Search found 11145 matches

by 1024MAK
Mon Jan 17, 2022 10:21 pm
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

It should also be possible to use a lower capacity EPROM in the socket. But this is something that I have not tried. Obviously some of the applications would have to be left out.

Mark
by 1024MAK
Mon Jan 17, 2022 10:00 pm
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

Colday wrote:
Mon Jan 17, 2022 9:34 pm
Is the MOS ROM a standard EPROM of any sort?
No. It’s a mask ROM, and hence more address lines, and hence a higher capacity compared to a EPROM with the same number of pins.

Mark
by 1024MAK
Mon Jan 17, 2022 5:15 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

Odd, very odd. The things that normally kill a chip are: reverse supply voltage (incorrect polarity), exceeding the maximum supply voltage, exceeding the allowable input pin voltage range, exceeding the maximum power dissipation level/temperature, or shorting of an output pin. I assume it’s not gett...
by 1024MAK
Mon Jan 17, 2022 4:53 pm
Forum: for sale / freebies
Topic: Looking for Electron with Plus 1 dust cover design ideas!
Replies: 14
Views: 370

Re: Looking for Electron with Plus 1 dust cover design ideas!

Lardo Boffin wrote:
Mon Jan 17, 2022 3:29 pm
They are white but the light is poor!
“There are four (blue) lights!”…

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Looking good 👍 8)

Please let us know about availability and cost. I presume more BBC Micro covers will also be available?

Mark
by 1024MAK
Mon Jan 17, 2022 4:51 pm
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

I wouldn’t say they go wrong more. Well, apart from the back up battery running down. But then, the same happens with other systems that have a RTC and /or battery backed RAM.

Mark
by 1024MAK
Mon Jan 17, 2022 2:29 pm
Forum: 8-bit acorn hardware
Topic: BBC B Issue 7, strong acrid burning smell
Replies: 5
Views: 218

Re: BBC B Issue 7, strong acrid burning smell

It could be that the seal was imperfect. And moisture got in…

It’s not the first time that a “new” Rifa capacitor has let go!

Mark
by 1024MAK
Mon Jan 17, 2022 1:55 pm
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

What does the master add to that list of custom ICs? I believe address decoding is one area, including the implementation of shadow memory and also enabling the HAZEL workspace for normal read/write and let execution (of the VDU drivers) to happen from the same address space. That sounds quite simi...
by 1024MAK
Mon Jan 17, 2022 10:27 am
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

Could still be a faulty 6522 VIA…

Mark
by 1024MAK
Mon Jan 17, 2022 12:18 am
Forum: 8-bit acorn hardware
Topic: BBC B Issue 7, strong acrid burning smell
Replies: 5
Views: 218

Re: BBC B Issue 7, strong acrid burning smell

Hi, I've got a BBC Micro issue 7, and I replaced the 2 RIFA X2 caps with identical RIFA replacements… After 1 hour on, the issue 7 is producing a very strong acrid burning smell. Nothing inside is very hot and the smell appears to be coming from the PSU. Any other caps known to fail that I can repl...
by 1024MAK
Sun Jan 16, 2022 11:48 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

My results on an issue 7 board: IC18 pin 7 with no sound 1.46V, with sound 1.72V IC17 pin 7 with no sound -1.46V, with sound -1.72V Diode D2 anode (right hand side) with no sound -1.46V, with sound -1.72V Diode D2 cathode (k, +, left hand side) with no sound -2.00V, with sound -2.08V Resistor R5 top...
by 1024MAK
Sun Jan 16, 2022 5:22 pm
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

My post above has just been edited…
by 1024MAK
Sun Jan 16, 2022 5:13 pm
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

What voltage does the board need supplied by the battery pack? If we are talking 3v or so, then with just the diode in place the 3.7v will sit around 3.1v? Acorn used three AA cells so that the RTC chip (“CMOS”) can maintain both the clock/time and it’s memory even as the cells discharged to 1V eac...
by 1024MAK
Sun Jan 16, 2022 11:14 am
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

The chosen solution was 3off AA duracells with a plastic overwrap, bundled into a shape that could be wedged into the spare space to the left of the keyboard. This connected to the existing PL8; I' think the wrapped duracell package also contained a diode, although the higher voltage of the duracel...
by 1024MAK
Sat Jan 15, 2022 11:45 pm
Forum: 8-bit acorn hardware
Topic: So, I bought a job lot - Master no.1 - Not a language
Replies: 60
Views: 1025

Re: So, I bought a job lot - Master no.1 - Not a language

The 4.7v AA's are lithium rechargeables, what's the odd's they could be used and actually be charged by the machine? Keep in mind that the Master circuit board as manufactured, supplies the main 5V power rail via a single diode to the battery pin header/connecter. That is, there is no fuse, current...
by 1024MAK
Sat Jan 15, 2022 12:40 pm
Forum: 8-bit acorn hardware
Topic: Electron Issue 6 differences
Replies: 11
Views: 415

Re: Electron Issue 6 differences

I'm still uncertain about LK7 which doesn't look bridged, but I think it must be connected to +5V somehow, just as the AUG indicates, but not in an obvious way. Otherwise, IC18 and IC19 would not function and the machine wouldn't work. The issue 4 board doesn't have this (as the SM indicates), so i...
by 1024MAK
Fri Jan 14, 2022 12:22 am
Forum: for sale / freebies
Topic: Looking for Electron with Plus 1 dust cover design ideas!
Replies: 14
Views: 370

Re: Looking for Electron with Plus 1 dust cover design ideas!

Thinking about this a bit, if the dust cover has a "hole" for the cartridges to stick through, it will be difficult to fit and remove... and impossible if there are ribbon cables attached. We also considered just covering the Elk and not the +1 but thought that may end up with the +1 woul...
by 1024MAK
Thu Jan 13, 2022 4:30 pm
Forum: 8-bit acorn hardware
Topic: Phillips Monitor for the Beeb
Replies: 2
Views: 142

Re: Phillips Monitor for the Beeb

Has it been stored in damp conditions? At the moment, assuming no one in the past week has tried to power it on, it’s perfectly safe to carefully remove the covers and carry out a visual inspection of the insides. If no signs of water/damp or other obvious problems can be seen, carefully remove any ...
by 1024MAK
Thu Jan 13, 2022 2:39 pm
Forum: for sale / freebies
Topic: Looking for Electron with Plus 1 dust cover design ideas!
Replies: 14
Views: 370

Re: Looking for Electron with Plus 1 dust cover design ideas!

Thanks! Is there anything people leave plugged in that would make it difficult to remove the cover if we go for the hole over the slots approach? Can anyone post photos of what they use plugged into their Elks please? I suppose this depends on if people leave their machine set-up or if they put som...
by 1024MAK
Wed Jan 12, 2022 12:21 am
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

It’s either IC17 or IC18… IC18 when powered up generates a sound until commanded to do something different assuming it gets a clock signal on pin 14. The MOS during start-up sets the attenuators for each channel to kill the sound. Then later on when the start up banner is printed, a VDU 7 ‘bell’ gen...
by 1024MAK
Tue Jan 11, 2022 5:27 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

By “get the sound chip to play a sound continuously” I simply mean use an appropriate simple BASIC command or program that in a working machine would produce a sound. It could be as simple as SOUND 1,-15,0,-1 It does not matter if the machine does not actually make the sound. The idea here is to try...
by 1024MAK
Tue Jan 11, 2022 3:54 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

Whoops, sorry, that’s what happens when I decide to move the paragraph about the speech chips around! :oops: #-o Yes the speech chips positions are IC98 and IC99. No, the references to chip pins are all IC18 unless I specifically say otherwise. If IC18 is in a socket, then after doing the tests on I...
by 1024MAK
Tue Jan 11, 2022 12:51 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

I don’t have an issue 3 board handy to check against, but a short circuit fault to a fixed level (0V/GND) on the 1MHz bus audio (analogue in) line should not cause a no sound problem, as R11 (100kΩ) would just cause the sound level to be lower rather than none at all. This is also very easy to test,...
by 1024MAK
Tue Jan 11, 2022 12:25 pm
Forum: 8-bit acorn hardware
Topic: BBC Master Compact PSU very slow to start
Replies: 3
Views: 241

Re: BBC Master Compact PSU very slow to start

Yes, the smaller of the three electrolytic capacitors on the top right of the board (as viewed with the input and output wires on the left) is the “start up” capacitor. Also test the values of all the larger resistors on the top right of the board. Some will have values of 100kΩ or higher. If the re...
by 1024MAK
Mon Jan 10, 2022 7:22 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

jarweb wrote:
Mon Jan 10, 2022 7:17 pm
Yes. It goes from the low level static noise to the same but with an additional buzzing sound.
Then at least two out of four sections of IC17 are working, as is IC19 (the LM386 power amp).

What voltage do you get on IC18 (76489) pin 7?

Mark
by 1024MAK
Mon Jan 10, 2022 6:55 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

Can you use a narrow screwdriver or wire or other suitable conductive item so that you can touch your finger against the conductive item while touching a pin on IC17 pin 13. Does this increase the noise from the loud speaker? What about if you do the same for pin 10?

Mark
by 1024MAK
Mon Jan 10, 2022 6:50 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

jarweb wrote:
Mon Jan 10, 2022 3:57 pm
I get +5V & -5V for pin4 & pin11 respectively, for both ICs. I'm assuming this is correct ?
Thanks
Yes, that’s correct.

Mark
by 1024MAK
Mon Jan 10, 2022 12:46 pm
Forum: 8-bit acorn hardware
Topic: BBC Micro Issue 3 - couple of issues
Replies: 34
Views: 873

Re: BBC Micro Issue 3 - couple of issues

Peter - as I said in the original post the -5V seems to be fine at the connection to the board. But if there are other places to check in case of shorts or opens etc then I'm open to suggestions. Test between IC17 (LM324) pin 4 to 0V/GND, then pin 11 to 0V/GND to confirm that the correct supply vol...
by 1024MAK
Mon Jan 10, 2022 11:11 am
Forum: 8-bit acorn hardware
Topic: Electron Boards - The remainder of the ones that were offered on FB
Replies: 6
Views: 371

Re: Electron Boards - The remainder of the ones that were offered on FB

I'll be using my new Aldi temperature controlled hot air gun. Clamping the PCB in a vise and using an IC puller. I'll publish the results of this method. Hoping it'll be quick! Dave H. Quicker than me with an electric paint stripper heat gun on maximum and a flat bladed screwdriver? :lol: Mark
by 1024MAK
Sat Jan 08, 2022 9:25 pm
Forum: 8-bit acorn hardware
Topic: Pins for logic reading CPU
Replies: 8
Views: 252

Re: Pins for logic reading CPU

To explain the clocks used with 6502 systems, it not only provides a timing source for the microprocessor. It also acts like a police officer directing traffic at a road junction. The traffic on the one road (the 6502) gets it’s turn to send or receive traffic from the data bus, then the video syste...
by 1024MAK
Sat Jan 08, 2022 9:18 pm
Forum: 8-bit acorn hardware
Topic: Pins for logic reading CPU
Replies: 8
Views: 252

Re: Pins for logic reading CPU

Thanks for this. So I was mostly there. So I should use 21 for ground, and pick up pin 3 for the 2Mhz signal to PD3. Cool. On a Beeb, you can use either pin 1 or pin 21 for 0V/ground, but it’s better to get used to using pin 21 in case you ever work on a machine or board with a modern Western Desig...

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