Re: Multinorm TV woes - no NTSC color display

["Bryan Parkoff" <nospam@nospam.com>]

"Linards Ticmanis" <ticmanis@gmx.de> wrote in message 
1154102830.819241.184350@75g2000cwc.googlegroups.com">news:1154102830.819241.184350@75g2000cwc.googlegroups.com...
> Hello,
>
> I've just acquired a small multinorm TV set (a Thomson 14 MG 135 to be
> exact) to use as a monitor for various old systems. According to
> advertisement, this TV should accept RF-modulated PAL and SECAM (B/G,
> I, D/K and L/L' variants), as well as baseband PAL, SECAM, and NTSC
> (both "real" NTSC 3.58, and the "NTSC 4.43" variant output by some PAL
> equipment).
>
> I've confirmed that the NTSC input basically works with the help of a
> DVD player set to NTSC output (this would show only black-and-white on
> my old TV).
>
Hello,

    I would try to answer your questions.

> However the TV refuses to display color for the signal from an Apple
> II. This Apple is an Apple II Europlus with the following
> modifications:
>
> 1.) I reversed the 5-jumper "Euroapple Modification" described in the
> old Reference Manual.
>
> 2.) I replaced the 14.25something MHz Quartz with a 14.318something MHz
> Quartz.

    It is not a good idea to swap 14.25MHz osc chip to 14.3MHz osc chip 
because Apple II motherboard has two different revisions.  First revision 
with 14.3MHz osc chip is designed for NTSC only.  Second revision with 
14.25MHz has a special circuit for PAL on the Apple II motherboard.

>
> There is no PAL color card in the Apple.

    I suggest to use Apple II motherboard which it has PAL circuit so you 
don't need PAL color card unless it is an alternative choice.

>
> Question No. 1, should this be enough to get the Europlus to create a
> NTSC signal again. If no, what else do I need to do. Could the circuit
> be detuned enough to lose color, and how would I tune it. The
> replacement quartz was newly bought.

    No, it won't work.  If you use NTSC monitor with PAL circuit 
motherboard, it will not work.  The only way is to use NTSC monitor in 
Europe.  You will need to have 120 volt to 240 volt converter so you will 
have 60 Hz on NTSC circuit motherboard and NTSC monitor.
    I do not think to lose color if 60Hz is incompatible to 50Hz.  It is to 
deal with 262 lines and 312 lines.  If NTSC monitor is connected to PAL 
circuit motherboard, I am sure that NTSC monitor will roll up because of 
difference between 262 lines and 312 lines.

>
> Question No. 2, does anybody know what parameters these multinorm TVs
> use to detect a NTSC signal and identify it as such.

    I am not sure, but I know that some monitors have a support of NTSC/PAL 
switches so it should work as long.

>
> Question No. 3, how could I possibly get the Apple to produce a NTSC
> signal this TV set "likes"?

    It is deep technical issue how Apple II produces video to the NTSC 
signal.  It is done by 14MHz which it sends one bit by one bit stream 
through the serial video cable to the NTSC monitor.  Then NTSC monitor picks 
up a group of four pulses to create color reference using 3.58MHz.  It has 
to restrict at 262 lines for NTSC.
    It has a deep explanation of technical video in the "Understanding the 
Apple II+" on chapter 8.  You can find PDF format somewhere when someone 
posted it on the newsgroups earlier.

Bryan Parkoff