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cobra 29 with no rf power
Posted: Monday 16th Apr 2007, 13:14
by NCrebel
i have a cobra 29 ltd-nw that is not putting out any power. i have changed the final and and still nothing. when i key the mic the meter drops to 0 and even on the swr cal setting it wont move. does any one have a clue to what i could do to fix this thing?
Re: cobra 29 with no rf power
Posted: Monday 16th Apr 2007, 21:49
by Rick
This message is in the wrong section.
Is the TX led come on when you key down?
What PLL is in your 29? and what is the PCB number?
Rick.
Posted: Tuesday 17th Apr 2007, 11:28
by NCrebel
yes the tx lights up and it does key up but no power. the # on the board is A068A-8-0. not sure what you mean by pll.
thanks and all the help will be very thankfull
Re: Cobra 29 with no rf power
Posted: Tuesday 17th Apr 2007, 20:54
by Rick
Check the voltage at the collector of the driver and final transistors in TX, also check D422 diode, the PLL should have a number like LC????? or U????.
If you can not do any test it would be best to take it to a radio tech to have the work done.
Rick.
Posted: Thursday 19th Apr 2007, 14:16
by NCrebel
final has 12 volts on center pin till you key the mic for tx and then no power on any pin and the pil is U544T and i can't find D422.it also looks like the copper side of the board is loose at the for right pin of the final.if that is the problem can a jumper be run ?
Posted: Thursday 19th Apr 2007, 15:12
by kc8mob
Fix any loose joint. It should be obvious what use to be where. So if you can tell where it is supposed to go, solder that bad boy.
The final should always have power, all the mic does is remove the front end of the receiver from the circuit when there is RF being generated by the transmitter. Which always has a signal low down in the chain. It just doesn't get the go ahead and then get amplified until you engage it.