Search found 2564 matches

by jonb
Wed Nov 06, 2019 8:33 pm
Forum: general
Topic: Today I received.....
Replies: 5487
Views: 441197

Re: Today I received.....

Happy days Mark.

I was a Psion registered developer. Designed and co-wrote Psion Accounts and Expenses. Not a big money spinner, we got 50 pence royalty per copy!
by jonb
Wed Nov 06, 2019 7:03 pm
Forum: general
Topic: Today I received.....
Replies: 5487
Views: 441197

Re: Today I received.....

Not just very similar. Exactly the same, bar the label. Brilliant machines.
by jonb
Sat Oct 26, 2019 9:46 am
Forum: off-topic
Topic: LOLPRICE
Replies: 2950
Views: 276495

Re: LOLPRICE

Elminster wrote:
Sat Oct 26, 2019 8:39 am
I had completely forgotten about that one. I had that back in the day, I ate a lot of weetabix and belonged to the weetabix club. Ah the memories of cutting out tokens from boxes and posting them off ......
You need neat wheat, mate!
by jonb
Tue Oct 22, 2019 2:31 pm
Forum: other vintage computer hardware, software and games
Topic: Tatung Einstein 256 Machine and Information Wanted
Replies: 23
Views: 597

Re: Tatung Einstein 256 Machine and Information Wanted

About Tattie Elite - It's a direct port of the Speccy version. Looks exactly the same.

By the way, I'm one of those heretics who prefers the Speccy version... as I spent many hours on it in my "yoof".
by jonb
Fri Oct 18, 2019 10:55 am
Forum: software & utilities for the pc, mac or unix
Topic: Greaseweazle - £2 disc archiver!
Replies: 9
Views: 816

Re: Greaseweazle - £2 disc archiver!

Mind if I ask a couple of questions? What can you do with the file it generates? Can it be converted to a format readable by, say, cpmtools? Can the device write the images back (for creating boot disks from downloaded images, for example? Reason I ask is I was rather impressed by this : http://cowl...
by jonb
Sat Oct 12, 2019 11:22 am
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Re: Advice request: optical solid state relays

This is the protection circuit with 4x4700 16v banked capacitors. KCProtector.jpg I had a discussion with the author and he thinks 10,000uf might do it. He explained that the circuit works as I thought - caps charge on the low power let through by the 470R +68R resistors, then discharge when the clo...
by jonb
Fri Oct 11, 2019 12:44 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Re: Advice request: optical solid state relays

The guy who designed the protection circuit posted another document (attached). I think this is a bit better, his waveforms show a 300v EMF spike after the solenoid is triggered. Maybe my scope setting is all wrong! He also clarified that it’s 16 millifarads or 160000uF. Blimey. I’ll experiment a bi...
by jonb
Fri Oct 11, 2019 8:43 am
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Re: Advice request: optical solid state relays

Mark, I'm going to try building the protection circuit that is shown in the document attached to the first post. The only thing I'm not sure about is the capacitor it uses to store energy to kick the solenoid when the battery runs low. I assume what the circuit does is to charge the cap while the cl...
by jonb
Thu Oct 10, 2019 8:24 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Re: Advice request: optical solid state relays

The scope trace isn’t lying.

That was measured across the solenoid connections using single shot. It triggered when the solenoid fired. Have I misinterpreted it?
by jonb
Thu Oct 10, 2019 2:07 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Re: Advice request: optical solid state relays

Mark, I updated the previous post with a description of the winding mechanism.

I measured the coil and it is 12.4 ohms but remember there's a 100 Ohm resistor wired across it. So the solenoid on its own should measure 14.15 Ohms.
by jonb
Thu Oct 10, 2019 1:00 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Re: Advice request: optical solid state relays

I'd have to get the scope out for that.. :) I measure a 1.5uS pulse across the solenoid when the contacts close. It looks like this: DS1Z_QuickPrint2.png I assume the pulse width is commensurate with the time it takes for the solenoid to energise and the contacts to open. The action of opening the c...
by jonb
Thu Oct 10, 2019 8:58 am
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Re: Advice request: optical solid state relays

Darn it. I had the clock running nicely and left it to soak test overnight. For some reason the contacts got stuck closed and the solenoid has burned out. It was running fine all day yesterday and I was setting its speed (what cock people call "regulating" it). I have spares but I need some help to ...
by jonb
Wed Oct 09, 2019 2:10 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Re: Advice request: optical solid state relays

Well.. > has a delay before it operates the output No, it needs to trigger the solenoid when the contacts close. > has hysteresis like properties so that once on, it continues to run rather than jittering. Yes, but only to trigger the solenoid with a pulse that is wide / strong enough to pull the wi...
by jonb
Tue Oct 08, 2019 12:39 pm
Forum: off-topic
Topic: Advice request: optical solid state relays
Replies: 15
Views: 388

Advice request: optical solid state relays

Hi This is a bit of a specific request. I have a classic car with a faulty electromechanical clock, which I want to repair. The clock has a solenoid which is used to wind the mechanism. The clock then runs for about two minutes, at which point a pair of contacts close, triggering the solenoid which ...
by jonb
Wed Oct 02, 2019 1:11 pm
Forum: off-topic
Topic: Why Is E-Bay Showing Me Other People's Recently Viewed Items?
Replies: 26
Views: 832

Re: Why Is E-Bay Showing Me Other People's Recently Viewed Items?

I don't think eBay uses the IP address to decide what your recently viewed items are, otherwise when you log in on a different line it'd get not show you your stuff. Seems to me your account is compromised and whoever has compromised it is using it. I'd change your password NOW and see if it fixes s...
by jonb
Wed Oct 02, 2019 8:21 am
Forum: for sale / freebies
Topic: Worth Taking a Look At
Replies: 2794
Views: 272759

Re: Worth Taking a Look At

eBay policy on digitally delivered goods: https://www.ebay.co.uk/help/policies/prohibited-restricted-items/digitally-delivered-goods-policy?id=4289 You can distribute if you have IP rights (this guy does not) but you must send physical media. He's put this disclaimer that it's all shareware / freewa...
by jonb
Mon Sep 16, 2019 4:00 pm
Forum: acorn atom and system
Topic: ICE T65/Z80/6809
Replies: 745
Views: 62310

Re: ICE T65/Z80/6809

Hey Dave, that's a professional bit of manual writing. Nice! A couple of questions: - current state of the Z80 emulator? - is it possible to emulate the 8080 processor? Sorry, I've not been reading all the posts (too many!).. Cheers JonB P.S. P2000C floppy drive has stopped working again, but at lea...
by jonb
Thu Sep 12, 2019 7:36 am
Forum: general
Topic: Today I received.....
Replies: 5487
Views: 441197

Re: Today I received.....

But.. what is it?

"New Music Magnet"?
by jonb
Tue Sep 03, 2019 7:00 pm
Forum: acorn atom and system
Topic: Acorn Atom's Value ?
Replies: 9
Views: 586

Re: Acorn Atom's Value ?

You may not recall but at the time I had 2 of them, an issue 4 and an issue 5. No point keeping them both so I sold the 5.

The left over one is in great condition with ROM/RAM, colour and SD card boards. No need for any finger waggling.

:D
by jonb
Tue Aug 27, 2019 1:04 pm
Forum: acorn atom and system
Topic: Acorn Atom's Value ?
Replies: 9
Views: 586

Re: Acorn Atom's Value ?

Looks like it's gone down in price. I sold one a few years ago on eBay for £360.
by jonb
Thu Aug 15, 2019 8:25 am
Forum: other vintage computer hardware, software and games
Topic: Superbrain Mystery Zener Diode
Replies: 43
Views: 1231

Re: Superbrain Mystery Zener Diode

Right. I found a matching NP capacitor in an Amstrad PCW chassis and I've swapped it in. It is of the large variety. We'll soon see if it pops. Only thing is, I'm worried that - being larger - the bang will be bigger (and the mess too). Time will tell!
by jonb
Thu Aug 15, 2019 8:22 am
Forum: hardware
Topic: what's the use of Mode 0
Replies: 24
Views: 1066

Re: what's the use of Mode 0

1024MAK wrote:
Wed Aug 14, 2019 6:47 pm

Oh Jon, you’re spoiled the fun by coming out with a very sensible and logical answer #-o
That'll be a first, then.

:lol:
by jonb
Wed Aug 14, 2019 6:31 pm
Forum: other vintage computer hardware, software and games
Topic: Superbrain Mystery Zener Diode
Replies: 43
Views: 1231

Re: Superbrain Mystery Zener Diode

I am not sure whether the zener diode is OK or not - but I do have a perfect, stable picture.
by jonb
Wed Aug 14, 2019 6:11 pm
Forum: other vintage computer hardware, software and games
Topic: Superbrain Mystery Zener Diode
Replies: 43
Views: 1231

Re: Superbrain Mystery Zener Diode

Hi Mark If you look at the first post https://stardot.org.uk/forums/viewtopic.php?f=45&t=16756#p231653 there is a schematic showing the capacitor C441 connected in parallel with the zener diode that was the original subject of the thread. I'm no expert but it looks like a part of the horizontal defl...
by jonb
Wed Aug 14, 2019 5:16 pm
Forum: other vintage computer hardware, software and games
Topic: Superbrain Mystery Zener Diode
Replies: 43
Views: 1231

Re: Superbrain Mystery Zener Diode

So this is interesting: https://electronics.stackexchange.com/questions/21928/can-you-make-a-non-polar-electrolytic-capacitor-out-of-two-regular-electrolytic Says I can make a non polarised capacitor by placing two polarised caps having the same values back to back, and the capacitance will be half ...
by jonb
Wed Aug 14, 2019 4:56 pm
Forum: other vintage computer hardware, software and games
Topic: Superbrain Mystery Zener Diode
Replies: 43
Views: 1231

Re: Superbrain Mystery Zener Diode

Hummm, it's popped again after only 90 minutes!

Do I conclude it is a matter of bad components or something else being wrong on the board? The image looked perfect until it blew (for the second time!)
by jonb
Wed Aug 14, 2019 3:46 pm
Forum: other vintage computer hardware, software and games
Topic: Superbrain Mystery Zener Diode
Replies: 43
Views: 1231

Re: Superbrain Mystery Zener Diode

No sooner said than swapped - this time I had spares (from the last repair)! IMG_5677.jpg It's a little concerning that this cap has blown, it being a new replacement only five months ago (and the machine hasn't seen a lot of use since). Noted during the repair was the huge disparity in size between...
by jonb
Wed Aug 14, 2019 3:27 pm
Forum: other vintage computer hardware, software and games
Topic: Superbrain Mystery Zener Diode
Replies: 43
Views: 1231

Oh dear..

I think I will have to resurrect this thread. I was debugging a program to setup a new RTC board when CRACK! and the screen went blank. I haven't had it apart to see what the problem is, yet, but there is some wispy grey fluff floating about and a not terribly nice smell. Could be a cap popped. Sure...
by jonb
Wed Aug 14, 2019 10:29 am
Forum: hardware
Topic: what's the use of Mode 0
Replies: 24
Views: 1066

Re: what's the use of Mode 0

Just thinking about it for a moment.. with a co-processor and Mode 0 on a decent monitor you could do all sorts of business like things without worrying about the memory constraints I alluded to. In other words, one might say the purpose of Mode 0 is to facilitate more professional uses of the machi...
by jonb
Tue Aug 13, 2019 7:25 pm
Forum: hardware
Topic: what's the use of Mode 0
Replies: 24
Views: 1066

Re: what's the use of Mode 0

1024MAK wrote:
Tue Aug 13, 2019 1:12 pm
The real purpose of MODE 0 is to have one of the highest graphics screens on a Beeb compared to contemporary competitors home computers...

Mark
This.

I well remember the excitement it caused. Little did we know there would be no memory left to use it!