Grant PC999AB

[bitbang]

Hi,

The PLL appears to be locked according to the voltages.
Check the VCO frequency is as expected on TP3, change the channel and confirm freq changes correctly.
With your freq gen set to 10.695MHz, see if you can inject signal into the IF, if nothing, can try 455KHz on the FM IF to see if there is anything there.

The voltage measurements show only one concern, TR33-7.69/8.09/7.9, this is different from expected and would indicate that the PA switch is on allowing audio from the mike into the main audio amplifier, you already sussed this..

This is the best pictures I have of the switch board, pretty poor quality.

Screenshot from 2024-02-01 21-47-30.png

Screenshot from 2024-02-01 21-58-30.png

Check also D60, D76 and D38 for shorts.

[14CS06]

Hello, does anyone have photos of the PB-005AA board connections??
Thanks

Hello









@+
Claude

[cb4ever104]

There's no point looking at your TX bias issues , or RX issues , until you're sure that your PLL and oscillator stages are working correctly . As bitbang said , "Check the VCO frequency is as expected on TP3, change the channel and confirm freq changes correctly."

So counter on TP3 . Make sure you have the correct frequencies here on all 3 bands (check ch 1 and 40) and modes , and repeat the service manual test on the 10.695 cct . Once you've confirmed that this section is fine , then I'd start with the RF generator on RX and take it from there . The bias issue will probably be an open feed resistor or maybe the diode . Normally an easy fix , but I'd leave the TX till the end .

[indaso2005]

Good morning.
Thank you very much for your help and photos, as soon as I get them I will let you know the results of the tests.
Thank you very much

[indaso2005]

First tests using service mode;
AM-L25MID- 16,488
AM-L22LOW-16.038
USB-L26MID-16,489
USB-L23LOW-16.039
LSB-L27MID-16.350
LSB-L24LOW-16.036

AM channel1-16,268 / channel40-16,709
FM-1 - 16,268 /40- 16,709
USB-1 16,269 / 40-16,709

Thanks

[cb4ever104]

I presume you're using the service manual ? If so , then you'll know that those frequencies are correct (more or less) . That being the case you'll need to continue with the 10.695 section , and then continue with what bitbang said earlier . "With your freq gen set to 10.695MHz, see if you can inject signal into the IF, if nothing, can try 455KHz on the FM IF to see if there is anything there."

[indaso2005]

Goodnight,
When I inject 10.695 MHz, a signal appears.
I don't understand what steps I should take at this stage.

[cb4ever104]

Goodnight,
When I inject 10.695 MHz, a signal appears.
I don't understand what steps I should take at this stage.

Send it to a radio engineer to look at .

S.

[indaso2005]

Goodnight,
When I inject 10.695 MHz, a signal appears.
I don't understand what steps I should take at this stage.

Send it to a radio engineer to look at .

S.

Goodnight
Thanks to all for your help.
I'm not used to repairing CB radios, normally my hobby is tube radios.
For this reason I asked for help.

[indaso2005]

Hello, anyone to help??
Thanks