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Message |
    
Derek460
New member
Username: Derek460
Post Number: 3
Registered: 11-2007
| | Posted on Monday, December 03, 2007 - 11:03 pm: | 
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i have a cobra 29 ltd classic i bought the 1969 final off copper . it just says 20w on the front not 1969 with the mitibishi logo on it but i figured it was just a remake no big deal . this is the first time i have tried this bigger final in a radio , but i have replaced stock ones before out of old radios i have. anyways after i turned it on i worked for like 2 mins then it smoked the R5 resistor . it is banded red red black gold. and the resistor is white in color with a black ceramic insulator on on side that it slides through . i replaced it and now i put my finger on it and after i turn it on in 5 seconds its to hot to touch so i shut it back off , any body have a clue whats wrong and what this resistor does its located directly left of the final . thanks for any postings . |
Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 282
Registered: 9-2004
| | Posted on Tuesday, December 04, 2007 - 12:49 am: |
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Its probably a current limiting resistor for the bias current to the final,the 1969 may be drawing more current than the stock final,the resistor sounds like a wire wound type,try replacing it with one with higher wattage rating, just a thought.
Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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Derek460
New member
Username: Derek460
Post Number: 4
Registered: 11-2007
| | Posted on Tuesday, December 04, 2007 - 6:35 pm: |
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hmm thats probably worth a shot but i still dont get why its getting so hot as soon as i turn it on without even key the mic , im worried if i change that resistor to like a 1 watt resistor wich is pretty big for a cb resistor if the resistor dont smoke will it fry my foil trace in my board.. ive messed with the bias alittle on my cobra 2000 using the test points but never on a mobile is that necesary to us this bigger final . |
Derek460
New member
Username: Derek460
Post Number: 5
Registered: 11-2007
| | Posted on Wednesday, December 05, 2007 - 9:07 pm: |
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ok ive did some more looking at my radio and the resistor thats blew and now is getting hot and wants to smoke is R56 (not R5) Its located directly left of final im hoping it did not blow the final too i have no clue on the bias of the radio frankly i dont no what bais even means ive read more about the mods on this website and it says to change some of the resistors and cap's i looked at the radio and they are fairly close to the final so maybe i need to change them for this final to work but ive heard you can just drop it in and it should work , should i have changed the stock final to a bigger one to , any help is very much appreaciated . thanks Derek aka CopenHagen |
Unit199
Advanced Member
Username: Unit199
Post Number: 570
Registered: 8-2003
| | Posted on Thursday, December 06, 2007 - 2:16 am: |
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When I did this mod to my 29, I changed the driver transistor to a 1957 and that was all I did and it works fine.
HARVE
UNIT199
CEF210
CVC#18
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Derek460
New member
Username: Derek460
Post Number: 6
Registered: 11-2007
| | Posted on Friday, December 07, 2007 - 8:21 pm: |
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ok ive put my original final back in and the radio works fine no problems , so i wonder why im having all this problems, i would really like to see for myself if i could gain anything from the bigger final , ( i know it has been argued by allot of people that the small amount you gain cant be seen on the other end, but i think it would help in driving kickers and ive heard its a more durable part), HMM i might just have to leave good enough allone even though i dont want to . |
Unit199
Advanced Member
Username: Unit199
Post Number: 571
Registered: 8-2003
| | Posted on Saturday, December 08, 2007 - 3:34 am: |
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They are right about what you gain is not worth the trouble. There is not enough difference to make it worth-while and it will not make any difference in driving in driving an amp. There are a lot of mods for radios out there that is not worth the effort of messing with. I have found out over the years, that the majority of them do not work like they are susposed to and are not worth the effort of doing them.
HARVE
UNIT199
CEF210
CVC#18
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Kzhorse
New member
Username: Kzhorse
Post Number: 2
Registered: 7-2008
| | Posted on Saturday, August 16, 2008 - 5:19 pm: |
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what is the original final in the radio?Have you looked up the specs to find out what is the emiter,base and collector? Is it a NPN or PNP transistor?You might have to criss cross the legs to get it right.
Just a thought,Scott |
Derek460
Junior Member
Username: Derek460
Post Number: 25
Registered: 11-2007
| | Posted on Sunday, August 17, 2008 - 10:34 pm: |
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ill have to do some checking on that kzhorse , ill get that info and post back. in a day or two.
CEF# 961 Local Handle CopenHagen
Getting down like charlie brown
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Allagator
Advanced Member
Username: Allagator
Post Number: 803
Registered: 9-2002
| | Posted on Tuesday, June 01, 2010 - 5:23 pm: |
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Kzhorse is rite if it is wrong it will feed back and burn other stuff up ! but when you criss cross the legs move up on the frame of the radio drill a new hole and remount it up higher from the bored then insulate the wires so nother will touch and you should be almost ready to go ! but ive seen this mod done in a 29 and it worked ok but not as good as some other mods !
Happy playing !
Allagator CEF115
KC9OKX |
