Uniden 510xl dead key

[nat19]

I was wondering does any body now how to adjust the dead key on a Uniden 510xl. I know its not the best radio but its going to be put in my jeep and
I don't want to tear up a good radio. With all of the mud and if the top is of there will be rain. I am going to run it with a kl60 amp once again this is not the best amp but I don't want to take any chances with a good one.

 

[Robb]

You will need to have the radio output turned DOWN 1 1/2 to 2 watts ('deadkey') use it with a linear amp. A simple adjustment at a shop; but it might cost a few bucks to get it done - maybe $10 or $20 if they aren't busy. Otherwise, it will sound a bit crappy. Rain is going to be a radio killer - if you cannot find a way to keep it off/out of the radio and amp!

I couldn't find anything on the internet that would tell one where to turn down the deadkey setting. Maybe someone on this site can give you that info. CBTricks didn't have it. Defpom does: http://www.radiomods.co.nz/pro500d510xl520xl.html
Cutting D14 will bring the modulation up; would be OK if using a stock mic - maybe too much with a power mic. AM power output is adjusted by tuning coils L6 and L5 with a power meter and using a dummy load - of course.

 

[sp5it]

AM power output is adjusted by tuning coils L6 and L5 with a power meter and using a dummy load - of course.

De-tuning those colis will cause to lower output power what is WRONG.
To lower DK use this circuit: http://www.dtbradio.com/varikey.gif
Mike

 

[Robb]

De-tuning those colis will cause to lower output power what is WRONG.
To lower DK use this circuit: http://www.dtbradio.com/varikey.gif
Mike

Thanks for the correction. I just wrote what the Defpom page said.

 

[nat19]

Thanks for the replys!

 

[loosecannon]

well, i could only find a schematic for the PRO 510e, but the AMC is D14 in both the XL and the E models, so, im assuming the chassis are the same in other respects. (they most likely are the same on the inside)

to lower the deadkey, you need to lower the voltage to the driver and final transistors.
the way to do this is to add resistance in series with the voltage path to them.

in almost ALL AM only radios, this voltage is fed through the modulation transformer, then through an "anti spiking diode" and on to the driver and final collectors. (in the 510e, it is D7)

you can look at almost any schematic for an AM only CB radio, and find this voltage line without too much trouble.

first, find the audio chip. most likely, there will be a symbol for a transformer next to it.
find the line going from the transformer, through a rectifier diode (the black ones with the silver stripe on one end. usually labeled 1N4003 or something like that on the schematic), and follow this line all the way to the driver and final collectors to confirm that you have the right line.

the rectifier diode should never be removed and replaced with a resistor or a wire jumper, as this can cause a large voltage spike to reach the transformer and burn through the insulation.

to lower the voltage going to the driver and final transistors and thus, lower the deadkey, you can add more of these diodes in series with eachother, or add 1/2 watt resistors in series with this diode.
the resistor values will have to be determined experimentally, but i would start low, like around 47 ohms, and work up from there.
the higher the resistance, the lower the deadkey.

if you choose to go the diode route; be sure they are all facing the same way as the original diode.

if you choose to go with the resistor route, add the resistor(s) to the banded end of the diode.

the modulation will not be lowered because it is already being coupled through 1:1 because the diode is already conducting.

this technique can be applied to many radios that dont have a convenient way to lower the deadkey to match an amplifier input.

for the KL60, i would go for a 1 to 1.5 watt deadkey.

as for removing the AMC diode, D14; i would be careful with that.
some of these radios use condenser microphone elements and dont take well at all to overmodulation.
i would try it with the AMC intact first, and if it works decent, i would live with it.

good luck with it,
LC

 

[vibrant93]

De-tuning those colis will cause to lower output power what is WRONG.
To lower DK use this circuit: http://www.dtbradio.com/varikey.gif
Mike

Ok newb here, not trying to hijack the thread but i'm in the same exact boat with this radio. Just got an xforce tnt 350hd box and don't want to hurt it. Just wondering if you can elaborate a bit on this diagram for me? How exactly do you tune it down? There aren't a lot of cb shops up here in Minneapolis and the one I did contact didn't seem too interested in helping me out. Like the original poster, the radio is a 510xl but has been tuned to a 6-7w dead key and has a 19-20w pep swing. I also have a stock 510xl and that radio still dead keys 4-5w which is too much for my liking. Thanks a bunch for any help possible! I really love these little radios.

Edit, I understand the verbage but need pics for this to click.

 

[loosecannon]

just use my instructions and you will be able to lower the deadkey without affecting the swing.

while i agree that 7 watts is a bit much to feed into an amp, your amp is a "HD" amp which means its made for high drive.

i wouldnt set the deadkey any lower than 3 watts.
that way you can actually key on people with your amp instead of just being heard underneath them, which is what a "swing machine" radio does.
LC