Search found 7829 matches

by 1024MAK
Fri Sep 14, 2018 10:56 pm
Forum: for sale / freebies
Topic: STH members eBay advice - buying & selling!
Replies: 38
Views: 9902

Re: STH members eBay advice - buying & selling!

The idea didn't originally come from PayPal. If you go to buy fuel at a "pay at the pump" on a payment card the pump sticks in an authorisation for £99 to the card issuer, to make sure you have the means to pay before giving you the fuel, and then submits the final transaction amount and the end wh...
by 1024MAK
Fri Sep 14, 2018 8:04 pm
Forum: for sale / freebies
Topic: STH members eBay advice - buying & selling!
Replies: 38
Views: 9902

Re: STH members eBay advice - buying & selling!

On the question of a buyer winning and never paying up seems to be it is high time auctions, including eBay were subject to non-repudiation by buyers, i.e. if you win an auction you should be forced to pay whether you have changed your mind on wanting the item or not. Not only would this make thing...
by 1024MAK
Fri Sep 14, 2018 7:45 pm
Forum: off-topic
Topic: Standing on the shoulders of giants - Ponders End Middlesex
Replies: 9
Views: 287

Re: Standing on the shoulders of giants - Ponders End Middlesex

Interesting collection and story. It reminds me of the story in the the thread "Thermionic Valve" about the wartime, Phillips and Mullard. It was clearly no accident that a large manufacturer of lamp bulbs ended up making radio valves too. The "standing on the shoulders of giants" concept is very i...
by 1024MAK
Fri Sep 14, 2018 7:23 pm
Forum: off-topic
Topic: Standing on the shoulders of giants - Ponders End Middlesex
Replies: 9
Views: 287

Re: Standing on the shoulders of giants - Ponders End Middlesex

Hi Martin Funny that your picture shows a ZX Spectrum box on the top shelf. As the term "Shoulder of Giants" reminds me of Geoff Wearmouth's ZX-81 "Shoulder of Giants" ROM. This is a customized ZX81 ROM variant by Geoff Wearmouth for the Sinclair ZX81 which uses space-saving techniques to make way f...
by 1024MAK
Fri Sep 14, 2018 4:11 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

See also the conversation at this link.

Mark
by 1024MAK
Fri Sep 14, 2018 3:25 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

Maybe it was Acorn getting carried away with themselves... thinking about a possible "mega" like ROM in the future, but forgetting that there is no point in routing CPU address lines A14 and A15 to any of the ROM sockets. As this is pointless due to the address decoding circuitry mapping RAM to the ...
by 1024MAK
Fri Sep 14, 2018 10:36 am
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

Just to be clear here, in the posts dated 13th September, we were talking about the connections to socket IC51 for the OS ROM, NOT the sideways 'ROM' sockets. Further, this is in relation to BBC B issue 7 boards. So, I've checked one of my issue 7 boards. This computer is a computer purchased direct...
by 1024MAK
Thu Sep 13, 2018 10:18 pm
Forum: hardware
Topic: I2C 4 U
Replies: 263
Views: 15840

Re: I2C 4 U

Did you get some I/O working with the 8574’s ? I’ve obviously never provided any specific test code for that particular module so just wondered if you managed to get the hang of the I2C rom commands. I’d like to think they’re fairly intuitive and ‘module friendly’ but I’m biased of course.... :) Ye...
by 1024MAK
Thu Sep 13, 2018 9:23 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

There is also the test ROM as detailed in the service manual. See this thread. May be worthwhile giving this a try. In the linked to thread (my post dated today - 13th September 2018) there is a zip file that contains the "raw" binary EPROM image file.

Mark
by 1024MAK
Thu Sep 13, 2018 9:12 pm
Forum: hardware
Topic: Test ROM BBC B
Replies: 4
Views: 1351

Re: Test ROM BBC B

See also this thread :wink:

Mark
by 1024MAK
Thu Sep 13, 2018 7:38 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

The RSTA reset to the system VIA (IC3) is only low very briefly at power up. As capacitor C10 charges via resistor R20, RSTA goes to logic high. Mark Thanks for the explanation. Checking this again with my logic probe, it appears to be flickering slightly. It's not going logic low but it's certainl...
by 1024MAK
Thu Sep 13, 2018 7:35 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

The EPROM socket for IC51 (where I have the Test ROM) has a mod on the reverse of the board. The track to pin 1 is cut, and pin 1 is jumpered to pins 27 & 28. My working BBC B is the same, perhaps this is a mod for using EPROMS rather than Mask ROMS or a fix of some kind? on a 27128 or 27C128 EPROM...
by 1024MAK
Thu Sep 13, 2018 5:40 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

The RSTA reset to the system VIA (IC3) is only low very briefly at power up. As capacitor C10 charges via resistor R20, RSTA goes to logic high.

Mark
by 1024MAK
Thu Sep 13, 2018 8:45 am
Forum: acorn atom
Topic: Atom 2k18 ?
Replies: 63
Views: 2109

Re: Atom 2k18 ?

There are companies that will manufacture key caps with customer specified legends. But they are not cheap.

I think the reference to eBay is relating to some sellers that sell parts of Beebs instead of whole machines. So keyboard assemblies can sometimes be found being sold on their own.

Mark
by 1024MAK
Wed Sep 12, 2018 2:12 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

Good, the voltage test indicates that power is getting to the whole board. Focusing on the keyboard (including LEDs) and sound chip problem. I know you have tried various different chips in various positions. I recommend putting a known good working 6522 VIA in position IC3 (the system VIA) that ide...
by 1024MAK
Tue Sep 11, 2018 7:23 pm
Forum: upcoming and recent events & exhibitions
Topic: ABUG SOUTH 18 to 20 January 2019 (Hampshire) DATE CONFIRMED
Replies: 15
Views: 454

Re: ABUG SOUTH 18 to 20 January 2019 (Hampshire) DISCUSSION THREAD

I have no current preference at the moment. But thinking about last winter, for the southern folk, January is often considered to be the most likely month when snow may fall, and the coldest hardest frosts may occur. And unlike further upcountry, just a few flakes of snow can bring all the transport...
by 1024MAK
Tue Sep 11, 2018 7:18 pm
Forum: upcoming and recent events & exhibitions
Topic: ABUG SOUTH 18 to 20 January 2019 (Hampshire) DATE CONFIRMED
Replies: 15
Views: 454

Re: ABUG SOUTH 18 to 20 January 2019 (Hampshire) DISCUSSION THREAD

Also keep in mind that the RISC OS SouthWest Show 2019 is on Saturday 16th February, 2019. Link to their site.

Mark
by 1024MAK
Tue Sep 11, 2018 7:37 am
Forum: for sale / freebies
Topic: BBC / ELK Dual Digital Joystick Adapter
Replies: 40
Views: 2988

Re: BBC / ELK Dual Digital Joystick Adapter

Bryce, I would if I could write PMs. It says, I did not post enough here on this forum. Well, this is my second post. At the moment I can't write PMs. Let's try if you could write a PM to me first. Maybe I can answer your PM. Thanks. Sorry, as a new member, currently you are unable to send or reply...
by 1024MAK
Mon Sep 10, 2018 10:30 pm
Forum: upcoming and recent events & exhibitions
Topic: ABUG Cambridge Sept 7th-9th 2018 BOOKING THREAD
Replies: 203
Views: 7500

Re: ABUG Cambridge Sept 7th-9th 2018 BOOKING THREAD

All the photos that I took are here including various taken around the Centre for Computing History museum.

Mark
by 1024MAK
Mon Sep 10, 2018 7:58 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

For running Tricky's test ROM, all other ROMs should be removed. The DRAM configuration should be in it's normal state for the first run. Then later, you can try with S25 in the different configurations. You have a number of symptoms, some of which may be related to one another. The first is the con...
by 1024MAK
Mon Sep 10, 2018 7:33 pm
Forum: hardware
Topic: BBC B beep of death
Replies: 30
Views: 784

Re: BBC B beep of death

Have you tried removing everything that is optional? Wasn’t quite sure from post. I.e. you can remove both 6522, 6845, disk controller chip and some of the serials (forget which off top of my head) and the machine can still boot. I.e. you tested in another Beeb, but did you just try leaving them ou...
by 1024MAK
Mon Sep 10, 2018 7:22 pm
Forum: hardware
Topic: I2C 4 U
Replies: 263
Views: 15840

Re: I2C 4 U

I've checked the ZX-042 DS3231SN eBay module that I received about 11 days ago (bought from ai_smart) and it has the same charging circuit as described in the link that Martin provided up thread. Same diode, same 200 ohm resistor (marked 201). I now have three of these modules from three different ...
by 1024MAK
Mon Sep 10, 2018 7:05 pm
Forum: hardware
Topic: I2C 4 U
Replies: 263
Views: 15840

Re: I2C 4 U

Is that the cooling curve of a hot can of fizzy orangeness? Assuming Ed is incorrect (?), what is that monitoring? (And thank-you Mark, it’s always nice to see one’s stuff being used...☺️) This is a photo taken at the Cambridge ABUG meet-up at the weekend. The display on the Beeb is the output from...
by 1024MAK
Mon Sep 10, 2018 10:55 am
Forum: hardware
Topic: I2C 4 U
Replies: 263
Views: 15840

Re: I2C 4 U

IMG_7807.JPG
by 1024MAK
Sat Sep 08, 2018 8:35 pm
Forum: off-topic
Topic: Cleaning PCBs
Replies: 8
Views: 372

Re: Cleaning PCBs

How many seconds/minutes/hours before someone says "dishwasher"? :lol: To remove flux, use 99% IPA and don't dilute with anything. Or use purpose designed flux remover. The flux should dissolve, but unless it drains off or is mopped up, you will be left with the PCB feeling sticky. If you have 'larg...
by 1024MAK
Sat Sep 08, 2018 5:23 pm
Forum: hardware
Topic: I2C 4 U
Replies: 263
Views: 15840

Re: I2C 4 U

Seldon2k wrote:
Sat Sep 08, 2018 4:17 pm
I first
encountered it in use in the late 1980's to early 1990's in RF tuners used in Satellite Receivers.
It also started appearing in other consumer "brown" goods like TV's in the 1980s. I'm sure I remember an article in the TV trade magazine 'Television'.

Mark
by 1024MAK
Sat Sep 08, 2018 12:19 pm
Forum: upcoming and recent events & exhibitions
Topic: ABUG Cambridge Sept 7th-9th 2018 BOOKING THREAD
Replies: 203
Views: 7500

Re: ABUG Cambridge Sept 7th-9th 2018 BOOKING THREAD

If some who are attending could take and share some pictures for those of us who can’t make it, that would be very appreciated! Funnily that you say that, I've just taken some... IMG_7749.JPG IMG_7748.JPG IMG_7747.JPG IMG_7746.JPG Later, I will give a link to larger, higher quality versions :wink: ...
by 1024MAK
Fri Sep 07, 2018 5:03 pm
Forum: hardware
Topic: Open source firmware for Gotek floppy emulator released
Replies: 162
Views: 13008

Re: Open source firmware for Gotek floppy emulator released

Thanks Ken. I will certainly try that when I try my next Gotek.

Mark
by 1024MAK
Fri Sep 07, 2018 4:34 pm
Forum: hardware
Topic: Open source firmware for Gotek floppy emulator released
Replies: 162
Views: 13008

Re: Open source firmware for Gotek floppy emulator released

So... I dug out my Windows 10 laptop. Copied the STMicroelectronics application to it. Updated the driver, and got a pop-up saying that the device was protected, did I want to unprotect it. Answered yes! Now Windows no longer wants to talk to the Gotek. FFS... So plugged the Gotek back into my Linux...