Cbm pet 320351 clone board

[mjnurney]

Hi guys I’m in the final process of testing a new pet motherboard but I need some help with the roms. The board shows 6332 roms, now what eprom can I use in this ?

I have a bundle of 2532a EPROMs which I can burn in an adapter but do I need to be worried about plugging them in to the pet. I’m searching for a pinout now…

I have ram but the next problem is composite out from it as I don’t own a 9 inch screen pet.thanks for any help.

mike.

 

[Chuck(G)]

Perhaps this will help

 

[mjnurney]

Ah great thanks. So I can’t just add eproms … makes sense

 

[Chuck(G)]

Note that the article recommends 2732, not 2532 EPROMs.

 

[dave_m]

Since you cloned the older 2001N board and not the universal board that has the /NOROM signal, I assume you have wired pin 21 of the ROMs to Vcc.
In that case, there is no issue with using the 2532 EPROM (4K byte) as a direct plug in. One can still obtain them from China vendors for a fair price. Or use the 2732 EPROM with a simple adapter.

 

[mjnurney]

Thanks, I’m not sure how he’s wired the rom sockets.
I have a feeling it’s a 1:1 clone but I’ll check

 

[Eudimorphodon]

Re: composite out, if that is an exact clone of a 2001-N fair warning, the video frequencies are pretty off spec compared to TV standards. You’ll need a pretty forgiving monitor. I couldn’t get the adapter I made to work, but some people have had better luck.

 

[AtomicZombie]

Yes, the 2001-N video signal is way off the spec. You need to invert the video output as well as the horizontal sync. The length of the horizontal sync is also way too long. In fact, the hsync is still active a good way into the active line!

When I did this fun project (PET to 1702), I had to rebuild and retime the sync signals in order to create video that was close to NTSC (close enough even for a capture board).

There are a few simple "PET 2 Composite" projects out there, but I found them to not produce decent video. Good luck!

Here is one I tried, and although it put out video on some of the monitors I tried, there were issues with the sync length causing some distortions.

http://www.dasarodesigns.com/product/commodore-pet-video-mixer/

The only proper way to rejig the PET video signal is to change the lengths of both the horizontal and vertical sync as well as the inversions.

If you are interested, I can send you my timing diagram, which is specified in cycles for the 8MHz pixel clock.

Brad

 

[Gary C]

A pet motherboard replica ?

Tell me more

We have a chassis, keyboard and monitor but no motherboard, will this be a private project or will boards or Gerbers be available ?