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cobra 148 unlock PLL
- Thread starter Robalo
- Start date
just a minute i scratching my head with you last tech note and thinking what to do. i just back from the airport and looking in to the radio and asking to talk to me lol.
Hmm. not sure if I should - anything wrong with it?
Hfe of 75 ? That - looks ok - a 1675 NPN - Hfe of 75 is in the ballpark - LOW but workable...
To be honest, it's used as a Unity gain amplifier - which changes the voltage into a current push...
Oh, oops, that means you WILL have to check...
Hfe of 75 ? That - looks ok - a 1675 NPN - Hfe of 75 is in the ballpark - LOW but workable...
To be honest, it's used as a Unity gain amplifier - which changes the voltage into a current push...
Oh, oops, that means you WILL have to check...
I found this info on line
You need to check the binary code going into the PLL, pins 16 through to pin 10, it is likely that a solder blob is shorting a couple of pins out, causing the PLL to jump to the wrong frequency, or there is some other fault causing an incorrect binary code.
So what you need to do is tell me what the binary code is for every channel, measure the voltage, anything below 1.5V is "0", above that is "1", you should see a distinct voltage difference between a "low" and a "high".
Example:
Ch 1: 1 1 1 1 0 0 1
Ch 2: 0 0 0 0 1 0 1
this is my next step
You need to check the binary code going into the PLL, pins 16 through to pin 10, it is likely that a solder blob is shorting a couple of pins out, causing the PLL to jump to the wrong frequency, or there is some other fault causing an incorrect binary code.
So what you need to do is tell me what the binary code is for every channel, measure the voltage, anything below 1.5V is "0", above that is "1", you should see a distinct voltage difference between a "low" and a "high".
Example:
Ch 1: 1 1 1 1 0 0 1
Ch 2: 0 0 0 0 1 0 1
this is my next step
@Robalo - Here's a Truth chart...
Also check to make sure you do NOT have a bent shaft in the channel selector - you may see you have channels thru the display - but if the cam or detent switch isn't making contact - even the Wafers and their individual wiper arms inside that program this truth chart thru that cable to your PLL chip - if the shaft is bent or "lobs" you may not get the results you want...
Also check to make sure you do NOT have a bent shaft in the channel selector - you may see you have channels thru the display - but if the cam or detent switch isn't making contact - even the Wafers and their individual wiper arms inside that program this truth chart thru that cable to your PLL chip - if the shaft is bent or "lobs" you may not get the results you want...
10 11 12 13 14 15 16
1 1 0 0 1 1 1 1
2 1 0 1 0 0 0 0
3 1 0 1 0 0 0 0
20 1 1 0 0 1 1 1
40 1 1 1 1 0 1 1
It working ok every think mmm
1 1 0 0 1 1 1 1
2 1 0 1 0 0 0 0
3 1 0 1 0 0 0 0
20 1 1 0 0 1 1 1
40 1 1 1 1 0 1 1
It working ok every think mmm
Original with radio?
IT's why I said something earlier about these Channel Selectors...
More than once have these things been dropped only to be quickly replaced back on the shelf like no ones' business. Only to later find the buyer returning them because the segments don't work or the channel knob doesn't turn too well...
Because they were dropped and bent the shaft...
It happens - more than once too...
IT's why I said something earlier about these Channel Selectors...
More than once have these things been dropped only to be quickly replaced back on the shelf like no ones' business. Only to later find the buyer returning them because the segments don't work or the channel knob doesn't turn too well...
Because they were dropped and bent the shaft...
It happens - more than once too...
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