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

Discussion in 'CB Radio Modifications' started by Moleculo, Apr 11, 2009.

  1. Moleculo Administrator Staff Member

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    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/miscellaneous/fet_papers/ekl/graphics/erf2030_cobra_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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  2. wooodchuck Member

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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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  3. NacIK Member

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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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  4. luis luna Member

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    (y)21gtl that is doing 50-55 watts with the irf520
     
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  5. Moleculo Administrator Staff Member

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    It should work fine...this mod is increasing the power output, not messing with audio changes.
     
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  6. narcbob Member

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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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  7. Moleculo Administrator Staff Member

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    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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  8. Dobber Member

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    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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  9. Moleculo Administrator Staff Member

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    Nope, it stays empty. You can skip the other stuff I added to the cbtricks instructions if you like the carrier real low. I don't like the way that sounds, so I like to bring the carrier up a bit.
     
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  10. Dobber Member

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    ok thank you
     
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  11. tnbigshow279 Member

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    erf2030 low watts

    I replaced the stock 2075 in my 25 GTL with a ERF-2030 and the companion part EN-1230, I followed the instructions provided, removed R38, R40, and C45. Made sure EN-1230 was correctly installed with POS. leg towards L12, Added 68pF Cap across C42 and removed it, L-10 slug was already gone. Put the Insulator between the new final and the chasis. I felt unsure about leaving R38 and C45 empty, but I DID!. I am getting 1/2 dead key with swing up to 8 watts. With 50% modulation. I wrote the place I purchased the final, they dont know why. I took it to a CB shop, they just lied to me. What could be wrong? Insulator between final and chasis bad? Bad final? Bad erf-1230? I was wanting to try to run a wire to the left leg on erf-2030 to up my deadkey but not sure if I should just yet. I was getting 120% mod and 4 watt DK to 14 watts with the stock final. Maybe I shoulda left well enough alone.
     
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  12. loosecannon break on through

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    the problem is that the 25GTL and the 25LTD are not exactly the same.

    yes, they are very similar, almost identical, but there are components in one that are not in the other, they used different finals and drivers, and some component values are slightly different in either radio.

    all this adds up to MOSFET mods needing little tweaks here and there to get them to work right.

    MOSFET mods are not as "plug and play" as the kit sellers would have you believe.

    the fact that you are swinging up to 8 watts shows that the final is indeed working, just not as efficiently as it should be.

    you will need to play with some cap values and maybe a few other things.
    each chassis is a bit different and these types of mods require some circuitry knowledge in order to make them work right.

    your best bet is to take it to a good shop and let them tweak it for you.

    just out of curiosity; what did the CB shop you went to tell you?
    LC
     
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  13. sr20gt30r Member

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    Hi guy's, Something I don't understand is the thing to do with the R38 resistor. The antenna output is welded on one leg of the resistor...
    And another thing, I heard that some people remove the c42 cap... ?
     
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  14. nick1boy Member

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    2030 mosfet cobra 25

    i just put the new final in my radio but the dead key is a little low and i was wondering about a dial a watt or variable power but i dont know how to go about it if anyone could give me some help that would be great
     
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  15. PLUMMER Member

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    Just out of curiousity on the coils and turns. Some have 4.5 turns or wraps exactly so from one side you see 4 and the other side you see 5. Then there are the ones with 5.5 wraps exactly and you see 5 & 6. I have a Uniden that has 3.5 wraps/turns, which length should the coil be exactly for this one and the 29's. There is also a mention about adding a 68pf cap to the left leg of the coil and leaving the slug in it for best tuning results. Sorry to ask these oversimplified ???? but which is the left leg depending on how your hold ing the chassis.

    You have to pay attention to which step or cap you did that lowered the dead key. Always a good idea to have a map or printout of the schematic and understand what your doing, plenty of videos for explaining each kind of step pretty good

    If your only getting half the expected power, then the tune is not delivering the other half, it needs to be done properly. If your way off double check the steps 3-5 times, sometimes you just have a bad component, don't reuse old parts to same $ unless your 1000%..
     
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