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40-45 watt ERF2030 mod for Cobra 25/Uniden 66/68

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  #1  
Old 04-10-2009, 10:00 PM
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Default 40-45 watt ERF2030 mod for Cobra 25/Uniden 66/68


I thought I'd post up a few extra details on the ERF-2030 mod for the Cobra 25/Uniden 66/68 since I haven't seen them floating around anywhere.

First, follow the instructions on CBTricks here: http://www.cbtricks.com/miscellaneou...bra_25_mod.pdf

Instead of removing R38 replace it with a 10K 1 watt. You can use higher values like 15K+ if you want.

If you don't want to make this mod reversable, instead of just removing he tuning slug from L10, take a turn off the coil and keep the slug to fine tune the output. Remember, you have to scrape the coating away from the coil wire to resolder.

If you're planning on using this radio with a linear that needs a low output, you will now have about a 2 watt carrier with about 40+ watts peak output.

Personally, I don't like the way a radio sounds with that little amount of carrier to peak ratio, so I like to bring up the carrier. Here's how you do it on this radio:

-Change C46 to a 390pf cap
-On the solder side of the board, run a small wire from the positive side of C114 with a 4.7K resistor inline toward the gate of the ERF2030. If you're looking at the face of the ERF2030, it's the left leg.

Now do a TX align on the radio.

This will bring the carrier up to about 5-6 watts. Total peak output will be usually be around 40-45 watts.

Personally, I still prefer doing these radios with the 2SC1969 final and 2SC2314 driver. It yields a little more power and I like the way it sounds a little better. You can combine parts of the two mods together if you want.

I think the 25LTDs are great little AM radios. They're a really good size for a mobile, are capable of a lot of power and you can use all the mods on them that are available on the larger 29 chassis if you're willing to take the time to cross reference the schematic.


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Old 08-01-2009, 02:02 PM
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I've done 2 cobra 25s with the irf 520s and could only get 25-28 watts peak. Is there anything I could do to bring the watts up some more or do I just deal with what I have and be glad it's not 15-18?

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Old 10-13-2009, 10:30 AM
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How well will this mod work with a sound processor? I am thinking about doing this mod to a 25 wx nw st that already has a DSP board installed in it. Also, I have been told that the 1969 can be installed in a 25 without installing anything else, just the final. Thanks.

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Old 10-13-2009, 08:59 PM
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21gtl that is doing 50-55 watts with the irf520

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Old 10-14-2009, 04:54 PM
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Quote:
Originally Posted by NacIK View Post
How well will this mod work with a sound processor? I am thinking about doing this mod to a 25 wx nw st that already has a DSP board installed in it. Also, I have been told that the 1969 can be installed in a 25 without installing anything else, just the final. Thanks.
It should work fine...this mod is increasing the power output, not messing with audio changes.

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Old 01-24-2010, 05:29 PM
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i have a 5 watt carrier and a peak of roughly 17 -19 watts. is that is not pep but just wattage. does that sound about right for the en1230/erf2030 mod?

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Old 01-24-2010, 10:56 PM
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Quote:
Originally Posted by narcbob View Post
i have a 5 watt carrier and a peak of roughly 17 -19 watts. is that is not pep but just wattage. does that sound about right for the en1230/erf2030 mod?
I don't know what you mean by, "is that is not pep but just wattage.". That power output seems pretty low to me, unless you're measuring AVG power instead of peak.

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Old 01-30-2010, 11:51 PM
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Default c45

hello moleculo. i have a question about the 40 watt mod for the cobra25 if you have the time to answer.the insturctions say to remove r38,r40,c45,but they dont say if you put any thing back for c45 or do you just leave it empty.. thanks for your time ..Dobber

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