| Author |
Message |
    
Bbmfic
Junior Member
Username: Bbmfic
Post Number: 17
Registered: 1-2003
| | Posted on Saturday, May 29, 2004 - 6:22 pm: | 
|
i would like to know if there is a NPC-RC mod for the 142 GTL Cobra Thank You |
Hootyal
Intermediate Member
Username: Hootyal
Post Number: 118
Registered: 9-2002
| | Posted on Sunday, May 30, 2004 - 7:36 am: |
|
This is what I did to my Washington...work's great!!!
President Washington/McKinley, Cobra 140/142,
Realistic TRC450/490,
Tram D80/D300, Midland 79-900, etc. (MB8719 single
final, single
conversion) transmitter modification instructions
including NPC
and final to linear in all modes mods.
1. Remove TR32
2. Jumper out R123.
3. Add a 10 uF 25 or higher volt electrolytic cap to
the following
spots: Attach the positive leg to pin 9 of IC4,
and attach the
negative leg to the junction of R121/D62/R204.
4. Set the driver bias to 50 mA.
5. Set the final bias to 100 mA.
6. Solder the end of the final bias wire that is
furthest from
the final transistor to the cathode (banded) end of
D60.
7. Set the dead-key power to 1.5 watts using VR6.
8. Tune the RF amp chain coils (L36 and L26 through
L29) for
maximum peak (modulated) output power.
9. Double check the dead-key power. If it's higher
than 2
watts, use VR6 to set it to 1.5 to 2 watts.
|
Bbmfic
Junior Member
Username: Bbmfic
Post Number: 18
Registered: 1-2003
| | Posted on Sunday, May 30, 2004 - 10:25 am: |
|
thank you very much ill try it out in a few days & let u know how it worked out thanks again BBMFIC |
Funtimebob
Intermediate Member
Username: Funtimebob
Post Number: 137
Registered: 5-2002
| | Posted on Friday, July 16, 2004 - 11:18 pm: |
|
" Solder the end of the final bias wire that is
furthest from the final transistor to the cathode (banded) end of D60."
Thats a little vague for me  what color is the wire? I dont have the schematic to follow what your describing. I understand that your talking about the end of the wire at the opposite end from the final but have no idea which wire it would be ( i have a 490 but dont have it in front of me at the moment |
Tech548
Moderator
Username: Tech548
Post Number: 138
Registered: 5-2004
| | Posted on Saturday, July 17, 2004 - 2:20 am: |
|
Funtimebob
I don't have a 142 or schematic in front of me either but what the instructions are refering to is the two long pins that stand up vertically in front of the large transformer that is mounted on the right side of the PC board.
Unsolder the wire (color unimportant) that is furthest from the final and resolder it to D-60 (protection diode), OR, you can just run it to a constant 13-14 volt source.
Basicly, all you're doing here is feeding the final with a constant power supply voltage. And speaking of that, personally, I ALWAYS set my power supplies (whether they be internal or external) at exactly 14 volts. Heck, most car batteries are running 14 + volts also.
I hope this may have cleared up any misunderstanding.
Jeff
Tech545 |
