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PET power transformer.

P

prime

Experienced Member
Joined
Sep 20, 2009
Messages
153
Location
Coventry, UK
Hi all,

I have one of the Universal PET boards with the 6845 video controller, that I'd like to power up. I have tested the board in my PET 3008 and it seems to work without problems. However I only have one PET case :(

So does anyone have the specs of the mains transformer please, or advice on powering the board independently of a PET case?

I guess I could disconnect the onboard PSU and feed in +5, +12 and -12 at appropriate points but that would then remove the ability to power it up inside the PET case should I choose to do so.

Cheers.

Phill.
 
prime said:
Hi all,

I have one of the Universal PET boards with the 6845 video controller, that I'd like to power up. I have tested the board in my PET 3008 and it seems to work without problems. However I only have one PET case :(

So does anyone have the specs of the mains transformer please, or advice on powering the board independently of a PET case?

I guess I could disconnect the onboard PSU and feed in +5, +12 and -12 at appropriate points but that would then remove the ability to power it up inside the PET case should I choose to do so.

Cheers.

Phill.
Click to expand...

PET motherboard (excluding the original 2001 with static RAM) need: 8-0-8 Vac (center tapped it means), this is rectified on the mainboard to obtain the 5V and the -5V rail, 16 Vac that gets rectified and regulated to 12V, then a separate 16 Vac secondary that goes inside the monitor that gets rectified and regulated on the monitor's PCB.
The original 2001 had only the 8-0-8 Vac input and a single 16 Vac secondary that went to the monitor PCB.
HTH
Frank IZ8DWF
 
daver2 said:
Don’t forget that the large smoothing capacitor is also external to the PET mainboard.

Dave
Click to expand...

Correct, I think he should know this, as he used another PET "PSU" to power-on the board.

Frank
 
One thing that has been niggling me is I was always under the impression that a universal board with the CRTC chip did not work correctly in a 2001N (3008-3032) setup and vice versa.

The video would be inverted (and shifted, especially when using the 2001N in a fat-40). The transformer schematics in my link above also show different power outputs from the transformer to power a 9inch or 12inch monitor (not relevant here I guess).

To remind myself I did a little searching and re-found this link ....which could be useful if the Op wants to power and use the board from the bench with a different monitor

http://www.vcfed.org/forum/showthread.php?45170-Composite-picture-from-a-CRTC-PET
 
Last edited:
>>> Correct, I think he should know this, as he used another PET "PSU" to power-on the board.

There is a little more to the interconnection of the capacitor than that though (if I remember correctly).

If you follow the interconnection on the transformer schematic from post #2, I don't think it works (as there is nothing feeding the positive side of the capacitor - and hence the +5V regulators.

Dave
 
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