| Cobra Mods Radio Modulation Power HH-70 RV-4 7 PLUS VR4 or CUT D8 L11, L12, L13 10 PLUS VR4 or CUT D8 L11, L12, L13 18 LTD CUT D13 or CUT R84 304, L305, L306 19 CUT D11 L5, L8, L9 19 GTL VR6 or CUT D9 L15, L16, L17 19 LTD VR6 or CUT D9 L15, L16, L17 19 LTD CLASSIC VR4 or CUT D7 L7, L8 19 M REMOVE C73 L8, L5, L3 19 PLUS RV501 or CUT C511 L305, L306 19 PLUS(Plastic Case) RV4 or CUT D8 L11, L12, L13 19 XS CUT D105 20 B&K CUT CD20 & CD21 T11, T10, C60 20 LTD CUT D13 20 PLUS RV501 or CUT C511 L305, L306 20 PLUS(Plastic Case) RV4 or CUT D8 L11, L12, L13 21 REMOVE C105 & C106 T11, T10, C60 21A(Old) CUT D24 L9, L8 21GTL VR5 or CUT D9 L13, L10, L9, L8 21LTD VR5 or CUT D9 L13, L10, L9, L8 21LTDCLASSIC VR4 or CUT D7 L7, L8 21PLUS CUT 1.5K res. next to TR34 L12, L10 21X VR207 or CUT D212 L212, L214 21XLR RT4 or CUT D13 L15, L12, L11 23PLUS RV501 or CUT D502 L304, L306, L307 25GTL VR5 or CUT D9 L13, L10, L9, L8 25LTD VR5 or CUT D9 L13, L10, L9, L8 25LTD CLASSIC VR5 or CUT D9 L10, L9, L8 25PLUS CUT 1.5K res. next to TR34 L12, L10 26 CUT D24 L7, L8 28 A CUT CD28 & CD29 T12, L2, L5 29 A (OLD) CUT D24 L7, L8 29XLR VR5 or CUT D14 L15, L12, L11 29 GTL VR4 or CUT D11 L14,L13, L12 29 LTD VR4 or CUT D11 L14, L13, L12 29 LTDCLASSIC VR4 or CUT D11 L14, L13, L12 29 LTD VR4 or CUT D11 L14, L13, L12 29 PLUS CUT D20 L12 31PLUS CUT D19 L13, L12, L11 32XLR CUT CD11 & CD12 L5, L3 3PLUS VR4 or CUT D17 L11, L9 39 LTD (S.O.S.) RV1 40PLUS RV104 or CUT D203 L305, L306 40X RV201 or CUT D203 or C215 L304, L305, L306 41PLUS VR4 or CUT D21 L19, L20, L21 45XLR VR105 or CUT D119 L113, L109 46XLR VR105 or CUT D119 L113, L109 47XLR VR105 or CUT D11 L113, L109 50XLR VR5 or CUT D119 L109 55XLR VR5 or CUT D119 L109 62XLR VR3 or REMOVE C67 L16, L15, L12 63GTL VR3 or CUT D11 L11, L10, L9 66GTL VR2 or CUT D4 L14, L15, L17 66LTD CUT R54 67LTD RV4 or CUT D212 L306, L307, L308 77X VR207 or CUT D212 L211, L212, L214 78X VR6 or CUT D9 L11, L12, L15 85 REMOVE Q17 L3, T4 86XLR CUT CD9 L3 CAM 89 ADD 1K res. in series with C110 L13, L12, L9 87 GTL VR6 or CUT D16 L17, L16, L13 89 GTL VR6 or CUT D16 L17, L16, L13 89 XLR VR5 or CUT D14 L15, L12, L11 90 LTD VR201 or CUT D203 L304, L305, L306 93LTD WX VR-3 L16, L17, L18 132 (OLD) CUT Q25 T14, T15, L3, C116, (ssb) R136 132 A CUT CD39 & CD40 L3, (ssb)R130 134 CUT D40 & D41 L8, L10 (ssb)VR15 135(OLD) CUT Q25 T14, T15, L3, C116 (ssb)R136 135 XLR R134 or CUT R125 L3, (ssb)R130 138 A (OLD) CUT D40 & D4 L8, L10 (ssb) VR15 138 XLR VR7 VR6 VR8, (ssb)CT7 139 VR12 or CUT D63 L12, L10, (ssb)VR15 139 XLR VR7 VR6 VR8, (ssb)CT7 140 GTL CUT R104 VR6, (ssb)VR7 142 GTL CUT R104 VR6, (ssb)VR7 146 GTL VR5 or CUT TR29 VR10, (ssb)VR6 148 GTL CUT R131 VR10, (ssb)VR11 148 GTL-DX(early) VR5 VR11, (ssb)VR7 148 GTL-DX (late ) REMOVE VR14 or CUT TR32 VR13, (ssb)VR12 148 GTL-B VR14 RV15, (ssb)RV13 148 GTL-DX(copy ver.) RV12 RV11, (ssb)RV6,RV3 1000 GTL VR6 or CUT D16 L17, L16, L13, (ssb) 2000 GTL CUT R131 VR10 (ssb)VR11 GTL 150 RV14 RV13, (ssb)RV12,RV4 Cobra Power Mods 2000 GTL,2010 CUT TR24 Change R126 to a 2.2k resistor Change R124 to a 4.7k resistor Tune L47,L48,L46,L45,L38 for max RF output AM Carrier Power VR10 Mod Meter VR7 AM Signal meter VR1 142GTL CUT TR32 Change R99 to a 2.2k resistor Change R94 to a 2.2k resistor Adjust L36,L37 for max RF output AM Power VR6 SSB Power VR7 VR1 "S"Meter VR2 Squelch VR3 TX Freq VR12 Mod Meter VR10 TX Power Meter 148GTL+F CUT TR24 Change R126 to a 2.2k resistor Change R124 to a 2.2k resistor Tune L37,L38 for max RF output 29GTL/LTD/CLASSIC CUT D11 Adjust L17,,L20,L21,L16{Some Models},L14 for max RF output Modification: Change stock final to a 2SC1969 Change stock driver to a 2SC1957,{some model use a 2SC2028 rf driver}Remove it Change R123 to a 0.47 ohm resistor Change R58 to a 2.7 ohm resistor Put a jumper across D8{by audio transformer} Change C71 to a 33uf 16volt polarized electrolytic capacitor Put a 47pf disc cap across C57 Put a 47pf disc cap across R55 For a higher dead key place a 100pf disc cap across C62{by rf driver} Key radio and say HEEELLLOOOOOO while adjusting L17,L20,L121,L16,L14 Some models dead key 8-10 watts swing 40-50PEP VR1 rx gain VR2 rx signal meter VR3 squelch VR4 AMC VR5 tx power meter VR6 antenna warning light 25GTL/LTD/CLASSIC CUT D9 Change R76 to a 1k resistor Change R43 to a 2.7 ohm resistor Change R108 to a .47 ohm resistor Adjust L10,L9,L8 for max RF output Modification: Change stock final to a 2SC1969 Put a jumper across the D10 diode that connects from VR5 to audio transformer{pc trace side} Adjust L10,L9,L8 again Change C91 to a 33uf 16volt polarized electrolytic capacitor Cobra 18RV, 23 Plus Change R505 (3.3k) to a 1k, Change R310 (2.7Ohm) to a .47Ohm, Retune L305, L306 Receive Boost Cobra 29 1. Locate pin 14 of the PLL chip, and the Positive (+) side of C-12. 2. Install a 22k-220k ohm resistor between these two points. The smaller the value, the more the receive is boosted. 3. If desired, this mod may be wired through a switch. How to make Cobra 29LTD,Classics slide on TX & RX 1)Remove D-18 , R-110 , C131 and R-112. 2)Put jumper were R-110 was. 3)Take orange wire from delta tune and unsolder it from board then resolder it to Tr-23 (Solder to the pin closest to front of board. It should have around 8 VDC on this pin.) 4)Put radio back together and if all is done right you should slide transmit 5-6 KCs up and down. For more slide change D-16 to a 1N-4007 Cobra 2000 No Audio on AM Transmit with good Carrier The Fix: This problem is more common in the "older" 2000's but is relatively easy to fix. Look for the collector of TR-23, you should read about 4.5 V with a dead key. If you find that this voltage is not present, check on the opposite side of R-120 for 6.5V. Most likely this voltage will not be present; if this is the case, C18 has shorted and needs replaced. This is a 330uf, 10V electrolytic capacitor beside L31. To prevent "future" problems, replace with a 16V. |
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