Repairing a broken Archimedes A3000 ... Update 14.05.17 - mouse progress - the mouse fully works too! I think, it's done

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YuT666
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Re: Repairing a broken Archimedes A3000 ...

Postby YuT666 » Thu Apr 06, 2017 6:51 pm

Thanks. i'll check these things at the weekend.

And ...

... connectivity of the keyboard to the PCB


Well, the only connection are the keyboard connectors on the PCB and the only things i could do, is to resolder all connector joints.
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Re: Repairing a broken Archimedes A3000 ...

Postby YuT666 » Sat Apr 08, 2017 11:51 am

Ok ...

I typed:

*st.
('cause i can't type an "u")

... and i received:

Acorn1.jpg
Acorn2.jpg


After that i typed:

*co. ba. 4
(it is only a example, cause i can't type "m" for mode ... so i tried to set Baud to 4 and i received a *prompt again, so i thought, it worked)

After that the status still showed "Baud 8" and not 4. I tried to change some other settings (Data, Truncate and some others, but there are still the old values).

Hm ...
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Re: Repairing a broken Archimedes A3000 ...

Postby Zarchos » Sat Apr 08, 2017 12:06 pm

Looks like a dead CMOS chip, to me.

They are still available, so I think you'll have to use your soldering iron ...

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Re: Repairing a broken Archimedes A3000 ...

Postby DutchAcorn » Sat Apr 08, 2017 12:19 pm

The CMOS chip is very close to the battery:

CMOS small.jpg


The battery acid may have killed the CMOS chip but first I would recommend checking the CMOS chip connectivity. The issue may well be caused by a corroded track on the PCB.
Paul

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Re: Repairing a broken Archimedes A3000 ...

Postby YuT666 » Sat Apr 08, 2017 1:25 pm

Yes, i'll check the tracks again ...

If everything looks ok, i buy a new cmos ic (found one at unholy eb**).

But i think, that the keyboard faults are a bigger problem ... i really don't know what to do now ...
Last edited by YuT666 on Sat Apr 08, 2017 1:34 pm, edited 1 time in total.
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Re: Repairing a broken Archimedes A3000 ...

Postby Zarchos » Sat Apr 08, 2017 1:28 pm

YuT666 wrote:Yes, i'll check the tracks again ...

But i think, that the keyboard faults are a bigger problem ... i really don't know what to do now ...


There's the possibility to connect an external keyboard to the A3000 (See on the motherboard).
Unfortunately I never managed to get all the necessary infos to do it.
How to do it was obvious for the few people who answered this existential questioning, but... not to me #-o

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Re: Repairing a broken Archimedes A3000 ...

Postby YuT666 » Sat Apr 08, 2017 1:36 pm

I think, i should replace both 74LS145 (it's not hard to do and i've some sockets here too) anyway to eleminate them as sources of the error.
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Re: Repairing a broken Archimedes A3000 ...

Postby DutchAcorn » Sun Apr 09, 2017 7:55 pm

I incorrectly assumed that the keyboard technology resembled the A300/A400 series. So it's a membrane affair. :?

Have you seen the circuit diagram of the keyboard interface?

A3000 Schematic.png


Again, corroded tracks are the first suspect. Using the diagram you can check the connections from the keyboard connectors to the components on the PCB.

If you do decide to replace the LS174s, please note that the battery acid may/will have weakened the pads on the PCB and that the solder will be harder to melt. Be prepared to fix one or two tracks...
Paul

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Re: Repairing a broken Archimedes A3000 ...

Postby YuT666 » Wed Apr 12, 2017 12:27 pm

Well, let's see, if i can get into that stuff ...

It looks like, that some of my ordered parts will arrive at saturday, so i can replace the CMOS ic (maybe i should socket this one).
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Re: Repairing a broken Archimedes A3000 ... Update 15.04.17 - made a mistake - no power

Postby YuT666 » Sat Apr 15, 2017 2:23 pm

Aaargh ... i'm an idiot.

I replaced the CMOS ic and tried to test the A3000 again ... a loose metal connector from one of my other cables touched the open power switch and *poff* ... there is no sign of life. No power LED.

I checked the fuse of the psu (F1,6A), but this one is ok (i replaced it with an other fuse anyway). I can't see anything burned.

What could i try? Thanks.

EDIT: Well, i forgot the connectors 3A fuse ... i replaced it and the A3000 is powering on.

I tried the same commands as above, but the CMOS is still dead. So it looks like a broken track or something else, 'cause the CMOS ic is definitely new.
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Re: Repairing a broken Archimedes A3000 ...

Postby YuT666 » Sun Apr 16, 2017 10:36 am

Can't follow the shematics, 'cause ... the IC4 and IC5 are a bit strange.

For example ... if keys "6" and "7" are not working, there is pin7 of the keyboard connector SK7. Good. Following the lines, it will be Y<5> ... good. So it will be IC4, but which pin? It has 16 pins, but the shematics are a bit obscure and i can't figure out the right pin of IC4 (it doesn't show 8 pins on each side). Sorry, but i'm not a shematics fanboy.

EDIT: Should be pin5 of IC4 ... and i'm realizing, that i'm only talking and writing here to myself the last posts.

DutchAcorn wrote:I incorrectly assumed that the keyboard technology resembled the A300/A400 series. So it's a membrane affair. :?

Have you seen the circuit diagram of the keyboard interface?

A3000 Schematic.png

Again, corroded tracks are the first suspect. Using the diagram you can check the connections from the keyboard connectors to the components on the PCB.

If you do decide to replace the LS174s, please note that the battery acid may/will have weakened the pads on the PCB and that the solder will be harder to melt. Be prepared to fix one or two tracks...
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Re: Repairing a broken Archimedes A3000 ... Update 15.04.17

Postby YuT666 » Sun Apr 16, 2017 3:32 pm

I soldered six wires for a test and almost all keys work now.

DSCN4023.JPG


I had a 7th wire from SK7s pin15 to IC5s pin 5, but all brighter pink keys associated to pin 15 are not working. These are the only keys which doesn't work.

The strange thing is, that i already soldered this wire and all pin 15 keys worked (so ALL keys of the keyboard worked), but i've to remove it to keep some structure in my wiring mess ... after that i soldered the 7th wire many times and it doesn't work again.

A3000 keyboard rows.png
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby DutchAcorn » Sun Apr 16, 2017 7:29 pm

Exellent progress Tom! =D>

Don't give up, you are nearly there :D

These battery acid repair jobs can be extensive and frustrating, the only way to get it fixed is lots of perseverance....
Paul

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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Sun Apr 16, 2017 8:02 pm

Thanks Paul, but i really don't know, what's wrong with SK7s pin 15 ... soldering to IC5s pin 5 looks right in the shematics (but maybe i've bad eyes) ...

Image

... but i doesn't work. I tried it again and again (as i mentioned it worked once, but ive removed it) ...
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby DutchAcorn » Sun Apr 16, 2017 8:51 pm

YuT666 wrote:Thanks Paul, but i really don't know, what's wrong with SK7s pin 15 ... soldering to IC5s pin 5 looks right in the shematics (but maybe i've bad eyes) ...

... but i doesn't work. I tried it again and again (as i mentioned it worked once, but ive removed it) ...


Looking at your picture IC5 pin 5 seems to be connected to pin 14 of SK7 instead of pin 15?
pcb pins.jpg
(42.59 KiB) Not downloaded yet
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Sun Apr 16, 2017 9:00 pm

No, that is pin 14 of SK7 to pin 4 of IC5. As i mentioned before, i removed the 7th wire from SK7 pin15 to pin 5 of IC5 (these are the only keys which don't work), 'cause i gave up after 1000 attempts. I soldered this one so often, but the brighter pink keys won't work ... so i removed the wire.
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby DutchAcorn » Sun Apr 16, 2017 9:19 pm

Just a thought, couldn't you connect pin 15 of SK7 to pin 4 of IC5? If the pink keys then work (with the wrong characters) at least you know the keyboard keys / membrane / connection to the PCB is ok. Alternatively you can connect pin 14 of SK7 to pin 5 of IC5 to isolate possible logic / PCB issues.
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby danielj » Sun Apr 16, 2017 9:20 pm

Have you checked whether pin15 is shorted to ground or +5V? It's a 4 layer board, internal corrosion could have caused some level of stupidity along those lines to have happened...

d.

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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Sun Apr 16, 2017 9:27 pm

How can i check this?

@Paul: Yeah, maybe i should try your advise ...
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby danielj » Sun Apr 16, 2017 9:46 pm

With a multimeter set to continuity (or low resistance) - put a probe on pin 15, then the other on a nearby pad that you know is ground, or +5V and see if they're connected?

d.

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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Mon Apr 17, 2017 9:11 am

I could try the 4th pad of LK4, this is 5V and near the keyboard connectors and the ICs, 'cause i can't find the pin assignment of LK8 (looks to be empty in the manuals).

Image
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Mon Apr 17, 2017 1:32 pm

There is no short circuit concerning pin 15. I resoldered the 7th wire and i measured the continuity from pin 15 (SK7) and pin 5 (IC5) and there is a signal. I've to check the keys again in a few minutes.

And guys ... could someone help me out with detailed pic of the soldered side of the CMOS IC (the back of the motherboard)? Would be great.
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby DutchAcorn » Mon Apr 17, 2017 8:17 pm

I know you don't like circuit diagrams but they can be helpful for checking the connections for the CMOS chip. You can find them here. Specifically for the CMOS chip this part is useful:

IMG_0874.PNG


Iirc the middle layer for the A5000 was used for connections to ground (0V) so you may not find the tracks on either side of the PCB. I'm on thin ice here though, not really sure. #-o
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Mon Apr 17, 2017 8:23 pm

Thanks Paul ... maybe your're right and my eyes aren't that good.

I post the picture i sent to you here too ...

Step8-new-solder.jpg


So the 2 circled pins look like, that they are originally connected/wired.
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby DutchAcorn » Mon Apr 17, 2017 8:34 pm

YuT666 wrote:Thanks Paul ... maybe your're right and my eyes aren't that good.

I post the picture i sent to you here too ...

So the 2 circled pins look like, that they are originally connected/wired.

Those are pins 3 and 4, they should / can be connected as they are both connected to 0V?
Paul

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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Tue Apr 18, 2017 7:45 pm

That looks ok on my board too ...

It was a long working day, so i haven't done anything for my Arc.

As i mentioned some days ago, i soldered a socket for the new CMOS IC (seems a bit strange for an IC with only 8 pins) and it looks like, that there's also a problem with the CMOS tracks. So what is the best way to test the CMOS IC or ... which track is mainly responsible for this IC's "life"?
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Wed Apr 19, 2017 5:47 pm

So lets have a look ...

All keys are working now! resoldered the 7th wire and here we go ...

Acorn 1.jpg


Acorn 3.jpg


The place of the battery leakage looks ok, but not as good as i expected. Soldered two pins for the battery and a socket for the new CMOS IC.

Acorn 4.jpg


Typed *Modules ...

Acorn 2.jpg


Well, the CMOS does not work yet, so this will be the next problem to solve.
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby IanS » Wed Apr 19, 2017 6:15 pm

Now the keyboard is working, have you done a delete power-on? Hold delete whilst powering on, hold it until you see the RISC OS banner.

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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby YuT666 » Wed Apr 19, 2017 6:33 pm

Yes, powering on with pressing "Delete" shows ...

1. A black screen with a white bar on each side for some seconds
2. A black screen with a white frame for some seconds
3. The usual prompt:

RISC OS 1024K
Supervisor
*

Powering on without "Delete" shows ...

1. A black screen with a white bar on each side for some seconds
2. The usual prompt.

So the difference is the black screen with the white frame. It looks like, that the Arc would show a different screen, but he can't get into it (don't know how to describe this situation exactly).
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Re: Repairing a broken Archimedes A3000 ... Update 16.04.17 ... almost all keys work, but pin15 keys don't ...

Postby Zarchos » Wed Apr 19, 2017 6:34 pm

and still some fancy values if you type STATUS
?


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