Search found 204 matches

by PhilYoung
Sat Mar 31, 2012 7:59 pm
Forum: for sale / freebies
Topic: [SOLD] Teac FD-55E "Mould-Proof" Floppy Drive
Replies: 7
Views: 1810

Re: Teac FD-55E "Mould-Proof" Floppy Drive

I'd be interested in that.

PM due to be sent imminently....
by PhilYoung
Thu Feb 09, 2012 5:07 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

Hi Phil, were you able to solve the 74LS04 mystery? Greetings Kees I'm afraid not, I was only able to borrow a scope for an hour or so, most of which was spent trying to work out how to drive the thing. It was inevitably a modern digital scope, only about 6 inches deep, I was thinking 'where's the ...
by PhilYoung
Tue Jan 17, 2012 9:22 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

As digital chips switch their outputs, for a short time some actually momentarily short out the supply. This can cause no end of problems. This is why decoupling capacitors are used (typically one 100nF ceramic for every one or two IC's).[/i][/b] I was always taught one for every pair of power pins...
by PhilYoung
Tue Jan 17, 2012 9:03 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

Most logic chips need a stable +5V dc supply with the voltage +/- 5%. So at least 4.75V up to 5.25V. However, it is much better to have the main supply voltage much closer to 5V or a little over (say 5.1V) as this allows for any voltage drops (e.g. like along any fine PCB tracks). As digital chips ...
by PhilYoung
Mon Jan 16, 2012 5:47 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

Thanks for the replies, lots of useful information. Hi Phil, the only thing I can think of is that the BREAK-key inverters of IC9 are causing problems because the reset line of the 8255 is after the first BREAK-key inverter. The 8255 is responsable for the beeper, the keyboard and video-modes so I t...
by PhilYoung
Sun Jan 15, 2012 9:00 am
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

Used to see that "funny" on ye olde Microtan/Tangerine 6502 SBCs. The clock circuit was VERY fussy about who's 74LS04 it would work with reliably (back in the days when "canned clocks" cost a holiday home and boat). I never saw a Microtan. I think they did a series on them in ETI, maybe around the ...
by PhilYoung
Sun Jan 15, 2012 8:44 am
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom - Seems to be Fixed

That is a touch odd. I don't have time right now, but I'll check what I have in mine (it actually needs unscrewing atm), then have a play with a few different makes and scope-it and see if we can see any differences. d. Well, I said it was working, I didn't say it made any sense...... If you have t...
by PhilYoung
Sat Jan 14, 2012 4:52 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom - Seems to be Fixed

After a lot of messing around, I seem to have fixed my Atom. But the cure seems a bit random. It turns out that if I use one (and just one) of the two original 74LS04s as IC9 (which is used for the 3.58MHz oscillator, inverts the Break key and inverts it back again, and buffers phi2) everything work...
by PhilYoung
Sat Jan 07, 2012 1:53 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

I'll wait for the 8255 to arrive before doing any more work, that will hopefully be an instant solution to the keyboard problem, Cheers, Phil Young The 8255s and 7445s arrived this morning courtesy of Beebmaster. Sadly they did not improve matters, so it's back to the magnifying glass, strong light...
by PhilYoung
Thu Jan 05, 2012 5:18 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

So all you need is Phill's Ram/Rom board. It has a decoded rotary switch at #BFFF, space for 16 #Axxx ROM's and you can flash the software in #Dxxx, #Exxx and the #Fxxx ROM and as extra .... the no snow option. Hmmm ... sounds like some advertising campaign !! :lol: Greetings Kees Yes, I'm intendin...
by PhilYoung
Thu Jan 05, 2012 2:14 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

Another just remembered data point, my AtoMMC board only re-initialises correctly on BREAK about half the time, but always comes up OK on power up. Or it does once I added a 10uF capacitor across the 0.1uF one originally fitted at C11 to slow up the Reset. The reset goes via two inverters on IC9, w...
by PhilYoung
Thu Jan 05, 2012 12:39 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

By the way, the trouble started when I tried to fit a no-snow board that you posted the design for somewhere (BBMMC google groups I think), so really it's all your fault.... :D Ok, maybe I forgot to mention that your keyboard stops working and your screen start flickering #-o but the the main thing...
by PhilYoung
Thu Jan 05, 2012 11:10 am
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

I've noticed an additional symptom - often when the keyboard is working okay, the sound isn't (so no beep on error 94 or whatever). Sound is generated by the 8255 as well, of course, which points more firmly in that direction. It's all intermittent thought (of course). Hi Phil, while renovating my ...
by PhilYoung
Thu Jan 05, 2012 11:02 am
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

I have been removing and inserting ICs and a small PCB on headers meaning that the board has been handled quite a lot, so I'm thinking it's likely to be a recently provoked dry joint, a newly broken track or possibly a short between tracks. Nothing visible though. I don't think this is a short. Fir...
by PhilYoung
Wed Jan 04, 2012 8:13 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

Yes, I have a multimeter, I'll have to go through it all systematically. I don't think damaged anything de-soldering the old sockets, they looked clean when they came out. Plenty of scope for screwing it up removing the 40-pin PIA socket of course, so I think I'll try a replacement first. Of course,...
by PhilYoung
Wed Jan 04, 2012 7:05 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Re: Faulty Atom

Thanks for the reply. IC9 has had a new turned pin socket because you need the 3.58MHz out of it for the noise killer, and the original socket was becoming loose due to the header stretching it. In fact, thinking back I replaced that socket first since I noticed that roughly the same symptoms earlie...
by PhilYoung
Wed Jan 04, 2012 5:49 pm
Forum: acorn atom and acorn system series
Topic: Faulty Atom
Replies: 30
Views: 3968

Faulty Atom

Edit - seems to be fixed (fingers crossed) see post 17 Hi, Apologies, this ended up quite long. My Atom has developed an intermittent fault (although saying it's intermittently working would be more accurate), and I was looking for some advice. Until recently it was working fine with a homemade 8k v...
by PhilYoung
Wed Dec 21, 2011 9:01 am
Forum: general
Topic: Has anyone else ever come across a VELA?
Replies: 69
Views: 10402

Re: Has anyone else ever come across a VELA?

The Linksys branded 9VAC (1000mA) adapter I used registered an output of 11.3VAC on my multimeter and the waveform that the VELA captured appears to peak at around +/-18V which is interesting. The supply wasn't under load for any of the measurements I observed. Paul I suspect that the 11.3Vac measu...
by PhilYoung
Fri Dec 16, 2011 1:06 pm
Forum: acorn atom and acorn system series
Topic: Interest in new run of Atom addons...
Replies: 16
Views: 4222

Re: Interest in new run of Atom addons...

I'd be interested in a colour board certainly, and possibly a RAM-ROM board depending on how I get on with my own version. A rough idea of the costs would be appreciated. Cheers, Phil Young Hi all, I'm about to do a new run of both the Atom RGB Colour board, and a new enhanced version of the RAM-ROM...
by PhilYoung
Sat Sep 17, 2011 10:27 am
Forum: acorn atom and acorn system series
Topic: AtoMMC2 firmware 2.5
Replies: 26
Views: 6343

Re: AtoMMC2 firmware 2.5

Hiya! I bumped the Atom firmware revision simply because I felt 2.2 was jinxed. Well, something like that ;) The interface firmware didn't need to change and has remained at 2.2. Thanks for clearing that up. Subdirectory support is limited to using them for storage. All directory manipulation needs...
by PhilYoung
Tue Sep 13, 2011 6:21 pm
Forum: acorn atom and acorn system series
Topic: AtoMMC2 firmware 2.5
Replies: 26
Views: 6343

Re: AtoMMC2 firmware 2.5

I've just upgraded to this release, it seems to have gone okay but a couple of questions: <REPT> <BREAK> confirms that the Atom Firmware (A000 version) is v 2.5 A However *HELP reports that the interface firmware version (and the bootloader) are version 2.2. Is this right, I would have though they'd...
by PhilYoung
Wed Sep 07, 2011 6:55 pm
Forum: acorn atom and acorn system series
Topic: Files adding to AtoMMC
Replies: 18
Views: 2992

Re: Files adding to AtoMMC

sirmorris wrote: I will post the files here later, after I've got my emulation back into MESS so I can check things.

C
Thanks. It works fine-ish (doesn't always initialise on 'Break') with the A000 version, but it would be good to have both versions for completeness.

Cheers,

Phil Young
by PhilYoung
Wed Sep 07, 2011 1:18 pm
Forum: acorn atom and acorn system series
Topic: Atom mods pt 3
Replies: 8
Views: 1927

Re: Atom mods pt 3

Hiya, are these colour boards and the rom/ram board for sale? I desperately need something to bring some stability to my atom! Its all piggy backed chips and dodgy solder lol #-o I'd be interested in some details as well. My 32K and 8K memory boards are done on veroboard and there is a danger of fr...
by PhilYoung
Wed Sep 07, 2011 1:12 pm
Forum: acorn atom and acorn system series
Topic: Files adding to AtoMMC
Replies: 18
Views: 2992

Re: Files adding to AtoMMC

Hi, AtoMMC needs files to be in the ATM format. This is described in the manual. I have a tool which can add the required headers, I'll search it out and post it here in due course. Am I right in thinking that BBCExplorer saves metadata separately in $$$ files or something like that? C There's a Ma...

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