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Uniden pc122xl no tx or rx
- Thread starter Caveman67
- Start date
Not a heck of a lot to go on. Could be a dead PLL. Could be corrosive glue ate one or both leads off the 10.240MHz crystal. Possibly the 8 volt regulator fried. Or maybe just a bad cap somewhere.
Not trying to be a jerk, that just comes naturally, but the more detail you can provide the easier it will be for the site members to offer suggestions on where to start looking.
Not trying to be a jerk, that just comes naturally, but the more detail you can provide the easier it will be for the site members to offer suggestions on where to start looking.
Hi
Just looking for a few hints as to where i should start i found one bad cap but that didnt fix it i dont know how to fault find all i know there is no tx no rx checked mic seems ok channel display comes on no tx light when i key up
I have Very limited electronic experience
Thanks joe
Just looking for a few hints as to where i should start i found one bad cap but that didnt fix it i dont know how to fault find all i know there is no tx no rx checked mic seems ok channel display comes on no tx light when i key up
I have Very limited electronic experience
Thanks joe
Does the S-meter move at all when connecting to an antenna and checking out the different channels? This is with RF Gain all the way to the right.
If there's some activity on the S-meter then it is likely to be receiving.
The reason your tx lamp is not lighting up could because you're using a microphone that's not correctly wired for the radio. That could also explain "no sound"..
Just guessing and starting by the most simple reason.
You can find the schematic here: https://cbtricks.org/radios/uniden/pc_122xl/graphics/uniden_pc122xl_sch.pdf
Some really basic checks.
Is the 8 Volt regulator working? IC4 pin 1 should be at 8 Volts as long as power is applied. It's a L7808 three pin regulator.
Is the 10.240MHz reference signal working? Should be on pins 12 and 13 on IC2, which is the PLL. It's a uPD2824 22 pin DIP IC.
Either one of these could cause the symptom you're seeing. Or like 19wrc333 said, an incorrectly wired mic could do it.
The single most-basic first check is to listen for a faint "pop" from the speaker as the power is turned on. If you hear that, turn it on, the volume up full, the ANL off, and turn the squelch knob end-to-end. Should be a softer "pop" as the squelch opens and closes.
And if if flunks those tests, the stuff listed above would be next.
73
And if if flunks those tests, the stuff listed above would be next.
73
I dont know if this accurate but google ai is telling me:
IC2 (uPD2824 PLL) pin 16 is the power supply pin and should be 5v dc. This is supplied via IC5. If its missing its 5v then IC5 could be blown.
IC2 (uPD2824 PLL) pin 15 is the lock pin, if PLL is not locked it will be low (0-0.3v dc) and will not TX, if PLL is locked it will show 4.5-5v dc
IC2 (uPD2824 PLL) pin 16 is the power supply pin and should be 5v dc. This is supplied via IC5. If its missing its 5v then IC5 could be blown.
IC2 (uPD2824 PLL) pin 15 is the lock pin, if PLL is not locked it will be low (0-0.3v dc) and will not TX, if PLL is locked it will show 4.5-5v dc
Attachments
Hi
Checked voltage at ic4 and have 13.5 at one pin and 8 volts at the other also i have no way of checking frequency at the pll do i need a scope for this measurement also no popping when radio is powered up no volume with squelch down at max volume its like its not switching between pa and radio but i checked the switch and it seem to be switching when i did a continuity test at the solder connection i replaced two 1000uf 25v caps next to power supply one was faulty maybe other caps need replacing radio didnt die whilst transmitting i put radio into moth balls and the next time i turned it on nothing
Thank joe
Checked voltage at ic4 and have 13.5 at one pin and 8 volts at the other also i have no way of checking frequency at the pll do i need a scope for this measurement also no popping when radio is powered up no volume with squelch down at max volume its like its not switching between pa and radio but i checked the switch and it seem to be switching when i did a continuity test at the solder connection i replaced two 1000uf 25v caps next to power supply one was faulty maybe other caps need replacing radio didnt die whilst transmitting i put radio into moth balls and the next time i turned it on nothing
Thank joe
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