Acorn A310 help.

discuss the archimedes & risc pc, peripherals and risc os/risc os on pi
Post Reply
nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Acorn A310 help.

Post by nzjavert » Mon Feb 03, 2020 1:59 am

I recently got my hands on an Acorn A310 with riscos 2 in bits. I have tried to power on the computer but will not display anything. I Looked online and the most common problems seem to be c37 tantalum capacitor, power supply, and the typical acorn battery leakage issues.

I have replaced all 3 capacitors with 25v 100uf caps as this is the standard go to repair to see what is wrong.
I have fitted a new battery holder and new batteries.
I have also checked the output of the power supply on each rail and am getting the correct 12v, 5, -5v on the correct pins.
I have reseated all the removable ic's.

I am not getting any display or any beep on boot up. I have tried the cmos clear (hold delete when turned on until it boots) and this does not do anything.
the caps lock and num lock lights turn on and off when pressed. the floppy drive does not flash but the light does stay on.

that is about as far as i can go without help. Does anyone have any ideas or had similar issues that could point me in the right direction.

Any help would be greatly appreciated.
Matt

Paul
Posts: 147
Joined: Fri Nov 15, 2013 10:39 am
Contact:

Re: Acorn A310 help.

Post by Paul » Mon Feb 03, 2020 7:18 am

You've probably done this, so, sorry! But...

Have you held delete or R during power on for a few secs?

Are you using the correct monitor? If scary, have you tun a signal to the TV's RGB selector via the scart lead? Othereise the TV will try to use composite.

You wont get floppy LED codes with RO2,but you could try fitting RO3.

Is there any obvious damage to the board?

Paul.

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Mon Feb 03, 2020 8:08 am

Hi Paul,

I have tried pressing delete while booting and holding it down for around a minute just to make sure...I seem to recall on my old risc os2 a3000 that it would take between 10 and 15 seconds longer to boot while this is done.

If i can avoid it, I really don't want to upgrade to riscos 3 or 3.1. My whole reason for wanting risc os 2 is purely nostalgia, however I may look at a piggy back switchable romset later on if i can get this going.

Monitor is the one the machine originally came with complete with scart plug. Unfortunately i have no tv that is compatible with a mono or rca type plug to test it on. I have no other machine to test the monitor on either so it is really hard to diagnose if that is an issue.

Another test i tried was a the control g, to get a beep, to no avail. Also tried shift break with a bootable disk in the drive and it made no sounds or attempts to do anything.

the board itself looks in really good condition. It does not look like it has ever had battery leakage. or any damage to it. I have had a look on Chris's acorns website at the a310s he has there and mine looks just like his riscos 2 board without a backplane etc

Kazzie
Posts: 1368
Joined: Sun Oct 15, 2017 8:10 pm
Location: North Wales
Contact:

Re: Acorn A310 help.

Post by Kazzie » Mon Feb 03, 2020 10:01 am

Have you looked at the service manuals for the A300/A310 here? I seem to recall that they have some fault-finding flowcharts for dead machines.
BBC Model B 32k issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
Acorn System 1 home-made replica

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Mon Feb 03, 2020 10:35 am

Hi Kazzie,

I had gone through a similar flow chart on another site however that seems to have a little more info further down in the text of the document than the last one I looked at. I will give some of those procedures a go tomorrow. I will update if there is progress or not.

There seems to be alot more information on repair of the later model 32bit machines than the earlier ones.

User avatar
DutchAcorn
Posts: 2185
Joined: Fri Mar 21, 2014 9:56 am
Location: Maarn, Netherlands
Contact:

Re: Acorn A310 help.

Post by DutchAcorn » Mon Feb 03, 2020 1:56 pm

nzjavert wrote:
Mon Feb 03, 2020 1:59 am
the caps lock and num lock lights turn on and off when pressed.
Are you saying the caps lock can be toggled using the caps lock key?

Is there a cooling fan installed and does it run?

What happens if you wait a few seconds after switching on, then press F12 and then press Copy (or ctrl-g)?
Paul

Image

steve3000
Posts: 2158
Joined: Sun Nov 25, 2012 12:43 am
Contact:

Re: Acorn A310 help.

Post by steve3000 » Mon Feb 03, 2020 7:40 pm

DutchAcorn wrote:
Mon Feb 03, 2020 1:56 pm
nzjavert wrote:
Mon Feb 03, 2020 1:59 am
the caps lock and num lock lights turn on and off when pressed.
Are you saying the caps lock can be toggled using the caps lock key?

Is there a cooling fan installed and does it run?

What happens if you wait a few seconds after switching on, then press F12 and then press Copy (or ctrl-g)?
Try what Paul suggests above.

If you can toggle caps lock on/off, this means the computer is running (ARM, MEMC and IOC at least must be functional), so the issue is the video output - either the monitor is faulty or the VIDC chip has failed. Both are possible, but if you're not getting any sound (Ctrl+G after pressing f12) then the most likely culprit is the VIDC chip.

RISC OS 2 will happily boot with failed VIDC, however RISC OS 3 will refuse and give a self-test error by flashing the floppy drive light.

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Mon Feb 03, 2020 8:01 pm

Hi DutchAcorn,
DutchAcorn wrote:
Mon Feb 03, 2020 1:56 pm
Are you saying the caps lock can be toggled using the caps lock key?
Yes that is exactly what i am say. They do toggle when pressed. Caps lock, Number lock and scroll lock all turn on and off when pressed.
DutchAcorn wrote:
Mon Feb 03, 2020 1:56 pm
Is there a cooling fan installed and does it run?
There was no cooling fan when I got the machine in pieces. I have just now fitted a small pc fan and it works perfectly.
DutchAcorn wrote:
Mon Feb 03, 2020 1:56 pm
What happens if you wait a few seconds after switching on, then press F12 and then press Copy (or ctrl-g)?
after turning it on nothing happens when i press f12 and then press copy or control g. I get no sound. I do get a faint click from the speaker when the machine is power cycled, reset via keyboard button, ctrl break or ctrl shift.

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Mon Feb 03, 2020 8:07 pm

Hi Steve3000,
steve3000 wrote:
Mon Feb 03, 2020 7:40 pm
so the issue is the video output - either the monitor is faulty or the VIDC chip has failed. Both are possible, but if you're not getting any sound (Ctrl+G after pressing f12) then the most likely culprit is the VIDC chip.
Ok thats interesting. It seems like the computer is operating just not displaying then. Do you know if an acorn a5000 VIDC chip will work in an A310? I have a battery leakage damaged a5000 that i can borrow parts from to check for operation.

I will also see if i can find a technical manual on the screen to see if that has failed. the monitor cable appears as tho it is intact however I will chuck a meter across it to ensure no broken wires inside

steve3000
Posts: 2158
Joined: Sun Nov 25, 2012 12:43 am
Contact:

Re: Acorn A310 help.

Post by steve3000 » Mon Feb 03, 2020 9:11 pm

nzjavert wrote:
Mon Feb 03, 2020 8:07 pm
Hi Steve3000,
steve3000 wrote:
Mon Feb 03, 2020 7:40 pm
so the issue is the video output - either the monitor is faulty or the VIDC chip has failed. Both are possible, but if you're not getting any sound (Ctrl+G after pressing f12) then the most likely culprit is the VIDC chip.
Ok thats interesting. It seems like the computer is operating just not displaying then. Do you know if an acorn a5000 VIDC chip will work in an A310? I have a battery leakage damaged a5000 that i can borrow parts from to check for operation.

I will also see if i can find a technical manual on the screen to see if that has failed. the monitor cable appears as tho it is intact however I will chuck a meter across it to ensure no broken wires inside
Yes a VIDC from A5000 would be fine in the A310, but the A5000 VIDC isn't usually (ever?) socketed, so you'd have to desolder this first - which could damage it unless you're good with a hot air rework station.

Another way to test the computer is functioning correctly without video, is pop a disc in the drive, press f12 and type *.

Also, check all the system clock is linked to VIDC through jumpers on PL3a. Jumpers should be 1-2 and 3-4, with 24MHz detected at pin 27 of VIDC.

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Mon Feb 03, 2020 11:44 pm

Hi Steve,
steve3000 wrote:
Mon Feb 03, 2020 9:11 pm
but the A5000 VIDC isn't usually (ever?) socketed,
I have just got my a5000 out of the storage cupboard. You are quite correct. just about everything is soldered on to the board. As i dont have a hot air rework i think i have to go down the replacement chip road.

One thing i have not noticed before and have just now noticed, is that the memc1a chip is blistering hot...too hot to touch.
Can i replace with this one?

https://www.ebay.com/itm/MEMC1A-10MHz-V ... SwjqVZC0nc

I am not sure what speed mine is, i think it is 8 mhz

I am also not getting any response from the floppy disc drive.

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Tue Feb 04, 2020 12:23 am

Well, things have gone from hrrmmm...to grrrr. after not getting a response form the floppy drive and the memc1a chip getting really hot it no longer has any lights on the keyboard an no response when pressing the caps lock etc.

i think i need to put this down for the rest of the day and do something else and come back again tomorrow.

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Wed Feb 05, 2020 4:57 am

Does anyone know where or of a technical reference manual for the a310? one that includes wiring diagrams and voltages etc at each point on the board.

Cheers

Kazzie
Posts: 1368
Joined: Sun Oct 15, 2017 8:10 pm
Location: North Wales
Contact:

Re: Acorn A310 help.

Post by Kazzie » Wed Feb 05, 2020 6:28 am

nzjavert wrote:
Wed Feb 05, 2020 4:57 am
Does anyone know where or of a technical reference manual for the a310? one that includes wiring diagrams and voltages etc at each point on the board.

Cheers
There are circuit diagrams for the mainboard at the very end of the module level service manual, on the page I linked to earlier.
BBC Model B 32k issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
Acorn System 1 home-made replica

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Wed Feb 05, 2020 7:14 am

Kazzie wrote:
Wed Feb 05, 2020 6:28 am

There are circuit diagrams for the mainboard at the very end of the module level service manual, on the page I linked to earlier.
DOH!. My my, do I feel a little stupid...lol. I mistook module service manual as the manual for podules...just a complete misread. Thankyou for the link and your help. hopefully will get back to have a look at this machine early next week. The next few days are a little busy.

steve3000
Posts: 2158
Joined: Sun Nov 25, 2012 12:43 am
Contact:

Re: Acorn A310 help.

Post by steve3000 » Thu Feb 06, 2020 10:35 pm

nzjavert wrote:
Tue Feb 04, 2020 12:23 am
Well, things have gone from hrrmmm...to grrrr. after not getting a response form the floppy drive and the memc1a chip getting really hot it no longer has any lights on the keyboard an no response when pressing the caps lock etc.

i think i need to put this down for the rest of the day and do something else and come back again tomorrow.
Yikes, none of the main chips in the Archimedes should ever get hot (or even warm) under normal conditions.

Before anything else, check the outputs from the PSU, disconnected from the Archimedes PCB but under a slight load (eg. a 5v computer fan) - make sure you're getting clean +5v and +12v (and FYI - you don't actually need the +12v plugged in to run the A310, providing you're running the base system with no fan or podule that is expecting +12v, but if you decide to run it without the +12v connected, make sure to tape up the +12v connector from the PSU with insulating tape, just in case).

Hope you can get it back functioning again...

nzjavert
Posts: 10
Joined: Sun Sep 22, 2019 7:00 am
Location: Hastings, New Zealand
Contact:

Re: Acorn A310 help.

Post by nzjavert » Thu Feb 06, 2020 11:15 pm

steve3000 wrote:
Thu Feb 06, 2020 10:35 pm
Yikes, none of the main chips in the Archimedes should ever get hot (or even warm) under normal conditions.

Before anything else, check the outputs from the PSU, disconnected from the Archimedes PCB but under a slight load (eg. a 5v computer fan) - make sure you're getting clean +5v and +12v (and FYI - you don't actually need the +12v plugged in to run the A310
Hi Steve,

That's what I thought! I don't remember any Archimedes I have ever owned, ever having temperature issues and one was set up in a glass conservatory in the middle of a New Zealand summer!

One of the first things i checked when I felt the heat, was the output of the psu as psu failure is a known issue in these machines. Everything was perfect coming out. One of the diagnostic hints in a fault finding chart was disconnecting the 12v and sadly made no difference. I think i need to sit down and study the wiring diagram with a multimeter at my side to test where the voltage is going or escaping from :)

sirbod
Posts: 1073
Joined: Mon Apr 09, 2012 9:44 am
Location: Essex
Contact:

Re: Acorn A310 help.

Post by sirbod » Sat Feb 08, 2020 8:38 am

Try removing the VIDC and see if you still have heat issues. If you do, you possibly have multiple issues, more than likely power related such as a short somewhere.

VIDC handles both video and sound, so the fact you have no sound, no video and a previously working CAPS LOCK points to the VIDC or traces in/out of VIDC being the original issue.

Post Reply

Return to “32-bit acorn hardware”