everything else I take out with me). PS: I just remembered how the emoticons work :wink:

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ideology
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Post by ideology » 16 November 04 9:10 am

$88! we offer you the following advice for $87:
  • remove the batteries
  • undo the two screws at the back
  • lift off the back cover
  • undo the two screws holding down the circuit board
  • lift out the circuit board and find the component marked IC3
  • orient the circuit board facing north so that the writing of IC3 points west
  • screw the circuit board back in
  • screw the back cover back on
  • replace the batteries
  • turn the unit on
  • disable monitor mode by holding down the monitor button (just below the PTT switch) until it beeps (about 2 seconds) and releasing :D
hope this helps!

Geof
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Post by Geof » 16 November 04 2:25 pm

Oh and don't forget to face Tokyo (or so be specific the Uniden HQ) wile performing the above. :lol:

SteelRat
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Post by SteelRat » 16 November 04 8:26 pm

Gee, so many helpful people, with such expert technical advice. And so specific too. :roll: And here I thought it was some internal component malfunction that prevented the normal mode of turning off the monitor function from working. And all along it was just that I faced the wrong direction. Mind you, the first 37 times I tried the pressing-in-the-monitor-button technique without success, I must have been holding my tonquge the wrong way too! :? Now, lets try the sage advice of the afore mentioned gurus of tech.....hmmm....unscrew cover.... locate component (bugger, it's not there!).....turn right way.....hold button......damn! Still doesn't work! :cry: Guess you won't be getting a cheque in the mail then. Still, if anyone else has advice on locating a replacement circuit board, please let me know. Thanks. :)

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EcoTeam
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Re: Uniden UHF radio help/component needed

Post by EcoTeam » 16 November 04 9:37 pm

SteelRat wrote:A couple or so years back I bought a pair of Uniden UH-040XRs. They have been great little units with nary a problem :D . Till now :evil: . The other day the one on my belt decided the 'monitor' function needed to be permanently on. This means there is a constant background static hiss, very loud :?. Everything else works fine, just can't get the damned thing back to normal 'quiet' mode. Uniden Australia offered to look at it, starting at $88, but that cost more than the unit :shock: . I pulled it apart (naturally :lol: ) and have decided that the entire main circuit board with the LCD display needs replacing (as everything is so bloody tiny and soldered in place and looks fine to my untrained eye). Putting in the circuit board component should just be plug-n-play stuff. Anyone know where I can get one? (Uniden don't sell such things apparently, and I like the unit as it uses AA batteries like everything else I take out with me). PS: I just remembered how the emoticons work :wink:
I have not opened mine to check, so this is only a general guess...
The Mon switch would presumably go directly into a logic input on processor, so that means it's likely to be one of two things:

1) The switch (or the track going to it) is shorted. You can check this by measuring the active side of the switch (the other side most likely goes to ground or power) with a voltmeter and ensure that the signal changes logic state when you press it. It should be between 0V and probably 3V or so. If not then something is shorted, shouldn't be too hard to track down.

2) The track from the switch to the processor is broken causing it to float, which may drag the line into the active state permanately. You can check this by following the tack from the switch into the processor and once again measuring the voltage as you push the switch, only this time measure on the actual processor pin. If the track is broken then it should be easy to fix with a bit of fine (30AWG) solid core "mod" wire.

3) The processor is cactus, in which case you are stuffed :roll:

Hope this helps.

EcoDave :)

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Post by EcoTeam » 16 November 04 10:00 pm

Ok, I couldn't resist!
I open my UH-040 :P

As I suspected, the MON switch is connected to ground and a track runs off to (presumably) the processor, although it runs under the LCD so I couldn't see.
There is also a capacitor across the switch.
I measured 1.75V across the swtich when open and of course 0V when pressed.
1) With the power off, if the resistance across the switch is 0ohms then the capacitor may be shorted, try removing it. If that doesn't help it's probably the processor which is cactus.
2) With the power on, if you don't get 1.75V across the swich then the track to the switch may be broken. In this case you should get 0V across the switch, but not zero ohms as above. A broken track may be hard to track down, but still possible.

EcoDave :)

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Post by ideology » 16 November 04 10:31 pm

does the unit beep after you hold down the button for two seconds?

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Post by Geof » 17 November 04 12:19 pm

I don't think your going to get a fully loaded pcb out of Uniden for a compeditive price. After you have done the "TeamEco" voltage check post your results. If the voltage remains high the switch us U/S. If there never is any voltage remove the switch and see if it comes back (if so the switch is short circuit).

If the switch is faulty post a close up photo and I may be able to help. (if you can't do this all is not lost it may just take a lot longer)

If your not confident soldering stuff that small best give it to some one that can before you wreck it.

I take it you have held down the button for a full 2 - 3 sec

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Post by teamkittens » 17 November 04 12:43 pm

Has anyone found a mod for the UH-040XR units to pump up the power? I've started looking around and have found mods for various other units but not for those yet...

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Post by Geof » 17 November 04 4:32 pm

Has anyone found a mod for the UH-040XR units to pump up the power? I've started looking around and have found mods for various other units but not for those yet...
Back in the old days when 2.5 watts was hot stuff in hand helds some one I knew found that if you switched them to low power and fed that into the rear end of a FM828 (450 - 500 Mhz type) that worked well... (a 5 watt FM828 of course :wink:) . You just have to sort out a ptt/RX-TX switching cct.

That isn't realy a hand held solution but could be good in car.

For a portable solution you could make a gain antenna - it would have to work better than those funny little loaded ¼ waves that are fitted and it wouldn't eat more battery + would have better RX.

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Post by Big Red Expeditions » 17 November 04 6:01 pm

If you really need the extra power, I strongly recommend getting a new "Foundation" amateur radio license. The government dropped the requirement for morse code at the beginning of the year given that no one actually uses it anywhere these days. So the exam now is very easy, and anyone with a bit of knowledge will pass easily. The benefit of this is that you can then go out and get an ameteur radio rig with massive output power. Big Red is fitted with an ICOM 207H with a massive 35w power on UHF CB bands, and up 50w on other bands. I can also scan restricted bands such as aviation, ambulance, couriers, rail, etc.

http://www.icomamerica.com/products/amateur/207h/

Geof
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Post by Geof » 17 November 04 9:14 pm

I strongly recommend getting a new "Foundation" amateur radio license.
Try telling that to the muggles you are going away with next week end who can't even fathem the concept of why they can't talk to each other on ch 1 duplex without a repeater (what's a repeater?) :roll: .

Sure 100 w on 6 meters would be nice :D in the bush but.....

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Post by alex » 17 November 04 11:09 pm

Big Red
with a massive 35w power on UHF CB bands,
I reckon this would probably melt a 1 watt handheld! :shock:

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Post by SteelRat » 18 November 04 8:11 am

I just logged on this morning for a quick look, so many replies! Thanks! To answer a few quick questions: I have held the mon switch a few seconds as required, get the multiple beeps that should turn it off (it does on the other operational unit) but no joy. I'll try and track down a multi-meter to check voltage, but as I never actually use the mon function (which for all I can see just turns off the auto squelch) I am now considering just removing the whole switch to see if this helps. I've contacted Uniden directly, their spares guy says there are NO circuit boards available at all, and no complete units sitting out back gathering dust either.

Geof
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Post by Geof » 18 November 04 11:58 am

I have held the mon switch a few seconds as required, get the multiple beeps that should turn it off (it does on the other operational unit) but no joy.
Not sure if you mean it beeps or not.. but if it beeps don't bother finding a meter for that purpose as you have confirmed the switch it's self is OK.

If it still beeps when pressed for 2 sec but dosn't change the mute status then we are in more trouble than we thought :cry: .

with a massive 35w power on UHF CB bands
I hope the ACA boys arn't reading this :lol:

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