500 Keyboard Problems

Just thought I would post and see if anyone has seen this before. Amiga 500 Rev 5 with a Samsung made keyboard (US, two membrane leads)

Intermittent problems with the Watchdog Timer error (Three blinks of CapsLock)

Swapped CIAs, swapped them back. No difference.

Noted that a shot of coolant on the MOS 6570 seemed to bring the keyboard back to life. This appeared to work even at a cold boot. So, a thermal issue, but it didn't matter if the chip was hot or cold.

I just finished re-flowing the solder on all of the pins on the 6570, and so far, it seems to be working. I've done multiple reboots. I let it sit off to cool down and started it up again without incident. I'll keep testing for a couple of days, but right now I'm very happy.

Originally Posted by Scottgfx

Just thought I would post and see if anyone has seen this before. Amiga 500 Rev 5 with a Samsung made keyboard (US, two membrane leads)

Intermittent problems with the Watchdog Timer error (Three blinks of CapsLock)

OK... I left the machine off for a few hours, and then resumed my testing. We now have a new behaviour: The caps lock key is no longer flashing, but the caps lock no longer works. (Light off, doesn't toggle) Keyboard does work though!!!

The caps lock did start working after letting the machine warm up awhile. So, this looks like a problem with capacitors?

Thank you for any insight.

[idrougge]

If your keyboard has a capacitor, it's a good idea to change that. It's been found to cause trouble on A2000 keyboards before.

I just ordered all of the capacitors and the ceramic resonator from DigiKey.

Apparently the parts on the Samsung version are the same as the Mitsumi... I don't see a C8 .1uF cap on the board though... OK, not the same, but close.

I chose to replace the resonator as well as it's right next to the MOS 6570 that I was shooting coolant on. the C3 22uF cap is right there as well.

At least I can't make things worse.

Originally Posted by Scottgfx

I just ordered all of the capacitors and the ceramic resonator from DigiKey.

Just wanted to add a note. I talked to an engineer where I work and showed him a picture of the keyboard processor board. He pointed out that the C3 capacitor was a tantalum. I had ordered regular ceramic one. He cautioned that the tantalum was specified for a reason and that I shouldn't replace it with a ceramic. There are three caps on my board that appear to be tantalum, C3, C5 and C10. I've gone ahead and done a second order from DigiKey of Tantalum replacements.

Also wanted to mention that I'm working off of the schematics and parts list done by nocash. I don't know nocash, but I'd like to buy him a beverage of his choice. Thank you.

Well I damaged some really fine traces that lead under the CPU, so I'm pretty much sure I killed it while trying to desolder some parts.

Anyone have a Samsung made keyboard I can have the circuit board from?