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Message |
    
Joesph12
New member
Username: Joesph12
Post Number: 2
Registered: 5-2014
| | Posted on Thursday, May 29, 2014 - 2:35 pm: | 
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Have a cobra 29 ltd classic been laying due to issue.Want to look into it.I got this used.Radio does rx tx.Under the hood looks like no screw drivers been in.
Issue is on RX the channel frequency is way off or so I suspect.I dont have a way to see.I know this-alot of channels are double triple some else where.Not to many channels where they should be.Example-channel 6 is 28 36 2 19 is 1 so on.
Is this a crystal mixer or what be bad or more a serious issue? I have cobra 29 parts can replace if I knew where to narrow to look? However even if replace a part my question is would I have to send radio out to a shop to put on a test aline back.The cost I could buy 2 so radios. The radio does this on tx to on a channel I cant get a reply.I dont think no ones turned any cans in radio I see no mods no dead key ajusted so I been lost radio has sat a year figuard Id learn how to use a forum.Any input help is greatful.Any exact number locations on circuit board and what to replace helps alot. |
Possum_lodge
Junior Member
Username: Possum_lodge
Post Number: 20
Registered: 5-2014
| | Posted on Thursday, May 29, 2014 - 11:44 pm: |
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I think you already answered your own question.
If it costs more to repair then what it is worth, then why bother trying to fix it.
There are just a couple of crystals in your radio, you have a basic fundamental frequency 455 khz, a Intermediate Frequency - IF the two are combined in the mixer stage and the output frequency is produced.
AM is used in CB radio because it is very easy to modulate and demodulate..
http://en.wikipedia.org/wiki/Superheterodyne_receiver
Basically what you are hearing is harmonics of the frequency generated by the radio.
Most likely a filter or a diode is blown.
There was a movie called Tommy Boy where a salesman - Chris Farley traveled around the country trying to sell his dad's brake pads..
His quote is - I can get a good look at a T-bone by sticking my head up a bull's ass, but I'd rather take a butcher's word for it.
Just looking inside of the radio isn't going to solve the problem if you don't know how to read a schematic, have the tools to diagnose the problem and the know how to understand how each component works... |
Holiday
New member
Username: Holiday
Post Number: 1
Registered: 6-2014
| | Posted on Thursday, June 05, 2014 - 7:14 am: |
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Hey possum_lodge. I'm having simular problems. Only I have a frequency counter on it and everything is 10-11Mhz instead of 26-27 MHz what do you think? |
Tech237
Moderator
Username: Tech237
Post Number: 1797
Registered: 4-2004
| | Posted on Friday, June 06, 2014 - 7:53 am: |
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Try flipping switches on the front panel. It sounds like someone expanded it and did a bad job. If this is the case usually they wired the front panel switches to control the banks of channels received.
Holiday - where if the counter connected?? It sounds like it is reading the VFO frequency
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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