Search found 7753 matches

by 1024MAK
Mon Sep 24, 2018 5:51 pm
Forum: hardware
Topic: I got a Freebeeb! Help needed…
Replies: 16
Views: 313

Re: I got a Freebeeb! Help needed…

The RAM chips are the two marked “HM6264LP-12” on the right hand side in the first photo.

These are 64k bit, which means 8k bytes. Both together gives one bank of 16k byte sideways RAM.

Mark
by 1024MAK
Mon Sep 24, 2018 5:46 pm
Forum: off-topic
Topic: Convert master psu to bench psu
Replies: 30
Views: 771

Re: Convert master psu to bench psu

Powerful stuff :D

Mark
by 1024MAK
Mon Sep 24, 2018 1:59 pm
Forum: hardware
Topic: I got a Freebeeb! Help needed…
Replies: 16
Views: 313

Re: I got a Freebeeb! Help needed…

Here are some pictures of the inside if that helps identify the addons (no flash used, because I didn't know if that might affect the contents of the EPROM). Use a piece of black insulation tape or a paper label to cover the window on the EPROM. It’s UV light that erases EPROMs. Daylight (sunlight)...
by 1024MAK
Mon Sep 24, 2018 10:29 am
Forum: hardware
Topic: Wobbly Cub
Replies: 6
Views: 85

Re: Wobbly Cub

Most electrolytic capacitors in a monitor (or TV) will be used for smoothing or decoupling the various power rails. Some are used for coupling signals between different stages (sub-circuits). A power rail where the smoothing capacitor is failing (loss of capacitance, or more likely, the effective va...
by 1024MAK
Mon Sep 24, 2018 9:49 am
Forum: hardware
Topic: Wobbly Cub
Replies: 6
Views: 85

Re: Wobbly Cub

Based on the extensive and detailed description of the symptoms, yes :lol:

Mark
by 1024MAK
Mon Sep 24, 2018 9:36 am
Forum: hardware
Topic: I2C 4 U
Replies: 263
Views: 15381

Re: I2C 4 U

The Plus 1 for the Elk uses a standard 74 series TTL chip for the two fire button inputs on the analogue port. The chip used is a tri-state buffer wired so it can only read the logic level on the fire button inputs. It is possible to extend the functionality in a new version of a Plus 1 (or equivale...
by 1024MAK
Sat Sep 22, 2018 10:34 pm
Forum: acorn atom
Topic: Meet my new Atom (warning: lots of images)
Replies: 16
Views: 274

Re: Meet my new Atom (warning: lots of images)

Looking more closely at your add on board, it seems to contain 4116 DRAMs (64k in total I think?). Mine has static ram, and ROMs, so is a different design. 4116 DRAM are 16k x 1 bit type. So eight of them gives 16k bytes. 4116 DRAM require +12V and -5V supplies in addition the the normal +5V supply...
by 1024MAK
Sat Sep 22, 2018 7:28 pm
Forum: hardware
Topic: I got a Freebeeb! Help needed…
Replies: 16
Views: 313

Re: I got a Freebeeb! Help needed…

There aren't lead fumes from leaded solder unless you evaporate it at ridiculously high temps. Which even high powered soldering equipment gets nowhere near. Try not to breath in the fumes from the flux (a fan helps here, as with no other airflow, your breathing will cause the fumes to drift toward...
by 1024MAK
Sat Sep 22, 2018 5:58 am
Forum: hardware
Topic: I2C 4 U
Replies: 263
Views: 15381

Re: I2C 4 U

KenLowe wrote:
Fri Sep 21, 2018 10:46 pm
... and it will be nice to have the user port freed up for other things again.
Like UPURS :lol:

Mark
by 1024MAK
Fri Sep 21, 2018 9:28 pm
Forum: hardware
Topic: I2C 4 U
Replies: 263
Views: 15381

Re: I2C 4 U

1024MAK wrote:
Thu Sep 13, 2018 10:18 pm
Next week, time permitting, I'll post up some photos of one of my modified DS3231 RTC modules
See photos...

As you can see, I’ve removed the SMD resistor from the top right of the board (as viewed). This completely disables the dodgy charging circuit :D

Mark
by 1024MAK
Fri Sep 21, 2018 8:28 am
Forum: for sale / freebies
Topic: BBC / ELK Dual Digital Joystick Adapter
Replies: 39
Views: 2844

Re: BBC / ELK Dual Digital Joystick Adapter

I have been trying to PM Tricky to discuss options and buying a fully assembled and ready to go unit, but the forum says I need to participate more before I can PM anyone. Any ideas how I can get around this? Cheers Lee Lee, you can ask for PMs to be enabled by using the Contact us link at the bott...
by 1024MAK
Thu Sep 20, 2018 6:13 pm
Forum: hardware
Topic: New econet setup
Replies: 49
Views: 743

Re: New econet setup

Rather, in close proximity to a 74LS244 (Octal Buffers And Line Drivers With 3-State Outputs) chip and in close proximity to a nine pin SIL (single in line) resistor pack (RP) (also known as a resistor array).... As the resistors define the logic high level, the links (acting as switches) define the...
by 1024MAK
Tue Sep 18, 2018 11:21 pm
Forum: programming
Topic: Beeb Shadow RAM, load image from disc?
Replies: 12
Views: 280

Re: Beeb Shadow RAM, load image from disc?

JGH is the person to ask. The whole point of the shadow RAM is that it is not normally in the CPU memory map. &3000-&7FFF shadow RAM (known as LYNNE) is available to machine code programs by manipulating the memory map latch (ACCess CONtrol) at &FE34. Details are in the Advanced Reference Manual for...
by 1024MAK
Tue Sep 18, 2018 10:29 pm
Forum: other vintage computer hardware, software and games
Topic: CRT repair
Replies: 10
Views: 392

Re: CRT repair

Could be a dry joint. Could be a poor plug or socket connection. Could be the contacts in the on/off switch. Could be the device that controls the demagnetisation of the screen. Could be a large electrolytic capacitor in the main power section.

Mark
by 1024MAK
Tue Sep 18, 2018 9:23 pm
Forum: projects
Topic: 160 x 128 mode
Replies: 21
Views: 421

Re: 160 x 128 mode

First, just to be clear, LCD TVs may or may not work with unusual signals, but they work differently (being a completely different technology) so will not be damaged by a non-standard signal. Feel free to try anything you like with the signal to these. Any modern-ish CRT TV should also not be damage...
by 1024MAK
Tue Sep 18, 2018 5:54 pm
Forum: projects
Topic: 160 x 128 mode
Replies: 21
Views: 421

Re: 160 x 128 mode

Yeah, I wouldn’t take the horizontal/line frequency down too low. Some 15625Hz CRT monitor’s and most CRT televisions use the line timebase running at 15625Hz to produce various supply rails for other parts of the set. And all generate the EHT voltage from the line output transformer. Most line time...
by 1024MAK
Mon Sep 17, 2018 10:04 pm
Forum: hardware
Topic: Elk disc controllers
Replies: 22
Views: 386

Re: Elk disc controllers

:arrow: If you want proper sub-directories, there's only one option...
by 1024MAK
Mon Sep 17, 2018 9:42 pm
Forum: hardware
Topic: AP3-4 - Redesign - First Thoughts
Replies: 23
Views: 871

Re: AP3-4 - Redesign - First Thoughts

danielj wrote:
Mon Sep 17, 2018 9:09 pm
Any better? :)
Only with beer goggles on... :(
by 1024MAK
Mon Sep 17, 2018 9:28 pm
Forum: hardware
Topic: AP3-4 - Redesign - First Thoughts
Replies: 23
Views: 871

Re: AP3-4 - Redesign - First Thoughts

The gotek uses USB by default, but it can use a very small one! (e.g. a Sandisk Ultrafit) :) Thanks, Daniel - List updated - Don't suppose there's a schematic that's black-on-white? See attachments :wink: Note: also included as a zipped file to get around the overzealous forum image compressor. Als...
by 1024MAK
Mon Sep 17, 2018 9:03 pm
Forum: off-topic
Topic: JDS6600 sig gen, earth and thoughts
Replies: 7
Views: 148

Re: JDS6600 sig gen, earth and thoughts

So 5V at 2A is not uncommon. It may be possible to find a better quality PSU.

Yes, the extra terminal for grounding would be on the signal generator.

Mark
by 1024MAK
Mon Sep 17, 2018 8:06 pm
Forum: off-topic
Topic: JDS6600 sig gen, earth and thoughts
Replies: 7
Views: 148

Re: JDS6600 sig gen, earth and thoughts

Yes. But in the longer term, you would be better off adding a 4mm green coloured socket or a “grounding” combined screw and 4mm terminal. Another way to make something floating with respect to the mains, is to feed the existing SMPSU via an isolating transformer (230/240V primary, 230/240V secondary...
by 1024MAK
Mon Sep 17, 2018 5:53 pm
Forum: hardware
Topic: New econet setup
Replies: 49
Views: 743

Re: New econet setup

You may also want to consider Dave’s latest cartridge, the Retro Hardware ARA III - Low Cost Writable ROM Cartridge - For the Electron and Master ;-)

Mark
by 1024MAK
Mon Sep 17, 2018 3:08 pm
Forum: hardware
Topic: Mitsubishi 4853 floppy drive problems
Replies: 12
Views: 235

Re: Mitsubishi 4853 floppy drive problems

And now breathe out...
by 1024MAK
Mon Sep 17, 2018 3:07 pm
Forum: hardware
Topic: Model B serial speeds
Replies: 11
Views: 354

Re: Model B serial speeds

Nice 8)

Mark
by 1024MAK
Mon Sep 17, 2018 12:57 pm
Forum: hardware
Topic: New hardware suggestion - Pi econet server
Replies: 33
Views: 901

Re: New hardware suggestion - Pi econet server

Following the famous phrase ‘if in doubt add another Pi’ could you put a Pi zero in a box with level shifters etc. and an econet connecter and use this purely to bit bang? It would take in raw econet data and convert it to something that the Pi server could use. It would also take meaningful data f...
by 1024MAK
Mon Sep 17, 2018 12:48 pm
Forum: hardware
Topic: Elk disc controllers
Replies: 22
Views: 386

Re: Elk disc controllers

See also the links in this post

Mark
by 1024MAK
Mon Sep 17, 2018 9:20 am
Forum: hardware
Topic: New econet setup
Replies: 49
Views: 743

Re: New econet setup

To answer the original question regarding use of the ROM sockets vs. sideways RAM, here is an extract from the Master Service Manual : LK18 plug, made West: Paged ROM/RAM Select. Two position link. When fitted in the West position, this link causes 16Kbyte of RAM to appear in each of the "sideways" ...
by 1024MAK
Mon Sep 17, 2018 9:06 am
Forum: other vintage computer hardware, software and games
Topic: Superbrain #1 : The ratty one
Replies: 91
Views: 3623

Re: Superbrain #1 : The ratty one

Does this system make use of a Drive Ready/Disk Changed (/RDY, pin 34) signal?

Or it’s timed out waiting for another signal from the drive?
Pin 26 /TRK00 Track 0
Pin 8 /INDEX Index

If one of these signals is missing, would this cause these symptoms?

Mark
by 1024MAK
Sun Sep 16, 2018 8:03 pm
Forum: hardware
Topic: Mitsubishi 4853 floppy drive problems
Replies: 12
Views: 235

Re: Mitsubishi 4853 floppy drive problems

If the wiring loom for the top head is removed from the connector on the board, that would do it! Alternatively, there could possibly be a link in the logic circuits that select which head to use. Or the input control from the control and data (the 34 way ribbon) cable by be disconnected somewhere. ...