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Message |
    
Pancake
Member
Username: Pancake
Post Number: 52
Registered: 3-2002
| | Posted on Saturday, July 30, 2011 - 12:43 pm: | 
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ok i just bought a cobra 29ltd classic (china)from a yard sale for a price that seemed too good to be true but i had high hopes that the person selling didnt know what the value of the radio was...
i get home and i want to test it ...i hooked it up to my car battery booster pack just for a quick test
after having the radio powered up for a while i get a smell of hot metal..NOT GOOD so i unhook everything and i go dig out my power supply before hooking it to the power supply i could feel the radio was still warm so i took the covers off to look for what was getting hot and why and found the area of the transformers was hot and also (if the radio is upside down with knobs towards you)the left rear corner where the aluminum heatsink divider is was hot i will try to include pics of 2 things that seemed wrong to me 1.) in the TR23 spot a 3 legged "chip" that it seems to me would normally be attached to the inside of the radio chassis is freestanding toward the center of the board and appears to be hot glued in place and it is defiantely a different glue than the factory uses [IMG]http://i37.photobucket.com/albums/e80/chevyssuck92/cb%20radio/IMGP2203.jpg[/IMG] and 2.)in spot L16 in the rear corner inside the headsink divider there is no "screw" in the center of this component but the other 2 components like this have one [IMG]http://i37.photobucket.com/albums/e80/chevyssuck92/cb%20radio/IMGP2196.jpg[/IMG]
when i hook it back up with the power supply now it powers up for maybe 4 seconds the radio will transmit but the needle wont move now and then it shuts off the power supply whether i am trying to transmit or if the radio is only turned on idle
DID I BURN SOMETHING BY POWERING THE RADIO WITH THE BATTERY PACK AND IS THERE ANY HOPE TO FIX IT ?? |
Tech833
Moderator
Username: Tech833
Post Number: 2012
Registered: 8-2002
| | Posted on Monday, August 01, 2011 - 2:08 am: |
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Yes, you probably did.
Those "battery booster" sets usually put out somewhere in the neighborhood of 17 to 20 volts. They are designed to give a quick burst of charge energy to a car battery. In the instructions for those, they mention turning off the radio, lights, etc. in the car for exactly this reason.
Never, ever hook car radios to a battery booster.
Your radio 'Mythbuster' since 1998
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Pancake
Member
Username: Pancake
Post Number: 53
Registered: 3-2002
| | Posted on Monday, August 01, 2011 - 12:38 pm: |
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Is there any component. That comes to mind that could be bad. The radio does power up. For 3-4 seconds and then. The power supply shuts off |
Billk44xx
New member
Username: Billk44xx
Post Number: 4
Registered: 7-2011
| | Posted on Monday, August 01, 2011 - 2:19 pm: |
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sounds like the regulator chip is bad..but thats just a guess |
Tech833
Moderator
Username: Tech833
Post Number: 2013
Registered: 8-2002
| | Posted on Thursday, August 04, 2011 - 10:05 am: |
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ANY of the ICs could be the problem.
Your radio 'Mythbuster' since 1998
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Pancake
Member
Username: Pancake
Post Number: 54
Registered: 3-2002
| | Posted on Friday, August 05, 2011 - 6:37 pm: |
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thanks guys so it sounds to me like i should chalk this one up to stupid mistakes call it a loss and keep it for the parts |
Lester_elm
Member
Username: Lester_elm
Post Number: 68
Registered: 12-2007
| | Posted on Thursday, August 11, 2011 - 3:30 am: |
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I would check the rf driver and rf output transistors. They may have an internal short. Check to see if any parts are getting warm/hot to the touch. It is definitely something shorted out to cause the power supply to shut down (over-current protection). Since it stays on for a few seconds, it may be an electrolytic capacitor failure.
CEF #964 HAM #276
Let's play radio!
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