The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Hi all.After some time i brought my early cobra148 gtl-dx down from the loft just to remanice the good old days.The radio was working fine before i put it in a box and up the loft.But now it has developed a problem with the channels they seem to be doubling up.What i mean is every 6 channels it repeats itself.
I dont know where to start so any help would be superb !
Thank's to all in advance.
And thank's for the use of the forum..

Is the display reading wrong? Or is the radio putting out the wrong frequency? If wrong frequency then you need to see what is going on at the PLL program pins (10 to 17). It could be one of three problems the channel switch or the binary adders or PLL chip. Check the program pins on the PLL with a Logic probe or DVM, See atached Truth chart.

Rick

Thank's rick for the reply but my cobra is a mk1 with the pll mb8719.It is reading the correct frequency and the correct channel display..i.e.12=27.555 but then ch6 is also 27.555.
i am getting double frequencys on al 3 bands low mid and hi. on all modes.

Hope this helps a little bit.

thank's again.

I had this with my Lafayette 1200FM. It turned out to be a broken track from the switch to the PLL. Look for cracks in the mainboard, dry joints around the switch/PLL, or where a wire may have broken/come adrift.

Thank's for that info m8.
I will have a look around the pll area tonight.
I shall keep u posted.

Check the N code on the PLL pins, on one of the duplicated channels, and then do the same on the other, if the N code is the same it is a control problem (bad solder joint, cracked trace, broken wire, faulty switch).

If the N codes are different, then the PLL has failed internally, and replacing the PLL would be the only way to fix it.

Thank's scott i will check all the joints on the pll.