27-10-2024, 01:36 PM
Hey Beeingdavid,
This group can certainly help with advice and encouragement on the fixing front. They've all helped me plenty of times, and now I get to help other people.
The "Microbee Hardware" channel is where I put most of my plaintive meepings :-)
BTW, My course of action for fixing your board would be as follows:
1) Check what voltage you're getting across one of the 74 series chips on the core board. If not 5v, investigate.
2) Clean the connectors between the main (lower) board and the core (upper) board. These are a common source of failure. Some deoxit on the sockets and an ink eraser on the pins should help.
3) Check the reset signal. If you have a fast multimeter, or a logic probe, this will help. An oscilloscope is very useful, and these days they have got ridiculously cheap, and will make light work of it. Check pin 18 of the right hand connector. It should stay low, then go high. (I had a world of pain with a bad reset circuit on one of my 'bees)
4) See if any chips are getting excessively hot, especially RAM chips. You can risk your fingertips, or get a contactless thermometer. If you have access to a thermal camera, this becomes trivial. Of course, it only helps with the core board chips.
5) At this point I would go and get some riser cards from someone. These allow you to lift the core board up and out of the way of the main board, and allow you to star looking at signals on the main board. Very useful things to have! You're in deep diagnostics territory here. Thank fully there are a lot of resources available to help diagnose. Test ROMs and the like.
Also, enjoy building up the Premium Plus. I love building kit computers now (I have built three computers, a console and two different core boards for my Microbee) and hope to pick up one of Ewan's new ones when they become available. So much fun, even when they don't work.
Cheers!
John
This group can certainly help with advice and encouragement on the fixing front. They've all helped me plenty of times, and now I get to help other people.
The "Microbee Hardware" channel is where I put most of my plaintive meepings :-)
BTW, My course of action for fixing your board would be as follows:
1) Check what voltage you're getting across one of the 74 series chips on the core board. If not 5v, investigate.
2) Clean the connectors between the main (lower) board and the core (upper) board. These are a common source of failure. Some deoxit on the sockets and an ink eraser on the pins should help.
3) Check the reset signal. If you have a fast multimeter, or a logic probe, this will help. An oscilloscope is very useful, and these days they have got ridiculously cheap, and will make light work of it. Check pin 18 of the right hand connector. It should stay low, then go high. (I had a world of pain with a bad reset circuit on one of my 'bees)
4) See if any chips are getting excessively hot, especially RAM chips. You can risk your fingertips, or get a contactless thermometer. If you have access to a thermal camera, this becomes trivial. Of course, it only helps with the core board chips.
5) At this point I would go and get some riser cards from someone. These allow you to lift the core board up and out of the way of the main board, and allow you to star looking at signals on the main board. Very useful things to have! You're in deep diagnostics territory here. Thank fully there are a lot of resources available to help diagnose. Test ROMs and the like.
Also, enjoy building up the Premium Plus. I love building kit computers now (I have built three computers, a console and two different core boards for my Microbee) and hope to pick up one of Ewan's new ones when they become available. So much fun, even when they don't work.
Cheers!
John
John "CheshireNoir" Parker
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One Dark Little Kitten
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One Dark Little Kitten