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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: Chain on June 21, 2005, 06:26:21 AM

Title: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Chain on June 21, 2005, 06:26:21 AM

So, i have another board (only board and keybo). it works well for couple of days, but i cant reset it on keyboard. only switch on/off on psu works :)

Where i must seek an error??? Some shorted traces on board?
PLEASE help me somebody with this issue, please!

Thanks for all your opinions guyz! I think it can be repaired, but i hane absolutelly no clue HOW  :-(  :-(  :-(

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Noster on June 21, 2005, 08:57:40 AM

Hi,

are you shure the keyboard is working completely? Have you checked the CTRL and AMIGA keys?
If the keyboard is in working condition the problem may be the result of a  defect Gary. Gary interprets the keyboard reset signal and produces the reset signals for the hardware.
If Gary is also ok, you would have to purchase a service manual for the A1200 and search for the small ICs that are involved in keyboard handling.

Noster

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Chain on June 21, 2005, 09:36:59 AM

i was testing about 4 keyboards - its the same problem. maybe prevous owner was trying something with keyboard adaptor and fried something. I have manuals, i will look for some small ics around, thanks, but without osciloscope it will be hard to find bad parts i think. i must buy one :)

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Chain on June 21, 2005, 09:48:50 AM

or maybe i must sell kidney first

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Tahoe on June 21, 2005, 11:31:01 AM

I have a A500 with the same problem, it could also be your KB MPU (keyboard IC). Most likely one of the Amiga keys doesn't work; try if you can move the mouse by pressing LA + Arrow or RA + Arrow. If the mouse moves the Amiga keys are fine, so you can check CTRL. If all 3 keys function normally it probably is a reset line failure somewhere.

There is a software fix for this though; reset command on aminet.
Although, if the amiga really crashes it is no good ;)

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Chain on June 21, 2005, 11:43:02 AM

all keys working very well, i tested a lot of combinations, only that damn reset doez not work, mysuteridesu :(

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Effy on June 21, 2005, 02:45:11 PM

Using an old pc keyboard with Din connector ??? Try pressing the 5 keys : LeftCTRL LeftALT RightCTRL RightALT DELETE ...

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Chain on June 21, 2005, 04:26:52 PM

PC keyboard? i dont have any adapters:(

But! aother issue! If its cold, reset work well, but after 30 minutes if i press reset then screens going to black and its over, after on/off psu it works. i dont get it  damn.

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: boing on June 21, 2005, 05:30:19 PM

Can you rephrase that in proper english?

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Chain on June 21, 2005, 09:33:59 PM

gomen :)
i had a russian teacher for english lessons, i will try.

If A1200 is cold (e.g. morning), combination ctrl-a-a works well.

But later (approx 20 minutes) if i press reset combinaton then screens going to black and amiga wont boot! (no drive seeking)

I must turn out PSU, wait (~20 minutes) and voila, reset works again.

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Stedy on June 21, 2005, 11:52:39 PM

Chain,

Take a look around the following components:

U13 (Keyboard Micro) pins 1 & 38, are the solder joints bright? These pins provide the PWR_BAR and KB_RESET signals respectively.

Check R626 and R623 are soldered OK, R626 does nat have a value in the schematics but it should be 1-10K I guess.

Put a volt meter on pin 38 of U13 and press and hold CTRL-AMIGA-AMIGA, does the output go from >2.4V to <0.8V? Try this again after the computer has been on for 20 minutes.

The A1200 schematics (http://ianstedman.co.uk/Downloads/A1200-schematics.zip) are here

Title: Re: WHY reset on keyboard doeznt work?? A1200 (another 1.D4, 3.0 ROMs :)
Post by: Chain on June 22, 2005, 11:14:22 AM

Respect!
Thanks a lot Stedy, its finally a useful answer!
I will try to measure.