Page 5 of 6

Re: How to build a creatiVision power supply

Posted: Mon May 01, 2017 6:34 am
by mark-emark
The damage, doesn't look so bad.
front.jpg
back.jpg

Re: How to build a creatiVision power supply

Posted: Mon May 01, 2017 3:10 pm
by Scouter3d
Hi,

I opened up my Creativision MKII (i guess yours is an MKII) an i found, that the internal PSU part is different to an MKI (and so different to the schematic one finds online...)

Using a 3 Wire Transformer (with centertapping) will NOT WORK with a Creativision MKII (not sure about the MKI, as i do not own one anymore...)
as it uses one Wire of the 18V AC as common Ground!!!!!

I made a very crude drawing of the insides of the CVMKII...

Any Electronic Gurus are welcome to comment, as i have no clue, why they built it that way... and if i am right in my opinion/conclusion?????

Greetings, TOM:0)
Creativision_MKII_internal_PSU_small.jpg

Re: How to build a creatiVision power supply

Posted: Fri Jun 17, 2022 4:22 am
by Mamejay
I know this is an old thread but wanted to ask about the multi tapped power supplies
I do not understand how this could have done so much damage to mark-emark computer.
They should be separate voltages.

Re: How to build a creatiVision power supply

Posted: Fri Jun 17, 2022 5:21 am
by Scouter3d
Hi Mamejay,

i am not sure, but the way the centertapped supply was wired to the MKII console the internal PSU design might have allowed all the current to flow thru one of the diodes...

Or "reconnect" the 18V AC to the transformer at the point where only 9V should be?

It might also be really important "where exactly" the wires from the transformer where connected too the plug = if the "polarity" would have been spwapped (as the MKII uses the "lower" brown wire as "Ground" and not the "upper" two wires" as it was shown in the diagram on the previous page) it might have worked?????

Many "IFs" and "MAYBEs" , but here in Austria it is too early in the morning to think straight :0)

Cheers, TOM:0)

Re: How to build a creatiVision power supply

Posted: Sun Mar 19, 2023 6:27 am
by kevgal
Gday guys, I use a dc supply for my Wiz. Its supplies +5 and +12. I could just run it form + 12 if I connected the +12 to to the 7805.
This one has the DC-DC converter in it so I don't need -5.
I have another version that doesn't use the DC-DC converter so I would need to add my own if I wanted to run from a standard DC regulated 12 volt supply (bypassing the 7812).
Attached is the circuit showing the differences.
I winder why they went to the trouble of adding a DC-DC converter in the first place?
Cheers
Kev

Re: How to build a creatiVision power supply

Posted: Sun Mar 19, 2023 7:31 am
by Scouter3d
Hi kevgal,

very interessting!

How did you connect the +5, +12 Supply exactly (external or internal) ? I would guess internal? directly to the 7805 and 7812?

Cheers, TOM:0)

Re: How to build a creatiVision power supply

Posted: Sun Mar 19, 2023 12:37 pm
by kevgal
Connected directly (via power switch) to the output side the 7805 and 7812 regs. via a D25 that also caries AV and joystick connections to my arcade machine. Rewired the power switch so can't use the AC plug any more.

Re: How to build a creatiVision power supply

Posted: Sun Mar 19, 2023 1:11 pm
by Scouter3d
Sounds cool! Cheers, TOM:0)

Re: How to build a creatiVision power supply

Posted: Mon Mar 20, 2023 2:15 am
by kevgal
I'm tempted to add a 7905 reg. to protect the ram since the only thing saving them is a zener diode. If that goes OC it will put around -20 volts on the -5 volt rail!

Re: How to build a creatiVision power supply

Posted: Fri Apr 21, 2023 2:43 am
by kevgal
Here is a photo of another CV using a single regulated 12v supply and a DC-DC +-5 volt converter. Removed RF module, regulators and massive capacitors, changed -5 volt series resistor from 1k to 200 ohms. (also shows the Genesis-CV connector and a simple video buffer)