Hi,
I couldn’t find a free schematic online but found [https://support.halabtech.com/index.php?a=downloads&b=file&id=497054&__cf_chl_jschl_tk__=pmd_c5514a9054b1a8a6e34ab1c3a5b7fde0dad24dba-1628835537-0-gqNtZGzNAjijcnBszQhO|this] which may be of interest.
The downside is that you have to create an account to download it, which I didn’t want to do, so I don’t know whether it is any good.