Search found 8 matches

by Doctor_Beaker
Fri Dec 31, 2021 12:41 pm
Forum: 8-bit acorn hardware
Topic: BBC B Issue 7 PCB Layout
Replies: 8
Views: 321

Re: BBC B Issue 7 PCB Layout

I have a diagram that shows where each IC is on the board. It's just a scan taken from the service manual, onto which I've annotated the IC idents to help fault finding. All the other component idents are as blurry as on the original, but it may help you.
by Doctor_Beaker
Tue Dec 21, 2021 11:14 am
Forum: 8-bit acorn hardware
Topic: Trace advice
Replies: 14
Views: 462

Re: Trace advice

You could try sticking the track down with a coat or two of PCB lacquer (obtainable from RS and perhaps elsewhere), though it comes in an aerosol, so it would be best to squirt some into a container and use a small paintbrush to paint the liquid onto the track. You can supposedly solder through the ...
by Doctor_Beaker
Thu Dec 16, 2021 9:28 pm
Forum: 8-bit acorn hardware
Topic: Poorly BBC B
Replies: 10
Views: 773

Re: Poorly BBC B

Well, the problem was a permanently high output level (varying between 3V and 4V) on pin 10 of IC45, which affected the display addressing. Chip replaced and all well now.
by Doctor_Beaker
Thu Nov 25, 2021 10:42 pm
Forum: 8-bit acorn hardware
Topic: Poorly BBC B
Replies: 10
Views: 773

Re: Poorly BBC B

Thanks for pointing that out, NJ.
by Doctor_Beaker
Wed Nov 24, 2021 12:03 pm
Forum: 8-bit acorn hardware
Topic: Poorly BBC B
Replies: 10
Views: 773

Re: Poorly BBC B

Hello Mark. Regarding having another beeb, the answer should be yes, but I've spent the past fortnight looking for it. I know that it accompanied us when we moved house and I never scrap or sell anything which could potentially be useful, so where it could be now is doing my head in. How can you mis...
by Doctor_Beaker
Wed Nov 24, 2021 12:11 am
Forum: 8-bit acorn hardware
Topic: Corrections to the Tribbeck circuit diagram for the BBC B
Replies: 41
Views: 5537

Re: Corrections to the Tribbeck circuit diagram for the BBC B

RAM chips IC53 to IC68 are type 4816AP-11 on my Issue 7 board. Don't know if there ever was a 4616. Also, on all these RAM chips, pin 2 is labelled D1 and pin 14 is labelled D0. To avoid confusion with data lines, these are data in and data out pins, so should be labelled DI and DO respectively. Wit...
by Doctor_Beaker
Tue Nov 23, 2021 10:05 pm
Forum: 8-bit acorn hardware
Topic: Poorly BBC B
Replies: 10
Views: 773

Re: Poorly BBC B

Thanks to all respondents for those useful comments. Working through them, here's what has been achieved today:- Test ROMS: At present, I have no means of making those. Power supplies: they're fine. ICs: I've pulled the CPU, VIAs and all socketed chips to the east, cleaned the pins, sprayed the sock...
by Doctor_Beaker
Mon Nov 22, 2021 4:23 pm
Forum: 8-bit acorn hardware
Topic: Poorly BBC B
Replies: 10
Views: 773

Poorly BBC B

Good day. This is my first post and unfortunately, it concerns a problem with my BBC B. If any knowledgeable persons on the forum have come across this before, or could suggest where to start looking, it would be much appreciated. I repaired the power supply a few years ago, after which the machine ...

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