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President Lincoln Radio - Mods and Fixes

aka Uniden HR2510 - Similar to HR2600, 2830 and others. This info has been compiled from various sources. I have not tested every mod on this page so Use these mods at your own risk. I am not liable for any damage to yourself or your equipment by following anything from my website. Read the disclaimer

My info will always be FREE. But if this helps you, please consider a donation to help keep the site going.

Replacement Output Transistors

Despite the fact that these outputs have gone out of production years ago, and despite most radio repair shops telling you for years that they cannot be bought anymore, there are MRF455 and MRF477 transistors on ebay at this moment (17/12/2010). They are quite expensive, but its well worth it to keep your radio going! However, if you cannot locate the original transistors then you should not worry, there are replacement transistors that will work.

UPDATE: There are a lot of cheap fake MRF455 and MRF477 transistors on ebay, so be aware... look at the item location, if it says Hong Kong or China then they MAY be fakes. Fake transistors will work (kind of) but you will find they will be a bugger to align and they will most likely be down on power as compared to originals.

MRF455 can be directly replaced with an SD1446. No other mods needed, Output Power should be about the same as original.

MRF477 can be directly replaced with a 2SC1945. You need to not put back the pair of capacitors off the transistor from the solder side of the board as they are now not needed... Output power will be limited to about 18-20 watts but the radio will work perfectly

The MRF477 can also be replaced with a 2SC1969, But it cannot be directly swapped... the legs need swapping around and it needs to be isolated from the heatsink. I do not recommend this, as the Output Power gained by using the 1969 instead of the 1945 is only about 2-3 watts in real world terms, so you might as well use a 2SC1945 as its a direct replacement.

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.

These mods are pretty simple, but if done wrong can damage your radio. Only attempt these mods if you are confident about what you are doing. Pictures of these mods can be found in most search engines.

Receive Mods

The receive on this radio can be described as constrained to say the least. There are loads of mods listed on the web to increase receive gain and make the radio less constricted, some good, some bad and some indifferent. The few mods that I will list here have been done to my own radio and have definately improved things.

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 or want to modify your radio.

R25 Transistor

Alternative for 2SC2999: 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 use, 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.

UPDATE: After using the radio for a while with the 2SC3356, I will be replacing the 2SC1674 (standard transistor). The 2SC3356 works ok and certainly better than the 2SC2999, but readable signals aren't breaking the squelch and thats a pain. The 2SC3356 may well have better specs over the 2SC1674 on paper, and maybe it shows higher gain when tested, But in real world tests with the transistor in the radio I have to say that the original 2SC1674 is the best. Before modding try fitting a new 1674 first, you may be surprised!

Swap C412 (on FM board) 47n for 10n: opens FM de-emphasis bandwidth giving a much cleaner and brighter tone to all FM signals, making weaker stations easier to hear. This is 100% recommended, a must if you use FM a lot.

Swap C35 0.039 for 0.022uf: For more treble on recieve audio. Makes radio sound less constricted.
Swap C36 0.0068 for 0.1uf: For more bass on recieve audio. Makes radio sound less constricted.

There are many more recieve mods on the web. These mods will make your radio sound a heck of a lot better and you may not need or want to do any other mods after these.

S Meter Mods

Replacing C302 on the processor board with a 0.1uf capacitor will make the internal meter more responsive. To add a external needle type meter, connect it to C302.

Beep Mods

The Lincoln beep is very distinctive.

Changing c72 and c74 from .0047 to .01 will reduce the beeps frequency making it sound 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 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 cuttoff point

If you find that the squelch "chatters" at the cutoff point, and your signal meter sits at around S5 on an empty channel, Replace the front end transistor Q101 (2SC1674) as it has gone bad.

TX Audio Mods

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

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