A310 Repair Update

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VintageMicro
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A310 Repair Update

Post by VintageMicro »

Hi I purchased a faulty A310 online and noticed it was already posted on here by the previous owner.

The replacement ram sockets that had been installed had broken traces on both sides of the board these were replaced and traces fixed and some socketed chips had bent pins, and now it boots up. :)

I don't have a set of test rom's so I am now a bit stuck, it boots to the RiscOS desktop but the mouse pointer is just a square block instead of an arrow and when I move the pointer down to bottom of the screen the mouse moving over the bottom menu area causing the screen to change, as shown below.

(note the display is via the Mono composite output)

Does anyone know if this behaviour would likely be a corrupt rom or the memory chips, any help would be great I don't have much experience with Archies.
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IanJeffray
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Re: A310 Repair Update

Post by IanJeffray »

Wow that's curious failure! The failure when you move to the bottom of the screen is really weird -- almost suggests some coupling between the cursor data (mouse pointer) DMA and the video DMA... so this could all be down to a flaky VIDC or something around there perhaps. I'd probably at leaast lift and reseat it to start with.

What happens if you try and change screen mode? MODE 13 or MODE 15 are good ones to try - 8bits per pixel. If you had it hooked to somethign other than mono video, you could configure the monitor type to SVGA or multisync then try MODE 28 or MODE 21 to really make VIDC stretch its legs.

It's possible (and even more likely given your description) that a RAM chip/address line has failed. It always surprises me how often RISC OS can manage to get right in to the desktop whilst the hardware can be really quite messed up.

If you CMOS reset you should get a floppy drive icon appearing on the desktop. Does the floppy work? Then you could get a RAM test app loaded in. If not, even a simple typed-in BASIC RAM test would be worthwhile.
VintageMicro
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Re: A310 Repair Update

Post by VintageMicro »

Thanks Ian this is the machine previously posted by traindriver, at least I got it to boot after a lot of de-soldering ic socket pins!

I will have to clean and check the floppy drives before connecting and testing as they are a bit manky, I have omniflop on an old pc and a gotek with flashfloppy so should be able to load up a disk are there any links to the Archimedes diagnostic test disk online or a good ram tester.

Thanks for the quick reply, the screen updates along a vertical line when you move the mouse pointer over the bottom of the screen
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IanJeffray
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Re: A310 Repair Update

Post by IanJeffray »

VintageMicro wrote:
Thu Sep 23, 2021 5:58 pm
Thanks Ian this is the machine previously posted by traindriver, at least I got it to boot after a lot of de-soldering ic socket pins!
Ah congrats - can't be far off now.

Did you check/fix these shorts?

Steve3000's memXX test would be worth a go -- except I just checked and it barfs if you only have 1MB :(
VintageMicro
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Re: A310 Repair Update

Post by VintageMicro »

Yes I fixed those shorts and there were also broken traces on the other side under the sockets, going to ic51 and ic52, I will have to double check all the ram chip traces just to make sure I got them all, but I think I did.

I will try to load a floppy disk bit of a challenge at the moment, the screen changes position when I move the mouse over the floppy icon so I have to randomly click around to select anything :shock:

Is there a link to the diag roms with a ram test or even a basic program ram test code would be ok.

Happy that it's now alive anyway, it was just a black screen before the repairs
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IanJeffray
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Re: A310 Repair Update

Post by IanJeffray »

VintageMicro wrote:
Thu Sep 23, 2021 6:29 pm
I will try to load a floppy disk bit of a challenge at the moment.
F12 to get a command prompt. Or hold keypad * on startup until the prompt appears - avoids desktop.
VintageMicro wrote:
Thu Sep 23, 2021 6:29 pm
Is there a link to the diag roms
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steve3000
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Re: A310 Repair Update

Post by steve3000 »

IanJeffray wrote:
Thu Sep 23, 2021 6:18 pm
VintageMicro wrote:
Thu Sep 23, 2021 5:58 pm
Thanks Ian this is the machine previously posted by traindriver, at least I got it to boot after a lot of de-soldering ic socket pins!
Ah congrats - can't be far off now.

Did you check/fix these shorts?

Steve3000's memXX test would be worth a go -- except I just checked and it barfs if you only have 1MB :(
Oh yes… I’ll have to deal with that!
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Re: A310 Repair Update

Post by steve3000 »

It’s very odd to see no floppy drive icon under RISC OS 2, since this OS doesn’t check floppy drive presence. It suggests your CMOS RAM is corrupt.

Have you tried resetting the CMOS RAM by holding Del before switching on and keeping it held while switching on, until it boots to Desktop?
VintageMicro
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Re: A310 Repair Update

Post by VintageMicro »

Yes I now have the floppy icon after a CMOS reset and the floppy actually works it also allowed me to format a disk and it verified ok, RiscOS seems to be working ok, now have my Gotek with Flashfloppy working and games with sound and graphics running fine, just still getting the weird RiscOS Desktop screen shifting movement when I move the mouse, I have ordered some replacement RiscOS roms incase they are faulty.

Does the Acorn dealer test disks image exist anywhere in .adf format, the manual refers to them
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IanJeffray
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Re: A310 Repair Update

Post by IanJeffray »

VintageMicro wrote:
Fri Sep 24, 2021 7:03 am
Yes I now have the floppy icon after a CMOS reset and the floppy actually works it also allowed me to format a disk and it verified ok, RiscOS seems to be working ok, now have my Gotek with Flashfloppy working and games with sound and graphics running fine, just still getting the weird RiscOS Desktop screen shifting movement when I move the mouse
Great stuff. There can't be too much wrong with it! I'd still be looking at issues near VIDC - did you reseat it? Do all games look OK, or have you seen other visual issues?
VintageMicro wrote:
Fri Sep 24, 2021 7:03 am
I have ordered some replacement RiscOS roms incase they are faulty.
I -think- RISC OS 2 still includes a CRC check, and also the faults you describe really don't sound like it's at all likely to be a ROM issue.

Did you order another RISC OS 2 set, or RISC OS 3? If it's 3, you'll need a carrier board even though the RISC OS 3 ROMS will physically fit, they won't work in an unmodified A310.
VintageMicro
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Re: A310 Repair Update

Post by VintageMicro »

Hi Ian

Weird thing is the games run fine no corruption etc just been playing lemmings all works fine and when you move the mouse no issues
, sound is good too, only get the mouse issue when on RiscOS desktop

I took out the VIDC and cleaned and checked and cleaned all the pins and the socket pins look ok
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IanJeffray
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Re: A310 Repair Update

Post by IanJeffray »

VintageMicro wrote:
Fri Sep 24, 2021 10:02 am
Weird thing is the games run fine no corruption etc just been playing lemmings all works fine and when you move the mouse no issues
, sound is good too, only get the mouse issue when on RiscOS desktop
If you leave the desktop via F12, then issue *pointer 1 to display the pointer again, do you still get video shifting happening when the pointer moves to the bottom fo the screen?

Very interesting fault!
VintageMicro
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Re: A310 Repair Update

Post by VintageMicro »

The issue seems to be related to the mouse pointer

As soon as I used F12 the screen displays correctly

after the pointer command it goes weird again :o
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IanJeffray
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Re: A310 Repair Update

Post by IanJeffray »

VintageMicro wrote:
Fri Sep 24, 2021 10:36 am
after the pointer command it goes weird again :o
This isn't an area I've any experience of, but ... /HSYC determins whether it's video or cursor DMA. If this is getting slugged, it could explain the weirdness... VIDC would be expecting cursor data, but MEMC is serving up video, explaining the messed-up pointer image. That would then knock-on to a "slip" in the video data which was served up to the cursor instead of video image. Check these pins fon VIDC and MEMC. If you have a multimeter, check for conenctivity. If you have a scope, check for activity relative to /VDRQ. Possible IC4 has gone a bit soft? (Had plenty of 74 logic fail on A3xx/A4xx machines).
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VintageMicro
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Re: A310 Repair Update

Post by VintageMicro »

I think its jinxed , its now dead again black screen and the memory chips rapidly warm up when powered on
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IanJeffray
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Re: A310 Repair Update

Post by IanJeffray »

VintageMicro wrote:
Fri Sep 24, 2021 12:28 pm
I think its jinxed , its now dead again black screen and the memory chips rapidly warm up when powered on
IMVHO - fit an IanS 4MB upgrade instead. RISC OS is a bit "limited" with just 1MB anyway.
Ian's board disconnects all the onboard RAM anyway - you could even pull it all out of it's getting hot.
VintageMicro
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Re: A310 Repair Update

Post by VintageMicro »

Thanks for the heads up yes replacing all the ram should help matters
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