Exxos Diagnostic Cartridge Issue - Jumper selections

[MacTech05]

I have, thus far, been unable to locate the correct schematics for my 1040 STFM motherboard model and rev. Therefore, I am uncertain as to which capacitors are specific to the Reset Circuit. I thought I would try replacing the Reset Circuit capacitors, if that is the problem. Also, if necessary, I have new Reset Switch if I need to replace it as well. Although, when the STFM finally stopped resetting and froze at the desktop, I was able to successfully use the Reset Button to restart the STFM. But it would just go into the cycle of resets again until it freezes.

I am afraid to try to use the Exxos Diagnostics Cartridge again. Not that I am not sure, even if the cartridge functions properly, it will identify the problem.

I did thoroughly inspect and clean the cartridge socket on the motherboard, as well as inspect the motherboard solder connections for the cartridge socket. All looked clean and properly shiny. Also, I did not find any bent or broken pins in the cartridge socket.

So, I am not certain as to my next steps, except to replace the Reset Circuit capacitors, if I can identify them.

Thank you to everyone that offered assistance and recommended actions.

Regards,
Randy

[stephen_usher]

If you can plug a serial terminal (emulator) into the serial port and then try the diag cart it may give you good diagnostics now that you have it configured correctly. It sends out a lot of info before it initialises the screen. It can’t hurt the system.

Having said that, the first thing I’d do now is reseat the PLCC chips one at a time, starting with the MMU.

[rubber_jonnie]

rubber_jonnie,

I plugged the cartridge in, chips up.

Great, we had somebody plug it in chips down on another thread, so I wanted to be sure.

What I would say is that these boards can be affected by manual handling, so IC's can shift in sockets and cause contact issues, so just be aware of that. You may need to tweak the IC pins & socket pins and clean them too to get decent contact.

I'd advise the use of a proper PLCC IC puller to avoid damage to the sockets and ICs.

[MacTech05]

rubber_jonnie,

Yes, I read that thread. I never would have thought of plugging in chips down.

I do have a proper PLCC puller. I pulled the only 2 PLCC chips on my board, cleaned them and reseated them.

I connected everything back up and turned on the STFM. It worked! So I began to reassemble it and tested again along the way. After I installed the top shield, I tested again and it went back to restarts. So, I moved the keyboard around and it started up fine. So, I installed the top cover and the bottom case screws. I tested again, and guess what? Restart cycle again. I rechecked the keyboard cable and place something under the keyboard and powered on the ST. It worked. I removed the item I had placed under the keyboard and tested again. This time it booted fine and I ran SysInfo. It ran fine, but when I exited SysInfo, It went back to the green desktop and I got 3 bombs.

So, I examined the keyboard bottom. If you recall, there is a small silver plate that makes contact with a specific section of the top shield. The silver plate had what looked like part of a label that had been removed and some paper and adhesive remained. So, I took a cotton swab and alcohol and cleaned it, removing the pieces of a label and adhesive. With the plate clean, I set the keyboard in its proper place and powered on the ST. It worked perfectly. I suppose it is possible the plate picked up some small pieces of paper and adhesive from my work bench. Anyway, so far so good. I will test again tomorrow and if it still works, I will reinstall the bottom cover. Hopefully, it will still work and I can move on to another project.

I am a little afraid to try the Exxos Diagnostic Cartridge again. I still want to test the keyboard key functions. All of this started when I plugged in the Diagnostic Cartridge with the jumpers set incorrectly. So, whatever those incorrect settings did, the STFM started with the restart/reset cycling. The jumpers are now correct, thanks to Exxos. I will muster up the courage to try the cartridge sometime during the next couple of days. Hopefully, it will be all good and I can test the keyboard.

Thank you for your help and suggestions.

Randy

[rubber_jonnie]

I am a little afraid to try the Exxos Diagnostic Cartridge again. I still want to test the keyboard key functions. All of this started when I plugged in the Diagnostic Cartridge with the jumpers set incorrectly. So, whatever those incorrect settings did, the STFM started with the restart/reset cycling. The jumpers are now correct, thanks to Exxos. I will muster up the courage to try the cartridge sometime during the next couple of days. Hopefully, it will be all good and I can test the keyboard.

Thank you for your help and suggestions.

Randy

I must confess that I hadn't ever thought about the purpose of that small plate, however I run both my STEs and some other STFMs without a top shield (And I've done it on the bench with no shields, so just the bare mainboard, and a KBD just plugged in too) and never experienced any issues, so I do wonder if that was truly the reason, or if it's something else and the moving about of parts has 'fixed' it.

Out of curiosity does the keyboard have a large piece of clear plastic covering all the jumper wires on the bottom of the keyboard? It should and I understand this is to insulate from the top shield.

You may have a keyboard fault that is doing a ctrl+alt+del so have you either tried a different keyboard or no keyboard (I don't recall if that works, but worth a try).

You may want to disassemble the keyboard and clean the board and look for cracks in the PCB that are causing intermittent contacts.

As for the diag cart, the jumpers just set the address in ROM for whichever diag ROM you want to rum, so it'll just crash the machine if the code is incorrect and intended for another machine. It should be perfectly safe to run, but as somebody else mentioned, you may want to hook up a serial cable to a PC running something like TeraTerm to see what it pumps out at boot.

[MacTech05]

rubber_jonnie,

Yes, the KB does have the large piece of clear plastic covering all of the jumpers. It was stuck in place very well. I do not believe it has ever been removed. I removed it to reflow the solder connection on the two DB-9 sockets since the mouse was intermittent. After reflow, the mouse works perfectly. while I had the KB apart I inspected everything to ensure there were not any other issues I needed to deal with.

I understand about the keyboard fault. However, I have had this 1040 STFM for many years has always worked great, until the mouse started to act weird. That is the reason I disassembled the KB. To reflow the solder on the DB-9 sockets.

I also disassembled the STFM to check the PSU, which did have a few "bulging" capacitors, so I recapped the PSU, including replacing the Bridge Rectifier. Mr. Koda at Best-Electronics in San Jose, California, recommended I also replace the Power Resistors. I cannot find a schematic for the Mitsumi SR97 PSU so I can verify the Power Resistors. I am pretty sure the big honking resistors are the Power Resistors, but I need a schematic to verify that.

I operated the STFM after all that I did, and it functioned perfectly for over a week. There were no issues until I plugged in the diagnostic cartridge, with the jumpers incorrectly positioned, and powered on the STFM. That is when the problem with the constant reset cycle began and continued until it froze and gave me either 3 or 4 bombs. I quickly turned the ST off, removed the cartridge, and powered on the ST. The continuous reset continued until it froze, but zero bombs. I did thoroughly inspect the cartridge slot pins and solder joints on the motherboard, then thoroughly cleaned the cartridge slot pins. I started it back up and tested several times. It worked great. I powered down and reassembled the top and bottom case and started it up. Back to the resets again. I powered down and removed the top case and started up. It worked well and tested it several times. Now when I was testing the KB was not positioned in its proper place. When I arranged the KB in its proper place, I started it up and resets began again. So, I powered down check the bottom of the KB and saw some type of adhesive and what looked like the pieces of a label. I used alcohol removed the pieces of paper and the adhesive. Powered on with the KB in the proper position, resting on the top shield. It worked properly and has been working properly for a couple of days. I will test again later today or tomorrow and if it is all good, I will put the top case back and secure with screws and see how it works.

I should probably still replace the power resistors once I determine which ones to replace and their values so I can order them.

I am going to try connecting the serial cable from the ST to my PC running TeraTerm, which will hopefully display the cartridge diagnostic menu on boot.

I really need to get this sorted out, so I can list for sale on eBay (hopefully).

Thank you for your patience.
Randy