Tongue-tied A3010

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Zarchos
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Tongue-tied A3010

Post by Zarchos » Mon Jul 28, 2014 9:08 am

Hello people !

Yesterday I had the opportunity to buy the A3010 owned by one of the French who's been quite active on the Archimedes and RISC PC.
This person is Alain Brobecker.
He's got an interesting web site, in case you didn't know, with lots of stuff he did (demos, tools) to download, with commented sources (BASIC and ARM).
http://abrobecker.free.fr/
It's very interesting, there's a lot of maths as, well, Alain teaches mathematics.
He's been a regular contributor to the star infos section in one of the UK Acorn user mags.

OK so back to the commie I bought.
It doesn't output any sound.
Does this symptom bring some repairing ideas to some of you ?
I think the most obvious place to look at is the group of capacitors between the ARM250 chip and the audio connector, but well who knows there might be something else to do ?
Testing the output pins of the LM324 operational amplifier (1:left, 4:right, with the ground on pin 11) in case this chip would be dead ?

Cheers,
Xavier.

steve3000
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Re: Tongue-tied A3010

Post by steve3000 » Mon Jul 28, 2014 10:20 am

Have you checked the headphone socket at the back? Any output (even very low level)?

If headphones ok but no sound from speaker on the A3010 then check the speaker plug, which is very easily pulled out.

If no output from either, check the headphone socket for any sign of damage - anything that could cause a short circuit - this would trick the computer into cutting off the internal speaker.

Those are the most likely faults - after that, then time to consider the circuitry...

Zarchos
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Re: Tongue-tied A3010

Post by Zarchos » Mon Jul 28, 2014 2:04 pm

Thanks Steve.
Yes I checked, double checked everything but in fact I discovered something with this A3010.
I omitted to indicate that the built in power supply has been dismantled and the A3010 has now an external power supply.
I was happy to see that, as I had received some months ago an a3010, broken during transport, in the power supply area, so I thought I could apply the same modification found in the A3010 #1 to the A3010 #2.

So I did on this A3010 #2 what had been done on the #1 : remove many parts in the built-in power supply area.
Then, as I had no external power supply available I disoldered the external power supply connected to the A3010 #1 and connected it to the A3010 #2.

And then... guess what... there's no sound coming from the A3010 #2.

So there's something wrong with this modification.
(Odds that the A3010 #2 is faulty as far as sound output is concerned are low, to me).

+5V, +12V, -12V, ground wires from the power supply are connected to the A3010 mainboard where you can read these indications, but it mustn't be enough.

I'll post photos this evening, and I'll have checked beforehand if the OA receives any voltage, which I doubt.
There's the need, I think, to solder at least one additional wire to feed the OA...

Cheers,
Xavier.

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1024MAK
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Re: Tongue-tied A3010

Post by 1024MAK » Mon Jul 28, 2014 4:59 pm

This just a guess, but it is possible that some of the audio circuitry needs a -5V supply.

Mark

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Re: Tongue-tied A3010

Post by s1paulr » Mon Jul 28, 2014 5:56 pm

I believe that the audio section is a single ended design and requires +12v, +5v as well as something called "clean Vcc" which I suspect is a filtered 5v rail, but I am not sure. The schematics can be found at Chris's Acorns if that would help you diagnose the issue. A quick look at the schematic of the audio section also explains why it sounds so horrible :(

Zarchos
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Re: Tongue-tied A3010

Post by Zarchos » Mon Jul 28, 2014 9:30 pm

Hi all and thanks for your interest.

Here is the promised photo of an A3010 with some parts removed in the power supply area.
DSC_0359[1].JPG
It's now only a matter of soldering the 12V, -12V, 5V, 0V wires from an external power supply to the locations where it's indicated on the motherboard.

I had no time to check what is output by the AO (I had not noticed in fact it's a CMS version, mounted on a daugtherboard plugged vertically, so it means measuring is going to be tricky).
If I remember correctly, on a CMS, the round bit indicates pin 1, so I should be able to measure easily what is available on the right side of the chip (it faces up).
See here : http://qubeserver.com/Qube/projects.html Unfiltered sound for the A3000 there's the chip and its pins.
On the right, so, there's the ground and the output for the right channel.
I'll have a more thorough look at the documentation of the LM324 tomorrow, to understand what therre's on the other pins.

Tonight I'm a bit in a bad moon as I managed to cut my both hands while repairing my malfunctionning A540.
After cleaning the dust in the power supply fans I decided to put the casing upside down and shake it gently, but the thing escaped, I tried to handle it before it hits the ground... it worked but I cut myself and lost some blood.
How stupid ... #-o

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Re: Tongue-tied A3010

Post by munchausen » Tue Aug 26, 2014 9:05 am

I had an idea with regards to this. My A3010 has a dodgy 5V line that will sometimes produce anywhere between 2.5 and 3.6V, other times it comes up as normal. I have to keep powering it on and off to get it to come up stable.

When it has the wrong voltage, I get horrible noises coming from the speaker, so the audio is clearly sensitive to the 5V supply.

Now what is interesting is that while trying to solve this problem I was looking at the 5V regulator, and it doesn't produce 5V, it produces 5.1V. This might not mean anything, maybe it was just designed like this because it was a close to 5V as they could get. But it could also mean that the audio system actually needs that little bit extra. Or perhaps your 5V line isn't stable enough.

It might also explain why they chose to use a switched 5.1 to 40V configurable regulator for the 5V line instead of just a standard 5V regulator.

I'm not really sure, but I thought it could be relevant.

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Re: Tongue-tied A3010

Post by Zarchos » Tue Aug 26, 2014 4:52 pm

Thanks for your interest.

I must say I think it would be very interesting not only for me but for the community to have this issue fixed.
As the power supply is on the motherboard, finding a way (the right way) to connect an external power supply to an A30x0 motherboard would be an intelligent solution to save machines where the power supply is out of order.

I had no time to check what I say I would do.
If somebody here (maybe you, as you're qualified) could read the A3010 schematics to see what could possibly be wrong, it would help tracking the cause of the issue.

I don't experience the problems you have with noise : I just don't have any sound output at all.
It's true I haven't checked the 5V from the power supply.... I (wrongly, I think) assumed that it was good as except for the sound issue, my 2 A3010s fitted with an internal IDE mini podule work a treat when I connect the external power supply.

Could it be possible that the 5V from the external power supply is dead, and the only circuitry that uses 5V in the A3010 is the audio ?
Again, if sbdy could read the schematic it would help, as I'm not able to decipher that properly.

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Re: Tongue-tied A3010

Post by munchausen » Tue Aug 26, 2014 5:13 pm

Well analogue electronics was never my thing, but I can see that the audio circuit certainly uses "Clean Vcc" a filtered version of the 5V line. It also needs the 12V supply and has dedicated grounds.

I'm sure your 5V line is fine, but the only other clue I've got about where the problem could lie is in the fact that the "normal" PSU provides 5.1 rather than 5V.

I'd assume the Clean Vcc is also ok because it is used all over the place, not just for audio. It might be worth measuring "clean Vcc" anyway though, just in case. The easiest place to find it might be pin 6 of the mouse connector.

Zarchos
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Re: Tongue-tied A3010

Post by Zarchos » Tue Aug 26, 2014 5:20 pm

Have you got a link to the mouse connector where I can read which pin is #6 ?
And which is ground, although I think the ground on the motherboard should be the same ground ah ah (my skills in electronic are now very limited, I forgot most of my HeathKit course when I was a teenager :roll: and that was in English when I was 14 or 15. Thanks Daddy !)

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Re: Tongue-tied A3010

Post by munchausen » Wed Aug 27, 2014 10:05 am

Looking at the A3010 now, pin 6 is actually not easy to get to, except by plugging a wire into the mouse connector at the back of the machine. I'll have a look later and try to find an easier place to test from and get back to you.

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Re: Tongue-tied A3010

Post by munchausen » Wed May 11, 2016 9:26 pm

@Zarchos I was just looking at how to go about replacing the PSU and I now know why sound doesn't work on your A3010 :D

You noted that you connected up +5V, +12V, -12V and GND to the points marked on the mobo. However, there are two +12V supplies in the A3010, +12V regulated and +12V unregulated, and they are completely separate (they actually run off different secondary coils from the transformer). If you look at the schematic, audio output needs the regulated +12V supply. The points on the motherboard that you soldered to are the unregulated versions: +12VU and -12VU. You can connect up to the correct place for the regulated +12V supply on one side of LK2 (which is up by the mains input socket). Without my a3010 handy (it's still in the garage) I don't know which side, but if you bridge LK2 (with solder or an actual jumper) it doesn't matter anyway, or you can just try it and see which one works.

My question is: what are the -12VU and +12VU actually used for? I don't see anything on the schematic. In fact even the regulated 12V supply doesn't seem to be used anywhere except for sound (12V isn't even used on the floppy connector as far as I can tell). Could you test running without +/-12VU?

If it only needs 5V and 12V it should be a really easy swap, much easier than diagnosing and fixing the built in supply (which I've already shocked myself on a couple of times)!

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Re: Tongue-tied A3010

Post by Zarchos » Thu May 12, 2016 6:31 am

Ah ah that is something interesting.

I add it to my 'to do list'.

Are you ok with the modifications made (by Alain's father) as far as components removal is concerned ?
Does all this make sense to you ?

As I said before I was very happy to get this A3010, because an external power supply solution (if working ok) can be :
- a really great solution for all these 'non working' A30x0 machines where the fault is a non reparable PSU (on the A3000 the PSU is in the casing, but on a distinct motherboard, so it can be replaced. Not true for the A3010 and A3020)
- an interesting solution (to me, and I don't ask you to share this view) to free some space in the casing to install a zip drive for example, an SD card (removable) reader, etc ...

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Re: Tongue-tied A3010

Post by munchausen » Thu May 12, 2016 11:10 am

Zarchos wrote:Ah ah that is something interesting.

I add it to my 'to do list'.
Great :)
Zarchos wrote:Are you ok with the modifications made (by Alain's father) as far as components removal is concerned ?
Does all this make sense to you ?
They look fine to me. In fact the 12V regulator is still in place (Q1) and that and the components around it could be removed if you want. Alternatively, instead of providing 12V directly to LK2, if you put something a little over 12V into TP1 Q1 should regulate +12V to LK2 and sound should work.
Zarchos wrote: As I said before I was very happy to get this A3010, because an external power supply solution (if working ok) can be :
- a really great solution for all these 'non working' A30x0 machines where the fault is a non reparable PSU (on the A3000 the PSU is in the casing, but on a distinct motherboard, so it can be replaced. Not true for the A3010 and A3020)
- an interesting solution (to me, and I don't ask you to share this view) to free some space in the casing to install a zip drive for example, an SD card (removable) reader, etc ...
I agree on both points. One of the reasons I stopped working on my a3010 IDE mod was that I had to turn the machine on/off tens of times before it would boot, due to an issue with the 5V line. I replaced some caps to no avail, and foolishly managed to shock myself a few times trying to diagnose the issue.

I note that according to the partis website their ATAPI driver works with RO3.11, so if you don't mind holes in your case you could put an IDE zip drive there (on an A3020 anyway).

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Re: Tongue-tied A3010

Post by munchausen » Wed Jun 15, 2016 8:05 pm

Just wondering if you did any testing with this yet?

I'm keen to know if the unregulated -12V supply is needed, as I'm looking for a PSU at the moment, and if it isn't used then it simplified things quite a lot!

EDIT: Also, does anyone know how much power the A3010 needs on the 5V rail?

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Re: Tongue-tied A3010

Post by Zarchos » Wed Jun 15, 2016 8:37 pm

munchausen wrote:Just wondering if you did any testing with this yet?

I'm keen to know if the unregulated -12V supply is needed, as I'm looking for a PSU at the moment, and if it isn't used then it simplified things quite a lot!

EDIT: Also, does anyone know how much power the A3010 needs on the 5V rail?
No sorry :?
In my list of things to do now I've got some keyboard connectors, it's repairing my ARM3 A3000 (but 1st I must find it back and so far researches proved unsuccessful :( . But good news I discovered I had 2 A3000s with IDE interface :wink: I had completely forgotten, and batteries haven't leaked yet but I should hurry working on them. Bad Apple will again have to wait #-o ).

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Re: Tongue-tied A3010

Post by munchausen » Fri Oct 14, 2016 1:55 pm

I think I've found the most inexpensive way to do this: grab an xbox 360 PSU (I just got one for a fiver posted on ebay) and mod it to simply provide 12V (at 12A!). Then you can use a 12V to 5V (5A) step down converter (something like this http://www.ebay.co.uk/itm/291764292104) to get the 5V supply. The hole where the mains lead currently enters the A3010 can be replaced with a socket, and the step down converter mounted inside the machine.

I'm going to have a go at this when the parts arrive next week. It should also leave a lot of extra room in terms of supply power (so if you did this on an A3020 for example, you would be able to have a minipodule, an HDD and a network card all at the same time).

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Re: Tongue-tied A3010

Post by munchausen » Wed Oct 19, 2016 4:14 pm

Success - my A3010 lives again!

Haven't managed to mount it all neatly yet, but it starts/shuts down completely reliably now :)

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Re: Tongue-tied A3010

Post by munchausen » Sat Oct 22, 2016 11:18 pm

Well I just got it sorted well enough that I can at least put the machine back together.

New socket is mounted using two newly drilled holes. Using a 4 pin connector, two pins to carry 12V and GND, and the other two to go to the A3010 power switch, used to turn the xbox PSU on and off using its 5V and standby pins.
IMG_1699.JPG
And from the other side, with 12V to 5V DC->DC. Not mounted properly yet, but the bottom is covered in insulation tape so its ok with the machine stationary. I'd like to make a plate to mount it on that will then screw in where the transformer originally stood.
IMG_1696.JPG
It looks as though there's enough room for an IDE zip drive if you did some cutting, I'm just not certain that there is software support but Partis PowerATAPI looks like a good candidate.

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Re: Tongue-tied A3010

Post by munchausen » Tue Oct 25, 2016 12:32 pm

Just realised I forgot to respond to the actual problem of this thread: The sound works fine. Just connect 12V to pin 2 of LK2. LK2 is located near the mains connector. Pin 2 is the side nearest the front of the machine.

Also, as far as I can tell -12V is not needed, and you also don't need to connect up the unregulated 12V. They don't appear to be used for anything, I think perhaps they are just available for expansions.

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