President Lincoln Radio Mods & Fixes

Frequency Mods:

As standard this radio covers 28.000MHz to 29.699MHz (or in some models 29.999MHz). There are 3 (known) different ways to expand (or "wideband") the radio down to 26.000MHz. I will list all 3 as I am led to believe that not all mods work on all radios. You must decide which is right for your radio.

Mod 1: The most simple mod is to solder a jump wire from the cathode of D312 to R389, however, this will not work on all radios.

Mod 2: Cut the ground trace connected to pins 34 & 35 on IC315, jump pins 34 & 35 to the free end of Resistor pack RR301.

Mod 3: Connect pins 34 & 35 of IC315 together.

There are many sites on the web with pics showing how to do these mods, so I won't bother putting pics here. (unless you really want them..)

Receive Mods:

Swap Q101 - 2SC1674 for 2SC2999 : Improved signal to noise ratio, weak stations that were in the noise can now be heard. Signal meter used to sit at 5 on an empty channel but now is at 0. Also squelch used to "chatter" at the point of cutoff, but now works fine. The only downside to this mod that I have noticed is that the signal meter becomes less accurate. UPDATE: I got annoyed with the signal meter not reading right and readable signals not getting through the squelch, so decided to put the transistor back to the original 2SC1674.

With a new 2SC1674 I got all the benefits and nearly as good S/N ratio as with the 2SC2999 (obviously the original 2SC1674 was worn out), the signal meter came back right and the squelch let the weaker readable signals through. I have since found out (thanks to James) that there are a load of fake 2SC2999's on the market. So, Before modding your radio I suggest you try fitting a new 1674 first, as this has given me good results and you may not need to mod.

Alternative for 2SC2999 in the mod above : As there are a lot of fake 2SC2999 transistors on the market and it is not easy to tell a fake transistor unless you got a load of hi-tech kit, I wanted to find a suitable replacement which would work well in this situation. On one of the Forums I go on, it was suggested to use an (NEC) 2SC3356 in the place of Q101 (2SC1674). The 3356 transistor is a tiny surface mount device but it can be fitted to the solder side of the Lincoln board as per pic on the right. The blue line being a link wire.

I have fitted one of these to my Lincoln and it seems to work ok. Try to get a 2SC3356 with the suffix R25/S (the transistor is marked R25) instead of R23 or R24 as the R25 has higher gain.

S-Meter Mods:

To add a external needle type meter all you need to do is connect it to C302 on the processor board.

SWR Meter Mods:

The internal SWR meter in the radio tends to read a little low, making you think you have a good SWR when you have not.

To improve this, replace R552 - 150ohm with 220ohm and R69 - 1k with 3.9k. This will make the meter a little more accurate.

Beep Mods:

The Lincoln beep is very distinctive. Changing c72 and c74 from .0047 to .01 will reduce the beeps frequency making it sound more like a George bleep.

To make the beep louder locate R96 - 2.7 Meg and replace with a 100k

To change the length of the beep, replace C110 - 10uf 16v with a cap at least 50v with more capacitance to lengthen or less capacitance to shorten the beep.

Increased AM Mic Gain:

Add a 1k resistor between the emitter of Q114 and the circuit board. (Q114 is located near the front of the circuit board in the center to the left of IC 104) This mod will increase the AM modulation while still allowing the ALC to work. Another Mod Suggests removing D129 to remove the ALC and AM limiting, but this is NOT recommended!

Squelch Chatter at cutoff:

TX Audio Mod:

Swap C57 - 0.068 with 0.1 to increase bass on outgoing modulation

Swap C58 - 0.0047 with 0.0022 or remove C58 to increase treble