Posted by: Mek
« on: April 16, 2023, 05:13:56 pm »I changed all smd 10n capacitors as I found that C15 was bad.
With SDA3302, the PLL LED indicator lights up after few seconds of tuning, but tuning voltage is still the same - 8.85 V.
With TSA1155, the PLL LED never lights up and tuning voltage is 0 V most of the time, but sometimes around 4 V, no matter the frequency.
In both instances, LED briefly flashes when power is applied. The 24 V lamps on output do not shine so clearly the output is not of correct frequency.
Today I did an experiment:
I lifted one leg of C8 (the one connected to oscillator Q1), and applied FM output from a small cheap FM transmitter there. I also removed Q1 so that there are no oscillations when that oscillator is now unused.
With this setup, it is working. The 24 V lamps on the output shine and I was able to tune the variable capacitor according to the instructions. This circuit takes around 0.8 A from a 12 V lab power supply. So the power part is OK. (Q2 and Q3).
I think I can live with that. I understand that those tiny FM transmitters for personal use were not available back in the days when the web page of this project was written.
So nowadays you can use them as a source of signal to amplify, and get rid of those exotic TSA and PIC chips. Hope it helps someone.
With SDA3302, the PLL LED indicator lights up after few seconds of tuning, but tuning voltage is still the same - 8.85 V.
With TSA1155, the PLL LED never lights up and tuning voltage is 0 V most of the time, but sometimes around 4 V, no matter the frequency.
In both instances, LED briefly flashes when power is applied. The 24 V lamps on output do not shine so clearly the output is not of correct frequency.
Today I did an experiment:
I lifted one leg of C8 (the one connected to oscillator Q1), and applied FM output from a small cheap FM transmitter there. I also removed Q1 so that there are no oscillations when that oscillator is now unused.
With this setup, it is working. The 24 V lamps on the output shine and I was able to tune the variable capacitor according to the instructions. This circuit takes around 0.8 A from a 12 V lab power supply. So the power part is OK. (Q2 and Q3).
I think I can live with that. I understand that those tiny FM transmitters for personal use were not available back in the days when the web page of this project was written.
So nowadays you can use them as a source of signal to amplify, and get rid of those exotic TSA and PIC chips. Hope it helps someone.