Stalker 4 - No TX. low modulation (Similar to blown o/p) Replace diode D10. Realistic TRC2005 - Delay in TX can be minimised by draining out some wax from the VCO block and slightly re-tuning VCO. Increase modulation by linking out R238 (Next to Mod. Horseshoe) Kernow Beta 2100 - To increase mod. link out R59. Hy-Gain 3 - Switchable bleep. Switch one leg of C6 on PTZZ053AOX relay board. Colt 444/Tristar 727 - No TX like blown o/p. Replace diode D16 located by mod. transformer. Murphy Homebase - Make compatable to cybernet wiring by moving wires on back of mic socket one place clockwise, looking from the rear of socket. DNT M40 - Hardly any RX and o/p transistor Hot. Replace o/p transistor. DNT CONTACT 40 - No TX can be caused by large thumbscrew damaging TX can (320 5796) President Lincoln - New legal type. Add 11m Band by soldering wire between top leg of resistor near TP307 and top leg of D312. Alan 78 Plus - Completely dead. Power reaching PCB. Check track where on/off volume switch goes to board. There is a thin strip of track there which burns out when cross connected. Intermittent TX - Maybe also drifting power. May be disc capacitor encased with wax in VCO housing having dry joint. This is hard to find unless wax is removed first. Ham International Jumbo - Mains Hum noticeable on FM and SSB garbling. Check the mains transformer. The original may have been removed and an "un-shielded" one fitted. The original ones windings are encased with a steel shell. Off frequency - Wont adjust via little trimmers. Replace them with red ones from scrap CB's or new ones. This can also affect the KC shift causing radio to stop transmitting when KC fully clockwise. If it wont trim bang on frequency try a different crystal. Crystals used - LL = 9.8275MHz, L = 9.940MHz, M = 10.0525MHz, H = 10.165MHz, HH = 10.2775MHz (Same as Multimode 2) Nato 2000 - Straight 40 UK is opened to LL/L/M/H/UK on AM/FM/SSB by changing over the two "IC's" on the seperate board. Swap them back to return it to its "Legal" setup REALISTIC TRC2002 - Transmitting without mic. TR17 transistor JWR M2 / ICOM ICB-1050 -10 Meter adaption CLICK HERE RANGER RCI-2950 - Channel buttons seem confused, SHF button and up/dwn scan mixed up - other odd faults - The tactile switches behind the push buttons become worn and lose their 'click'. These need replacing and all will return to normal. Tactile switches available from Rapid Electronics, order code 78-1120 (7p ea) Change display colour - The bulbs on the display can easily be replaced by 5mm high intensity LED's. Make sure you wire them the correct way round as they are diodes. These will last much longer than bulbs and are available in Blue/Red/Yellow/Green. Silence the bleep - These radios bleep whenever anything is changed which may annoy some people. On the back of the front panel you will see a little black bleeper with two wires coming off it. Cut the black wire to 'disable' this function. CIRCUIT BOARD LAYOUTS REFERENCING VR ADJUSTMENTS (SILVER HORSESHOE) BOARD LAYOUT FOR 134AOX CYBERNET BOARD LAYOUT FOR AMSTRAD / HARVARD BOARD LAYOUT FOR AUDIOLINE BOARD LAYOUT FOR MAXCOM 4E / 21E PTBM121D4X DISCUSSION/REPAIR AND BOARD LAYOUT NEW TRANSISTOR COMPAIRABLE REPLACEMENTS HERE NEW MURPHY CBH 1500 HOMEBASE PAGE HERE (UNDER CONSTRUCTION) COBRA 148GTL-DX PAGE HERE (UNDER CONSTRUCTION) HAM INTERNATIONAL JUMBO PAGE HERE (COMING SOON) BREMI BRL-210 .pdf SADELTA ECHO MASTER PLUS .pdf Thats all for now but REMEMBER... Most older CB's have been around since 1981 or earlier and will quite likely suffer from Dry joints caused by dirty component legs, corrosion or incorrect consistancy of solder used in the flow solder process. Many faults can be caused by this so its wise to gently brush along the back of the circuit board with a finger noting where any difference is noticed and re-soldering joints in that area. (Careful with mains homebases though) If your struggling and cant find the cause of the fault... sit back or go and make a cup of tea.... And try again later. A refreshed approach is often adventagious. New components are getting very hard to source now so never throw away any scrap CB's. Either save them, or donate them to your local rig doctor who will appreciate the Gesture or send them to me :o) e-mail [email protected] |
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| GENERAL CB REPAIRS 3 |
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