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+8v on TX only on Uniden 980

KennyD

Member
Oct 28, 2013
46
4
18
Connecticut
Hey guys, I'm hoping someone here could tell me where to find a +8v source on transmit for a Uniden 980? I want to put a RFX-85hd on it.
 

Hey guys, I'm hoping someone here could tell me where to find a +8v source on transmit for a Uniden 980? I want to put a RFX-85hd on it.
I believe I saw the bell tech do a 980 video with a RFX-75 one time. Maybe you can look it up and find what you're looking for.
 
I'd get the rfx150 and fan kit and install that one. Much easier to install from what I've heard. The rfx85's are a pita to mess with. Good luck getting going right. Hope you get your answer, but I know the mic has +8vdc source for wireless mic use.
 
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Just find the voltage regulator along the chassis rail and then test the leg voltages with a meter.
Gotta learn to do this stuff sometime . . .

Right, But I need to find 8 volts only when in transmit mode. I have been poking around this thing with a DMM and haven't found it.
 
I'd get the rfx150 and fan kit and install that one. Much easier to install from what I've heard. The rfx85's are a pita to mess with. Good luck getting going right. Hope you get your answer, but I know the mic has +8vdc source for wireless mic use.

The RFX-85HD is just like the 150. It doesn't replace the finals. Just needs the 8v to key the amp in transmit.
 
I knew the 85 was different than the 75. But the question was about the 980 so I thought you might benefit from some useful information from the video on the 980/75. There could be an updated video with the 85 somewhere. Try lesscom. Bet he has some good info.
 
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I knew the 85 was different than the 75. But the question was about the 980 so I thought you might benefit from some useful information from the video on the 980/75. There could be an updated video with the 85 somewhere. Try lesscom. Bet he has some good info.

Oh I see. Well I can find 12 volt on transmit at Q203. I wonder if the RFX can tolerate that?
 
Oh I see. Well I can find 12 volt on transmit at Q203. I wonder if the RFX can tolerate that?

Just use a simple resistor voltage divider circuit to give 8V. You want to just choose values where you have one resistor at X Ohms and the second resistor is 2X Ohms so for example a 100Ohm and 200Ohm resistor or a 1K and 2K resistor. So, using a 1K and 2K resistor for example, solder the 1K and 2K resistors in series. Put the spare end of the 1K on the +12V source and the spare leg of the 2K to ground. Tap off where the resistors are linked and it'll give you roughly 8V.

Personally if it were me I'd modify the RFX instead and put the voltage divider on the PTT input so you never have to modify another rig. To do that you'd disconnect the wire from the socket, connect your voltage divider to the socket as above (1k spare leg to socket, 2k spare leg to ground) and put the wire that originally went from the socket to where the resistors are linked.
 
+ 8 volt on the Uniden 880 is under the top Cover in the right rear 3/4 in from rear1/2 in from side ,, use a voltmeter it's actually 8.22 volts
 
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