| Author |
Message |
    
Ironeagle
New member
Username: Ironeagle
Post Number: 1
Registered: 1-2006
| | Posted on Tuesday, January 24, 2006 - 8:51 pm: | 
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i have a rci 2990 that was working great. then one night i was running 75% power during a transmission and the radio shut down. i opened up the radio and found that the transitor type voltage regulator was smoking. i turned power switch back on for 15 seconds and heard a hum in speaker and popped resistor 112 wich is near the vol reg. i replaced both regulators and resistor. still radio does not fully power and still hear hum in speaker. any suggestions? |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1086
Registered: 9-2004
| | Posted on Tuesday, January 24, 2006 - 10:14 pm: |
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what were the part numbers of the transistors that you replaced? (i mean their name, not what number they are on the PC board)
what were the names of the parts you replaced them with?
matt |
Ironeagle
New member
Username: Ironeagle
Post Number: 3
Registered: 1-2006
| | Posted on Tuesday, January 24, 2006 - 11:24 pm: |
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they where 7808a and b754
i hope this helps
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Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1101
Registered: 9-2004
| | Posted on Saturday, January 28, 2006 - 4:40 pm: |
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iron eagle, try replacing the bridge rectifier in the power supply of that radio.
if you have an external power supply, hook it up to the radio and see if it powers up. if so, you've found your problem.
it doesnt have to be a high current supply. just use one with three amps or more, and dont key the mic if its less than 20 amps.
also, if you can, replace the big filter caps in the power supply with larger value ones.
ex: if they are 4700uf 50v, replace them with 6800uf 50v.
dont use anything less than a 50volt rating.
good luck,
matt |
Pogo12
New member
Username: Pogo12
Post Number: 6
Registered: 3-2005
| | Posted on Saturday, May 27, 2006 - 12:54 am: |
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Changing the 7808 and 2sb754 is not enough.You have to change the (2)2n3771 bi-polar transistors on back( back left side of radio if you are facing the radio).These parts are really undersized amperage wise for running this radio full out.If you run it at about 10 to 15 watts deadkey on AM you will have bettter luck but you first have to change the back transistors. |
