A2000 only outputting in monochrome

[deicidal]

Well I finally got back to my A2000 project yesterday and fixed F5 that had blown, however when I connect an a520 to the RGB port I am only betting a black and white picture, any ideas anyone?

[8bitbubsy]

Sounds like the RGB isn't getting fed to the RGB port properly... Take a look at the circuit between the video decoder and the RGB port. Check the components carefully.
I'd also suggest taking a look inside your A520 if this is the first time you've tested it.
Stupid question time: Have you ever gotten color from this Amiga? Are you sure your monitor/TV can handle its output format (NTSC/PAL)?

Another smart way of testing the RGB port is to use a monitor like 1084S and an RGB cable -- or an RGB SCART cable.
There might be a problem even earlier, like before the video decoder chip.

[deicidal]

Well I tried a couple of A520's but same result. TV can handle both NTSC/PAL signals. As for the amiga no I have never had a colour signal out of the board.

I will check the board like you suggested and see if that turns anything uo from my limited elctronics knowledge (already managed to drop the soldering iron on my leg last night lol ).

[8bitbubsy]

It's not very likely that you'll find any errors without proper tools... But look for more burned-out resistors, broken/bad circuit traces, shorts etc.

[Fingerlickin_B]

Time for my stupid question: Have you made sure that both the A520 & A2000 are the same colour system (that is, both PAL or both NTSC)?

PZ.

[8bitbubsy]

AFAIK, the A520 takes RGB output + csync (or maybe hsync+vsync combined) and converts it to composite. This means that it should work regardless of NTSC/PAL.

EDIT: I was wrong, I stand corrected by Toni Wilen.
So yeah, Fingerlickin_B made a good question for you deicidal.

[Toni Wilen]

PAL and NTSC Amiga master clocks are different. Only PAL Amiga can produce correctly timed PAL color signal using PAL A520 and vice versa.

[deicidal]

Thats a very good point, er without sounding stupid what do i look for on the a2000 baord to determine if its the NTSC or PAL model.

If it is an NTSC model, I have a PAL acid damaged board would it be possible to swap some of the chips to make it PAL?

[Zetr0]

@Decidal

you sir - have a PM =)

(or will very shortly)

[deicidal]

Should also mention that i tried an opalvision card with an a520 again and this also gave me a mono output.

I will try my scart cable when i get chance and see what that produces, but the a2000 is round at my gf's at the moment and for some stupid reason she has a seriouse lack of resources for my geek time.

[deicidal]

Well had a quick play with it at the weekend and a bit last night, unfortunatly time is very scarce at the moment. Anyway after a few ideas from Zetro that indicated that its PAL.

Hooked it up to a ATS-90 Amiga Titling System and used its svhs output and got a colour picture.

Then had the sodding obviouse idea of running sysinfo on it and its confirmed that it is a PAL model.

So still none the wiser as to why i generally get a monochrome picture out of it.

[Fingerlickin_B]

I cannot find any information about the ATS-90, so have no idea what it is.

If you change colours to 2 in prefs/screenmodes, you get black & white, but if you got colour with this ATS-90 device, then it couldn't be that simple...

PZ.

[deicidal]

Its not the preferences as even the insert disk is B/W.

As for the ATS-90, im not entirely sure what it is either, it came with the a2000 as part of a video editing deck, I can only assume its for putting text in front or behind video. Tried google but that didnt get me very far on identifying it either.

Unfortnatly the MFM HDD in the a2000 is also in a bad way so getting information is also proving tricky, anyone recomend a good hdd checking/repair tool?

Still can't complain the whole system todate has only got me about £15.

Cheers for all the ideas everyone

[pandy71]

Weird idea but maybe with time (aging components) chroma subcarrier deviate more than allowed by PAL decoders (usually more than +-150Hz from 4433618.75Hz chroma subcarrier is BW picture on screen)

[Zetr0]

its also possible that the CCK (colour clock) might be out or not working.

this ones a funny one to be honest and its kinda the thing Pandy71 mentions

The fact is you have a good b/w picture, so the video hybrid is surely working or you wouldn't get that-
Another fact is the A520 cannot provide colour either is very interesting here.

does the A520 work on any other amiga?

I have about 4 A520's here, a couple are from the early A500/A2000 era and they are very VERY poor in terms of output - one of them is so ghastly you just cannot use it as all the clolour are blaring out to the screen - the other flicks between bad colours and black and white on its whim/fancey

Now the ATS-90 having SVideo out would mean that it has its own encoder or enconfing ciricuit based on the RGB V/H and a pal colour clock - its unlikely it would source that from the Video Port as its too noisy, so it probably got its own PAL Oscilator. (much like the A520's) with that Xtal it then has its own Colour Clock (CCK) generation - I suspect that the CCK on the A2000 is either not being fed (bad caps perhaps?) to the 23 pin Video Port - insofar as the A520 - I can only ask that you test them on another Amiga?

[deicidal]

When I tested the job lot of a520's on my a500 they all produced colour outputs, but i only tested 2 on the a2000, so will give them all a try to see if that makes a difference.

[Loedown]

What about looking for the colour burst, if indeed an oscilloscope is handy?

[Fingerlickin_B]

There isn't a chance that both your colour issue & HDD trouble are are actually related to a dying PSU is there?

Given the machine came with video editing hardware, one might assume that the PSU has seen a fairly hard life, powering loads of peripheral devices & such...

PZ.

[deicidal]

Alas I don't have a handy oscilloscope.

As for the HDD I think it could well be just on its way out as its a geriatric 40mb mfm hdd and sounds like read / problems from the noises its making.

[pandy71]

Scope is not enough precise to measure frequency (something like VM700 from tek is recommended for this kind measurements )

but anyway A520 is one of the poorest PAL encoders i ever seen... quality was always bad and i can only imagine that with time is not better but only worse

so my advise is take some decent modern analog PAL encoder or even duplicate circuit from A1200 - quality will be better.

btw from descriptions seems that ATS-90 is a genlock