Acorn 28-AKF17 CRT Advice Sought

[GreyAreaUK]

Morning all. I found I had an Acorn 28-AFK17 monitor that I'd forgotten about, and I'm keen to use it with MiSTer.

I have the analogue board, so I have a VGA port to use.

Here is a picture of the back:

9e54YB8.jpg (2.44 MiB) Viewed 2518 times

I'm utterly clueless about the mister.ini's CRT settings, so I was wondering if someone could suggest some good starting values?

I've bought a 15-pin to 9-pin cable (and a 9-pin gender changer) so I can physically connect the two together. And while I get an image, it's distorted and rolling.

My mister.ini (relevant bits, I think) looks like this:

[MiSTer]
key_menu_as_rgui=0
forced_scandoubler=0
ypbpr=0
composite_sync=1
vga_scaler=0
vga_mode=svideo
hdmi_audio_96k=0
keyrah_mode=0x18d80002
vscale_mode=0

vscale_border=0
menu_pal=0
hdmi_limited=0
direct_video=0
fb_size=0
fb_terminal=1

These settings seem to be close, but the image is green and rolling vertical over about a 3-second interval.

Can anyone suggest any settings I might tweak, or other routes I might take? I have a VGA->Component cable arriving today as a possible alternative connection method, since I don't know for sure my current cable+adaptor is correct.

Many thanks.

[mapf]

Hi,

the monitor is a 15KHz RGB(analog) monitor, so it will work with MiSTer. You need to make sure that your adapters connect the right pins. You can find pinouts here: https://stardot.org.uk/forums/viewtopic.php?t=10956

Also, you want

Code: Select all

vga_mode=rgb

in your ini file.

[GreyAreaUK]

Hi,

the monitor is a 15KHz RGB(analog) monitor, so it will work with MiSTer. You need to make sure that your adapters connect the right pins. You can find pinouts here: https://stardot.org.uk/forums/viewtopic.php?t=10956

Also, you want

Code: Select all

vga_mode=rgb

in your ini file.

Thanks - I've set vga_mode back to rgb, but it results in a completely distorted display:

LbHwV1b.jpg (3.87 MiB) Viewed 2517 times

With regards pinouts, I confess they wouldn't make much sense to me, so I'm sort of reliant on pre-made cables.

Edit: Thank you for the confirmation that it should work, though - that in itself is very good to know

[GreyAreaUK]

From the Stardot link above I read this:

Note that the AKF-17 doesn't support a Vsync - it expects a composite sync input on pin7!

Does that mean that composite_sync needs to be set to 1? I've tried setting that, but there with no obvious change.

[mapf]

With regards pinouts, I confess they wouldn't make much sense to me, so I'm sort of reliant on pre-made cables.

The diagrams show which pin carries a specific signal, you need them both for MiSTer analog (from the wiki) and your monitor. Use a multimeter to confirm that blue is connected to blue, green is connected to green, red is connected to red and composite sync is connected to composite sync.

If you want something premade: The Acorn looks to be from the same assembly line as certain Commodore 1084 monitors made by Phillips. They have the same 9-pin dsub input and there are ready-made cables for them. Examples: https://ultimatemister.com/product/mist ... ore-1084s/

and as you are from the UK: https://www.ebay.com/itm/123965671001

(I cannot guarantee that either of these cable will work, and this is not an endorsement for the particular shops)

[mapf]

From the Stardot link above I read this:

Note that the AKF-17 doesn't support a Vsync - it expects a composite sync input on pin7!

Does that mean that composite_sync needs to be set to 1? I've tried setting that, but there with no obvious change.

Yes it needs this setting, and the correct pins need to be connected.

[GreyAreaUK]

Many thanks for the input - I don't have a multimeter sadly, so I'm having to resort to pot luck on pre-made cables. I've got a couple arriving over the next few days, so I'll see how it goes from there.

Are there any other mister.ini settings that you would advise checking? For instance, using 'vga_mode=rgb' gives me garbage, but 'vga_mode=svideo' gives a (poor) picture, but feels wrong.

Edit: This should be arriving Monday. Under a fiver so even if it doesn't work it 's no real loss:

O3KveGq.png (853 KiB) Viewed 2371 times

[Chilli_Vibes]

I believe the AKF-17 is really a rebadged Philips CM8833 MkII, and if that is correct, then the video pinouts should be the same.
The following works on my CM8833 Mk II,

https://www.ebay.co.uk/itm/320754731999

Problem is, you won't be able to go straight from that cable to the Mister, you will need something like the following.

https://www.ebay.co.uk/itm/114489119197

That will work for the Mister's analogue board. If you want direct video from the digital board, then you will need something like the following, and not the link directly above.

https://www.amazon.co.uk/gp/product/B075GZ8DX7/

And even then, you will still need a VGA to SCART cable, and the adapter from my first link. So that's 3 adapters if you go the direct digital way, and you have to hope no lag is introduced along the way. You won't get any lag is you stick to the analogue way, as long as your Mister has the analogue board.
Hope that helps.

[GreyAreaUK]

Well, the wee adapter dongle I bought also didn’t work. Ho hum.

I’ve ordered one of the cables suggested by mapf (don’t worry, won’t blame you if it also doesn’t work )

It occurs to me that I don’t know for sure the monitor isn’t faulty - I have nothing I know of that I can plug it in to, or at least nothing working.

We’ll see. Should be here later this week.

[GreyAreaUK]

I GOT IT WORKING!

And of course I get it working the morning after I order the cable, but that's fine because my working cable is two cables and two adaptors. There are more weak-points than individual components!

Basically I found I had an early Archimedes monitor cable (9-pin D male<->female) so I thought I've give it a try. So my cable is:

MiSTer -> VGA Lead -> 15pin-9pin adaptor -> Archimedes cable -> 9pin gender changer

I'm amazed it works, but it kinda does. Only problem now will be finding out which cores support the analogue output. Trying the AO486 and Archimedes cores gave me garbage on screen, but the C64 and BBC cores were fine. Resolution issue, maybe?

[FoxbatStargazer]

AO486 doesn't have a real analog output, you have to set up a video_mode. See the thread in that forum about plain/15khz TV for some suggested resolutions.

I thought archimedes is inherently high resolution computer so could be tough to use well on a 15khz display. At least most DOS 200p games in AO486 map pretty well to SD resolutions.

The vast majority of console and arcade cores are for 15khz so should display well right now, as well as a good chunk of computers. Although rotated arcade games probably won't be super playable.

[GreyAreaUK]

Yeah, finding a working video_mode for the AO486 core on this monitor is proving to be a challenge, not helped by the fact that video_mode lines are an area where I am utterly clueless. Plus I have to keep in mind that this monitor is far from VGA spec (I think?)

Suspect I may be better off sourcing a decent 'proper' multi sync SVGA CRT - although that is a whole other problem!

[Chilli_Vibes]

The Acorn AKF17 is an Archimedes 15hz Monitor, it was built for the first A3000 series (not the later A3010/A3020 etc..), and it's output was 15hz - Heck, you can even use it on a regular CRT TV. The Archimedes core has 15hz issues, and has never been fixed properly for a 15hz CRT.

[GreyAreaUK]

The Acorn AKF17 is an Archimedes 15hz Monitor, it was built for the first A3000 series (not the later A3010/A3020 etc..), and it's output was 15hz - Heck, you can even use it on a regular CRT TV. The Archimedes core has 15hz issues, and has never been fixed properly for a 15hz CRT.

Ah, thank you. To be honest I’d probably still use the Archimedes core on a flat screen - it’s not one where I’m after all of the ‘back in the day’ experience