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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: orange on July 28, 2004, 02:15:22 PM

Title: A1200 8520
Post by: orange on July 28, 2004, 02:15:22 PM

Someone, please tell me which one of A1200s CIA chips is ODD?

I've been searching the google for hours and found only adverts  

Title: Re: A1200 8520
Post by: blobrana on July 28, 2004, 02:21:22 PM

LOL
It`s not the even one

er, oh you mean like, U7 is odd?

< U8 IS Even,>





[i hope] :-)

Title: Re: A1200 8520
Post by: orange on July 28, 2004, 02:29:24 PM

Is that (U7) the one near keyboard connector or the one near floppy?

Title: Re: A1200 8520
Post by: blobrana on July 28, 2004, 02:38:29 PM

Hum,
Did you see the LINK (http://www.sothius.com/hypertxt/welcome.html?./additional/a1200addition.html) with the photos of mobo on it?

hold on....i`ll see

Can`t find it...is it not printed on the CHIP/mobo?

UPDATE:
U8 is next to the floppy pin socket

Title: Re: A1200 8520
Post by: Doobrey on July 28, 2004, 04:31:30 PM

Yup, U7 is the the one next to the keyboard socket.. the one that says "U7" in white next to it (just above the missing P9A connector)  :-P
 Got a broken serial or parallel port by any chance ?

Title: Re: A1200 8520
Post by: orange on July 28, 2004, 06:12:03 PM

I'm not sure. Thanks for the info.

Can parallel be tested without connecting anything to it?

I'm suspecting Alice for freezing, too. It gets pretty hot few moments after powerup (43Celsius or 108F).
Any way to test it?

Title: Re: A1200 8520
Post by: Doobrey on July 28, 2004, 11:29:53 PM

Doh, silly me...
 U7 handles some of the parallel port, keyboard,joy/mouse port and some parts of the floppy.
 U8 does the rest of the parallel port, some other floppy port bits, and the serial port.

 It`s not 100% possible to check the parallel port is working without plugging something in.
 You can write data to the port and read it back to see if that side of the chip works, but you can`t tell if the data actually went out the other side intact without having something there to read/use it.

As for Alice, it sounds like something is shorting out..

Actually, check for shorts around pins 11 and/or pin 21 on the U7 CIA, as they go to Alice. Maybe the CIA problem is causing the Alice problem too  :-(

Title: Re: A1200 8520
Post by: orange on July 29, 2004, 07:56:32 AM

OK.
I forgot, how do you count pins on chip, clockwise or anticlockwise?
The one with circle is number one, right?

Title: Re: A1200 8520
Post by: Doobrey on July 29, 2004, 01:41:15 PM

Amiga-stuff.com have a very handy little diagram here (http://www.amiga-stuff.com/hardware/pinnumbering.html#plcc) on pin numbering.

BTW, is this the same A1200 you`re have problems with on  comp.sys.amiga.hardware? ..broken pin on the CIA or something?

Title: Re: A1200 8520
Post by: orange on July 29, 2004, 04:23:17 PM

yes, it is. The pin just seems unused, everything "works" as before without it.

I'd like to check voltages of IDE and Alice.
It should be pin 52 for +5V and pin 58 for GND on Alice, right?

41 and 42= +5V, 43=GND for IDE.
BTW, which pin is 1 on IDE connector? There is number 1 printed on PCB, but I suspect its 44 actually?


Can I check Alice voltages with digital multimeter (can it break something?)

Title: Re: A1200 8520
Post by: Framiga on July 29, 2004, 05:02:16 PM

Quote

BTW, which pin is 1 on IDE connector? There is number 1 printed on PCB, but I suspect its 44 actually?


Can I check Alice voltages with digital multimeter (can it break something?)

erm . . . if there is a 1 printed on PCB, you can bet that it is the N.1 :-)

For the flat-cable connector, is the red one.

You can't break anything with a multimeter . . .pay attention do not touch 2 pins at the same time.