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Phantom CB Modifications

CAUTION! The following modifications should be performed by a licensed technician only! We are not responsible for any damages to radio equipment nor any legal ramifications you may or may not suffer by performing these modifications.

The information on this page was gathered from several different sources including the internet and are displayed here for informational purposes only. They are not intended for non-qualified persons to perform and may render your radio illegal to operate under the FCC Rules & Regulations.

If you choose to ignore the information above, at least ensure that any alteration that you do does not breach any laws in your country. If you ignore this too, then you choose to risk the loss of your amatuer licence, a very large fine, confiscation of your equipment, or even imprisonment!

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Cobra Mods
  Radio - Modulation - Power
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 - L7, L6, L5
18 PLUS - CUT D12 - L 7
18 RV - RV501 or CUT D502 - L304, 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
21 GTL - VR5 or CUT D9 - L13, L10, L9, L8
21 LTD - VR5 or CUT D9 - L13, L10, L9, L8
21 LTD CLASSIC - VR4 or CUT D7 - L7, L8
21 PLUS - CUT 1.5K res. next to TR34 - L12, L10
21 X - VR207 or CUT D212 - L212, L214
21 XLR - RT4 or CUT D13 - L15, L12, L11
23 PLUS - RV501 or CUT D502 - L304, L306, L307
25 GTL - VR5 or CUT D9 - L13, L10, L9, L8
25 LTD - VR5 or CUT D9 - L13, L10, L9, L8
25 LTD CLASSIC - VR5 or CUT D9 - L10, L9, L8
25 PLUS - 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
29 XLR - 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 LTD CLASSIC - VR4 or CUT D11 - L14, L13, L12
29 LTD GOLD - VR4 or CUT D11 - L14, L13, L12
29 PLUS - CUT D20 - L12
31 PLUS - CUT D19 - L13, L12, L11
32 XLR - CUT CD11 & CD12 - L5, L3
33 PLUS - VR4 or CUT D17 - L11, L9
39 LTD (S.O.S.) - RV1
40 PLUS - RV104 or CUT D203 - L305, L306
40 X - RV201 or CUT D203 or C215 - L304, L305, L306
41 PLUS - VR4 or CUT D21 - L19, L20, L21
45 XLR - VR105 or CUT D119 - L113, L109
46 XLR - VR105 or CUT D119 - L113, L109
47 XLR - VR105 or CUT D119 - L113, L109
50 XLR - VR5 or CUT D119 - L109
55 XLR - VR5 or CUT D119 - L109
62 XLR - VR3 or REMOVE C67 - L16, L15, L12
63 GTL - VR3 or CUT D11 - L11, L10, L9
66 GTL - VR2 or CUT D4 - L14, L15, L17
66 LTD - CUT R54
67 LTD - RV4 or CUT D212 - L306, L307, L308
77 X - VR207 or CUT D212 - L211, L212, L214
78 X - VR6 or CUT D9 - L11, L12, L15
85 - REMOVE Q17 - L3, T4
86 XLR - 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 - R79 (ssb) R87
132 XLR - R134 or CUT R125 - 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 & D41 - L8, L10 (ssb) VR15
138 XLR - VR7 or 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 prod. model) - VR5 - VR11, (ssb)VR7
148 GTL-DX (late prod. model) - 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


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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 AAUUUDDIIOOOOO 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 (2.7 Ohm) to a .47 Ohm, Retune L305, L306
Cobra 90LTD Cut D203, Change R320 (5.6 Ohm) to a 1 Ohm, Change C335 (100pf-NPO) to a 150pf-NPO, retune L304,L305,L306


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Galaxy Mods
DX 2527 - VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR11...Driver Bias, VR12...SSB ALC, VR13...Hi Power, VR14...AMC, VR15...AM Low Power, VR16...SSB Low Power, VC 1....10.240, VC 2....10.240.
DX 2517- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5....FM Deviation, VR 6....SSB Carrier Balance, VR 7....TX Offset, VR 8....CW Beep Level, VR 9....RF Meter, VR10...Final Bias, VR11...Final Bias, VR12...Driver Bias, VR13...SSB ALC, VR14...AM/FM High Power, VR15...AM Modulation Meter, VR16...AM Modulation, VR17...SSB Power, VR18...AM/FM Low Power, VR601..13.8 Volt Power Supply.
DX 22B- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR11...Driver Bias, VR12...SSB ALC, VR13...High Power, VR14...AMC, VR15...AM Low Power, VR16...SSB Low Power, VR21...TX Offset, VC 1....10.240, VC 2....10.240.
DX 11B- VR 1....AM/FM S-Meter, VR 2....SSB/CW S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR10...Final Bias, VR11...Driver Bias, VR12...SSB ALC, VR13...AM/FM High Power, VR14...AM Modulation, VR16...CW Tone Level, VR20...Final Bias, VR21...TX Offset, VR601..13.8 Volt Power Supply, VR803..AM/FM Low Power.
DX 77HML, DX 88HL, and DX 99V- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR10...Final Bias, VR11...Driver Bias, VR12...SSB ALC, VR13...AM/FM High Power, VR14...AM Modulation, VR16...AM/FM Low Power, VR20...Final Bias, VR21...TX Offset.
Unmarked VR in R189..AM/FM Medium Power for DX 77HML only.
DX 33HML, DX 44V, DX 55V, DX 66V, and DX 73V- VR 1....AM/FM S-Meter, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 8....RF Meter, VR12...Low Power AM Modulation, VR13...AM/FM High Power, VR14...High Power AM Modulation, VR16...AM/FM Low Power.
Unmarked VR in R188..AM/FM Medium Power (DX 33HML only)
Unmarked VR in C139..Med Power AM modulation (DX 33HML only)
DX 949,DX 959- VR 1....AM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM Squelch Range, VR 6.....SSB Carrier Balance, VR 7....TX Offset, VR 9....RF Meter, VR10...Final Bias, VR12...Driver Bias, VR13...SSB ALC, VR14...AM High Power, VR15...AM Modulation Meter, VR16...AM Modulation, VR17...SSB Power, VR18...AM Low Power, VC1....10.240.
DX 2517 and DX 2527-
Symptom:Buzzing or motorboating sound in either the transmit or receive.
Problem: TR602 is oscillating
Cure: Replace C602 with a .01uF cap {Cap is located in the power supply board}.
RG 66,99,DX2517 Replace Q54 2SB754 60watt 7A with a higher power 2SB817 100 Watt 12A. Derating of this component will cool operation, provide better voltage stability,decrease wobble, allow voltage increase to 14.5 volts comfortably. (replace 10 volt caps in this section of the radio to a minimum of 16 volts before increasing supply voltage to this level)and provide faster swing rise time, Replace Q37 2SA473 to a 2SA1012-0 or ECG153 this will improve the clarity and volume of the modulation and it will also run a lot cooler.



Disabling Talkback


DX 33HML
Disconnect wire located in TR30

DX 44V, DX 66V, DX 73V
Disconnect wire located in J15

DX 77HML
Disconnect wire from resistor R244

DX 88HL
Disconnect wire located in R189

DX 99V
(original type echo board) Disconnect wire located in TR35

DX 99V
(smt type echo board) Disconnect wire located in J15 next to R244

DX 11B
Disconnect wire from diode located in R244

DX 22B
Disconnect wire from diode located in R327



Talkback Mod

Talkback can become distorted if these radios have been "peaked," and there is no cure because
the talkback just amplifies what goes to the RF section. Try adding a 470k ohm resistor from junction
of C155/R207 to the junction of C187/R235 on the solder side of the board. This will also give you
clean talkback on SSB and FM. Try different values of resistance to get the amount of volume you want.
The less the resistance the louder the talkback will be.



DX 2517

Symptom:
Talkback squeals when mic gain is at max
Problem:
Excessive drive to IC-8 pin 4
Cure:
Replace R-221 with a 200K ohm resistor


Roger Beep Mods

The tone and time of the roger beep on the 10 Meter mobiles can be changed as follows:
The roger beep tone is controlled by R181 which is 220K ohms:
for a higher tone try 150K to 200K ohms
for a lower tone try 270K to 2M ohms
The roger beep time is controlled by C134 which is 2.2uF@16V DC:
for longer time try 5uF or 10uF@16V DC
for shorter time try 1uF@16V DC



Clarifier Mods
Some people have asked how to make the fine clarifier control track on transmit and receive
like the coarse clarifier control. Below are the mods for our 10 Meter SSB mobile models
(DX 77HML, DX 88HL and DX 99V) as well as the mod for the DX 2517.


10 Meter SSB Mobiles
Remove R141
Remove D38
Solder bridge J106 pin 54 to 8 volts

DX 2517
Remove D68
Remove R113
Add jumper from R113 to 8 volts





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Uniden Mods
Radio  -  Modulation  -  Power
PRO 510,520XL - CUT D14 - Adjust L6,L5,L4 for max RF output
PC66XL - CUT D9 - Adjust L10,L9,L8 for max RF output
PC76XL - CUT D11 - Adjust L17,,L20,L21,L16{Some Models},L14 for max RF output
PC122 - ******** - Adjust VR5 AM Power VR10 SSB Power VR11
GRANT XL & MADISON{UNIDEN 8719PLL} - CUT TR24 or R131 - Tune L37,L38 for max RF output
GRANTDX EXPORT - CUT TR32 - AM Power VR13,SSB Power VR12
ZACHARY T.(2816 pll) - VR6 or cut D16 - Adjust L13,L12,L11 for max RF output
WASHINGTON (858 pll) - VR7 or cut D23 - AM Power VR8, SSB Power CT7, TX Coils L32,L30,L29,L28
WASHINGTON{MB8719} - CUT TR32 - AM Power VR6, SSB Power VR7, VR1 "S"Meter, VR2 Squelch, VR3 TX Freq, VR12 Mod Meter, VR10 TX Power Meter


Uniden Power Mods
 Radio  ---   Try This
WASHINGTON{MB8719} - 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
ZACHARY T(2816 pll) - VR6 or cut D16 - Remove C128 (.47uF). Remove TR16. Replace R132 (1k) with a 470 Ohm. Replace R50 (3.9 Ohm) with a 1 Ohm. Re-tune coils L13,L12,L11 for maximum forward power output. Jumper C61 with a 67pF capacitor. Replace TR10 (2SC2029) with a 2SC1969 then tune L16,L17 and spread L14 For even power across band. Remove D13 and replace with a jumper.
GRANT XL & MADISON{UNIDEN} - CUT TR24 - Change R126 to a 2.2k resistor, Change R124 to a 2.2k resistor, Tune L37,L38 for max RF output
PC76XL - 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 AAUUUDDIIOOOO 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
PC66XL - 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

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