Search found 9167 matches

by 1024MAK
Sat Oct 19, 2019 7:28 pm
Forum: hardware
Topic: Electron Plus 3 PSU with vanilla Elk?
Replies: 4
Views: 38

Re: Electron Plus 3 PSU with vanilla Elk?

kieranhj wrote:
Sat Oct 19, 2019 7:03 pm
Is it safe to use the black 21V PSU for an Electron Plus 3 with a regular Electron without the Plus 3 attached?
Yes.

Mark
by 1024MAK
Fri Oct 18, 2019 10:04 pm
Forum: hardware
Topic: Fixed: Not seeing all ROMs in Model B
Replies: 8
Views: 343

Re: Fixed: Not seeing all ROMs in Model B

Good to hear that you are up and running :D

Well done =D>

And thank you for posting in the fault finding index :D

Mark
by 1024MAK
Fri Oct 18, 2019 1:49 pm
Forum: software: other
Topic: Serial port BASIC commands
Replies: 16
Views: 416

Re: Serial port BASIC commands

A PDF of the datasheet for the MC6850 is here.

Mark
by 1024MAK
Fri Oct 18, 2019 1:42 pm
Forum: software: other
Topic: Serial port BASIC commands
Replies: 16
Views: 416

Re: Serial port BASIC commands

MC is a prefix used by Motorola The suffix often includes a letter to indicate the type of package, but can also identify other features. Lead or lead free pins, improved version, speed rating, etc. The two most common suffixes for a DIL / DIP plastic package are N and P, but it varies between diffe...
by 1024MAK
Thu Oct 17, 2019 11:31 am
Forum: software: other
Topic: Serial port BASIC commands
Replies: 16
Views: 416

Re: Serial port BASIC commands

My plan in the meantime was to output bytes at say 9600 baud on the serial port, then convert these bytes to MIDI using an Arduino. Ahh, back in the old days, it was possible to wire up two UARTs (the type that did not need a microprocessor to set them up) back to back with a little glue logic to d...
by 1024MAK
Thu Oct 17, 2019 11:25 am
Forum: software & utilities for the pc, mac or unix
Topic: Greaseweazle - £2 disc archiver!
Replies: 6
Views: 200

Re: Greaseweazle - £2 disc archiver!

So are you going to give this a go?

And will you be comparing it to a Kryoflux system?

Mark
by 1024MAK
Wed Oct 16, 2019 12:06 am
Forum: hardware
Topic: Fixed: Not seeing all ROMs in Model B
Replies: 8
Views: 343

Re: Not seeing all ROMs in Model B

Does anyone have any knowledge about what I should be seeing on the outputs of IC20? IC20, a 74LS139, the half used in the ROM selection circuitry, does the following: It takes a binary input on pins 14 and 13. Each of which can be logic one (high) or logic zero (low). So in total, four combination...
by 1024MAK
Mon Oct 14, 2019 9:22 pm
Forum: emulators
Topic: MAME: Internal ROM/RAM expansion boards
Replies: 16
Views: 495

Re: MAME: Internal ROM/RAM expansion boards

Oh there are other interested people watching. Myself (apart from being rather busy at the moment, so very little time for hobbies), don’t have any of the rare beasts you need information on, hence it’s hard to help.

But please do keep at it. Your hard work is appreciated :D

Mark
by 1024MAK
Mon Oct 14, 2019 2:55 pm
Forum: other vintage computer hardware, software and games
Topic: Show us your retro computers
Replies: 103
Views: 8321

Re: Show us your retro computers

You have way too much time on your hands :shock:

=D> =D> =D>

Mark
by 1024MAK
Sun Oct 13, 2019 5:11 pm
Forum: other vintage computer hardware, software and games
Topic: Show us your retro computers
Replies: 103
Views: 8321

Re: Show us your retro computers

stephen_usher wrote:
Sun Oct 13, 2019 3:54 pm
Do a Google search for the QL Forum.
https://www.qlforum.co.uk/
Especially this sub-forum https://www.qlforum.co.uk/viewforum.php?f=10

Mark
by 1024MAK
Sun Oct 13, 2019 12:26 pm
Forum: hardware
Topic: Problems booting beeb issue 4
Replies: 73
Views: 1452

Re: Problems booting beeb issue 4

Here are the voltages asked for by 1024MAK... VLCC 1 = 4.96 VLCC 2 = 4.93 VLCC 3 = 4.87 They are a little bit low, but are within +/- 3% of 5V. Any suggestions on where to go next will be appreciated. Sorry to say Dave, but we rewind a bit. Can you please try the memory test program in this thread ...
by 1024MAK
Sat Oct 12, 2019 11:20 pm
Forum: acorn atom and system
Topic: YARRB [SOLD OUT]
Replies: 256
Views: 16010

Re: YARRB [switching to CLEAR 3]

When I set my probe on that track (pin 4 of the header right next to the 6502 on the Yarrb board, then I see a steady 4 MHz wave with some undershoot. But from that moment, the Atom won't go to CLEAR 3 any more. It stays in normal mode. As soon as I remove the probe, it goes into CLEAR 3 again. I c...
by 1024MAK
Sat Oct 12, 2019 7:25 am
Forum: hardware
Topic: BBC micro: Astec PSU recap
Replies: 3
Views: 135

Re: BBC micro: Astec PSU recap

The Rifa X2 capacitors are the only ones that normally self destruct (with the smelly smoke). Metallized Polypropylene Film Capacitors do degrade over time (their capacity drops), but are not known to self destruct like the Rifa type. Have a look at the soldering. It may be that someone else has alr...
by 1024MAK
Fri Oct 11, 2019 1:30 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 311

Re: Advice request: optical solid state relays

So from the ‘scope display images, the pulses look to be around 15ms to 25ms long. The current waveform is a good demonstration of how the current through an inductor ramps up from zero up to a value limited by the resistance of the wire. I’m not sure why the author decided to include a Zener diode....
by 1024MAK
Fri Oct 11, 2019 1:07 pm
Forum: stardot.org.uk
Topic: PM system, when is it activated for new users?
Replies: 21
Views: 1046

Re: PM system, when is it activated for new users?

It is also important to read through this thread.

Mark
by 1024MAK
Fri Oct 11, 2019 12:56 pm
Forum: stardot.org.uk
Topic: PM system, when is it activated for new users?
Replies: 21
Views: 1046

Re: PM system, when is it activated for new users?

I'm not sure I'm famous enough to fill 25 22 posts long autobiography. It’s not about just making 25 meaningless posts. It’s about being part of a community. And the suggestion was for you to start by introducing yourself and your activity with Acorn and/or other home computers over the years (talk...
by 1024MAK
Fri Oct 11, 2019 11:53 am
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 311

Re: Advice request: optical solid state relays

I would NOT assume 16mF means 16uF, as I don’t think a 16uF capacitor would store enough energy. In fact, I’m certain that 16uF would be too low. I was perplexed when I saw that value in the diagram. As it is unusual to use mF and capacitors with values of 16000uF are available, but are large and ex...
by 1024MAK
Fri Oct 11, 2019 7:19 am
Forum: general
Topic: Today I received.....
Replies: 5448
Views: 430604

Re: Today I received.....

today I received this: IMG_3948.JPG So now I have my own scope \:D/ =D> It is amazing how many hours you can lose playing with a scope, I just spent all evening trying to do an eye diagram of i2c comms, and failed miserably. Was more of a squashed mango diagram. It’s astonishing how many hours disa...
by 1024MAK
Thu Oct 10, 2019 8:12 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 311

Re: Advice request: optical solid state relays

jonb wrote:
Thu Oct 10, 2019 1:00 pm
I measure a 1.5uS pulse across the solenoid when the contacts close.
Wow, that is an amazingly short pulse from an electro-mechanical system :shock:

I have to ask, are you sure about this?

Mark
by 1024MAK
Thu Oct 10, 2019 5:43 pm
Forum: hardware
Topic: Model B - Issue 7 - Beep of doom
Replies: 7
Views: 257

Re: Model B - Issue 7 - Beep of doom

I still think a poor connection (DIL socket, link, power connector etc...) or dry solder joint is the most likely. Try gently tapping one corner of the board with the plastic handle of a screwdriver. Tricky’s Test ROM does not care if there is any working RAM, it will run anyway, so it is best to le...
by 1024MAK
Thu Oct 10, 2019 4:04 pm
Forum: hardware
Topic: Model B - Issue 7 - Beep of doom
Replies: 7
Views: 257

Re: Model B - Issue 7 - Beep of doom

Yes, inspection of, and continuity testing of the pins of the ROM chip (in the socket) to either the underside, or relevant CPU pins is the next logical step. As a single contacts failure can cause a world of pain...

Mark
by 1024MAK
Thu Oct 10, 2019 1:08 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 311

Re: Advice request: optical solid state relays

Use a 100Ω resistor in each leg (+ & -) between the solenoid and the ‘scope, with a 1N4148 diode wired anode to + and cathode to - (so that normally it will not conduct). That will provide a good level of protection for the ‘scope. If you know the resistance of the coils of the solenoid, that can gi...
by 1024MAK
Thu Oct 10, 2019 12:37 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 311

Re: Advice request: optical solid state relays

I was thinking of using a simple timing circuit that then controls a transistor. Once triggered, the timer would switch on the transistor for a defined time period, producing an output pulse of current to operate the solenoid. How long is the pulse to the solenoid? Are we talking hundreds of millise...
by 1024MAK
Wed Oct 09, 2019 11:38 am
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 311

Re: Advice request: optical solid state relays

Hi Jon I’m fairly certain that your circuit will not do what you want. Also R2 (27Ω) as drawn will only act as a heater and power waster :shock: If I understand you, what you want is a circuit that has a delay before it operates the output has hysteresis like properties so that once on, it continues...
by 1024MAK
Tue Oct 08, 2019 4:11 pm
Forum: acorn atom and system
Topic: Yarrb - redesigned
Replies: 15
Views: 497

Re: Yarrb - redesigned

Like 8)

Mark
by 1024MAK
Mon Oct 07, 2019 10:40 pm
Forum: hardware
Topic: Teletext Adapter Service Manual
Replies: 16
Views: 317

Re: Teletext Adapter Service Manual

Yikes! I never realised that these Astec modulators were so poor. I guess I've been lucky to never have had to rely on it for using the computer. We either had mono composite video into a green screen or RGB into a monitor. I don't remember the Spectrum, C64, Amiga, Sega etc. being this bad (could ...
by 1024MAK
Mon Oct 07, 2019 8:19 pm
Forum: acorn atom and system
Topic: A slightly dog-eared Atom
Replies: 30
Views: 923

Re: A slightly dog-eared Atom

balford wrote:
Mon Oct 07, 2019 7:53 pm
Yep, I’ve done three damaged posts on this machine, and splitting all three made removal quite easy without damaging the frame or springs.
Yet another meaning to the phrase “splitting the Atom” :lol:

Mark
by 1024MAK
Mon Oct 07, 2019 8:14 pm
Forum: hardware
Topic: Teletext Adapter Service Manual
Replies: 16
Views: 317

Re: Teletext Adapter Service Manual

The ASTEC UM1233 UHF Modulators are well known to me for their ability to drift as their temperature changes. I have a TV set up so that six channels are all tuned to about channel 36, so when using or testing a computer that uses a ASTEC UM1233 UHF Modulator, I can channel hop as the modulator outp...
by 1024MAK
Mon Oct 07, 2019 2:47 pm
Forum: hardware
Topic: Which cassette drive for Acorn Atom
Replies: 15
Views: 273

Re: Which cassette drive for Acorn Atom

xp2002 wrote:
Mon Oct 07, 2019 11:58 am
(just to be sure, you're not the same Mark I assume? :D )
No :lol:
He goes by the user name ‘RetroClinic’ on this forum.

Mark
by 1024MAK
Mon Oct 07, 2019 10:13 am
Forum: hardware
Topic: Which cassette drive for Acorn Atom
Replies: 15
Views: 273

Re: Which cassette drive for Acorn Atom

I also ordered a PSU (it's missing) and I will get a Gotek that's that will work with a Beeb, but perhaps also with the Atom. Be careful with power supply units. The Atom was originally designed to be supplied with a 8V 1.5A PSU. Then inside, two 7805 (or equivalent) series pass voltage regulator c...