A3000 display trouble

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Pfsteel
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A3000 display trouble

Post by Pfsteel »

Hi all,

I've just picked up an Acorn A3000 and had to replace the cmos chip just below the battery as it wasn't booting. I've now got it booting up with a new battery and the new cmos chip so it boots straight into the desktop Risc OS 3.0.

My problem is that the screen keeps jumping right and left. Vertically it's fine. I'm using a cable that I got with it to convert RGB to Scart and then I have a Scart to HDMI box. I know the scart to hdmi box works fine because I use that (with a different Scart cable) for my BBC Master 128 and the cable worked with a scart tv (without the convertor box but I no longer have that tv). The picture just jumps right and left randomly but otherwise is perfectly clear. Is it because I’m using an lcd screen now with a converter box or the cable or could the replaced cmos chip had caused a problem?

I did reset the configuration (DEL on boot). The mouse and everything works fine including the memory (4MB) and floppy drive.

Do you think it's the cable or have I done a shoddy job replacing the cmos chip? I hope it's not the soldering of the chip because that was damn hard and above my paygrade..

Thanks
Paul
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flaxcottage
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Re: A3000 display trouble

Post by flaxcottage »

Unlikely to be the CMOS chip. The SCART cable is the most likely culprit.

The A3000 has a mono video output. It uses a RCA to RCA lead. Does this show the same problem? If not it will be the SCART lead. Otherwise could be the A3000 video circuitry.
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Pfsteel
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Re: A3000 display trouble

Post by Pfsteel »

Thanks.

I've ordered a cable from retro clinic but it’ll take time to get over to the US.

Can anyone explain what’s wrong in layman’s terms?

When I was in the UK with the same a3000 in December, that cable worked fine with the 24” flatscreen tv plugged into the scart socket. Now I’m back in the US, using the same scart cable plugged into an upscale box and into another basic lcd screen it ‘works’ but the picture keeps jumping left (off the screen) and back again. The image itself is clear. I’ve tried it on another cheaper lcd screen and the same thing happens.

From the reading I’ve done I’ve not seen anyone have the ‘jump left then back’ problem and normally it’s rolling screens or blank screens. Could this be a config problem or can I narrow it down to the lcd panels not liking the image?
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flaxcottage
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Re: A3000 display trouble

Post by flaxcottage »

The A3000 produces a PAL-standard video output. Is your LCD TV in the states a UK model or a US model? US TV uses the NSTC-standard. That could be the problem.
- John

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Pfsteel
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Re: A3000 display trouble

Post by Pfsteel »

They're from the States but the Scart to HDMI box can convert between the two (apparently)..

I've tried now on a number of modern panels and they all do the same thing. They immediately pick up the picture and display it in colour really clearly with no artifacts. The image doesn't scroll and is perfect except for the fact it keeps jumping left (and looks like wrapping. back round on the right) and then it flicks back to the correct position again.
20220110_152915.jpg
20220110_152924.jpg
then flips back to the other.. Seems random.. jiggling the cable make no change even in the speed of change.
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IanJeffray
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Re: A3000 display trouble

Post by IanJeffray »

Is there a good reason you're going via SCART rather than just a VGA lead? Many panels still have VGA inputs. I'd consider that better for diagosis than all this extra whackery digitising the SCART to HDMI.
Pfsteel
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Re: A3000 display trouble

Post by Pfsteel »

Good point. My lcd panels don’t have vga (well one crappy one does but the a3000 came only with the 9pin vga to scart lead) and I have the scart to hdmi convertor from using a bbc master and it’s worked fine for that.. I didn’t think it’d be this complicated to be honest.
steve3000
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Re: A3000 display trouble

Post by steve3000 »

It can't be the CMOS chip, as that has nothing to do with video output, it just holds various settings for the computer.

The fact your SCART to HDMI converter works with a BBC micro, doesn't mean it will work with an A3000, as they use different video timing for their screen modes. I have a SCART to HDMI box which is very fussy, it doesn't like my A5000, but is happy with my A3000. Most likely is your converter is simply not syncing correctly to the A3000 output. Luckily, the A3000 is also much more flexible in terms of output than the BBC, and you can change settings fairly easily.

Things to try. First load !Configure, choose "Screen" and set the monitor type to "Normal", then select default screen mode to 12, see if this helps. Next try turning on and off "Interlace", as the converter may be expecting an interlace signal (as the BBC outputs). If that still doesn't help, you can press f12 and type "*Configure Sync 0" and then press return twice to get back to the desktop. If that doesn't help, or the screen goes blank, carefully press f12 and type "*Configure Sync 1" and press return twice. If that still doesn't help, press f12 and type "*Configure Sync Auto" and return twice, then go back to !Configure and change the monitor type to "Multiscan" and the default mode to 20 (this is actually higher than normal TV resolution, but some SCART to HDMI converters accept this and deinterlace to provide full benefit of high resolution). Now repeat everything above that you did for the "Normal" monitor type... Hopefully one of those settings will work.

If that fails, the best option would be as Ian suggests if there's a VGA input on the panel - although if your plan is to run old games, VGA brings some other issues...but then you can always look into LCDGameModes :D
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IanS
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Re: A3000 display trouble

Post by IanS »

You could try swapping the sync polarity, see if it makes any difference. Try adding (or removing, if already fitted), LK26 &/or Lk27.
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Pfsteel
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Re: A3000 display trouble

Post by Pfsteel »

Thanks both.

I’ve tried all the combination of the screen mode suggest by steve3000 but no change in the problem.

I’ll try the link changes suggested by Ian tomorrow when I can remove the floppy drive to access them..

I’ve ordered a 9pin to ‘modern’ vga convertor from Amazon and will try that Wednesday. I’ve also ordered the a3000 vga to scart from retro clinic which will take a whiles to arrive in the US.

After that I guess it’s shipping the tv that it worked on from the Uk to try that :/

Retro kit certainly seems more dark arts than science
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IanJeffray
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Re: A3000 display trouble

Post by IanJeffray »

Pfsteel wrote:
Tue Jan 11, 2022 1:41 am
I’ve ordered a 9pin to ‘modern’ vga convertor from Amazon and will try that Wednesday.
It's rather unlikely that any Amazon-sold product will be suitabe for the proprietary Acorn 9-pin pinout.
Do you have a link to the product?
chrissawer
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Re: A3000 display trouble

Post by chrissawer »

IanJeffray wrote:
Tue Jan 11, 2022 2:00 am
It's rather unlikely that any Amazon-sold product will be suitabe for the proprietary Acorn 9-pin pinout.
Do you have a link to the product?
I use an Amazon-sourced 9 to 15 pin VGA cable on my A410/1 and it works fine. I took a chance on a cheap one - "TOOGOO(R) 1.4M RS232 DB9 9 Pin Male to VGA Video 15 Pin Male Adapter Cable Light Gray".

I presume the A3000 has the same pinout?
Pfsteel
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Re: A3000 display trouble

Post by Pfsteel »

I ordered this one:

https://www.amazon.com/gp/product/B08GY ... UTF8&psc=1

Is there a 'correct' one I can get from Amazon? I don't see these on Ebay for the specific purpose.

It's like I need a way to do a horizontal adjustment like the monitors of old.
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vanpeebles
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Re: A3000 display trouble

Post by vanpeebles »

https://www.amazon.co.uk/YACSEJAO-Seria ... p_d_rp_1_t

I used that one as recommended by some peeps on the chat. It works on an A310 and an A410.
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IanJeffray
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Re: A3000 display trouble

Post by IanJeffray »

vanpeebles wrote:
Tue Jan 11, 2022 3:07 pm
https://www.amazon.co.uk/YACSEJAO-Seria ... p_d_rp_1_t

I used that one as recommended by some peeps on the chat. It works on an A310 and an A410.
Ok, I'm very surprised, Nice. Hilarious signal names for a video cable.
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IanJeffray
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Re: A3000 display trouble

Post by IanJeffray »

IanJeffray wrote:
Tue Jan 11, 2022 3:15 pm
vanpeebles wrote:
Tue Jan 11, 2022 3:07 pm
https://www.amazon.co.uk/YACSEJAO-Seria ... p_d_rp_1_t

I used that one as recommended by some peeps on the chat. It works on an A310 and an A410.
Ok, I'm very surprised, Nice. Hilarious signal names for a video cable.
I continue to be very surprised -- I always thought the Acorn 9-pin video port was a compltely proprietary pinout. I guess not. I ordered one of these https://www.amazon.co.uk/gp/product/B00HJUDHV8 and it's working very nicely - definitely surprising to me!
Pfsteel
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Re: A3000 display trouble

Post by Pfsteel »

Okay so..I tried a 9pin vga to 15 pin vga as above…no picture at all so no worky. I did however get a mono cable and that worked perfect ..in mono..no jumping from normal to left and back again.

I’ve ordered another vga to scart lead from the Uk from retroclinic (if memory serves) and I’ll wait for that.

Is it possible it’s not the cable but the video chip or something else?
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SKS1
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Re: A3000 display trouble

Post by SKS1 »

Quite likely that your monitor doesn't accept low-frequency modes through the VGA port - for this you'd have to (using your composite video connection) configure MonitorType 3 and WimpMode 27, then Ctrl-Break and see when happens on the monitor's VGA input then. You can always power-on-DEL to get back to defaults.

The Acorn 9-pin video port was defined just before VGA came out - it's the same form factor as EGA. Wasn't the very first VGA 9-pin? I've used 9-to-15 adaptors since forever for the old systems.
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Pfsteel
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Re: A3000 display trouble

Post by Pfsteel »

SKS1 wrote:
Sat Jan 15, 2022 12:35 am
Quite likely that your monitor doesn't accept low-frequency modes through the VGA port - for this you'd have to (using your composite video connection) configure MonitorType 3 and WimpMode 27, then Ctrl-Break and see when happens on the monitor's VGA input then. You can always power-on-DEL to get back to defaults.
Wow so this actually worked using the 9pin vga cable to 15pin vga! And no jumping Left-Right- Awesome!!

So now I get a 640x480 at 57Hz (reported by my lcd). It messes up the Mono image completely but now works via vga and in colour so already a massive improvement - Thank you!

Is it the Monitor type that got this working in vga or the Wimpmode?

I did a search and found that WimpMode 28 is 640x480@256 which also works. I've tried MonitorType 4 with WimpMode 28 and that still works...

So am I able to get into higher resolution screen modes? I assume not given the A3000 only has a mondo Video or VGA output (which is 640x480@256 max) right??

P
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IanJeffray
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Re: A3000 display trouble

Post by IanJeffray »

Pfsteel wrote:
Sat Jan 15, 2022 8:58 pm
So am I able to get into higher resolution screen modes?
With a VIDC enhancer, providing a higher clock to the VIDC, you can get 800x600. But beware this also steals quite a bit more RAM bandwidth. 800x600 is more sensible on 12MHz-bussed machines (A540, A3010/A3020/A4000 and above)

IMVHO MODE 27 is the best compromise for stock A3000s - 640x480x4bit. Your machine will feel rather sluggish in MODE 28 (640x480x8bit colour) as it's using double the RAM bandwidth to run the video output.
Pfsteel
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Re: A3000 display trouble

Post by Pfsteel »

Thanks for all your help. I’m gonna stick with 640x480x16 for now until I get the blaster sd card podule working…actually I’ve ordered another new one from cje as I’m tired of the copying of files to pc, bbc, then a3000 to fail each time. Shame the guy who sold it kept the sd card and reset all the params :(
steve3000
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Re: A3000 display trouble

Post by steve3000 »

Pfsteel wrote:
Sun Jan 16, 2022 9:35 pm
Thanks for all your help. I’m gonna stick with 640x480x16 for now until I get the blaster sd card podule working…
if you have difficulty running games with VGA monitortype configured, try using LCDgamemodes (link in my post above) this allow many games that don't typically work with Acorn's standard VGA modes to run.
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