RCA 1861, NTSC and a DEC VR-201

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Fri Sep 24 07:37:37 1999

> to eliminate sources of failure. When I try to hook a COSMAC VIP up to it, I
> get nothing. The numbers (from the RCA 1861 spec sheets) look like this:
>
> NTSC 1861 _at_ 1.76064 Mhz 1861 @ 1.764000 Mhz 1861 @ 3.579545/2
> -------- ------------------ ------------------- -----------------
> Line 15750 Hz 15720 Hz 15750 Hz 15980 Hz
> Field 60 Hz 60 Hz 60.11 Hz 60.99 Hz

But vr201 is not NSTC timing or scan rates. the 1861 was designed to
drive TVs (or TV monitors).

> VR201 is sensitive to a 30 Hz difference in the horizontal freq. Barring
> the chance that I can locate a 3.528 Mhz xtal before the VCF, am I hosed

No way. It's not the 30hz in frequency it's the serperate sync and
different front and back porch timing.

> a kind soul. As it stands now, I'll have to hope for a kind soul to help
> me with a standard NTSC monitor (I've just tested the VIP with a more
> ordinary Commodore 1084S).

That's what you want a TV with a video input, or a RF adaptor(pixiverter).

> Can any video guru's shed any light on my dilemma? Is the VR201 that
> sensitive? Is there a way to get around this?

You mich make internal adjustments but the seperate sync lines are not
generally NTSC compatable. It's a misapplication, Vr201 is not a generic
monitor.

Allison
Received on Fri Sep 24 1999 - 07:37:37 BST