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President Lincoln replace the Final Power transistor | Radioaficion Ham Radio

President Lincoln replace the Final Power transistor


HR2510 / President Lincoln replace the Final Power transistor

The idea of this modification is to replace the Final Power transistor, Using Motorola MRF455 - Doing this gives you some advantages.

• Higher output,- about 40-50W SSB

• A way to replace the 'hard to get' original MRF477

HR2510 / President Lincoln replace the Final Power transistor

MRF477 and MRF455 is quite different!!!

- MRF477 vs. MRF455 Pinout -

These 'pinout' images illustrates the problem using the MRF455 transistor in replacement of the original MRF477,- You need to mount the MRF455 Transistor to the heat-sink and make connections to the pcb using tree short 'hookup' wires. Se also the illustration below.

HR2510 / President Lincoln replace the Final Power transistor

MRF455 Hookup wires and HR2510 Main-PCB connections

HR2510 / President Lincoln replace the Final Power transistor

HR2510 Heatsink with Final Transistor MRF455 Mounted

The above image shows the HR2510 Heatsink with the MRF455 and hookup wires mounted on it,- I de-assembled the Heatsink to be able to drill the screew-holes to me able to mount the MRF455 transistor,- Se also the drill-diagram below.

HR2510 / President Lincoln replace the Final Power transistor

This mode also require that you replace the Pre-driver Transistor Q134, NOTE! the NTE340 use a different pin-out, simply turn the transistor 180dgr when putting it in place.

Both transistors use the TO92 Case, But the NTE340 is named 'TO92 Giant' because it is a bit longer on the top.

Comparative Transistor data Transistor Type Descriprion

NTE340 Si-NPN RF-Power/Tr, 86V, 500mA PQ=0,6W

2SC2086 Si-NPN RF-Power/Tr, 75V, 1A, PQ=0,45W(27Mhz)


Output power mod for the Uniden HR2510 & HR2600

Uniden's HR2510 & HR2600 10 Meter Amateur radio's are nice for single band operation, but a little more output power is desirable for portable use.


M.T. Stacey KC4HGH in Septembers issue of 73 Amateur Radio (1989) Published his findings on power modifications to the HR2510.

The modifications that follow are based on his works with some additions:


The factory has the HR2510 & HR2600 output power levels set for continuous duty. I.E. AM,FM & CW 10 Watts, SSB - 20/25 Watts. The radio is capable of much more output power for intermittent operation like SSB.




Relocate capacitors to bottom of Board. (This is to allow spreading of the tuned/trap output coils.



Replace Pre-driver Tx (2SC2086D) w/ ECG-340 (Note pinout change) 2510/2600's w/ the 2SC197 3 device require no pinout change.



Replace output Transistor Q133 the MRF477 w/ MRF455 use short hookup vires as described above



Replace Bias current limiting resistor from 82 ohms to 68 ohms 1/2 watt device.



Pull bias jumper board out of the circuit. Place a current meter (100ma) between pins

TP2 and TP4



Adjust Final bias for 80-85 MA, USB position. No Modulation.



Fire radio up with power meter and 100W dummy load attached. Adjust ALC for Maximum. 1Khz tone is helpful.



Mode to AM/FM

Spread coils for maximum.



AM/FM power adjustment, 20 Watts is easily obtained. I think 25/30 may be pushing it in this Mode. (Melt Down.) Adjust controls for your desired levels.



My experience in increased output levels are as follows: "SSB Mode."

HR2510 = 32 Watts RMS (1Khz Tone) / 45.2 Watts PEP HR2600 = 37 Watts RMS (1Khz Tone) / 52.3 Watts PEP

The above measurements are made with Bird 43 into a 50 ohm load.

Download MRF455 datasheet from Motorola RF POWER TRANSISTOR NPN SILICON

President Lincoln
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