Need help/suggestions on a dead C4P-MF
Posted: Tue May 30, 2017 1:08 am
Hi All,
First thread I have started here, but have lurked quite a bit and responded to a few posts. I find this forum great, quite useful, and FRIENDLY!
I'll try and keep this post as short as possible (hard in this case since I don't have a very specific question). I have a basically stock C4P-MF as described in my signature. I say basically since it started out as a cassette based system but was factory modified to add one 5" mini-floppy. Note, I'd really like to keep it as original as possible.
I pulled the system out of storage after 35 years of storage from it's original, fitted foam packaging/box. I spent a few good solid days (over a few weeks), re-seating some cables, chips, etc and finding a monitor that would display the signal (turns out my 51" plasma TV worked best of all things), and investigating if ASM, EM and the 9-bit Basic utilities worked. The only problem I noticed was that I clearly had an overheating issue. When I spent more than somewhere between 15 and 25 mins running and/or coding things, the computer would become unresponsive, but not shut down. I did check to see if a hard reset immediately after the hang would reboot successfully, which it did. However, using this approach, the computer was too hot to reliably run programs (i.e. I would get BASIC errors, which did not appear if I let the computer cool properly for 30 mins or so). From this point on I carefully monitored how hot the computer was getting. In retrospect, I should have at this point started to investigate the overheating issue while I could still measure voltages, etc.
What finally happened was that after coding a routine to test the audio, and running it successfully, I forgot abut the thermal time factor. I was so over joyed at having everything working as expected, and it looked great, and I WAS FINALLY DONE! I was just sitting there admiring it, clarity of the text, etc. So, I wasn't typing anything, or running anything that would have shown my non-responsive " thermal hung up state". To my horror, it just shut down while I was taking a few photos. I'm not sure if I remember properly, but it didn't sound like a normal shutdown. Just seemed to go dead quiet. I am assuming it is a power supply issue, but this is where my lack of knowledge comes in, If I put in a new fuse, it just blows it out in about 1/2 sec, at the point that it seems the machine is just getting ready to start boot-up.
So, I can't power it up to put a voltage meter in there. I am thinking of various approaches, but this is where I could use the forum members help and critique.
1) Can I just disconnect the power supplies (I have 2, believe one is dedicated to the 527 memory expansion board) from all the circuitry it powers, jump the fuse, and check the output?
2) I could just remove the one power supply from the circuit that powers the 527 memory expansion board (and remove the board) and see if I luck out and have only one bad power supply?
3) Order and put in a new power supply, at least for testing purposes (I'd like to keep it "stock" as I said previously)? If this is a good approach, what type of power supply do I need> Specs, etc?
4) Am I already thinking down the wrong path!?! Could I have blown a chip or something? I pulled all the boards and checked them and the cables for obvious electrical/thermal damage and saw none.
Finally, which I hope is a minor issue, when pulling the boards (which I've done numerous times), I snapped off a pin from one of the 16 pin blue connectors. D'OE, what an idiot. I'm hoping I can scrounge up a new one of those, or a complete 16 pin ribbon cable? Is this part hard to get?
Anyways, thanks for reading this far. I'm kicking myself for not just shutting her down and going on to investigate the thermal issue later. Any and all comments and suggestions welcome and appreciated.
First thread I have started here, but have lurked quite a bit and responded to a few posts. I find this forum great, quite useful, and FRIENDLY!
I'll try and keep this post as short as possible (hard in this case since I don't have a very specific question). I have a basically stock C4P-MF as described in my signature. I say basically since it started out as a cassette based system but was factory modified to add one 5" mini-floppy. Note, I'd really like to keep it as original as possible.
I pulled the system out of storage after 35 years of storage from it's original, fitted foam packaging/box. I spent a few good solid days (over a few weeks), re-seating some cables, chips, etc and finding a monitor that would display the signal (turns out my 51" plasma TV worked best of all things), and investigating if ASM, EM and the 9-bit Basic utilities worked. The only problem I noticed was that I clearly had an overheating issue. When I spent more than somewhere between 15 and 25 mins running and/or coding things, the computer would become unresponsive, but not shut down. I did check to see if a hard reset immediately after the hang would reboot successfully, which it did. However, using this approach, the computer was too hot to reliably run programs (i.e. I would get BASIC errors, which did not appear if I let the computer cool properly for 30 mins or so). From this point on I carefully monitored how hot the computer was getting. In retrospect, I should have at this point started to investigate the overheating issue while I could still measure voltages, etc.
What finally happened was that after coding a routine to test the audio, and running it successfully, I forgot abut the thermal time factor. I was so over joyed at having everything working as expected, and it looked great, and I WAS FINALLY DONE! I was just sitting there admiring it, clarity of the text, etc. So, I wasn't typing anything, or running anything that would have shown my non-responsive " thermal hung up state". To my horror, it just shut down while I was taking a few photos. I'm not sure if I remember properly, but it didn't sound like a normal shutdown. Just seemed to go dead quiet. I am assuming it is a power supply issue, but this is where my lack of knowledge comes in, If I put in a new fuse, it just blows it out in about 1/2 sec, at the point that it seems the machine is just getting ready to start boot-up.
So, I can't power it up to put a voltage meter in there. I am thinking of various approaches, but this is where I could use the forum members help and critique.
1) Can I just disconnect the power supplies (I have 2, believe one is dedicated to the 527 memory expansion board) from all the circuitry it powers, jump the fuse, and check the output?
2) I could just remove the one power supply from the circuit that powers the 527 memory expansion board (and remove the board) and see if I luck out and have only one bad power supply?
3) Order and put in a new power supply, at least for testing purposes (I'd like to keep it "stock" as I said previously)? If this is a good approach, what type of power supply do I need> Specs, etc?
4) Am I already thinking down the wrong path!?! Could I have blown a chip or something? I pulled all the boards and checked them and the cables for obvious electrical/thermal damage and saw none.
Finally, which I hope is a minor issue, when pulling the boards (which I've done numerous times), I snapped off a pin from one of the 16 pin blue connectors. D'OE, what an idiot. I'm hoping I can scrounge up a new one of those, or a complete 16 pin ribbon cable? Is this part hard to get?
Anyways, thanks for reading this far. I'm kicking myself for not just shutting her down and going on to investigate the thermal issue later. Any and all comments and suggestions welcome and appreciated.