general2

Telcom TC9000/Grandstand Gemini/Grandstand Homebase - Crystal filter. Replace the ceramic filter with a 1k filter and remove R85 (330R)
Harvard 400M - Poor RX, Replace 3N201 near trimmer next to o/p trans. A 3SK45 can be used.
Inteceptor - Crystal filter, Fit crystal in place of FT1, replace transformer Rx4 with KASCK3892A. Fit 1k resistor between filter and Rx3 transformer
Sh�gun - LED bar Driver LB1415 can be replaced with LB1405
Icom IBC1050 - Varies its RF gain as you use the squelch. This is caused by a diode which isnt on the circuit diagram. Fortunately its the only diode on the track side of the circuit board so if you dont want this "facility" cut it out.
Has a tendancy to go deaf - because T101 goes open circuit. replace this transformer with a Toko 113CN2K159DZ from "circkit"
Bremi BRL210 Linear - are potentially lethal because the mains earth runs along a 1" by 5" strip of PCB. The PCB often cracks at the supporting bolt and leaves the case un-earthed. Drill the case clean the area and secure a good earth with a solder tag and bolt...
B30 Linears - Low TX can be caused by a poor earth between the case and the PCB.
Bremi BRL31 PSU - 2200uf reservoir capacitors dry out causing low voltage on load.
Quazar CB - Switching transistor (2SC1815) behind mic socket goes short circuit causing low audio hiss on RX with TX light remaining on.
Radiomobile 202 - PLL not locking, replace D2 (6v2 Zener diode) Low audio - replace Q15 (2SA733)
Communicators/Manor Kestral/Planet/Serpent - Stuck on TX. Q22 goes short circuit, replace with a TIS91. No RX and TX, stays on when keyed, check D13 near relay.
LCL/DNT 2740 - Relay dropping out, replace Q11
LCL Economy 40FM / Enterprise - Small resistor in series with voltage supply track to PLL LC7137 pin 18 burns out. Replace with 270R. Mixer coil adjuster could be inadvertantly screwed in causing loss of receive. (coil is towards rear and has small adjuster)
Binatone Speedway - 134AOX board, Low audio, poor sensitivity on RX, low power on TX, replace Q18
Harvard/Alba Handheld - 40 channel handset, No modulation on carrier although carrier itself is ok and the roger bleep can be "just" audiable, locate the diode D20 closest to the hi/lo pwr switch. This diode is under-rated and should be replaced with a 1A type such as a 1N4001.
Harrier CB HQ - 134AOX board, Has only two core mains lead. Replace with 3 core for earthing safety.
Pegasus 7 - Change C184 to 2n2. R155 to 2k2 to improve echo.
Colt 444 and Ham Int. FM Rig - No TX at all. Replace the diode in front of the modulation transformer with a 3A type.
Crystal filter - Remove ceramic filter and the 220 ohm resistor connected to it. No re-tuning necessary.
Murphy CB1500 Homebase - Low power output on TX can be caused by burnt out L7. You can rewind this yourself if necessary with 68 turns of 30SWG enammeled copper wire (The plastic cover can be cut away and discarded).
Grandstand Hawk / Lowe TX40 - Crystal filter, Replace C65 (3pf) with the crystal filter. Re-tune L16 and L17.
Falcon / Compact 40 - T1 can be replaced with a Toko 113KN2K241DC.
DM315E Echo Mic - Using DM432 board. Two un-soldered tags on slider can cause "hum". Solder link them to 0v.
Ham Relax Power Mic - This mic is very bassy on most rigs and can sound muffled. The following modification can be used on other mics too. Remove old mic insert and fit tandy Electret cartridge (270-092B) cushioning it in foam rubber. Connect screen to 0v ground. If a resistor is used between original insert and PCB remove it . Connect the inner core of tandy insert to the PCB via a 10uf tantalium capacitor. Connect the +ve lead from the tandy insert to the battery +ve(VCC) On the ham relax mic remove the top cut capacitor from between the FET and the volume control slider on the component side of the board. Volume control housing can cause "hum" so solder its tags to 0v rail to eliminate it.
Altai Pwr/Echo mic - Echo drops and finally dissapears when battery goes low. Replace battery even though it still works as a power mic.
Sirtel 2002 and 313P Mics - The mic clip screw on the back can be over-tightened to cause a short which results in intermittant speech. Fit a piece of insulating material under screw base.
Realistic Noice Cancelling Mic - The PTT switch can return too far and mute the audio. Build up the inner of the trigger with hot glue or similar.
Fidelity 3000 Homebase - Connect 18k resistor from unused end of RF gain pot to regulated + supply. This will increase the effectiveness of this control.
JWR Mk 2 - To improve squelch replace the 470R resistor besides pin 9 and 10 with a higher value.
Rig lights up but no TX/RX - Try replacing D203 (5.6 Zener diode) No TX can be caused by R327 and/or R127
Fluttering Oscillation - on both TX and RX , replace audio IC (Also ICOM)
On AM version - No Audio and RF carrier output and no modulation on TX is caused normally by the audio IC.
Low RX and TX - can be caused by a faulty Output Transistor especially in Stalker 9 type sets.
Blows Fuse - Check insulating washers and bushes on all heatsink transistors. also. obviously, check protection diode
Jesan KT750 - Emergency CB transciever. Problem. Weak modulation. Link out R25 (18k) and adjust RV1. This set also can have very low power output caused by a bad solder joint C71 (Near output transistor Q13, 2SC2078)
JWR/ICOM - Fluttering oscillation on both TX/RX, replace audio IC.
Did you Know? - The MC145106 PLL chip can run on a supply voltage of upto 9v so on some rigs with this PLL you can increase the supply voltage from 5v to 8.5v to increase the VCO range.
LCL 2740(DNT) - No TX but meter indicates normal operation. On these rigs the meter is driven via diode D15 and pre-set R98 (100ohm) the voltage however is taken from the driver stage and not the output stage as in most other rigs. The fault can lie anywhere between the driver stage and the antenna socket but is usually the output transistor itself.
Communicator NI440DX/Serpant/Planet - No RX or TX but the rig lights up. Replace the 7808 voltage regulator which is Q21 in front of the Audio IC
Rama Echo Chamber - and similar. Not working at all. No LED lighting. RF choke coil in 0v line goes open-circuit. Bridge it with a wire link or replace with a coil from a scrap rig.
RA201 Reverb - Blows fuses. Transistor at the front of the PCB is actually a S.C.R. (Thyristor) Remove this and the echo will work ok or replace it to give over voltage protection again.
Most "Midded" Rigs - After fitting"piggy back" board the UK block wont work. Fit a small value capacitor between pins 19 on the 7132/7137 PLL's
PSU Test - After repairing a PSU connect a 12v car indicator bulb across outputs and check voltage again. On load the voltage may drop which can be a faulty transistor or dried out reservoir capacitors.
Superstar 360/Cobra 148 - No audio on AM but everything else ok, try 2SA1012 on right hand side of board. Also can cause symptoms like a dead output transistor.
Transit 40FM - Stuck on one chanel, up and down doesnt seem to work. Check the solder joints on the back of up/down board, they tend to break away easily.
Antenna Fault - Transmitted audio breaks up especially whan mobile. After checking mic is ok theres a good chance its the antenna coil itself. Check coil and repair if possible, might just need link to coil re-soldering. This often happens to modulator coils, easily damaged in boots.
PT40 / Lowe Etc - Very low modulation. Replace IC5 (BA402) front right of PCB.
Sh�gun FM - No channel display until mic keyed. Replace Q401 (2SD667)
Team TRX 40 - TX but no modulation. Back of mic socket is PCB mounted and the holes in it are far too large. Re-solder the pins in the holes.
Planet 2000 - Received signal dissapears after transmitting. Only a hiss can be heard. Re-tune L8 and L7
Uniden PC40 - This rig has 40 FM and 12 AM channels. If you look at the back of the PCb near the front end you will see a 10 ohm resistor. Disconnecting this will give you the full 40 AM channels but will still be at 1w.
Talk Back - for Superstar360FM/Cobra 148 Disconnect one leg of D80 and insert a switch in series with it.
For Superstar 3600/3900/Excaliber SSB/Galaxy 2100/Texas Star 2100 disconnect one leg of D90 and insert a switch in series with it.
Jesan KT5005 (White) - D11 (Right of output driver) goes open circuit resulting in no TX.
Superstar 120 AM/FM - Stuck on TX. When you press mic PTT you get RX. Replace diode next to relay.
DNT Transit - Type rig. Stuck on channel 9. No TX/RX. PLL IC 5121/01 is blown. Changing 5121/01 for 5121/00 can change rig from UK to Mid and vice versa.. Slight Tuning adjustment may be required.
Uniden Uniace 400 - Shorts when switched on. Change un-marked diode next to JP2 at rear of rig.
Realistic TRC 2005 - Increase mod by linking out R238 next to mod pot. No TX power, Tune RV202 + check L206 (by output transistor) then R204 (Supplies power to Output Transistor).

GENERAL CB REPAIRS 2

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