A500 keyboard, reset problem

orange · 30 October 2010, 22:17

Strangely one A500 here won't reset unless the keys are pressed for about 6seconds or more. is that normal? (because the manual says to always wait 5sec or something)
when pressed shortly caps lock blinks one time and there is no reset.

Merlin · 30 October 2010, 22:22

Does this machine have a ROM switcher inside it? Some automatic ROM switchers used the old 'three finger salute' to change ROMs.

It could just be dirty contacts on the keyboard though.

orange · 30 October 2010, 23:10

no ROM switcher.the kbd contacts seem fine, everything else works.

could it be some capacitor that takes time to 'fill up'?

Merlin · 31 October 2010, 00:54

That was going to be my next suggestion, that the caps need to be replaced. Electrolytic caps can have that 'ramp' effect that you describe, particularly if they have dried out or leaked.

Take a good look at the caps, to see if any have 'raised' or 'domed' heads, compared to others on the board; that's a strong clue that the capacitor has failed.

orange · 31 October 2010, 17:05

they all look normal. I need schematics for that little PCB, anyone got it?

Merlin · 31 October 2010, 19:01

Quote:

Originally Posted by orange

they all look normal. I need schematics for that little PCB, anyone got it?

What little PCB? As fas as I am aware, the standard A500 doesn't have a little PCB; do you know if your machine has been upgraded at all?

It sounds as if someone has added in a RAM upgrade at some time in your machine's past. How much memory does your machine display at the Workbench screen?

Jope · 31 October 2010, 19:43

Quote:

Originally Posted by orange

they all look normal. I need schematics for that little PCB, anyone got it?

I could send you a working one that no longer has LEDs in it. You could easily move those from your old controller board.

orange · 31 October 2010, 21:48

hey Jope, that's nice of you, but its not worth the trouble, really. I have several a500. and i just like repairing stuff. if it fails its not a big problem waiting several seconds to reset .

@Merlin
every A500 keyboard has little PCB in the corner, unlike A1200.

Merlin · 31 October 2010, 22:31

Ahh, I see. It's been quite some time since I had an A500 in bits.

orange · 04 November 2010, 19:11

@Merlin

you were right from beginning, it was bad contact on one of keys. so I used liquid silver and some graphite spray; works great now.

thanks.

Merlin · 04 November 2010, 19:51

Thought so; a great result!!

30 October 2010, 22:17	#1
orange Registered User Join Date: Apr 2007 Location: Belgrade Posts: 567	A500 keyboard, reset problem Strangely one A500 here won't reset unless the keys are pressed for about 6seconds or more. is that normal? (because the manual says to always wait 5sec or something) when pressed shortly caps lock blinks one time and there is no reset.

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30 October 2010, 22:22	#2
Merlin AmiBay MegaMod Join Date: Mar 2007 Location: Manchester, UK Age: 62 Posts: 1,163	Does this machine have a ROM switcher inside it? Some automatic ROM switchers used the old 'three finger salute' to change ROMs. It could just be dirty contacts on the keyboard though.

30 October 2010, 23:10	#3
orange Registered User Join Date: Apr 2007 Location: Belgrade Posts: 567	no ROM switcher.the kbd contacts seem fine, everything else works. could it be some capacitor that takes time to 'fill up'?

31 October 2010, 00:54	#4
Merlin AmiBay MegaMod Join Date: Mar 2007 Location: Manchester, UK Age: 62 Posts: 1,163	That was going to be my next suggestion, that the caps need to be replaced. Electrolytic caps can have that 'ramp' effect that you describe, particularly if they have dried out or leaked. Take a good look at the caps, to see if any have 'raised' or 'domed' heads, compared to others on the board; that's a strong clue that the capacitor has failed.

31 October 2010, 17:05	#5
orange Registered User Join Date: Apr 2007 Location: Belgrade Posts: 567	they all look normal. I need schematics for that little PCB, anyone got it?

31 October 2010, 21:48	#8
orange Registered User Join Date: Apr 2007 Location: Belgrade Posts: 567	hey Jope, that's nice of you, but its not worth the trouble, really. I have several a500. and i just like repairing stuff. if it fails its not a big problem waiting several seconds to reset . @Merlin every A500 keyboard has little PCB in the corner, unlike A1200.

31 October 2010, 22:31	#9
Merlin AmiBay MegaMod Join Date: Mar 2007 Location: Manchester, UK Age: 62 Posts: 1,163	Ahh, I see. It's been quite some time since I had an A500 in bits.

04 November 2010, 19:11	#10
orange Registered User Join Date: Apr 2007 Location: Belgrade Posts: 567	@Merlin you were right from beginning, it was bad contact on one of keys. so I used liquid silver and some graphite spray; works great now. thanks.

04 November 2010, 19:51	#11
Merlin AmiBay MegaMod Join Date: Mar 2007 Location: Manchester, UK Age: 62 Posts: 1,163	Thought so; a great result!!

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