Search found 56 matches

by arkleyjoe
Sat Feb 22, 2020 6:55 pm
Forum: hardware
Topic: Acorn A540 Restoration
Replies: 7
Views: 312

Re: Acorn A540 Restoration

Actually I have managed to work out which capacitors they are. In case it is of use to others. Acorn A540 PSU X2 Caps: C1 PME271M capacitor,100nF 275Vac https://uk.rs-online.com/web/p/paper-capacitors/0210500/ C35 PME271M capacitor,220nF 275Vac 20.3mm https://uk.rs-online.com/web/p/paper-capacitors/...
by arkleyjoe
Sat Feb 22, 2020 12:42 pm
Forum: hardware
Topic: Acorn A540 Restoration
Replies: 7
Views: 312

Re: Acorn A540 Restoration

Does anyone know if there are Schematics available for the Acorn a540 PSU. The part number is 0186/015. I need to replace caps C1 and C35 but they are so badly blown I can not tell what they originally were. They are the X2 type caps.
by arkleyjoe
Fri Feb 21, 2020 9:19 pm
Forum: hardware
Topic: Acorn A540 Restoration
Replies: 7
Views: 312

Re: Acorn A540 Restoration

Without a battery / keyboard (del) will I get supervisor like on and A3000 ???
by arkleyjoe
Fri Feb 21, 2020 4:17 pm
Forum: hardware
Topic: Acorn A540 Restoration
Replies: 7
Views: 312

Acorn A540 Restoration

Hi Stardot Folks, I am about to embark on my A540 restoration project. The machine has / had fairly extensive battery leakage lots of nice green mess but once cleaned is looks fairly superficial. Some very light continuity testing suggests there is nothing too horrendous (but lets wait and see) I di...
by arkleyjoe
Sun Nov 03, 2019 1:03 pm
Forum: wanted
Topic: WANTED: A3000 motherboard.
Replies: 0
Views: 396

WANTED: A3000 motherboard.

Hi,
I am looking for an A3000 Motherboard. Does anyone have one for sale?

Joe
by arkleyjoe
Sat Sep 28, 2019 3:16 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

Ok so still more progress (I think) So when I boot I get a red screen, if I allow it to go through the POST sequence I still see the same error as my previous post. However after say 1 min. it ends up on a black screen with a dash. If I reset I get an error message on the screen saying no keyboard p...
by arkleyjoe
Thu Sep 26, 2019 7:39 pm
Forum: hardware
Topic: A3000 PSU capacitors
Replies: 11
Views: 620

Re: A3000 PSU capacitors

I do not think you can ever really argue against replacing old electrolytic caps in something this old. It is going to either be needed now or saving you an inevitable job in the future.
by arkleyjoe
Thu Sep 26, 2019 7:31 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair

So I have still more progress. I now have a red screen and a post code error. I realised that there was a problem with a couple of the jumpers. LK17 and LK18. Pin 1 of LK18 was shorted to ground. Now I have fixed this I am getting a red screen and a POST error. 0000 0000 0000 0000 0000 0011 0000 100...
by arkleyjoe
Thu Sep 26, 2019 7:15 pm
Forum: hardware
Topic: A3000 crackling (right) speaker
Replies: 20
Views: 1181

Re: A3000 crackling (right) speaker

Tills wrote:
Wed Sep 25, 2019 12:06 pm
I am wondering whether the tantalum caps attached to two of the VIDC's supply rails might also be worth replacing.
possible for sure, but much less common.
by arkleyjoe
Mon Sep 23, 2019 11:41 am
Forum: hardware
Topic: A3000 crackling (right) speaker
Replies: 20
Views: 1181

Re: A3000 crackling (right) speaker

Tills wrote:
Mon Sep 23, 2019 11:15 am
only when it's warmed up a little after a few minutes
Yeah very true, it's almost certainly the caps.
by arkleyjoe
Mon Sep 23, 2019 6:59 am
Forum: hardware
Topic: A3000 crackling (right) speaker
Replies: 20
Views: 1181

Re: A3000 crackling (right) speaker

Looking at the schematic, it seems there are several electrolytic capacitors that are exclusively related to the right speaker outlet and a couple specifically inline before the headphone jack branches off. I'd strongly suspect those. Your screen dipping in colour may not be directly related but cou...
by arkleyjoe
Sun Sep 22, 2019 9:10 am
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

I wonder if someone can help me understand if my thinking is correct on this. I have tested all of the address lines that run between the MEMC, ARM and the 573 ICS. With reset pressed, those address lines all appear to cycle correctly, all have 5v pk to pk and all behave the same on each IC. This is...
by arkleyjoe
Sat Sep 21, 2019 12:13 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

The other signalling lines between the MEMC and ARM would be worth a look too. Ok so while all continuity looks good I see that ABRT is asserted high and so this explains the lack of CAS If an ABRT is generated during an N-cycle, the -RAS strobe will be activated as usual, but the -CAS3 - -CASO sig...
by arkleyjoe
Thu Sep 19, 2019 4:30 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

The ROM chips should be enabled by the Rcs signal which is generated by the MEMC on pin 60. It's active low, and goes via R14 to pin 22 (Chip Enable) of each ROM socket. What do you see? Ok so indeed there was a problem there that I did not spot with multi meter is a previous test. With the scope I...
by arkleyjoe
Wed Sep 18, 2019 5:13 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

A lack of Phi 1 on the LE pin could explain most of the lack of activity on IC29,30. Let's hope you find something useful. :) Hi Kazzie, So still more progress, it turns out there were indeed some broken traces around IC29,30,31. With these repaired and everything continuity tested I am seeing the ...
by arkleyjoe
Thu Sep 12, 2019 7:42 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

If you can note which address lines aren't pulsing correctly, that might suggest a fault with one of the above. Ok so I have made a little diagram of what I am seeing. In that diagram. Black = Low, Red = High and Green = Pulsing. Pin 7 on IC31 is curious as the opposite is pulsing. Also is the LE p...
by arkleyjoe
Thu Sep 12, 2019 4:24 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

Actually I just realised that I do seem to be getting some of the address lines pulsing on the other side of the 573 logic chips. IC29,30,31 in particular 31 seems to have most of the lines working. The address lines also seem ok on the ARM. I assumed this meant IC29,30,31 needed replacements, but h...
by arkleyjoe
Wed Sep 11, 2019 3:39 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

Do you have the correct jumpers fitted on the board. Specifically LK28/29. Actually no. I realise that I missed those two as they were originally used by the Super VIDC that was fitted. Thanks you! So some more progress thank to the excellent support here. So I am at the next step: 6) Check for the...
by arkleyjoe
Mon Sep 09, 2019 3:21 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

Ok so I have made a little progress after replacing IC47 and X3 as suggested in the manual. 1) Check for system RESET — look for a delayed signal on power on (on IC13 pin 29). Passed 2) Check that the signal RST driving IC 44 pin 44 and IC37 pin 9 is not stuck high. Passed 3) Check for main system c...
by arkleyjoe
Mon Sep 02, 2019 10:37 am
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

Ok I will report back once the new replacement IC in place.
by arkleyjoe
Mon Sep 02, 2019 7:58 am
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

Kazzie wrote:
Sat Aug 31, 2019 4:33 pm
I can't see any pictures attached...
oops.

Here they are.
These are the output from LK28 and IC47, pins 3, 4, 5 and 6,
by arkleyjoe
Sat Aug 31, 2019 10:49 am
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

An additional question. I am trying to work out if a HC49 crystal would be an equivalent to the HC18. Is that referring to the size / package ?
by arkleyjoe
Sat Aug 31, 2019 10:29 am
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

Something seems to have changed on this board since I first started attempting to work out what is going on with it. Either that or I previously missed one of the tests. So I have been looking at page 46 of the a3000 service manual. Working though the tests it recommends. 1 Check for system RESET — ...
by arkleyjoe
Sun Aug 25, 2019 11:22 am
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

1: What frequency are the clock signals, and what is the bandwidth of your oscilloscope? Remember that a 10MHz square wave is effectively a Fourier series of sine waves at 10MHz, 30MHz, 50MHz, etc. If your oscilliscope only has a 15MHz bandwidth, all you'd see would be the first sine wave. I will c...
by arkleyjoe
Sun Aug 25, 2019 10:03 am
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

Hey Guys, I wonder if someone may be able to help me. So I have meticulously worked my way though fixing all of the maybe 40 or so breaks in the traces. I have continuity tested the board and I am happy the main PCB should be ok. I have tested the machine and I get a black screen. Only sign of life ...
by arkleyjoe
Mon Aug 05, 2019 8:11 pm
Forum: hardware
Topic: Can anyone tell me what this MOD is?
Replies: 11
Views: 595

Re: Can anyone tell me what this MOD is?

I have also just realised that is says (c) WE 1991 on the board.
by arkleyjoe
Mon Aug 05, 2019 8:06 pm
Forum: hardware
Topic: Can anyone tell me what this MOD is?
Replies: 11
Views: 595

Re: Can anyone tell me what this MOD is?

No I look at those hi res photos I can see that the corrosion is getting to that PCB also!
by arkleyjoe
Mon Aug 05, 2019 8:01 pm
Forum: hardware
Topic: Can anyone tell me what this MOD is?
Replies: 11
Views: 595

Re: Can anyone tell me what this MOD is?

Thanks that would be great. Looking again at your pics above, it definitely could be the Watford Super VIDC enhancer, because this used serial I2C to communicate (rather than programming via the AUX latch that most other VIDC enhancers use)...and in your photo, the two black probes to the expansion...
by arkleyjoe
Mon Aug 05, 2019 7:45 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

IanS wrote:
Mon Aug 05, 2019 6:49 pm
Have you got the battery out of the A540?
Not yet, TBH I did not realise it was on the board. I thought it may be like the 440 where it was a separate battery holder. I will do that ASAP.
by arkleyjoe
Mon Aug 05, 2019 7:43 pm
Forum: hardware
Topic: A3000 battery damage repair.
Replies: 35
Views: 1913

Re: A3000 battery damage repair.

danielj wrote:
Mon Aug 05, 2019 5:55 pm
but it doesn't dissolve the salts that you produce when you mix acid+base, it just smears stuff around.
That is really interesting actually I had noticed I was getting more residue than I would like. I will try your approach.