Atom Frozen /Break won’t reset Help

[Albuzz]

I’ve recently brought my ancient Atom out of the loft… it’s been there untouched for almost 40 years and I’d like to get it up and running again.

It’s a kit machine built by me in 81 and was in regular use before going into storage… that said I can’t actually remember if it was working when I put it away, but it isn’t working now!

Out of the box I did some basic checks and it was totally dead at first, but after reseating most of the chips it managed to display the Acorn Atom and block cursor without the >.

Following advice on the forum I stripped out all the unnecessary chips and proceeded on minimum configuration.

After much coaxing and repeated pressing break, eventually got the > but couldn’t get the keyboard to respond. I tracked this down to a rather odd “1” key that has an inverted operation where make and break is reversed so pressing the key breaks the contact and releasing makes the contact, so holding down the key allowed the keyboard to then work and hey presto the machine worked.!

The current problem is that 99% of the time I don’t get the “>” and the machine is effectively frozen. Repeatedly pressing break does the reset but most of the time (99%) reboots without the >. Very occasionally it will get to the > after which it works perfectly and usually after this the break reset seems to work 3 out of 5 attempts but if I then turn the machine off, I get back to the 99% status.

It actually seems to be getting worse now, probably more like 1 in 300 breaks.

I’ve looked at the reset pulse with a scope and it’s definitely ok at the 6502 and 8255.

Any pointers where I should look next would be very helpful

Many thanks
Alan

[Multiwizard]

Sadly I can't give you much advice...

But do you have any pics of your nice Atom,, please...

It sounds like you have an Issue 4 Atom...

Thanks in advance.

[roland]

Pictures will give us an impression of your current Atom configuration. First step: is the 5V ok?

BTW if a key is stuck you can easily check it out by pressing the REPT key.

[Albuzz]

Sorry for the delay getting back.. what a great site this is.. on delving a lot more I found various pointers re: similar issues and thankfully this is now sorted. I still need to do sone thorough testing but it lives!

There weee a few issues preventing a tidy boot but the main one was a poor joint on one of the 6502 pins. No one to blame but me since I assembled the machine 40 years ago

Can anyone help in identifying a Rom on ic24? I obviously knew 40 years ago but I haven’t a clue today? Is there a simple way to identify it?

Thanks for your comments and pointers

[hoglet]

Can anyone help in identifying a Rom on ic24? I obviously knew 40 years ago but I haven’t a clue today? Is there a simple way to identify it?

I don't see any ROM in IC24 - the socket in your photo is empty!

[Albuzz]

Apologies.. I was running minimum configure there.. I’ll post another photo tomorrow.. there’s no markings on the Rom just a blue dot sticker.

[oss003]

Also C11 is missing which is a delay for the reset/BREAK.

Is that extra board with the wires an autorepeat?

Greetings
Kees

[hoglet]

Apologies.. I was running minimum configure there.. I’ll post another photo tomorrow.. there’s no markings on the Rom just a blue dot sticker.

Can you post a screen shot of PRINT $#A000

[Multiwizard]

& what is underneath here?... (just curious )

[janrinze]

That must be LEDs..

Had that on my ATOM in a long lost past

Curious about the flatcable that comes from underneath the PCB

[Albuzz]

Taking points in order:

1. C11 is actually mounted on the other side of the board (can’t recall why) but it is there and break works just fine now.

2. After dumping the Rom contents I could see it’s a Programmers Toolkit and found documentation for it courtesy of stardot.com. Thanks Hoglet. Linked to it and verified it works ok. Again I don’t remember installing or using it but I clearly did!!

3. Poking out at the bottom is a set of LEDs connected via a small circuit and toggle switch connecting them to the printer port via a removable ribbon cable. Modified many years ago so a program could output to it (for no particular reason) !

The other circuit board provides the ability to switch from 1 MHz to 2 MHz using the spare #B002 line… happy days.

A couple of pics ..

Thanks for all the posts and help.

PS the wires crossing the keyboard are to swap a couple of broken keys with less used ones. The keyboard has definitely seen better days. I hope some future owner can live with that!