A310 restoration

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paulv
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Re: A310 restoration

Post by paulv » Sun Apr 28, 2019 12:47 pm

That IFEL ARM3 upgrade is the UBER rare only ~400 CPU's made 36MHz version of the ARM 3 chip. The fastest ARM3 there is...

For a tenner for the entire machine, I'd say you have the bargain of the century if only the ARM3 board works...

Paul

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Re: A310 restoration

Post by Kazzie » Sun Apr 28, 2019 1:27 pm

paulv wrote:
Sun Apr 28, 2019 12:47 pm
That IFEL ARM3 upgrade is the UBER rare only ~400 CPU's made 36MHz version of the ARM 3 chip. The fastest ARM3 there is...

For a tenner for the entire machine, I'd say you have the bargain of the century if only the ARM3 board works...

Paul
I think the ARM3 upgrade is from the £83 one.

Either way, my A420/1 is all sorts of shades of purple with envy... =P~
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Re: A310 restoration

Post by DutchAcorn » Sun Apr 28, 2019 4:02 pm

Did you have the floppy drive connected? If so, you can check if it flashes a fault code.
Paul

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Re: A310 restoration

Post by simonm » Sun Apr 28, 2019 4:15 pm

paulv wrote:
Sun Apr 28, 2019 12:47 pm
That IFEL ARM3 upgrade is the UBER rare only ~400 CPU's made 36MHz version of the ARM 3 chip. The fastest ARM3 there is...

For a tenner for the entire machine, I'd say you have the bargain of the century if only the ARM3 board works...

Paul
Wow, that sounds like good fortune then! :shock: I thought it seemed strange that the crystal said 36Mhz when the upgrades on Chris' acorns all talk about 25Mhz etc. I see there's a retro-kit page for this upgrade too.

And yes, this was in the £83 machine.

I've ordered a PLCC extraction tool, so I'll try swapping the upgraded CPU out of here into the other working machine and see what happens.
DutchAcorn wrote:
Sun Apr 28, 2019 4:02 pm
Did you have the floppy drive connected? If so, you can check if it flashes a fault code.
Great idea thanks, I'll try that.

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Re: A310 restoration

Post by simonm » Sun Apr 28, 2019 4:57 pm

simonm wrote:
Sun Apr 28, 2019 4:15 pm
DutchAcorn wrote:
Sun Apr 28, 2019 4:02 pm
Did you have the floppy drive connected? If so, you can check if it flashes a fault code.
Great idea thanks, I'll try that.
Hmm... plugged in floppy drive (tried two different drives). Nothing - no LED activity, not even a powerup seek. I'm going to try swapping the motherboards with the other computer, to rule out the PSU being dodgy.

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Re: A310 restoration

Post by simonm » Sun Apr 28, 2019 9:31 pm

Ok I tried the motherboard in the other machine and same result, so that helps to eliminate the PSU to some degree. The fact that there's only 2 speaker clicks (seems to be 5 on a good powerup), and no display output indicates it's not even getting to the stage where the POST runs...
Last edited by simonm on Sun Apr 28, 2019 9:34 pm, edited 1 time in total.

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Re: A310 restoration

Post by danielj » Sun Apr 28, 2019 9:41 pm

5.6V - was that under load? Sounds a little high...

d.

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Re: A310 restoration

Post by paulv » Sun Apr 28, 2019 9:41 pm

Ok, so are you booting without the colour card fitted? If so, you may be missing the jumpers you need to connect the sysclock to the VIDC chip at the very least.

You will need a jumper on 1-2 and 3-4 of PL3a to use the machine without the colour card I believe.

Paul
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Re: A310 restoration

Post by simonm » Sun Apr 28, 2019 10:28 pm

paulv wrote:
Sun Apr 28, 2019 9:41 pm
Ok, so are you booting without the colour card fitted? If so, you may be missing the jumpers you need to connect the sysclock to the VIDC chip at the very least.

You will need a jumper on 1-2 and 3-4 of PL3a to use the machine without the colour card I believe.

Paul
Good thinking - yes I was booting without that, not realizing it had board configs. Putting the jumpers back onto PL3a gives me a red screen now at least. Thanks.
danielj wrote:
Sun Apr 28, 2019 9:41 pm
5.6V - was that under load? Sounds a little high...

d.
I'm reading 5.6V from the spade connectors on the motherboard from the PSU. In terms of under load, there's nothing attached to the PSU other than the motherboard. It does seem high. :?

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Re: A310 restoration

Post by simonm » Sun Apr 28, 2019 11:02 pm

Aha, I reconnected the floppy drive and it's now flashing error codes at me. So those PL3a jumpers must have been necessary to get the POST to start maybe. Decoding the fault code gives me 00020101.
I'm reading that as a RAM control line failure, and CMOS RAM checksum fail ? (no flag for ARM3 detection though... :? )

The RAM board was quite gunked when I first started out. Also, that big capacitor across IC68 seems like someone's added it for some reason... (although IC68 is the speaker driver as Paul has mentioned in this related thread).

So I wonder if something has failed on the RAM board. Would it be worth trying to swap the RAM board from the other machine?

EDIT: looks like the whole thing is soldered in, so that's not an easy option anymore. I thought they were just plugged in like the ROM boards. :roll:
Last edited by simonm on Sun Apr 28, 2019 11:50 pm, edited 5 times in total.

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Re: A310 restoration

Post by paulv » Mon Apr 29, 2019 6:17 am

Have you done another DEL on power on since getting the VIDC clock reconnected? If not, do this first to see if the CMOS RAM checksum error goes away. If it does, then we're making progress. If not then we may have a common issue in reading the CMOS and accessing RAM so it'd be a look at the schematics to determine what the culprits may be.

If it were me, if there's no progress, I'd be checking the MEMC1a and RAM line buffer chips before looking at the RAM on the board. Given the proximity to the batteries, I'd look at IC1 and 2 on the RAM board and the only other things I'd do is extract and re-seat MEMC and the ARM3.

The ARM 3 is running as the ROM wouldn't get as far as it did.

The capacitor on the audio driver is a factory fitted thing so if you have any beep at all, the audio should be OK.

Paul

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Re: A310 restoration

Post by myelin » Mon Apr 29, 2019 5:45 pm

simonm wrote:
Sun Apr 28, 2019 11:02 pm
Also, that big capacitor across IC68 seems like someone's added it for some reason... (although IC68 is the speaker driver as Paul has mentioned in this related thread).
My A310 has one of those fitted also... definitely looks like a fix/addition, but maybe a standard one given that we both have them?
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Re: A310 restoration

Post by simonm » Mon Apr 29, 2019 8:17 pm

Thanks for the help so far everyone!
paulv wrote:
Mon Apr 29, 2019 6:17 am
Have you done another DEL on power on since getting the VIDC clock reconnected? If not, do this first to see if the CMOS RAM checksum error goes away. If it does, then we're making progress. If not then we may have a common issue in reading the CMOS and accessing RAM so it'd be a look at the schematics to determine what the culprits may be.
So I just tried this but same code reported, 00020101. I don't know if its relevant or not, but the keyboard is unresponsive during the POST sequence - caps lights cant be toggled for example. I know the keyboard is ok, because it works on the other machine.
If it were me, if there's no progress, I'd be checking the MEMC1a and RAM line buffer chips before looking at the RAM on the board. Given the proximity to the batteries, I'd look at IC1 and 2 on the RAM board and the only other things I'd do is extract and re-seat MEMC and the ARM3.
I can try the re-seating when the PLCC tool arrives. Do the ARM3 boards just lift out by manually pulling then?
The capacitor on the audio driver is a factory fitted thing so if you have any beep at all, the audio should be OK.
So since myelin reports having the same cap too, thats 3 upvotes for it being standard, so now its more of an anomaly that the other machine doesn't have one!
Last edited by simonm on Mon Apr 29, 2019 8:20 pm, edited 1 time in total.

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Re: A310 restoration

Post by paulv » Mon Apr 29, 2019 8:46 pm

simonm wrote:
Mon Apr 29, 2019 8:17 pm
So I just tried this but same code reported, 00020101. I don't know if its relevant or not, but the keyboard is unresponsive during the POST sequence - caps lights cant be toggled for example. I know the keyboard is ok, because it works on the other machine.
That sounds fine so let's break down what we've got and what we should expect.

&20101 where

2 = RAM control line failure
0
1 = CMOS RAM checksum error
0
1 = Self-test due to power-on

I had this error on my A5000. But that machine reports &20141 because the 4 is for the "PC-style IO world detected" whereas the A310 has the IOC chip and no PC-style IO.

I fixed the A5000 by replacing the SMT RAM line buffer chip (a 74AC138 in the A5000).

Also note that even though the A5000 is an ARM3 machine, the POST didn't get that far so doesn't report the ARM3 is detected...

For the A310, you need to be looking at IC59 on the motherboard which is a 74ALS138. I'd also investigate IC77 which is used for bank switching and feeds into the ALS138. Your problem here is that they're under your RAM board but I suspect if your A300 RAM expansion is like mine, one of those two chips will have been transferred or replaced by a chip on your RAM expansion... It's a guess but I believe it'll be IC59 that's transposed onto the RAM expansion board.

I can't make out what IC 7 (EDIT: IC7 looks like ALS138 but the 8 is blurry) and 11 are on your photo's but if there's no ALS138 or equivalent on the expansion, I'd look at the 74F245's as a starting point as it's probable that they are used as RAM line buffers on your RAM expansion board. I'd also check that the three wires you need connected to the underside of the MEMC socket on the motherboard have good solder joints and that they have good continuity.

This fix addressed both the CMOS and RAM control line errors on my A5000.

Paul
Last edited by paulv on Mon Apr 29, 2019 9:03 pm, edited 2 times in total.

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Re: A310 restoration

Post by paulv » Mon Apr 29, 2019 8:55 pm

simonm wrote:
Mon Apr 29, 2019 8:17 pm
I can try the re-seating when the PLCC tool arrives. Do the ARM3 boards just lift out by manually pulling then?
The capacitor on the audio driver is a factory fitted thing so if you have any beep at all, the audio should be OK.
So since myelin reports having the same cap too, thats 3 upvotes for it being standard, so now its more of an anomaly that the other machine doesn't have one!
Given the error, I'd say there's no need to pull the ARM3 or MEMC now.

The cap is definitely factory fitted but very early models may not have had it and it probably became and FCO where any machines that came in for servicing had it applied and any new machines had the work done before shipping. I'd have to double check that but it wouldn't surprise me as Acorn did this in other areas of the A300 series motherboards including around video output to reduce disc I/O interference on high res screen modes.

EDIT: in fact your motherboard has the FCO applied for the video interference reduction already in place.

Paul
Last edited by paulv on Mon Apr 29, 2019 8:59 pm, edited 1 time in total.

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Re: A310 restoration

Post by simonm » Mon Apr 29, 2019 9:40 pm

paulv wrote:
Mon Apr 29, 2019 8:46 pm
For the A310, you need to be looking at IC59 on the motherboard which is a 74ALS138. I'd also investigate IC77 which is used for bank switching and feeds into the ALS138. Your problem here is that they're under your RAM board but I suspect if your A300 RAM expansion is like mine, one of those two chips will have been transferred or replaced by a chip on your RAM expansion... It's a guess but I believe it'll be IC59 that's transposed onto the RAM expansion board.

I can't make out what IC 7 (EDIT: IC7 looks like ALS138 but the 8 is blurry) and 11 are on your photo's but if there's no ALS138 or equivalent on the expansion, I'd look at the 74F245's as a starting point as it's probable that they are used as RAM line buffers on your RAM expansion board.
Ok great, I think the board design must be the same as yours, as your guesswork is spot on:

IC77 is a 74HC75E, sitting under the board opposite IC59. (I sure hope this doesn't need replacing!! :shock: )

IC59 is a socket, with header pins up to above where IC 7 is. IC7 and IC11 are 74ALS138 as you said.
2019-04-29 22.06.03.jpg
IC67 and IC51 are at each end of the board and are similar to IC59 where there are just sockets with header pins up to the board above.

I'm wouldn't know how to go about testing the chip, but I'm willing to learn! However, I dont have a logic probe or any such tools (yet). If its simpler to just speculatively replace it, I'm happy to try that approach?
I'd also check that the three wires you need connected to the underside of the MEMC socket on the motherboard have good solder joints and that they have good continuity.
Now this I can do! :D
UPDATE: They are fine. Joints are clean, continuity good.
Last edited by simonm on Mon Apr 29, 2019 10:00 pm, edited 1 time in total.

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Re: A310 restoration

Post by IanS » Mon Apr 29, 2019 9:43 pm

paulv wrote:
Mon Apr 29, 2019 8:46 pm
For the A310, you need to be looking at IC59 on the motherboard which is a 74ALS138. I'd also investigate IC77 which is used for bank switching and feeds into the ALS138. Your problem here is that they're under your RAM board but I suspect if your A300 RAM expansion is like mine, one of those two chips will have been transferred or replaced by a chip on your RAM expansion... It's a guess but I believe it'll be IC59 that's transposed onto the RAM expansion board.
I think that RAM board has one ram chip at each end of the board has been transferred from the motherboard to the RAM card.

I've never tried it, but removing a memoey card from an A310/A305 looks like a bit of hassle. they not only transfer a few (normally 3) chips from the motherboard, they also have connections to many of the resistors on the leading edge of the board.

e.g.
a310-mem.png

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Re: A310 restoration

Post by simonm » Mon Apr 29, 2019 9:59 pm

Indeed - it looks even more permanent from the other side - resistors soldered directly onto the pins etc. :shock:
2019-04-29 22.55.00.jpg
These fitting instructions for a Simtec board look similar and certainly not for the faint hearted!

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Re: A310 restoration

Post by simonm » Mon Apr 29, 2019 10:42 pm

In the spirit of initiative I did some light research on how to fault find these chips.
I read that its sometimes a quick useful test to piggy back the suspected chips with new chips to see if that fixes the issue?
Also I read that using a logic probe to test if certain pins are floating or continuously high or low instead of pulsing or fixed level is another diagnostic. (I sound like such a n00b :lol: ). So I think I'll order a logic probe and some chips to try both of these techniques, it's interesting to learn all of this, and pretty much the reason I wanted to attempt it!
Last edited by simonm on Mon Apr 29, 2019 10:43 pm, edited 3 times in total.

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Re: A310 restoration

Post by steve3000 » Mon Apr 29, 2019 10:44 pm

Wow! Well done finding an A310 with that rare 36MHz ARM3 and a colourcard! That is a very high spec A310, in fact very similar to the one I had BITD (long since gone) which also had the 36MHz ARM3, IFEL RAM u/g + IFEL podule backplane and ICS IDE...although I never owned a colourcard, that'd have been the icing on the cake :)

FYI The modified dual colour power/IDE LED although looking 'hacked' was a standard part of the ICS IDE interface.

Hope you get the RAM fault resolved and the computer back up and running, it will be a very accomplished machine!

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Re: A310 restoration

Post by simonm » Mon Apr 29, 2019 10:51 pm

Thanks Steve. A dual colour LED makes much more sense. And who knows maybe it IS yours?! Did you sell it onto a video enthusiast?! :lol:

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Re: A310 restoration

Post by simonm » Mon Apr 29, 2019 11:12 pm

In other odyssey news, I've been on ebay looking at chips. Rock and roll.

So, there's SN74ALS138N and DM74ALS138N and SN74ALSAN chips on ebay. TIL that the "SN" and "DM" bit is the manufacturer (Texas Instruments and National Semiconductor respectively), but out of curiosity whats the difference between suffixes for a 74ALS138N and a 74ALS138AN ? Are they compatible just different packaging?
The DM74ALS138N ones are the cheapest - are they ok to use?

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Re: A310 restoration

Post by steve3000 » Tue Apr 30, 2019 12:50 am

simonm wrote:
Mon Apr 29, 2019 10:51 pm
Thanks Steve. A dual colour LED makes much more sense. And who knows maybe it IS yours?! Did you sell it onto a video enthusiast?! :lol:
Ahh, I would love to think that my old A310 was being looked after somewhere... but alas not. Mum said she cleared the entire contents of the loft to the tip, while I was at uni back in the late 90s, so except for a few random bits I found in a shoebox she'd missed in the garage (some discs, manuals, my A310's original ARM2 chip and a PLCC extractor tool!), the rest will be rotting away under several 100 tonnes of landfill somewhere in the vicinity of Birmingham...

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Re: A310 restoration

Post by paulv » Tue Apr 30, 2019 5:40 am

The main issue I see with this now is that we can't see if there any battery damage to the PCB or RAM expansion board so if there's a dodgy track, replacing the chips won't fix it.

I know it's tricky but I think desoldering the board would have to be my next step after the chips have been verified so the tracks can be inspected and repaired if necessary.

Paul

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Re: A310 restoration

Post by danielj » Tue Apr 30, 2019 6:13 am

Time to buy the desoldering gun, Simon :)

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Re: A310 restoration

Post by daveejhitchins » Tue Apr 30, 2019 6:36 am

Nice ideA interface :mrgreen:

IIRC that version has pin 1 tied to +5V. There's a mod to connect pin 1 to an address line allowing an upgrade to the firmware. I'll see if I can find the post . . .

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Re: A310 restoration

Post by steve3000 » Tue Apr 30, 2019 6:40 am

When desoldering multiple pins at once, without a desolder gun, I've had some very good success recently using Chipquik alloy. Although it's marketed for SMD work, it's been great when removing thorough-hole ICs and sockets from an A3000 I've been working on (more on this soon), because the very low melting point solder alloy allows you to free up multiple pins at the same time. A good clean up is required after, though.

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Re: A310 restoration

Post by daveejhitchins » Tue Apr 30, 2019 6:50 am

The mod procedure, for the firmware update is here. I can do this for you, if required (?)

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Re: A310 restoration

Post by simonm » Fri May 03, 2019 10:24 pm

Oh. My. Days. The gods are good.
I piggy backed two new 74LS138N chips on the ones on the RAM board, and it boots to desktop! :shock: [-o< There I was with my pen and paper in hand ready to capture the next POST error!
It's another 4Mb, RISC OS 3.10. My deepest gratitude to everyone and especially paulv for the LS138 advice.
2019-05-03 23.10.31.jpg
to my surprise, I saw a blue screen then a desktop!
2019-05-03 23.11.52.jpg
risc os 3.10 & 4mb
2019-05-03 23.13.35.jpg
piggy back for the win
(sorry about the wierd rotations in the pics, forum must be ignoring the exif tags or something)
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Re: A310 restoration

Post by paulv » Sat May 04, 2019 6:24 am

=D> =D> Happy Dance =D> =D>

Paul

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