| Author |
Message |
    
Kid_vicious
Member
Username: Kid_vicious
Post Number: 57
Registered: 9-2004
| | Posted on Tuesday, December 07, 2004 - 6:20 pm: | 
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so this is the second cobra 139xlr i have seen that has big black marks around R153. this resistor sits right behind a 2SC1419 regulator. after having read that these are junk, i knew why the resistor had blown. the problem i am having now is that i dont have a schematic for this radio so i dont know the value of this resistor. its kinda hard to read through the charcoal! LOL
i imagine that some of you techs have seen this problem a million times and could tell me the resistor value from memory. i think it is a 1 watt resistor and it is covered with teflon if this helps. (its like they knew the IC was junk and tried to remedy the problem with a piece of teflon.) in my madison both are connected to a big heat sink upside down. havent looked at R153 in that radio yet.
BTW, i did the mic circuit changes to the madison. (D21 and D22 and the resistor changes.) my findings were that the mod works great, but if you're running a power mic; then dont exceed 33K on R78. squeal city! (some mods suggest going to 56K for this value) coppers mod list is correct. thanks in advance for any help.
I LOVE OLD RADIOS!!!
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Doublemm
Junior Member
Username: Doublemm
Post Number: 21
Registered: 5-2002
| | Posted on Thursday, December 09, 2004 - 7:19 am: |
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send me a email i got the info you want. |
Kid_vicious
Member
Username: Kid_vicious
Post Number: 73
Registered: 9-2004
| | Posted on Saturday, December 11, 2004 - 8:39 pm: |
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doublemm, just chacking to see if you got my email. thanks again.
matt |
Kid_vicious
Intermediate Member
Username: Kid_vicious
Post Number: 111
Registered: 9-2004
| | Posted on Wednesday, January 05, 2005 - 10:02 pm: |
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just for the sake of anyone who runs across this thread, the value of R153 is 47 ohms at 1/2 watt. if this resistor is black, replace it. and replace ALL of the 2sc1419's with nte 152's.
matt |
Viking
Intermediate Member
Username: Viking
Post Number: 185
Registered: 2-2002
| | Posted on Thursday, January 06, 2005 - 10:58 am: |
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Thanks for the update Matt. |
