Hi @ Ralph Kimotho,
Here’s a link to the [https://elektrotanya.com/panasonic_sa-dk2.rar/download.html|service manual] for your system.
To download the file, when the sentence below the document preview box changes from ''This file is downloadable free of charge …processing…'' to ''This file is downloadable free of charge: Download,'' click on ''Download,'' as this is the download link. Be patient, it takes a little while to find the file.
As it is a .rar file you need a program such as 7Zip or Win Zip to extract the .pdf files that are in the .rar file.
Once you have the service manual in .pdf format you can use the schematic diagrams contained in the manual’s files to test the voltage rails to make sure that the correct voltage is being supplied on each rail. This is the first step, after that you go on what the results show
''Be safety aware when you do this as there is lethal voltages appearing on the power board.''
If you don’t know what you’re doing you can cause more problems that what you had before you started, not only to the stereo system but also to yourself.
If in any doubt leave it to the experts. Contact an electronics repair service specializing in audio systems and ask for a quote.