A1200 or how to test for a faulty surface mount 8520?

[gizmomelb]

Hi all,

title says it all, does anyone know where I can please find an A1200 service manual , or even better a 'how to identify a faulty surface mount 8520 CIA chip' please?

Thank you.
Gizmomelb

[Jope]

Unless it gets hot to the touch, you've got to look at the symptoms the machine is giving..

[musashi5150]

What makes you think your CIA is iffy gizmomelb? Post us some symptoms.

A few things you might be experiencing: Bad keyboard, mouse/joystick buttons not so good, bad floppy loading, bad serial/parallel ports, timing problems (which could cause other faults)... etc...

[gizmomelb]

Hi jope/musashi5150

thanks for the reply. I'm fairly certain the 8520 at u7 is faulty, as there is no response from the keyboard (mouse and floppy work fine) and if I pull the keyboard out and try it on another machine the keyboard is fine.

I was hoping someone might be able to tell me expect voltages/resistance/signals to test for with my multimeter. The only real way to be sure is to pull the 8520 and solder on a socket, then swap the other 8520 I guess, but I'd prefer to try to test first off if possible.

Thanks.

(edit, musashi5150 posted while I was typing this )

[Jope]

It is either the keyboard controller or the CIA at fault here.

One way to test this is to solder a connector for an external big box keyboard directly to the CIA. This way you can determine whether the CIA works.. There are instructions on how to do this at the hard/hack dir of Aminet. (A1200 keyboard hack or something close to that)

[gizmomelb]

Hi Jope,

I'll have a hunt for that.. I removed the keyboard from the A1200 and tried it in a different A1200 and the keyboard worked fine, then tried the known working keyboard in the suspected faulty A1200 and it didn't work. I'm sure if I tried something through the parallel port I may end up with errors also.

Sigh, now to hunt for a replacement 8520 surface mount for the A1200, just in case the big keyboard test fails

[ganralf]

Try if the keyboard reset (ctral-a-a) works. If not it is quiet likely the keyboard controller. If it works it's the cia.

[gizmomelb]

Hi Ganralf,

yup, CTRL-A-A definately works, so it's the CIA

bollocks


thanks for the help, now anyone got an 8520 they want to sell please?

[Zetr0]

I may have a spare a1200 mother-board m8, it wont fire up as the video chip is fried, its in storage at the mo, if you have no luck finding one before next weekend you can have the board for postage my friend.

let me know say friday next week m8

[gizmomelb]

Hi Zetr0,

many thanks, you're a gentleman and a scholar!

Regards,
Gizmomelb

[Zetr0]

indeed i am a scholar i am at UNI : D)

[coze]

hmm, seeing this thread reminded of a faulty A1200 mobo I had. Everything worked fine, but the mouse right button didn't work. Actually it was like the right button was stuck and was sending signal even if it was not pressed. I could get into early boot menu with only left button pressed. Also when playing cannon fodder, the soldiers shoot always like if the right button is pressed. I thought it was a mouse problem first, but trying different mouses and mobos I saw it was the mobo. I used that board as a backup adf writing unit by using right amiga + right alt buttons as right mouse button at workbench. Is there anything I can do for that board ? I think this started after I plugged in a MS serial mouse into mouse port by mistake or pluggin the 2.5 ide cable into ide port by mistake.

[Jope]

Originally Posted by ganralf

Try if the keyboard reset (ctral-a-a) works. If not it is quiet likely the keyboard controller. If it works it's the cia.

I had an A600 with a fried keyboard controller that did a keyboard reset just fine. :-)

I'd still try it with an external keyboard wired directly to the CIA to be sure.

[Chain]

[QUOTE=coze]hmm, seeing this thread reminded of a faulty A1200 mobo I had. Everything worked fine, but the mouse right button didn't work. /QUOTE]

RMB goes to PAULA, not to CIA chip

Originally Posted by gizmomelb

thanks for the help, now anyone got an 8520 they want to sell please?

Hi Gizmo ,

You're quite welcome to an old A1200 mobo I have lying around.

( for the small price of ....... ermm , $0 )

let me know...