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CB Radio History from its early days
CB Radio Repairers in the UK
Telecom TC9000/Grandstand Gemini/Grandstand Homebase crystal filter.
Replace the ceramic filter with a 1k filter and remove R85 (330R)

Harvard 400M - poor RX, replace 3N201near trimmer next to O/P transistor. A 3SK45 can be used.

Interceptor - crystal filter. fit crystal in place of FT-1. Replace transformer RX4 with KACSK3892A. Fit 1K resistor between filter and
RX3 transformer.

Shogun - LED bar driver LB1415 can be replaced by LB1405.

Icom ICB1050 - Varies its RF gain as you use the squelch . This is due , helpfully, to a diode that is not shown on the circuit diagram!
Luckily it is the only diode on the track side of the circuit board. Just cut it out if you don't want this 'facility'.
Has a tendancy to go 'deaf' because T101 goes open circuit. Replace this transformer with a TOKO 113CN2K159DZ from 'Circkit'.

Bremi BRL210 - Linears are potentially 'LETHAL' because the mains earth goes to a 1" wide by 5" long stip of PCB. The PCB cracks
at the supporting bolt and leaves the case unearthed. Drill the case, scrape away the paint by the hole and fix on a good solder tag
and bolt. Don't leave this to chance, do it and stay safe!

B30 Linears - Low TX can be caused by a poor earth between the case and PCB.

Bremi BRS31 PSU - 2200uf capacitors can 'dry out' causing low voltage output 'on-load'

Quasar CB - Switching transistor (2SC1815) behind the 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 Kestrel/Planet/Serpent - Stuck on TX, Q22 goes short circuit, replace with TIS91
No RX and TX stays on when mic keyed, check D13 near relay

LCL/DNT 2740 - Relay dropping out, replace Q11.

LCL Economy 40FM - Small resistor in series with voltage supply track to LC7137 pin 18 burns out, replace with a 270R. Mixer coil
adjuster can apparently screw itself in causing loss of receive. This coil is towards the back and has a small adjuster.

Binatone Speedway - Low audio, poor sensitivity on RX and low power on TX - replace Q18.

Harvard/Alba 40ch Handhelds - No audio on TX although otherwise the carrier is perfect and the roger bleep can just be heard.
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
1N4001

Harrier CBX HQ - Has only 2 core mains cable. Replace this with a 3 core cable and fix a secure earth for safety.

Pegasus 7 - Change C184 to 2n2. R155 to 2K2 to improve echo.

Colt 444/Ham International FM - No TX at all. Locate and replace the black diode which is in front of the modulation transformer
with a 3A type - Crystal filter, remove the ceramic filter and the 220 Ohm resistor connected to it. Fit a 1K5 resistor and crystal filter
instead. No retuning is necessary.

Murphy CBH 1500 Home Base - Low power on T/X can be caused by a burnt out L7 (27uH). You can rewind this yourself if
necessary with 68 turns of 30SWG enamelled copper wire. The plastic cover can be cut away and discarded.

Grandstand Hawk/Lowe TX40 - Replace C65 (3pF) with a crystal filter. Retune L16 and K17.

Falcon/Compact 40 - T1 can be replaced with a TOKO 113KN2K241DC.


DM315 Microphone - using DM432 board, two unsoldered tags on slide may cause hum. Solder them to 0V.
Ham Relax Hand Power Mic - The mic is normally very 'bassy' and sounds muffled on
most radios. The following mod can be used on other battery powered microphones too.
Remove the original mic insert and fit a Tandy electret insert (270 092B) cushioning it in
foam rubber. Connect the screen to 0V ground. If a resistor is used between the original
insert and the PCB remove it. Connect the inner core of the Tandy insert via a 10uf
tantalium capacitor. Connect the +ve lead from the Tandy insert to battery +ve (VCC) on
the Ham Relax mic. Remove the top cut capacitor from between the F.E.T. and the
volume control slider on the component side of the board - The volume control housing
can cause hum, Solder the volume control slider tags to the -ve rail to eliminate hum.
Alti Power Echo Mic - The echo dissapears when the 9v battery voltage runs low.  

Sirtel 2002/313P microphones - The mic clip screw on the back can be over-tightened to cause a short which results in intermittent
speech. Fit a 'sticky fixer'under the screw base.

Realistic Noise Cancelling Mic - The switch can return too far and mute the audio. Build up the inner case or the trigger with hot
glue.

Cybernet 134 - Change C109 (10uf next to Q14) to 1uf to speed up the squelch option. - Adding 3K3 in series with the squelch pot
will keep out signals under '1' S point on the meter which are normally too noisy to hear anyway. - Add a BC108 or BC238 as shown
below...
Don't check to see if your soldering iron is hot by putting it on your tounge. It affects the taste of your tea... not good

Fidelity CB 3000 Homebase - Connect 18k resistor from unused end of RF gain control to regulated +ve supply. This
increases/improves the effectiveness of this control.

Uniden - Conversion to 'Mid and UK' block.
Connect the TC9106 on top of the TC9119 piggy back style but leave pins 3,4,5,6 and 7 free.
Cut track to pins 4 and 5 of TC9119.
Link TR17 collector to junction of D6 and R33.
Connect pin 5 of TC9106 to bottom of your new bandswitch.
Connect pin 5 of TC9119 to the top of the new switch.
Connect track previously disconnected from pin 5 to the middle of the new switch
Change C62 to 18pf
Solder 33pf cap across C64
Tune VCO and output coils for level operation across both bands.

Midland Port A Pack - The LED driver is TL489 CP (IC2)
No TX power, try replacing R147 which is the resistor supplying power to the output transistor.
Uniden Uniace 400 (PR27GB) - Shorts out fuse in power cable when switched on, the protection diode is OK. Change unmarked
diode next to JP2 at the rear of the radio.
Very low RX, check filter
No modulation, replace 4558D (IC4)

Amstrad 900/901- Broadband VCO 27uf to 33uf (located rear of VCO can)
Bad RX, check/replace T9 can which can be damaged by someone using long threaded thumb screws.

Cybernet Chassis - Very bad RX, try T10. No TX at all, try 501 (Q2) and/or 724 (Q1) at the rear of the radio.
Rotel 220/230 - Mid block fitting requires a positive display fitting as the standard ones are negative. You can use the channel display
from a scrap Midland 2001 type radio to keep it the original colour and the associated wires to the channel selector board need
swapping over to change it from - to +.

Communicator/Planet - No TX at all and only just receiving, try Q22 (A719) and also check the relay.

Binatone Route 66 - PLL IC can be PLL02A or LC7136 depending on the board configuration.

Jesan Pro 800 - PLL IC is an MC145106P

Realistic TRC 2005 (PR27GB) - Increase modulation by linking out R238 which is located next to the modulation pot.
No TX power, tune RV202 plus check L206 which is locatedby the output transistor then R204 which supplies power to the output
transistor.

Stalker 4 - No TX and low mod, similar to blown output transistor. Try replacing diode D10.

Cybernet 134 VCO can - This can be replaced with a VCO can from an Amstrad/Mustang type board.

Cybernet Channel 9 Switch to 19 conversion. On the Cybernet 134AOX circuit boards where the radio has a channel 9 priority
switch you can adapt this so it goes to channel 19 instead of channel 9. This adaption also includes how to wire the display so it
correctly displays Ch19 as well. Please click on the link to go to the page.

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Cybernet 134AOX - 3 different squelch adaptions, please click on
the link to the right to go to the squelch adaption page
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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. Swapping over the TC9106 PLL
chip for a TC9119 PLL will put the radio on the UK27/81 band.

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).




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