Vic20 - build new din power supply
Posted: Wed May 17, 2017 12:10 am
Hi
I've recently got a nice Vic-20 bundle off ebay, and currently in the process of restoring it.
I replaced all the caps and powered it up it work first time and appears to operate perfectly
but the power supply is buzzing like a kicked bee hive.
So while I am waiting for sunshine for the retr0bright to be effective (I live in South Wales UK) I thought I would rebuild the power supply.
Its one of the wedge shaped beige models with a Din plug and dual voltages 9v ac and 5v dc,
its also filled with epoxy as usual, hopefully I can remove the block of epoxy so I can reuse the case.
I intend to reuse the small pcb but replace the 5v linear 7805 to a shinny new switching equivalent possibly a Murata 78sr 1.5A,
Obviously replace the capacitor on the pcb, but I am unsure about which transformer to get,
I have found a few PCB mounted type that appear to be suitable, 230v to 2x9v ac 3.2vA.
Is 3.2vA enough headroom as I believe the original is 9v ac 1A, 5v DC 1.5A.
Now my question is can the two 9v ac outputs be used separately or do they need to be combined?
My first thought was to use one 9v side direct and the second 9v side to power the 5v switching regulator,
but I am unsure if that is correct to do it like that.
Or should they be combined to provide one 9v output first before I wire up the outputs if that makes sense.
Basically I'm unsure of the correct electrical theory for this project.
I've recently got a nice Vic-20 bundle off ebay, and currently in the process of restoring it.
I replaced all the caps and powered it up it work first time and appears to operate perfectly
but the power supply is buzzing like a kicked bee hive.
So while I am waiting for sunshine for the retr0bright to be effective (I live in South Wales UK) I thought I would rebuild the power supply.
Its one of the wedge shaped beige models with a Din plug and dual voltages 9v ac and 5v dc,
its also filled with epoxy as usual, hopefully I can remove the block of epoxy so I can reuse the case.
I intend to reuse the small pcb but replace the 5v linear 7805 to a shinny new switching equivalent possibly a Murata 78sr 1.5A,
Obviously replace the capacitor on the pcb, but I am unsure about which transformer to get,
I have found a few PCB mounted type that appear to be suitable, 230v to 2x9v ac 3.2vA.
Is 3.2vA enough headroom as I believe the original is 9v ac 1A, 5v DC 1.5A.
Now my question is can the two 9v ac outputs be used separately or do they need to be combined?
My first thought was to use one 9v side direct and the second 9v side to power the 5v switching regulator,
but I am unsure if that is correct to do it like that.
Or should they be combined to provide one 9v output first before I wire up the outputs if that makes sense.
Basically I'm unsure of the correct electrical theory for this project.