NeXT Computers

[chrisrot]

Hi,

I wonder what's the difference between the NTSC and the PAL version of a Dimension board ?
The quartz crystals in the video encode/decode part are probably different. Are there other hardware differences ?

Are there two versions of boot eprom ?

Thanks
Christoph

[Rob Blessin Black Hole]

Shows PAL verse NTSC I probably need to resize images but it shows in closeup detail, Here is an FAQ on Dimensions boards
http://www.nextcomputers.org/NeXTfiles/Docs/FAQ/Hardware/NeXT_Dimension/nd-faq.txt


_________________
Rob Blessin President computerpowwow ebay sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community since 2/9/93

[chrisrot]

Hi Rob,

thanks for sharing the pictures.

I searched through the schematics again very carefully and spotted the signal "VID_NTSC" on page 4 and 11.
On page 4 it's connected to U56, pin 4.
On page 11 it's connected to U4, pin 7 which switches between PAL and NTSC mode according to the datasheet. There are also two 1k resistors (R131/132), one of them is not populated.

I believe that one difference between NTSC and PAL boards are these resistors and they select NTSC or PAL. On NTSC R132 is populated, on PAL R131 is populated.

These resistors are located on the lower right quarter of the board directly on the right edge above the oscillator. If I spotted it correctly on your pictures, on the NTSC board the upper one is populated and on the PAL board the lower. Could you please check that on your boards ?
(I made a details from your picture showing these resistors but don't know how to upload them)

If my assumption is correct one should be able to change a NTSC board into a PAL be switching these resistors and (of course) changing the two oscillators Y1 and Y2.

Best regards,
Christoph

[chrisrot]

Hi,

it's me again. Today I simply moved the 1k resistor from R132 to R131, i.e. the VID_NTSC signal is now tied to ground instead of VCC.
Now, my dimension is identified as PAL type.
I haven't checked whether it realy accepts PAL signals because the lack of an SVHS cable.

I also wonder what this large inductor is used for that is missing on the PAL version near the THT electrolytic capacitor.

ciao
Christoph

PS: Where do I find NeXTTV and the other Dimension demos ?

[barcher174]

Good work. I had suspected this to be the case, but haven't come across a PAL board to try. I think the 3.3 developer CD has the demos you are looking for.

[chrisrot]