A3000 post-battery-leak-repair

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mark.treleaven
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A3000 post-battery-leak-repair

Post by mark.treleaven »

Hi guys, I have a bit of a mystery.

I recently aquired an Acorn A3000. The battery had leaked so I removed it cleaned up the board and without a battery fitted did a test power up using a bench power supply connected to the board where the regular PSU would connect.

It turned on and outputted fine (providing I held down delete) while powering it up.
I have since fitted a replacement battery (Varta Mempac 3/V150HT 3.6V), powered up using the delete to set config to defaults and since then the system has been working fine.

I got a replacement PSU for it, upgraded RISC OS from 2.00 to 3.11 and fitted a ZIDEFS CF podule from CJE Micros, all that is working great as well.

I have just got a copy of the A3000 dealer test disc, it says in the Service Manual if you get an message saying Unknown UUT there is a memory fault, but the memory test on the disc passed. The battery backed up RAM however failed, but I don't know why as it has been keeping the config while the machine has been off (sometimes for several weeks).

I have pics of the test disc screen shots if they are helpful, also I have a list of *help modules and the config status of my machine

there seems to be a econet module fitted as well, but the computer does not "see" it, configure app in RISC OS has "net" greyed out.
and *podules only shows the ZIDEFS board fitted, the other 3 spaces are showing as empty.

P.S all the lights on the keyboard apart from the Power light work, I have checked the keyboard flat connectors and they are OK and I took the keyboard apart and checked the LED that is also fine. But that is not important as it is just asthetics.

Can anyone shed some light on this
Thanks in advance
Mark Treleaven
Last edited by mark.treleaven on Fri Sep 13, 2019 10:48 pm, edited 1 time in total.
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Tills
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Re: A3000 post-battery-leak-repair

Post by Tills »

It might be that the CMOS RAM is reported as failing because the IC (PCF8583P) is defective in another way. It is known that after a long period without battery power the CMOS IC fails to keep time (as a real-time clock, which is its other function). It might be worth checking if the computer keeps time after you turn it off, or whether it is 'frozen' in time.

Incidentally, you can pick up a PCF8583P on ebay for a few pounds. I bought mine for 99p, including postage from the Far East, last year!
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mark.treleaven
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Re: A3000 post-battery-leak-repair

Post by mark.treleaven »

Thanks Tills

I have ordered a replacement PCF8583P on the chance that is the issue.

My machine does keep time ok and its not frozen.

One question, I do not have a IC programmer, do I need to get one in order to "program" this IC before fitting it in to the A3000?

I have my current CMOS settings saved to a floppy thanks to the Dealer Test Disc so that is not a problem
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Re: A3000 post-battery-leak-repair

Post by Tills »

No programming necessary; it's a standard chip, used by many little devices, even today (in a slightly different, surface mount package). You might want to socket it.

You should be able to restore your current settings to it without issue.

For my part, I have another difficulty in my own post-battery corrosion repair. My mouse has given up on the y-axis completely. I've replaced all the link wires/zero-ohm resistors in that area of the board (two of which were completely shot), and replaced the socket also. I'll double-check the traces, but I think it's the mouse. Any experience in this issue?

Tills
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Re: A3000 post-battery-leak-repair

Post by mark.treleaven »

Thats good to know there is no programming

I have not got an original Acorn mouse, but I do have an adapter that allows optical usb mice to be connected to the A3000 mouse port.

I have not had any issues with my mouse at all.

The only issues I have is trying to get my A3000 to "talk" to my Windows 10 pc via a serial cable and terminal software, the power light on the keyboard not working, the Econet module does not appear to work, the CMOS may be broken (as you know) and lastly via the scart cable to a lcd TV the image sometimes "blanks" for a second or two but the A3000 does not stop working while the screen is blank.

Apart from that everything is good

Sorry I could not help with the mouse issue.
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Re: A3000 post-battery-leak-repair

Post by philpem »

Tills wrote:
Sat Sep 14, 2019 10:13 pm
For my part, I have another difficulty in my own post-battery corrosion repair. My mouse has given up on the y-axis completely. I've replaced all the link wires/zero-ohm resistors in that area of the board (two of which were completely shot), and replaced the socket also. I'll double-check the traces, but I think it's the mouse. Any experience in this issue?
Which type of mouse are you using?

The old, boxy Archimedes mice had two common issues -- the bearing spring going weak over time (the RISC PC mouse suffers especially badly from this), and the switches failing over time (contact corrosion or just plain wearing out). You can remove the spring and stretch it out a little to fix that, it manifests as "skidding".

The more curvy RISC PC mouse drives the IR LEDs quite hard and tends to burn those out after a few years. Spare LEDs are available from Rapid, but need a bit of PCB butchery (some tracks cut and wires added) to adapt the board to the Kingbright LED's pinout. You'll also need to play around to get the LED alignment right. Make small changes to the angle until you can move the mouse in all four directions without the cursor jittering or juddering.

I'm stunned how many people chuck "broken" Acorn mice away when they can be fixed with £20 of investment... and that's if you need a soldering iron...
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Re: A3000 post-battery-leak-repair

Post by philpem »

mark.treleaven wrote:
Sat Sep 14, 2019 10:59 pm
The only issues I have is trying to get my A3000 to "talk" to my Windows 10 pc via a serial cable and terminal software, the power light on the keyboard not working, the Econet module does not appear to work, the CMOS may be broken (as you know) and lastly via the scart cable to a lcd TV the image sometimes "blanks" for a second or two but the A3000 does not stop working while the screen is blank.
The A3000 serial port is a bit weird. There's an Acorn application note on it. Firstly it's not fitted as standard -- you need to fit a serial upgrade (Retroclinic is currently selling them on ebay and I can recommend them). Secondly it tends to drop characters at high baud rates... 19200 should be safe though probably not much higher. The machines with PC-style I/O (A3010 and later) have serial buffers which reduces the chance of that happening.

Power light on the keyboard not working -- that's either an issue with the keyboard connection (corrosion on the connector or damaged conductive graphite on the cable). Membrane issues aren't unknown either. It's repairable but might be a bit of a faff.

SCART issue with the TV -- some LCD TVs don't like the output from Acorns. I'm having issues with waviness in the video on my A3010 which goes away after a few minutes powered on. I suspect that's bad capacitors or a dodgy crystal. Regardless, it's enough to really upset my TV.
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Re: A3000 post-battery-leak-repair

Post by davidb »

philpem wrote:
Sun Sep 15, 2019 12:16 pm
The A3000 serial port is a bit weird. There's an Acorn application note on it. Firstly it's not fitted as standard -- you need to fit a serial upgrade (Retroclinic is currently selling them on ebay and I can recommend them). Secondly it tends to drop characters at high baud rates... 19200 should be safe though probably not much higher. The machines with PC-style I/O (A3010 and later) have serial buffers which reduces the chance of that happening.
I remember that there was an application note, though I don't remember which one it was. A related note appears to be "234 Peripheral Interfacing via the Serial Port" (available at 4corn) but I thought there was a separate one and a replacement (software) serial module.

Edit: Found the serial patches here. Part of the ReadMe says:
These two modules are written to run under RISC OS 3.10, and improve integrity of serial communications (particularly receiving) at speeds of 9600 baud and above. They were included in the ROM distribution for RISC OS 3.11, and as such are not needed on systems equipped with this version of the OS.
Last edited by davidb on Wed Sep 18, 2019 11:00 am, edited 1 time in total.
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Re: A3000 post-battery-leak-repair

Post by Tills »

philpem wrote:
Sun Sep 15, 2019 12:11 pm

Which type of mouse are you using?
A Type 1 mouse, I think. The issue is electronic rather than mechanical. I've checked and the little wheel does rotate past the IR diodes. The diodes appear to emit IR (my digital camera picks it up!). I've now double-checked the continuity from the mouse to the pins on the keyboard and mouse decoder IC on the motherboard; they're all fine.

I'm going to hive this off to a separate thread ...
Last edited by Tills on Sun Sep 15, 2019 2:42 pm, edited 2 times in total.
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Re: A3000 post-battery-leak-repair

Post by hubersn »

philpem wrote:
Sun Sep 15, 2019 12:16 pm
The A3000 serial port is a bit weird. There's an Acorn application note on it. Firstly it's not fitted as standard -- you need to fit a serial upgrade (Retroclinic is currently selling them on ebay and I can recommend them).
Special wiring is needed for the "old" serial port based on the 6551. I'm sure the diagram is in the csa FAQ. It was a VERY frequently asked question back in the 90s.
Secondly it tends to drop characters at high baud rates... 19200 should be safe though probably not much higher.
19200 baud is the upper limit of the 6551 as used in Acorn Archimedes machines because of the crystal's frequency used (IIRC). This is absolutely reliable on an ARM2 A3000 if you use the 3.10 patches Acorn issued shortly after release (something to do with IRQ stuff), or use plain 3.11. Additionally, you absolutely need to use an extended serial buffer. I always used David Pilling's effort: https://www.davidpilling.com/serial.zip

16 KiB input and 4 KiB output was always fine.
The machines with PC-style I/O (A3010 and later) have serial buffers which reduces the chance of that happening.
I don't think this is correct. The multi I/O chips inside the A5000/A30X0/A4000 use a 16450 compatible UART which does not have any hardware buffer. The 16550 inside the Risc PC however has 16 bytes hardware buffer.

It is a long time since I last used an Acorn's serial port...probably 1996 before getting my ISDN/DSL router. So I reserve the right to be wrong :-)

Have fun
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Re: A3000 post-battery-leak-repair

Post by mark.treleaven »

thanks for the info hubersn

I have got realterm on my windows 10 pc, a Prolific USB to serial adapter, a standard 9 way null modem cable and I am using !Connector on the A3000.

The A3000 has RISC OS 3.11 ROMS fitted.

Due to the other issues mentioned before in the thread I have ordered myself a new CMOS IC and replacement crystals for X1, X2 and X3 to be on the safe side. These should all be arriving by the weekend, so will try again with the new bits fitted and the serial buffer software installed.

The service manual for the A3000 says it has "IBM-PC RS232 Standard layout" and lists the pinout.

I do have the serial port upgrade fitted on my A3000.

When I type on the A3000 it shows up on the terminal window on realterm but it does not work the other way.

I have been using 9600 buad 8n1 set on both machines, and I did manage to send a text file from the A3000 to realterm it only spat it out on the terminal window did not actually save it as a file.

But whenever I try and send anything to the A3000 I get a permanent "negotiating" message on the receive window of !Connector.
Last edited by mark.treleaven on Mon Sep 16, 2019 10:41 pm, edited 1 time in total.
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Re: A3000 post-battery-leak-repair

Post by hubersn »

mark.treleaven wrote:
Mon Sep 16, 2019 10:37 pm
But whenever I try and send anything to the A3000 I get a permanent "negotiating" message on the receive window of !Connector.
It sounds a lot like the typical handshaking problem when using a "standard" cable.

See here for info, answers 2.7 and 2.8 for general info and nullmodem wiring:
http://www.riscos.org/csafaq/part2.html#2_7

And here for a non-nullmodem serial cable with "Acorn wiring":
http://www.riscos.org/legacy/serial.html

You need to switch Connector to use the Serial Blockdrivers and use the "Internal" driver, NOT the "InternalPC" one. And set both sides to "Hardware Handshaking".

Then, everything should work.

Have fun
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Re: A3000 post-battery-leak-repair

Post by mark.treleaven »

thank you again hubersn

I will give that a try before I start working on the A3000 at the weekend when all the parts arrive I am waiting for and will update you.
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Re: A3000 post-battery-leak-repair

Post by mark.treleaven »

Just a quick update to everyone regarding the Dealer Test Disc

I think I found out why it was showing "Unknown UUT" when testing.

I think he program on the disc is only looking for RISC OS 1.2 or 2.0

In the Main folder there is a basic file called COMPTYPEA

There if a DEFFNswvers near the top that shows
A=INKEY(-256)
IF A=160 THEN 1.3
IF A=161 THEN 2.0

I manually typed this in to basic on my A3000 and got the result 164 as I have the RISC OS 3.11 ROMs fitted

I have added the line
IF A=164 THEN 3.11

A little further down is DEFPROCsetmIdb, there are 4 lines that have vers=2.0 in them, I have changed those to vers=3.11 and now when I run the test software it does correctly ID my machine as a BBC A3000+RS232+1M MEMORY

I still have not got around to re-testing my COM port issue before all the bits arrive this weekend, but will let you all know what happens.
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Re: A3000 post-battery-leak-repair

Post by mark.treleaven »

I have re-tried the serial port.

It is still the same, I can type on the A3000 and it shows up on the Windows PC terminal window and if I cange from ZModem to ASCII I can send basic text files to the PC (but with an error on A3000 "This error should not be possible 0:1).

But I can't send anything from the PC to the A3000.

Realterm does show that when I type or try and send the TX is flashing with data, but that is all I get.

I have got a 9db plug coming I am going to make up a serial loopback plug and test the port with the dealer test disc
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Re: A3000 post-battery-leak-repair

Post by Kazzie »

mark.treleaven wrote:
Wed Sep 18, 2019 8:06 am
I have re-tried the serial port.

It is still the same, I can type on the A3000 and it shows up on the Windows PC terminal window and if I cange from ZModem to ASCII I can send basic text files to the PC (but with an error on A3000 "This error should not be possible 0:1).

But I can't send anything from the PC to the A3000.

Realterm does show that when I type or try and send the TX is flashing with data, but that is all I get.

I have got a 9db plug coming I am going to make up a serial loopback plug and test the port with the dealer test disc
I would strongly suspect the wiring in this instance (probably the handshaking). If you haven't got any sense out of it by the weekend, I'll check the pinout of the cable that I've used for connecting my A420/1 and PC, as well as the software settings used.
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Re: A3000 post-battery-leak-repair

Post by Cutter »

Mark

Did you see my earlier thread on serial port connections from PC to A3000 here: viewtopic.php?f=16&t=17713 ?

In particular the link to the pinout for the cabling you need to follow?

I made my own cable up as none of the pre-made null modem cables you can buy seemed to have the correct wiring once I started checking.

Other things I missed originally were: forgetting to set to Zmodem on both the A3000 and PC side, and also making sure that you've set 8n1 both in your terminal programs, but also (on windows) on the serial ports themselves through device manager (i.e. you might have issues if you've set your terminal program to 19,200, 8n1 but your serial ports are set to say 9600 8n1 in device manager).

If you have Riscos 3.11, you don't need any other software on the A3000 to make it work, as long as you've fitted the serial upgrade chips themselves.

I use Teraterm on the PC and confusingly, if I go select File, then "send file" it doesn't work. I have to select File, then Transfer, then Zmodem, then Send (and then select the file to send).

As Kazzie says, most likely issue is the wiring in the null modem cable if it's one you've bought...
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