Seeking help with Acorn Archimedes A3000 repair

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Seeking help with Acorn Archimedes A3000 repair

Postby mons2b on Tue Sep 20, 2016 9:31 pm

HI

I am hoping someone here might help me with my A3000 which im trying to save the motherboard on. I got it many years ago. Has Tam Int K8 on it. I assume its Tamaki Intermediate but who knows.

Anyway.. I belatedly read they were known for the clock battery leaks ruining them after I tried to turn it on and it went into a command line prompt instead of the expected desktop.

I whipped it open and sure enough the battery was pushing discusting orange poison out the top. I clipped it off and threw that away. Fine so far.. Then did the vinegar and meths/alcohol treatment which made some parts turn a interesting shade of blue green. The thing I need help with is there was a little very fine wire "bodge" that was connected at two points in that area and during my cleaning one end came off and I dont know where it was connected! So im a bit worried what might happen. Now of course ive looked hard online and all the pictures I can see of A3000 motherboards do not show this mysterious wire. I dont know if its a super early edition of the mother board or if its related to the onboard hard drive or ram expansion. I dont think so but still that leaves what the heck is that little wire for? What was the other end connected to?

If you have no ideas then can any of you hazard a guess by looking at the end that is still connected and that area its located? I hope. Photo below showing the mysterious wire. Note its the little tiny wire not the larger one where the battery directly was. Ive got the end of a pen pointed at the wire concerned.

John
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby mons2b on Fri Sep 23, 2016 4:01 pm

No one has any idea?
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby Gibsaw on Fri Sep 23, 2016 4:23 pm

I'm not 100% sure, as I don't know the A3000 at all.

However, being still connected and relatively stiff, that wire will have physical constraints. Without holding the board in my hand and being able to examine it closely, it looks like there was something connected to a pad just above where it says LK6 in the first photograph.
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby mons2b on Tue Sep 27, 2016 9:35 pm

HI Gibsaw

Thanks! I think you might be right. Ill let you know how it turns out!

John
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby andyg on Thu Sep 29, 2016 5:41 pm

Yikes! There's some serious corrosion happening there!

Good to see another sign-up from Christchurch.

I'm hoping to announce a special event for retro computer fans in CHCH fairly shortly. In the meantime, keep Monday evening 17th Oct free!
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby mons2b on Fri Sep 30, 2016 3:12 pm

Hi Andy

My vinegar treatment made the corrosion look worse than it is because I didnt dilute it. It reacted with the metal surfaces (and existing slight battery contamination) instantly changing them to punk rock shades of blue green. It wasnt left to sit just put on gently with a cotton bud I then went over it with meths, distilled water and back to alcohol again after that.

I wouldnt use undiluted vinegar again, a lesson not to take online advice without a grain of salt. Im hoping it will be ok. If not Ill have to replace whatever parts are needed. I am going to do a non destructive mod to change the clock batteries to AA Nimh using the existing AA battery compartment underneath. I have the necessary battery tabs ready to go just need to resolder that bodge wire and then some wires to the battery compartment.
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby tezza on Sun Oct 02, 2016 1:28 pm

Yes, whether vinigar or baking soda is best for a clean up depends on the battery. The idea is to neutralise the corrosive element, not add to it. Some batteries leak acidic goo (in which case use slightly alkaline baking soda solution) while others leak an alkaline mixture (in which case slightly acidic vinigar is best).
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby mons2b on Sun Oct 02, 2016 11:49 pm

An update. A3000 still boots but stops at the supervisor command prompt. Corrosion from the battery or the vinegar got into the keyboard connector and now the keyboard doesnt respond partly. I believe this relates to the traces on the membrane coming off when i removed the keyboard to generously rinse the area in pure alcohol to put a stop to any remaining corrosive elements.

I have ordered a silver conductive pen that I hope to use to recreate the traces on the membrane. Does anyone know what type of connector is used on the main board for the keyboard? I may be better off removing them and installing new ones. I tried to resolder the mystery wire but it wouldnt take so ive given up on that for now. Since its in the mouse area I think it was a non factory bodge to alter the mouse speed. I cant confirm but that is my suspicion.
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby MisJiF on Wed Oct 05, 2016 10:50 am

Hi,

I've not seen that mod on an A3000 before and I've looked a fair number of A3000s. Going by it's length, it does look to have been attached to the pad next to the LK6 label on the MB, or maybe even to a pin of IC6.

The service manual is here if that helps:
http://chrisacorns.computinghistory.org ... 3000SM.pdf

Only other things I can suggest is to clean up all the contacts around LK6 and IC6 and using a magnifier, see if there is any uneven solder on a part. That would indicate where it used to be soldered to.

When switching on RISC OS without a battery present, you will need to hold down the Delete or R keys to reset the CMOS. Hold them down until you see something on the screen. If it's working, it will get rid of the Supervisor prompt and you should get the desktop come up.

Also, ask on http://www.stardot.org.uk/forums/
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Re: Seeking help with Acorn Archimedes A3000 repair

Postby mons2b on Wed Oct 05, 2016 1:40 pm

MisJiF wrote:Hi,

I've not seen that mod on an A3000 before and I've looked a fair number of A3000s. Going by it's length, it does look to have been attached to the pad next to the LK6 label on the MB, or maybe even to a pin of IC6.

The service manual is here if that helps:
http://chrisacorns.computinghistory.org ... 3000SM.pdf

Only other things I can suggest is to clean up all the contacts around LK6 and IC6 and using a magnifier, see if there is any uneven solder on a part. That would indicate where it used to be soldered to.

When switching on RISC OS without a battery present, you will need to hold down the Delete or R keys to reset the CMOS. Hold them down until you see something on the screen. If it's working, it will get rid of the Supervisor prompt and you should get the desktop come up.

Also, ask on http://www.stardot.org.uk/forums/


Thanks a lot MisJif! Ill remember that when I next try the keyboard again. Ive ordered replacement ICs for the ones near the battery if they prove to be faulty so fair I think its just the keyboard connector which is effected. :(
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