HR2510 Misc. Enhancements.
Increasing the Receive Audio I
The HR2510 does not have a by-passed emmiter in the audio circuit. To correct this, Add a 4.7uf 16v Electrolytic capacitor across (in Parallel) with R152 (a 560 ohm resistor). This modification will increase the receive audio.
Board location diagram or
Component location diagram
Increasing the Receive Audio II
This mod will increase the AM reception: Replace the AM Detector diodes (D111 & D112) with better Schottky Barrier diodes. You can use ECG 583 or NTE 583 diodes or 1N6263 or equilvalent. (In the HR2600 the diodes are labelled D11 & D12).
Increasing the Receive Audio III
This mod will increase receive strength and dynamic range, resulting in louder, cleaner signals while actually reducing noise levels. All you need to do is to replace the existing IF Amp transistor with a new one which has greater frequency response and lower noise characteristics. Once installed you will need to adjust your “S” meter for more realistic readings.
1.) Remove diode D101(see note 2) and remove Transistor Q101, Q1 in the HR2600.
2.) Replace Q101 with a ECG or NTE 23(see note 1), Q1 in the HR2600.
Q location diagram for 2510/2600/HTX-100
Note 1: The new transistor has a different pin out from the original. You will need to reorient the new transistor to work. With the flat side of the transistor facing you and leads pointing down : Existing leads of Q101 = 1 2 3 , the replacement ECG or NTE, you will need to cross the first lead to the last = 2 3 1 .
Note 2: 'D101 removal' Comment from J. Shorney(and others) "this diode provides AGC control to the front end, and would seem to leave the radio more susceptible to front end overload if removed." The suggestion would be to leave D101 intact.
Mute circuit improvement
To Improve the operation of the Mute circuit, remove C137 and R199. These two components are connected to the base of Q117.
Roger Beep Mods
The Roger Beep in the HR2510 is ‘Unique’ but kind of wimpy..To modify this, locate R96 (a 2.7 Meg. ohm resistor) Remove and replace with a 100K ohm 1/8 watt resistor. This will increase the amplitude of the beep.
To change the duration (length) of the beep, replace C110 (10uf 16v ) remove and replace with a capacitor at least 50v with more or less capacitance to lengthen or shorten the beep to your preference.
These components are located to the left (facing the front of the radio) of IC 104.
Component location diagram
Adding an external meter to the HR2510
To add a needle type meter all you need to do is connect
it to C302 on the Microprocessor.
Cure for High SWR with covers off
Usually this problem is caused by the fact that Uniden did not install an insulator between the MRF477 Final and the heatsink.
The mounting tab of the MRF477 (and MRF497) is 'Power' Ground and the heatsink is 'Chassi' Ground.
Meeting through the final can cause a 'RF ground loop effect' which tends to cause the High SWR issue.
The cure is to add an insulator between the Final and heatsink. Be sure to add a thin coat of Thermal Grease to both sides of the insulator.
Fix for the 'Weird Dead Key' Problem(thanks to YaesuTom)
If your 2510 or Lincoln mysteriously goes into transmit all by itself , or when first turned on, Locate the 2 disc capacitors connected in parallel
on the bottom of the main board that are connected across the output final, unsolder one leg (disconnecting the caps from the circuit) that should fix the
'Weird Dead Key' problem. These caps are the 38MHz pull off for the final, and have been known to cause this issue.
NOTE: The final stays powered even with the radio turned off, and this could cause problems if your radio is prone to the 'Weird Dead Key' problem.
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More information to be added soon so come back often.