do we still use UHF modulators ?

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81

Should a new ULA be able to drive the UHF modulator ?

Yes. I like a wavy image.
4
27%
No. Composite only is fine.
11
73%
 
Total votes: 15

User avatar
Andy Rea
Posts: 1418
Joined: Fri May 09, 2008 2:48 pm
Location: notts UK

do we still use UHF modulators ?

Post by Andy Rea » Tue Mar 13, 2018 6:53 pm

As some of you may know i am developing a new ULA replacement.

so should it be able to drive the UHF modlator? Or is composite video only ok.

Regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

User avatar
gammaray
Posts: 457
Joined: Sun Apr 17, 2016 2:44 am
Location: Texas

Re: do we still use UHF modulators ?

Post by gammaray » Tue Mar 13, 2018 7:59 pm

UHF/VHF across the pond. Compatibility...?

I guess I could buy extra '1000's for parts.
Finish what you start. Truth is over the mountaintop or six feet under.
4 x TS1000, 2 x TS1500 , 2 x timex 2040 printer, 1/2 x timex 2020 cassette deck, ZXPAND+AY, ZeddyNET, ZXBlast..., unfinished Spectrum...Still no life!

McKlaud
Posts: 126
Joined: Tue Dec 19, 2017 10:02 pm
Location: St Albans, UK

Re: do we still use UHF modulators ?

Post by McKlaud » Tue Mar 13, 2018 9:36 pm

Andy Rea wrote:
Tue Mar 13, 2018 6:53 pm
As some of you may know i am developing a new ULA replacement.

so should it be able to drive the UHF modlator? Or is composite video only ok.

Regards Andy
Hi Andy

In my ULA development I dropped compatibility with the modulator. However if you think about the 100% drop-in replacement for the original ULA you should leave the ability to drive the modulator.
Claudius
----------

Moggy
Posts: 1626
Joined: Wed Jun 18, 2008 2:00 pm

Re: do we still use UHF modulators ?

Post by Moggy » Tue Mar 13, 2018 9:38 pm

GODDAMMIT!!! I didn't fight a war just to look at wavy lines...(Sorry wrong forum)

Compo-wotsit just fine for me young sir. :D

Plus I think most of us have Karl's super composite board fitted and there can't be many old B/W CRT sets floating about that would need the modulator.

Just my tuppence worth.

McKlaud
Posts: 126
Joined: Tue Dec 19, 2017 10:02 pm
Location: St Albans, UK

Re: do we still use UHF modulators ?

Post by McKlaud » Tue Mar 13, 2018 9:47 pm

Well, with some new ULA's replacement no any super composite board is needed. The ULA could drive a TV directly with the proper black level.

See this below
Attachments
zULA_prot_09.jpg
Claudius
----------

Lardo Boffin
Posts: 747
Joined: Sat Nov 26, 2016 2:42 am

Re: do we still use UHF modulators ?

Post by Lardo Boffin » Tue Mar 13, 2018 9:48 pm

It was actually a tough call to vote for composite only as it does mean that broken zeddies which are not comp modded won’t be fixable with this ULA however I suspect that this will be a minority and most people given a choice would go composite!
I have bought a fairly large number of zeddies (I think around 20 having had a quick look at my eBay emails) while having a year of refurbishing and only found 1 out of them all where the UHF was actually usable even on a glass screen telly. All the rest produced from poor to impossible to read pictures.
ZX81 iss 1 (bugged ROM, kludge fix, normal)
Iss 3 with ZXVid, another in nearly perfect box
TS 1000 iss 3, ZXPand AY, ZX8-CCB & ZX-KDLX
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Spectrum 48k
Toastrack + DIVMMC future

User avatar
Paul
Posts: 942
Joined: Thu May 27, 2010 8:15 am
Location: Germanys west end

Re: do we still use UHF modulators ?

Post by Paul » Tue Mar 13, 2018 10:00 pm

Would Modulator compatibility raise the cost of the ULA replacement significantly? Or is it the time required for development that makes you ask?
It would be better have at least one replacement ULA that could be a repair for Zeddies with broken ULAs and drive its Modulator.
Would it be possible to offer a addon that gives modulator compatibility?
Kind regards
Paul
In theory, there is no difference between theory and practice. But, in practice, there is.

McKlaud
Posts: 126
Joined: Tue Dec 19, 2017 10:02 pm
Location: St Albans, UK

Re: do we still use UHF modulators ?

Post by McKlaud » Tue Mar 13, 2018 10:05 pm

Paul,

In my case the cost is a secondary issue, because we are talking about difference in voltage levels at the pin 16 of the ULA only. The development time could be longer but I think, both variants are feasible.
Claudius
----------

User avatar
1024MAK
Posts: 1968
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: do we still use UHF modulators ?

Post by 1024MAK » Tue Mar 13, 2018 10:21 pm

Do I still use ZX81s using the UHF RF output, yes. But only because the LCD TV that I use makes a decent job of displaying ZX81 and ZX Spectrum UHF pictures. And, I normally only use this for testing machines that are 'new' to me. Of which have not been modified yet.

When doing anything else, I use ZX81s that output a composite video output. If the ZX81 has a Sinclair ULA, either my version of the composite video modification. Or one of PokeMons crystal clear modules (ZX8-CCB - that I can never remember the name of, sorry, have to look it up each time :oops: ).

One problem with using the UHF RF output, is the frequency of the carrier oscillator in the modulator drifts as the ZX81 (or ZX Spectrum) electronics warms it up. Meaning I have to channel hop my TV to the next channel (which is tuned to a slightly different frequency).

Mark

McKlaud
Posts: 126
Joined: Tue Dec 19, 2017 10:02 pm
Location: St Albans, UK

Re: do we still use UHF modulators ?

Post by McKlaud » Tue Mar 13, 2018 10:46 pm

Has anyone got any schematic diagram or datasheet of the UM1233 modulator? I would appreciate if you could share it, please.
Claudius
----------

Post Reply