Uniden 980 SSB, AM power pot

[jtsmith82391]

So I picked up a non-working Uniden 980 SSB and took the cover off. Upon looking around, I discovered that the AM power pot was no where to be found. Of course Uniden hasn't released a repair manual, so I'm at a loss. All I need to know is the value of the trimmer pot. Any help would be greatly appreciated. It looks like someone might have tried to do a basement wattage adjust and just cranked the little guy off of the board. I have looked EVERYWHERE for any info on this and wouldn't you know it? Nothing. Its labeled rt206 on the board. Thanks!

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[prcguy]

Without a diagram to go by I would take a jewelers loupe and see if you find any info on the other pots like tiny little "1k" or some other common way of marking resistor values. If most of the pots are the same value then its probably safe to put one in that's the same as the rest.

I suspect its somewhere in the 1k ohm to 5k ohm range and its probably safe to start with a 1k.
prcguy

 

[kf4eyr]

i would look the inside over looking for it,,, if it is lodged somewhere and you apply power might get more damage than get fixed,,,

 

[KD8DVR]

Radios come from the factory set to be compliant with Fcc rules.

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[jtsmith82391]

Radios come from the factory set to be compliant with Fcc rules.

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Right... do you have a point?

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[jtsmith82391]

Thanks everyone for the suggestions. I'm just going to leave it be for now. Hopefully before too long someone will leak the repair manual or even a parts list. It's in pristine cosmetic condition. It won't be worth it to me to send it in to have it repaired. So it'll look good on the shelf for now. It's a gamble when you buy rummage sale items. Lesson learned, at least it wasn't an expensive lesson lol

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[TheSpaceMann]

So I picked up a non-working Uniden 980 SSB and took the cover off. Upon looking around, I discovered that the AM power pot was no where to be found. Of course Uniden hasn't released a repair manual, so I'm at a loss. All I need to know is the value of the trimmer pot. Any help would be greatly appreciated. It looks like someone might have tried to do a basement wattage adjust and just cranked the little guy off of the board. I have looked EVERYWHERE for any info on this and wouldn't you know it? Nothing. Its labeled rt206 on the board. Thanks!

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Did you try contacting Uniden? I would assume that someone in their tech department could help.

 

[KD8DVR]

Right... do you have a point?

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Yes. User adjustment is unnecessary.

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[jtsmith82391]

Yes. User adjustment is unnecessary.

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Ok, well you clearly didn't read my post correctly. This info should've been passed on to who originally purchased the radio..... try re-reading the OP and take a look at the picture. I highly doubt they manufactured this unit without the the AM power pot. But then again, stranger things have happened.

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[KC4RAF]

Jtsmith, that board COULD be used in a different model

cb. After opening and repair many transceiver in the past, I've seen where this is the case. Example; the Cobral 148 gtl cb is the same board used in the Cobral 2000 gtl. Also goes for some of the President models, etc.
Have you tried to power the unit on? That's one of the things I would've checked first if you haven't. Is there any sound at all, if so, what's it like?

 

[Weaksignal]

CBRadioMagazine.com - The only online CB Magazine in the world did a review of the Uniden 980. The AM power adjustment pot (RT206) in question looks visually identical, when compared to the trimmer pot RT205, (AMC), AM modulation control. Perhaps the same specification and value?... Not sure.

 

[jtsmith82391]

It still powers on and everything else works as it should, just no AM TX.

I'm going to use a jewelers loupe and see if there are any markings on the other pots. If so, maybe I can find someone with the same radio to let me take a look and see what it's supposed to be. I've just been busy and haven't had much free time to get back to it. If I do happen to find anything out, I'll make sure to let cbtricks know. so it'll be out there for anyone else facing a similar issue. It's ridiculous how small the components are on those SMT boards.

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[prcguy]

Looking at the board layout I suspect you can bridge the two pads furthest away from the RT208 markings with a 1k resistor as a test and it will probably come to life with some AM power. One of the solder pads is ground, another feeds the circuit upstream and one probably connects to a fixed voltage or switched fixed voltage.

One side of the pot would be ground, one side to the voltage source and the wiper probably goes to the circuit upstream. I still think the original pot was probably around 1k, probably not much less and probably not more than 5k ohms. You can get a small plastic enclosed Bourns pot off Ebay cheap, glue it to the side of the chassis and wire it to the pads and get on the air.
prcguy

It still powers on and everything else works as it should, just no AM TX.

I'm going to use a jewelers loupe and see if there are any markings on the other pots. If so, maybe I can find someone with the same radio to let me take a look and see what it's supposed to be. I've just been busy and haven't had much free time to get back to it. If I do happen to find anything out, I'll make sure to let cbtricks know. so it'll be out there for anyone else facing a similar issue. It's ridiculous how small the components are on those SMT boards.

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[jtsmith82391]

I gave up. I decided to gift it to a friend who primarily utilizes ssb. From now on I'll only purchase radios that have available service manuals. Lesson learned. Sorry it has taken so long for me to reply, my phone decided it didn't want to work properly any longer. Again, I want to thank everyone for their suggestions. Hope you all have a great day! 73's

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[bharvey2]

Post deleted by user.

 

[KC4KTY]

Size of resistor

I could have told you the correct size of Resistor.

I have been doing this for more than 35 years. Anyways if you had been patient we could have had
that radio up and runing.

I could have sent you the correct part. Ham Radios have been using surface mount components for years.

I could have read the size off of the resitor in mine or read it with a meter.

Real easy fix.

To bad you gave the radio away. My 980 did 3 watts out of the box on AM and only about 7 watts SSB
Now it does the 4 watts AM and 12 watts SSB.
Most radios work the same way and just know where to look is the ley to these things.

That is a voltage regulator resistor to set up the correct voltage to the driver stage.
the value of that resistor is 3K ohms. you can get by using a 5K resistor and it would still work.

This is for anyone else who goes into adjust it and breaks the Resistor that controls the AM power
output.

Here is the reason the radios are set for 3 watts AM. Please look at the specifications in the receiver
part you will see the Audio output is this.

Audio output (10% distortion) : 2.5 watts
Audio Output Max 3 watts

For 100% modulation 3 watts of RF takes 3 watts of Audio

If you look at the Uniden 880

it has Audio Output (10% distorion) : 4 watts
Audio Output Max 5 watts

Uniden 880 can run 4 watts of RF since you have 4 watts of Audio.

100% modulation

With the 980 set to an RF output at 4 watts
Do not expect more than 75% modulation( still cab be uesd at this amount)

This is the reason you find all Uniden 980SSB radios set at 3 watts RF output so you get 100%
modulation.

I would set it to 3.5 watts if you want more power.

You will get 87.5 % modulation very close to 90% modulation.

Anyways I hope this is a large help. I have been a license ham for 35 years as well license
technition for communications equipment.

If you like SSB get a 980 if you like AM get the 880
The 880 will deliver you 4 watts output with the full 100% modulation.


Thanks