Dead A305

discuss the archimedes & risc pc, peripherals and risc os/risc os on pi
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Re: Dead A305

Post by BeebMaster »

Need to get some conductive superglue then so these sockets don't keep coming loose!
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Re: Dead A305

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I'm just remembering...I think I did get to the RISC OS 3 Desktop OK when I had it in 512K mode didn't I?
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Re: Dead A305

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BeebMaster wrote:
Tue Oct 12, 2021 1:41 pm
I'm just remembering...I think I did get to the RISC OS 3 Desktop OK when I had it in 512K mode didn't I?
For reasons as yet unknown, it doesn't work on real hardware, but does work in Arculator.

Even the RISC OS 3 installation guide says only 1MB or upwards is supported.
c.f. viewtopic.php?p=304091#p304091
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Re: Dead A305

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Spose if I could get the chips I could fill up the empty row of sockets.

Before I forget, a couple of video things. First, do all these Archimedes era machines need 5V feeding into SCART from elsewhere to get a picture? Hitherto I thought it was only the A3000 which was like that. And can I build or buy a proper lead that doesn't need a flying wire precariously going somewhere else?

Second, as the A305 and A420/1 have been sharing the same monitor this week, I've noticed that the picture from the A305 looks distinctly "grainy" compared to the A420/1. Dunno whether that's just different video hardware between the two, or may be related to this problem with the VIDC being on the separate board. I'll try and get some pictures soon to compare. I was full of elation last night when I'd fixed the data abort thing, and planned several picture sets to show the A305 being revived, but first I think I need to sort out the new old problem. Think I'd better take out all 4 of the main chips and make sure the contacts are good. I noticed a bit of fluff or debris hovering about near one of the edges of the IOC chip and when I tried to clear it away it went further in, so that's probably not helping.
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Re: Dead A305

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While I had all the chips out, I decided to put VIDC & MEMC back on the motherboard and leave out the RAM expansion board. This setup now is giving me the same problem - sometimes no video, nothing happens, and sometimes it will start up correctly. So I think that means we can rule out the RAM board as being the cause of this problem.

It's intermittent and I can't understand what causes it. It just seems that a few power cycles eventually makes it come alive. I haven't yet seen it corrupt the screen and stop working in this configuration, but I expect if I leave it on long enough it will.

I've been happily using the RISC OS 3 desktop with only 512K, although I didn't have enough memory to load !Alarm, !Configure and !Edit at the same time. The only filer window I've tried is ResourceFS because there are no drives attached.
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Re: Dead A305

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BeebMaster wrote:
Tue Oct 12, 2021 5:45 pm
I've been happily using the RISC OS 3 desktop with only 512K,
Well isn't that bonkers. 3.10 or 3.11 ?
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Re: Dead A305

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RISC OS 3.11. Mind you, it's had a CMOS reset or twelve, so most of the memory allocations are zero. But the whole thing's bonkers! It will now do the screen corruption and reset cycle thing without the RAM expansion board present. Very, very odd. I think it's as near to its original state as I can get it now, apart from the bodges around the serial interface, and the RISC OS 3 ROM board which is fixed solidly and won't move.
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Re: Dead A305

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She's been behaving quite nicely for the last couple of hours, maybe she's a bit of a raver and just prefers the night time.

Started to re-assemble her now, RAM board back on, floppy drive in, backplane in. I should be able to post some screenshots soon, been doing plenty of recording with my new DVD recorder. After that I will put the podules back in and try my luck at fitting a Winchester as was my intention some weeks back.

This and the A420/1 have reminded me just how lovely these original Archimedes machines are, these were the best ARM machines by far. I'd struggle to do without my RPC 700, and I've even rehabiliated the much-maligned (mainly by me) A3010 into the BM Econet, but none of the post-Archimedes machines have anything like the style of these beauts.
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Re: Dead A305

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Well now, this is also odd. When I said the picture looked grainy, when it comes out on the DVD it's definitely rose-tinted!
October2021d141.png
Compared to a similar picture from the A420/1:
UseA4201-4.png
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Re: Dead A305

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BeebMaster wrote:
Tue Oct 12, 2021 10:58 pm
Well now, this is also odd. When I said the picture looked grainy, when it comes out on the DVD it's definitely rose-tinted!
LIkely because it's definitely not had FCO E011 applied, which you yourself advised me of just a few weeks ago - a simple fix to apply and does make a big difference.
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Re: Dead A305

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Right. Just as I'd nearly reassembled her! Well I've got the diode but not the cap.

Does that A305 picture look pink? Cos I am getting extremely confused now. Playing back the recording on the HDD of the DVD recorder is the right colour, playing the dubbed DVD in the DVD recorder is the right colour. Playing the DVD in my PC, or a copy of the files from the DVD in my PC, and the colour is pink. Playing the DVD in my laptop using external monitor and the colour is not nearly as pink. If I reprocess the pictures from the same copy video file I first copied from the DVD using the same ffmpeg command on my laptop, the result showing on the PC screen is identical. If I alter the red colour correction settings in my PC's graphics card I can reduce the pink to a more normal level, but that messes about with everything else. So I really don't understand.
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Re: Dead A305

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BeebMaster wrote:
Tue Oct 12, 2021 11:58 pm
Right. Just as I'd nearly reassembled her! Well I've got the diode but not the cap.
In that thread, I also completed FCOE009 at the same time btw. I should have mentioned that there.
They're quite specific 43R's.
BeebMaster wrote:
Tue Oct 12, 2021 11:58 pm
Does that A305 picture look pink?
Yes. Likely due to low levels in general I'd guess.
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Re: Dead A305

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BeebMaster wrote:
Tue Oct 12, 2021 11:58 pm
Right. Just as I'd nearly reassembled her! Well I've got the diode but not the cap.
Oh! I read the text file of FCO E011 I posted, and that says "22mF" - I was thinking what the hell is that! Since when has "m" meant "micro"? I very likely have 22uF, although radial not axial.

Although I think it is more likely to be the E009 mod that I will need to do, when my head clears. Hopefully in the meantime imagemagick will fix these screen caps for me.
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Re: Dead A305

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BeebMaster wrote:
Wed Oct 13, 2021 12:09 am
Since when has "m" meant "micro"? I very likely have 22uF, although radial not axial.
For some time before anyone started getting all SI on the job, I believe? Certainly I've seen mF elsewhere in Acorn docs, and it's not milli-farads!

I still reckon 10uF should be fine -- that's what the other machines use (see the start of the thread I just referenced).
I did fit 22uF though, just to be compatible with the FCO.
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Re: Dead A305

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And FCO E009 says 43W resistors, did W mean Ohms back then as well?

5,100 resistors here and not a single 43R...........
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Re: Dead A305

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BeebMaster wrote:
Wed Oct 13, 2021 12:24 am
And FCO E009 says 43W resistors, did W mean Ohms back then as well?
Yeah that one's weird. I'm possibly guessing a typesetting error converting from an omega? It's repeated throughout that FCO. But there are other grammar errors in there too.

FCO E011 and E009 are both presented with all these errors corrected in the Serviving module FWIW.
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Re: Dead A305

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A bit of Imagemagick has helped, saves me having to break the A305 again to re-record the fix when I've done these other mods!
October2021d141.png
Still don't understand why the DVD player shows it OK but it looks terrible in the PC.
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Re: Dead A305

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Here are 4 stages of pinkness taken with camera.

A305 feed passing through the DVD recorder to the TV attached to DVD recorder. Not very pink at all:
PinkA305-1.jpg
Recording of the above playing on the same setup. Perhaps slightly pink:
PinkA305-2.jpg
Same recording but playing on the PC. Extremely pink:
PinkA305-3.jpg
A305 connected directly to TV set, no DVD recorder involved. Maybe slightly pinker than the live picture passing through the DVD recorder:
PinkA305-4.jpg
Is all that being caused by the absence of these FCO mods?
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Re: Dead A305

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Wow, my brain is hurting now.

Here's the A305 recording playing on RPi4 with Dell monitor. Doesn't look too bad at all:
PinkA305-5.jpg
And now here's the Pi showing the picture I took of the PC monitor/TV set. A bit pink, but not as pink as it looks on my PC screen:
PinkA305-6.jpg
So I think part of the pinkness is being added either by the PC or the monitor connected to the PC.
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Re: Dead A305

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CPC finally sent me the 43W resistors today, so I am trying to psyche myself up for more A305 butchery. I already replaced 4 caps that didn't need replacing, so I hope this works! I might take the advice in the FCO and snip the existing parts away and solder new ones onto the old leads, rather than trying to get them off the board completely.
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Re: Dead A305

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BeebMaster wrote:
Sat Aug 28, 2021 6:14 pm
There are some quite good pictures here already, although I will make a new set:

https://www.beebmaster.co.uk/32bit/A305.html
Those Watford podules are not so common, have you dumped the ROMs?
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Re: Dead A305

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No, but I can do, as long as they're no bigger than 27256.
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Re: Dead A305

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I did it. But being the scaredydog I am, I did it in stages, changing the 3 resistors R20, R41 and R59 for 43 Ohm which still left it a bit pink but much improved from originally.
October2021f081.png
October2021f085.png
Then I snipped out R39:
October2021f090.png
October2021f096.png
October2021f103.png
Praise be (B C A305!)
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Re: Dead A305

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BeebMaster wrote:
Sat Oct 23, 2021 12:04 am
Then I snipped out R39:
=D> =D> =D>

Did you (already) do the cap & diode too?
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Re: Dead A305

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No, I was going to do that first originally as I already had the parts. But it seemed that the pinkness was more likely being caused by the wrong resistor values, so when they arrived, I did that mod (E009). I may do the E011 mod if it's likely to improve things even more.
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Re: Dead A305

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I did the cap & diode mod (E011). It doesn't look to have made any difference to the colour or brightness, but there is now a slight shadowing or ghosting in the top third of the screen which it didn't do before.
October2021f132.png
October2021f139.png
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Re: Dead A305

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BeebMaster wrote:
Fri Oct 22, 2021 5:27 pm
No, but I can do, as long as they're no bigger than 27256.
I'd be surprised if they're bigger considering they're from 1987/88ish, fingers crossed.
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Re: Dead A305

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Right, the ground work is being prepared. The EPROM programmer is at Station 1, in a different room to the main setup, and next to my modern (1990!) laserdisc player, which is needed to play "Day of the Daleks" which I have now located, which happens to be the next story in my Dr. Pertwee thread, so by a happy concatenation of circumstances, as Jeeves said to Bertram Wilberforce, that looks like it will all work out very nicely, and I can exterminate the EPROMs at the same time.

I'm not going to tempt fate by saying that it's the fourth successive day that the A305 has started up from cold without any problems, so I didn't say that at all.

When I've imaged the podule ROMs, the podules are going back in and then I am going to fit a Kyocera hard disc.

On a general point, do the Archimedes-era machines (300/400 series) have a charging circuit to the battery? I always use rechargeable ones anyway just in case, but I changed the Master-style 3 AA battery pack (with diode & resistor) I fitted originally for a 2 AA pack without diode/resistor.
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Re: Dead A305

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BeebMaster wrote:
Tue Oct 26, 2021 1:48 pm
do the Archimedes-era machines (300/400 series) have a charging circuit to the battery? I always use rechargeable ones anyway just in case
No. Use Alkalines. And not Duracell crud.
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Re: Dead A305

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In between hiding behind the sofa...
ReadEPROMs1.jpg
ReadEPROMs2.jpg
...here are the ROMs from the Watford Video Digitiser and Watford Hard Disc podules from my A305. I did them in lo and hi halves on my Morley EPROM programmer, and joined them together so hopefully they are all there. The hard disc one looks wrong but the video digitiser one seems OK.
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