Search found 202 matches

by mw0uzo
Wed Jan 18, 2017 1:34 pm
Forum: hardware
Topic: Acorn electron repair log
Replies: 6
Views: 766

Re: Acorn electron repair log

Yeah, I've got my eye out for a 32 channel one. Will get one when funds allow.
Waiting on memory ICs and 16 pin sockets.
by mw0uzo
Wed Jan 18, 2017 12:52 am
Forum: hardware
Topic: Acorn electron repair log
Replies: 6
Views: 766

Acorn electron repair log

This is a repair log for an Acorn Electron. SV204776.JPG Blob type ULA SV204780.JPG - No yellow LED light - PSU ok - DC converter ok. - Keyboard break ok - Generates video with horizontal thick yellow or white lines. SV204781.JPG - Capture of CPU /RS, CLK, SYNC, RnW, D7-D4 shows execution for a very...
by mw0uzo
Wed Jan 18, 2017 12:16 am
Forum: hardware
Topic: BBC B+ Repair log
Replies: 35
Views: 2452

Re: BBC B+ Repair log

Ok, I'll put in DFS 2.26. Thinking about what other ROMs that could go in. MMC DFS and the MMC COP114 tools rom. ADFS. That could go in with the DFS. I might as well 'compact' all the ROMs into 32K devices as they've all got to be recreated. Are there any other essential ROMs you use? I have yet to ...
by mw0uzo
Tue Jan 17, 2017 10:20 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

danielj wrote:Has it arrived? Does it live?!

*munches popcorn*

d.
Not arrived yet, hopefully tomorrow...

Didn't arrive today either. Or again today!!! #-o Or today :x
Image
by mw0uzo
Tue Jan 17, 2017 5:04 pm
Forum: hardware
Topic: BBC B+ Repair log
Replies: 35
Views: 2452

Re: BBC B+ Repair log

Daylight won't wipe them, may be in 10yr LOL It's Basic2 first 8000-BFFF, then second MOS C000 to FFFF. I have my worker imaged, & should be same as emulator files, will check later.... Ah ok, great you've saved me some cursing! So in the image it should be BASIC 2.0 0000-3FFF MOS 2.0 4000-7FFF Loo...
by mw0uzo
Tue Jan 17, 2017 3:52 pm
Forum: hardware
Topic: BBC B+ Repair log
Replies: 35
Views: 2452

Re: BBC B+ Repair log

If you have a week, using daylight might do it. Yeah I wondered this, what would be better. It's pretty grey and cold out there. It probably won't work under the fluorescent tube either :lol: Just checked them, no obvious bit changes. I'll just have to wait for the eraser to arrive or get some new ...
by mw0uzo
Tue Jan 17, 2017 11:58 am
Forum: hardware
Topic: BBC B+ Repair log
Replies: 35
Views: 2452

Re: BBC B+ Repair log

Taking the ROM out and reading it in the EPROM programmer, showed it was knackered, the data was gone! I found the DFS ROM that was in it, that was shot too, and I tested a few other ROMs that read fine. So is the MOS/BASIC "ROM" actually a EPROM, or a non-windowed EPROM/PROM? Mark It was a non win...
by mw0uzo
Tue Jan 17, 2017 11:06 am
Forum: hardware
Topic: BBC B+ Repair log
Replies: 35
Views: 2452

BBC B+ Repair log

This is a repair log for a broken BBC B+ with the dreaded Beeeeeee of death. The machine is in very poor condition outside: SV204767.JPG Inside not so bad, some corrosion throughout. SV204765.JPG It was stuffed with ROMs, I took them all out apart from the MOS/BASIC rom and cleaned contacts, but sti...
by mw0uzo
Mon Jan 16, 2017 10:56 pm
Forum: hardware
Topic: Star LC-10 dot matrix printer
Replies: 15
Views: 2154

Re: Star LC-10 dot matrix printer

Thanks for all the extra information. I will get a new ribbon, as when I was using the printer today, one of the pins had stuck. It unstuck after printing for a bit, but I bet it stuck due to lubrication being removed by the small amount of IPA on the ribbon. To be sure, i'll loosen the head and put...
by mw0uzo
Mon Jan 16, 2017 10:34 pm
Forum: hardware
Topic: VR1 for M128?
Replies: 2
Views: 312

Re: VR1 for M128?

I would lift one leg on C10, the one connected to pin 3 of of IC13. Then connect a 10k trimpot between that leg and Gnd/0V and the wiper to pin 3. It looks like there's just enough room next to the speaker for one of those small trimpots with a small plastic shaft fitted. Drill a hole, epoxy the tri...
by mw0uzo
Mon Jan 16, 2017 10:26 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Congratulations on the repair =D> , I've been following it with great interest despite not really having any useful suggestions to make! Like everyone else, I couldn't see how a faulty ROM could have caused the problem. But I was somewhat confused right from the start by this: I ordered a TurboMMC ...
by mw0uzo
Mon Jan 16, 2017 7:25 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

trixster wrote:Great work! =D>

So is that both Masters alive and kicking?
One's working. The other will very probably hopefully had better *** work when the 74f74 arrives tomorrow to fix it. :lol:
Socket is fitted so it should be plug n play.
by mw0uzo
Mon Jan 16, 2017 6:29 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

I used EELOAD the other day - it loads and also verifies. Installed the MMC card reader and rom. It all works! Used RLOAD to load in four roms, that all works. Connected up the printer and printed something out in View I've yet to get Elite to work from the image that's on the MMC, probably I have ...
by mw0uzo
Mon Jan 16, 2017 1:20 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

I'm not familiar with the master, but i think you should be able to use the sideways ram srload and it's friends to copy a ROM into ram and then into sideways ram. If you do this with basic, Dfs or adfs, I think you can disable the original and see if it still works. I guess you could move the offi...
by mw0uzo
Mon Jan 16, 2017 12:02 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

I don't have the balls to install the ROM yet and try the MMC interface, even though it turns out I didn't screw it up. I think I'll just leave it on for a day or two to make sure its OK. I'd like to test the sideways RAM. Is there a quick type-in to test? Maybe copy a system ROM into the sideways R...
by mw0uzo
Mon Jan 16, 2017 11:34 am
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Went ahead and replaced the System VIA on the 2nd Master. IT WORKS!!!!! \:D/ \:D/ \:D/ \:D/ \:D/
Desoldering and cost efficiency 100% =D> 8)
Ah, excellent. Let's hope it stays working, it's been on long enough to *Configure etc
by mw0uzo
Sun Jan 15, 2017 10:24 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

OK, that's new to me! It must be a similar thing to say a bad zener or rectifier diode. Sometimes you'll get one that works initially, then dies. You put the equipment away in disgust, then it works when you try it again (and you think yay) only for it to die again a short while later. Not sure the...
by mw0uzo
Sun Jan 15, 2017 10:12 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

BigEd wrote:Temperature is a thought, but it wouldn't take several days to recover. Does it need several days?
Yes it does, which is why i'm thinking bad IC. A bad gate/transistor recovers partially with no power, only to fail when operating voltage is applied for a short length of time.
by mw0uzo
Sun Jan 15, 2017 10:03 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

A long time constant like that sounds to me like the big caps in the PSU, somehow. Can you swap PSUs? Or indeed, measure the power supply rails? These are ok, rails measure good. I'd say this sort of behaviour is typical of a dying IC, although I would have also expected some thermal influence whic...
by mw0uzo
Sun Jan 15, 2017 9:44 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Time for a detailed fault description on the other Master. When left for a few days, will boot with Beep, then hang with no keyboard response after 20-30s. Attempts after that result in shorter working time until the dreaded Beeeeeeee occurs. But there is more at this point. Display initialises in M...
by mw0uzo
Sun Jan 15, 2017 5:45 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

*Really* looking forward to get the PiCoPro running now though (well done btw =D>, potential to drive the GPU on the Pi, sound hardware, use the SD card, lots of other stuff. )
by mw0uzo
Sun Jan 15, 2017 5:42 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Don't you have two dead masters though?! Or has one been fixed already? I have just checked the other one, and the 1MhzE clock seems OK when it dies, so definitely a different fault. Expected now, if not slightly disappointing! :lol: Oh, and after that an Elk and a BBC B+ and a 128k toastrack specc...
by mw0uzo
Sun Jan 15, 2017 5:39 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Just one possibility to bear in mind - if an output of a chip is stuck, it could be that the chip is bad, or it could be that the track is shorted or that one of the receiving chips is bad. It might be possible to tell, by snipping and lifting the pin, putting in a small resistor and monitoring the...
by mw0uzo
Sun Jan 15, 2017 5:32 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Ah, that makes complete sense now. I can't see how this would be related to anything you did with the ROM. Just an unlucky co-incidence. Dave Yes, I was convinced I had made an error. That also means the other Master is going to be a completely different fault. Challenge #2 :lol: I don't fancy my l...
by mw0uzo
Sun Jan 15, 2017 3:47 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Desoldering efficiency: 14/246 = 5.6% or 17.5 times more desoldering than necessary or 1750% :lol: :lol: At least when I break it again attaching hardware and homebrewing, recovery is an IC swap away. And I have plenty of spares. On that note, cost efficiency is 3.9% ha ha ha However, it's not worki...
by mw0uzo
Sun Jan 15, 2017 2:36 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Ok current state of unit - a working log this Old CPU, Old PBC, New RAM, VIAs swapped. I've taken a capture of D7-D4 and everything looks good Sync pattern 1,2,3,1,2,1,1,1,2,1,1,4,2,3,1 etc so it's executing ROM properly. So after all the desoldering work A15-A0 and D7-D0 very likely OK. Having a po...
by mw0uzo
Sat Jan 14, 2017 6:50 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Also, if we can confirm that the BD data bus read does not match what's actually on the BD data bus, then the corruption of the read is happening CPU side rather than on the other, as PBC has been replaced. Something to do with IO reads not working properly. What signals to the CPU that the read ha...
by mw0uzo
Sat Jan 14, 2017 6:00 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

I think what I'll do to end the day is to capture data bus and check that its executing at all. Then we can attack on a new day.
by mw0uzo
Sat Jan 14, 2017 5:44 pm
Forum: hardware
Topic: Dead BBC Masters - ROM screwup leading to main system damage
Replies: 234
Views: 10579

Re: Dead BBC Masters - ROM screwup leading to main system damage

Also, if we can confirm that the BD data bus read does not match what's actually on the BD data bus, then the corruption of the read is happening CPU side rather than on the other, as PBC has been replaced. Something to do with IO reads not working properly. What signals to the CPU that the read had...