Use cash to pay down accounts payable account equation?

I'm not exactly sure what you are asking, the journal entry for a cash payment to pay down an account payable is as follows:

Account Payable (debit) $$$$

Cash (credit) $$$$

Paying down an account payable is paying partial, so take for example you owe $1500 for a computer you purchased on account and you wish to pay $500 towards the balance. The Journal Entry would be.

Account Payable (debit) $500

Cash (credit) $500