Resurrecting A5000

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Pasty
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Resurrecting A5000

Postby Pasty » Wed Aug 23, 2017 3:02 pm

Hi I am trying to resurrect an old A5000. I did manage to get it to initialise and get to the desktop but the kbd did not work although the mouse did.
I have replaced the cmos battery with a separate AAA rechargeable to be on the safe side but there was very little if any damage around it. I am now finding that the kbd works but it will only go the the supervisor prompt and "-" repeats every 2 or 3 secs. If I press return it says "File ------- not found error &D6" If I then type DESKTOP I get the same for DESKTOP. The floppy does not flash during startup. I have tried Power on + DEL and Power on + R but this does not seem to help. Can anyone give me some help here please? I hope I have provided enough info.

RobC
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Re: Resurrecting A5000

Postby RobC » Thu Aug 24, 2017 9:36 am

Sounds like the CMOS RAM isn't responding to changes. If you can, check the circuit around the CMOS RAM IC - including checking that the IC is getting power and a clock signal.

If the circuit checks out, I tend to replace the CMOS RAM IC and clock crystal on any machines where the battery has run out as they don't seem to like being without power for long periods.

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DutchAcorn
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Re: Resurrecting A5000

Postby DutchAcorn » Thu Aug 24, 2017 9:44 am

Welcome! :D

Just for clarification; when you say you can only use the keyboard to go to the Supervisor prompt do you mean that you can go to the prompt from the desktop using the F12 key?

Do you get into the desktop after booting? The comment that the mouse is working *suggests* that you do (or was that before changing the battery?).

Can you check if the Del key works when in Supervisor mode? A keyboard issue may prevent a successful CMOS reset.

The keyboard circuit is nowhere near the CMOS circuit on the PCB so my first thought would be to check the keyboard connection and cable because of the intermittent "-".
Paul

Pasty
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Re: Resurrecting A5000

Postby Pasty » Thu Aug 24, 2017 12:37 pm

Hi again

The machine did initialise and get to the desktop with the mouse working but the kbd did not work ( This happened before I changed the battery but not always ). I now find that it behaves erratically. Sometimes I have no video output but the kbd lights up and sometimes when I power on it just goes to the supervisor prompt but my kbd is now working perfectly and that includes the Del key. I can type status and see all the settings. Are these stored in the CMOS? and if so I suppose the CMOS is OK). So this A5000 will not startup (mostly the case) or just goes to the supervisor. I am sorry that this is not too helpful as there are too many sometimes this and sometimes that - all very frustrating. I used to work with Acorns in a school and set up an administration system running over Econet and wrote some bits of educational software. I was hoping to look back at some of this as I remember the Acorn/ARM story with affection. Any further help will be much appreciated. ( I have a Risc PC700 with StrongArm but that is also not working )

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1024MAK
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Re: Resurrecting A5000

Postby 1024MAK » Thu Aug 24, 2017 1:23 pm

Hello and welcome to StarDot

Do you have a multimeter? If yes, it's a good idea to test the voltage on the terminals of the new battery, and on the supply pins of the RTC (CMOS) chip. Test both before powering on and then test both again after powering on.

And yes, all the normal configuration settings are stored in the battery backed SRAM in the RTC (CMOS) chip.

Mark
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Pasty
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Re: Resurrecting A5000

Postby Pasty » Thu Aug 24, 2017 3:07 pm

Hi again

I do have a multimeter but I don't know which pins to test on the 8583? I have got it to start at the supervisor and looked at the status and modules ( see attached images). I have seen that No Boot is set but doing *configure boot makes no difference? Does this help the investigation?
Attachments
DSCF5398.JPG
DSCF5399.JPG

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DutchAcorn
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Re: Resurrecting A5000

Postby DutchAcorn » Thu Aug 24, 2017 3:09 pm

*status will show you configuration settings even if the cmos chip is removed. It's just that those settings are corrupted / not useable.

The fact that *config boot does not alter status points to CMOS logic failure.

Battery damage can be hard to spot and the tracks in the CMOS / battery area of the PCB are very thin.

Can you post a picture of the CMOS area of the PCB (around where the battery was)?

If it starts to supervisor can it then later start in Desktop mode without you resetting cmos settings inbetween (holding Del on start-up)?
Paul

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daveejhitchins
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Re: Resurrecting A5000

Postby daveejhitchins » Thu Aug 24, 2017 3:12 pm

Welcome to the Forum, Pasty . . . Enjoy . . .

I'm sure you'll have all your machines up and running soon, with the help of the Forum members - Good luck :D

Dave H :D
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Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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DutchAcorn
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Re: Resurrecting A5000

Postby DutchAcorn » Thu Aug 24, 2017 3:14 pm

Pasty wrote:Hi again

I do have a multimeter but I don't know which pins to test on the 8583?

Pin 8 (+) and 4 (-)
Paul

Sanxion
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Re: Resurrecting A5000

Postby Sanxion » Thu Aug 24, 2017 3:22 pm

I have been following this post with a mixture of trepidation, excitement and suspense...I anxiously await a successful outcome.. (particularly as I am about to acquire an A5000 myself...).

8)

Pasty
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Re: Resurrecting A5000

Postby Pasty » Thu Aug 24, 2017 3:42 pm

Hi I have attached photos of the area. I can see some corrosion on the tracks - the camera is better than my eyesight. Del + power on does not go to desktop.
Attachments
DSCF5404.JPG
DSCF5403.JPG
DSCF5401.JPG

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1024MAK
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Re: Resurrecting A5000

Postby 1024MAK » Thu Aug 24, 2017 4:35 pm

PCF8583 pin-out:
Image

PCF8583 Data sheet here (PDF)

VDD (pin 8 ) is the positive supply pin.
VSS (pin4) is the 0V/"ground" pin.

When the computer is switched off, the voltage between pins 8 and 4 should be very similar to the voltage across the battery terminals.

When the computer is turned on, the voltage on the chip, on pins 8 and 4 should be between 4.3V and 5V. The voltage on the battery terminals should be greater than when it was switched off, and rising very slowly. Depending on which type (as in rated voltage) you have fitted, may never get as high as 4.3V.

Mark
Attachments
IMG_5187.JPG
PCF8583 Pin-out
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flaxcottage
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Re: Resurrecting A5000

Postby flaxcottage » Thu Aug 24, 2017 7:02 pm

A lot of those PCB connections look to be very corroded and these are in the power circuit to the CMOS chip.

rtc.jpg


You can use the CMOS/RTC diagram above to check connectivity and voltages. I had a similar problem with one of my A5000s and a couple of the links to the battery and +5v had corroded away.
- John

Currently running Level 4 Econet with BBC B, BBC B+ 128K, Master 128K, 4Mb A3000, 4Mb A3020, 4Mb A4000, 4Mb A5000 dual FDD; UK101; HP41CX setup; Psion 3a, 3mx and 5mx; Z88; TI-58c, TI-59 and printer, HP-16C programmer's calculator

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DutchAcorn
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Re: Resurrecting A5000

Postby DutchAcorn » Fri Aug 25, 2017 4:43 am

Pasty wrote:Hi I have attached photos of the area. I can see some corrosion on the tracks - the camera is better than my eyesight. Del + power on does not go to desktop.

It needs cleaning up to prevent further decay. You can use white vinegar first to stabilize the alkali that have leaked from the battery and then rinse with (distilled) water. Then let it dry for a day (or two). You can speed up drying by putting the pcb in an oven.

This process may visually reveal the track damage. After cleanup it is time to track down the fault(s).

Edit: I just noticed that there is also some corrosion on the tracks around the IDE socket, you may find that the floppy drive and / or harddisc do not function (correctly). The hard disc activity led track runs just south of the battery socket so it is good to check if that still works (after cleanup).
Paul

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1024MAK
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Re: Resurrecting A5000

Postby 1024MAK » Fri Aug 25, 2017 6:33 am

For more info, search this forum for White Vinegar
Here is one such thread :wink:

Mark
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Pasty
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Re: Resurrecting A5000

Postby Pasty » Fri Aug 25, 2017 7:24 am

Thanks for those very helpful replies. I will do the clean up and then test the tracks for continuity where possible but I am not sure about the best method to make repairs. I could try soldering fine wire to bridge damaged sections but the tracks are very fine! Any ideas on the best approach? The floppy did work when I did manage to get to the desktop (not any more) and the HDD gave a disc error 08 @ :4/00000C00 so comments about tracks around the IDE socket look like being the culprits.

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1024MAK
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Re: Resurrecting A5000

Postby 1024MAK » Fri Aug 25, 2017 7:48 am

If the track is very thin, especially if it has been damaged / attacked by the battery leakage, run a wire from component pad to component pad or to a through-hole via.

Mark
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Pasty
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Re: Resurrecting A5000

Postby Pasty » Fri Aug 25, 2017 9:21 am

Ok I have cleaned up the board with white vinegar, rinsed it off and dried it in the sun and gently with a heat gun. I have checked the continuity of all the tracks that looked bad and all seem OK. I have mounted the mobo back in the case and switched on - no video output. I left it for about 10 mins and tried again and it goes to the supervisor. I used the multimeter to check the before and after voltages on the CMOS. CMOS and battery were about 1.3V before and then after power on the CMOS voltage was about 4.3V and the battery was about 1.4V so I guess all these are OK. I guess the next step is to see if there is a clock signal to the CMOS? I have an oscilloscope if that helps?

RobC
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Re: Resurrecting A5000

Postby RobC » Fri Aug 25, 2017 9:37 am

Pasty wrote: I guess the next step is to see if there is a clock signal to the CMOS? I have an oscilloscope if that helps?

It's worth checking - should be 32.768KHz as shown in the schematic.

However, given the circuit seems okay though, it's more likely that the CMOS RAM chip will need replacing.

Pasty
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Re: Resurrecting A5000

Postby Pasty » Fri Aug 25, 2017 12:17 pm

OK I have put the scope on pin 2 and got a sine wave with a bump on it at a frequency of approx 30kHz so I guess the X5 is OK? There is also a clock signal but the freq is too high to measure. I can get another 8583 if that is the next move and I pressume the best way to fit it is to cut the existing legs and mount the new one onto the pads with a tiny dab of solder for each one?

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DutchAcorn
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Re: Resurrecting A5000

Postby DutchAcorn » Fri Aug 25, 2017 1:59 pm

One more check: do pins 5 and 6 on the 8583 connect with pins 44 and 45 of IC8 (the IOC)?

Those are the data lines the A5000 uses to read from / write to the CMOS chip.
Paul

Pasty
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Re: Resurrecting A5000

Postby Pasty » Fri Aug 25, 2017 2:42 pm

Yes pin 5 of 8583 connects to pin 44 on IC8 and pin 6 of 8583 connects to pin 45 of IC8.

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DutchAcorn
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Re: Resurrecting A5000

Postby DutchAcorn » Fri Aug 25, 2017 3:09 pm

Pasty wrote:... I can get another 8583 if that is the next move and I pressume the best way to fit it is to cut the existing legs and mount the new one onto the pads with a tiny dab of solder for each one?

Yes, cut the legs, desolder the legs one by one, clean the pads, put a very thin layer of solder on the legs of the new chip. Then, while pressing down on the chip, you can fix it in place by shortly heating each leg to the pads with the iron.
Paul

Pasty
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Re: Resurrecting A5000

Postby Pasty » Fri Aug 25, 2017 3:39 pm

OK I have ordered the chip and will report back when I have done it. Thanks to everybody for everything so far.

steve3000
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Re: Resurrecting A5000

Postby steve3000 » Sat Aug 26, 2017 6:42 am

Hi, welcome to the forum!

I must say, looking at those pictures of your CMOS RAM/RTC chip and surrounding circuitry, the damage doesn't look bad (at least compared to some of the thoroughly corroded Archimedes I've rescued in the past), so I'd say you've definitely got a good chance to get yours running :)

A failing CMOS RAM chip could certainly explain some of the issues you're seeing, but as you've got some time to wait for your replacement PCF8583 to arrive, I'd suggest another line of attack first...

With the intermittent faulty keyboard problems you've had - I'd actually suspect the keyboard itself. Collected dirt/dust in the keyboard is a common cause of intermittent function, can stop the delete+power-on function from working, and is very easy to fix. Have you opened up the keyboard and cleaned it out thoroughly? As well as opening and cleaning out any dirt/dust I'd also recommend carefully taking apart the metal frame inside the keyboard unit (it's held by lots of black plastic clips), to expose the two keyboard membrane sheets, these should separate easily but may feel stuck together depending on how much use they've had. Once apart, give them a wipe on both sides with a non-abrasive damp cloth. Then wash and dry everything else before putting back together. Keyboard will feel like new, and should have no intermittent faults.

After this, try switching on+holding delete again (press the "Del" key while computer is off, keep it held down while switching on, and only release it when you hear the "beep"). Does the computer reliably boot to the desktop? Next interrogate the modules and status again and also check the computer's time with *Time. Does the time increment when the computer is off? If not, this is a good sign of failed CMOS RAM/RTC chip or failed battery circuit.

Pasty
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Re: Resurrecting A5000

Postby Pasty » Tue Aug 29, 2017 1:01 pm

OK I have the new chip ( I ordered 8583P which seems about twice the size of the original but I managed to solder it in by bending the legs somewhat. Pins 6 and 7 got soldered together but I think pin 7 has no connection so left it). When I power on + DEL it goes to the supervisor prompt but I can change status settings now so I suppose the CMOS is working fine? I tried *desktop but it said there was not enough memory in the module memory area! RMASize was set to 2008K so I increased it to 4000k with the same result. I have attached a screen shot. Any ideas please?
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DSCF5430.JPG

steve3000
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Re: Resurrecting A5000

Postby steve3000 » Tue Aug 29, 2017 1:04 pm

Pasty wrote: When I power on + DEL it goes to the supervisor prompt but I can change status settings now so I suppose the CMOS is working fine? I tried *desktop but it said there was not enough memory in the module memory area! RMASize was set to 2008K so I increased it to 4000k with the same result. I have attached a screen shot. Any ideas please?

Holding on Del+power on should enter the desktop automatically, not supervisor, so something's wrong. Are you holding Del for long enough?

Pasty
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Re: Resurrecting A5000

Postby Pasty » Tue Aug 29, 2017 2:50 pm

I have tried your suggestion to clean the kbd and that has done the trick - I now go to desktop (photo attached). PROGRESS! But my floppy will not work it just says drive empty when I put a disk in and fire it up ( It worked a week ago when I ocassionaly managed to get to the desktop). I also have a problem with the HDD. When I configure as 1 IDE it takes a long time before returning to the desktop and if I click on it it says disc error 08 @ :4/00000C00. Likewise when I power on having configured the 1 IDE it takes a long time initialising.
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DutchAcorn
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Re: Resurrecting A5000

Postby DutchAcorn » Tue Aug 29, 2017 3:38 pm

Pasty wrote:I have tried your suggestion to clean the kbd and that has done the trick - I now go to desktop (photo attached). PROGRESS!


=D> Well done! Let's hope that you did not replace the CMOS chip because of a keyboard malfuction (you did report that the keyboard was working perfectly earlier...). Let's just assume that the CMOS chip was faulty as well 8)

Pasty wrote:But my floppy will not work it just says drive empty when I put a disk in and fire it up ( It worked a week ago when I ocassionaly managed to get to the desktop). I also have a problem with the HDD. When I configure as 1 IDE it takes a long time before returning to the desktop and if I click on it it says disc error 08 @ :4/00000C00. Likewise when I power on having configured the 1 IDE it takes a long time initialising.


You may have to trace the connections of the IDE and floppy connectors if you can't visually find a broken track.

I had to trace the IDE socket with an A5000 and documented where the pins of the IDE socket correspond with on the pcb. See http://www.stardot.org.uk/forums/viewtopic.php?f=16&t=11059&p=137068#p137579
Paul

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Re: Resurrecting A5000

Postby steve3000 » Wed Aug 30, 2017 9:38 am

Pasty wrote:I have tried your suggestion to clean the kbd and that has done the trick - I now go to desktop (photo attached). PROGRESS!

Great to see that!
Pasty wrote:But my floppy will not work it just says drive empty when I put a disk in and fire it up ( It worked a week ago when I ocassionaly managed to get to the desktop). I also have a problem with the HDD. When I configure as 1 IDE it takes a long time before returning to the desktop and if I click on it it says disc error 08 @ :4/00000C00. Likewise when I power on having configured the 1 IDE it takes a long time initialising.

If the floppy drive icon appears on the desktop, then (at least with the A5000), this confirms the drive has been detected by SuperIO chip - so that's a very good sign. First check the floppy drive cabling at the back of the drive and in particular, check it is correctly plugged into the socket PL10 on the A5000 PCB. If you suspect PL10 may be faulty, there are actually two floppy drive sockets on the A5000, so try moving the connection to PL11.

It is possible the drive is failing, or is just contaminated with dirt/grim inside. Do you hear the drive motor engage briefly when you switch on the computer? If so, the motor is probably OK. Do you have a 3.5" disc drive head cleaning disc? Also try different floppy discs, because sometimes old floppy discs get contaminated, and these can cause the drive to report empty.

As for the HDD, this error looks like the sign of a failed HDD. Is it a real hard disc, or a replacement CF or SD card? Have you ever seen the HDD working - if it is a real drive, does it make the correct spin-up noises? Once the floppy drive is functioning, then you can try reformatting the HDD :)


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