This version allows Parallel/Series Transformer configuration
and uses an adjustable LM317 Voltage Regulator.
Potentiometer Trimmer P1 adjusts the voltage.
The top of R1 220 Ohm resistor is exposed and a Voltmeter connection from there
(positive lead) to ground will allow measuring/adjusting the voltage.
Also, there is no actual connections to the transformer without jumpers.
It can be configured as Parallel or Series according to the jumpers.
Nice project, but its a dangerous project with the live AC voltage (110-230V) on your PCB. The isolation is not sufficient (in fact there is no isolation). I would never use live voltage on a PCB if not needed. An external AC to DC power adapter would be a safer choice here (and most of the time cheaper than the transformer alone). Also I am wondering if the heatsink is capable enough of dissipation the heat. A class AB amp will be hot. I would have positioned the TDA with its back to the edge of the PCB, then you can mount a proper heatsink.
Also a bit of a odd place for the power switch. Why not put in on the mains side otherwise you will have your transformer powered even when it’s switched off.
As poster above said, it’s far safer to remove the mains from the PCB.
Admittedly, I am a self taught incompetent when it comes to electrical/electronics design. That said, it is my opinion that this project, as posted here, has the potential to cause harm or even loss of life if it is attempted by someone who downloads the files and does not understand the dangers of mains voltages. Particularly as it appears that the design and the PCB layout have not been built and verified.
Thank you all for your advice. Some reply comments are now deprecated since most recent update.
I took into consideration all of the various suggestions to validate this project.
I isolated the input mains with proper USA lead coding: Black is ‘Live’ White is Neutral.
I added a standard 5x20mm fuse block for safety.
I placed a DPST power switch on the input to the transformer.
I added a SPDT switch to the external power connection so that it
disconnects from the power supply if external power is applied.
The reverse biased 1N4001 diode is to protect against external power
wrong polarity.
I increased the size of the TO-220 Heat Sinks and placed both the
LM317 Regulator and TDA2003 Amp IC on the edge of the board to allow
mounting both to a metal chassis to add heat dissipation.
I increased the size of the polarized power capacitors to represent
50V 1000uF Electrolytics.
I also replaced the 9mm volume potentiometer with a 16mm one.
The LM317 Voltage Regulator P1 Trimmer Potentiometer is clearly marked
to indicate Voltage Adjustment and there is a ‘V+ Test Point’
reference text next to Resistor R1 (place voltage test lead on top of it).
I uploaded the PentaLogix Viewmate Gerber File: TDA2003AMP_VMATEGBR.zip
to JLCPCB and did a ‘DFM Test’ (Design for Manufacture).
Everything was acceptable. Because I added Top and Bottom Ground Copper Pour Layers
JLCPCB DFM defines these as SMD/VIA connects and displays a harmless warning.
Est.: $8 USD/5 Printed Circuit Boards + Shipping, Fees, Tax = about $15.
