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Here is a good set of power/audio mods for the Cobra 148GTL. I couldn't find these in the search, so I reposted it.

Also applies to:
Cobra 148GTLF
Cobra 2000GTL
Undien Grant XL
Uniden Grant LT

1. Carrier Adjustment: VR10. If lower carrier is desired, change R196 near VR-10. Try about 270 ohms.
2. Change R114 to a 10K, and C46 to a .2 monolithic, this will widen up the audio on AM.
3. The AMC is TR-26. You can remove it, and still have good results on AM, the ALC for SSB is not effected by this. If you don't want the AMC disabled, leave it. the other way to disable the AMC is cut R131. Check both to restore AMC from previous mods.

4. If extra frequencies have been added, perform the following to widen up the band pass filters to recover lost power at the highest and lowest frequencies: C163 - 4pf, C41 - 3pf

5. R180 - Jumper it. This brings up the gain of the TX mixer.

6. IC TDA6130 - Pin 12 to ground through 100 ohm resistor. Upper left, pin 14 = ground.

7. Remove the AM regulator, (usually a 2SC1419) and replace it with a 2N6487.

8. C174 - remove, add 1000uf electrolytic. connect POS to base of yellow wire next to it. If the yellow wire is too far away, it might be easier to connect the POS leg to the leg of the AM regulator closes to the back of the chassis via the bottom of the radio.

9. For 148F, change C18 to a 1000uf electrolytic, 16V

im surprised that those mods couldnt be found around here through searching, but then again, i have had many troubles with the way the search feature works on this forum.

i just have a couple of things i believe should be changed on the list.
these are just my findings, and should not be taken as gospel.
(unless you pray to the almighty loosecannon. then, go ahead LOL)


i will address #4 last.


5. the purpose in jumpering this resistor is to keep the bias from going negative.
(these are justin depolis's words, not mine)

6. this is the mod that increases the gain of the transmit mixer.
also, you might want to include the older chip that is used here: the S042P.

7. might want to mention the part number here. its TR41.


8. probably some different wire colors used in different chassis. maybe add that the negative lead of the cap goes in the negative hole left open by the removal of C174, and that the positive lead of the cap goes to the base of TR41. (lead closest to the rear of the radio)

9. dont know why this would only apply to the 148F.
this cap is in the mic circuit. the stock cap wasnt rated for enough voltage and would fail. increasing the value of this cap will help keep the mic from squealing when audio gain in the radio is increased.


now, for #4.

C163 can be increased to 4 or 5 pF, but increasing the value of C41 actually makes the tuning of L6 too narrow.
the effect will be that L6 will peak over a very narrow range causing the gain to fall off quicker towards the band edges than it did with the stock 2pF cap there.

a better mod is to leave C41 as a 2pF cap and solder a 1pF cap from the emitter of TR14 to the lead of C41 that connects to L5.

now, i must say here that these are my own findings, and i have never heard anyone else's opinion on this mod. i do know that this is what i observed personally.

just trying to help clarify things,
LC

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