Re: Apple Lisa 2/5 I/O Board COPS Error

Yes, a simple meter is all you need. Even an analog one will do.

First of all, when using a meter on digital circuits, it's important to watch were your probe tips go. You don't want to slip and short out the chip! When I was testing mine I used a springy hook probe to hook onto the chip pins, but if you don't have one just keep a steady hand :)

If you remove the top of the Lisa there are several holes in the metal chassis that make a convenient spot to stick the black ground lead.

If you do a google search for "COP 421 Datasheet" you'll find this document: http://pdf.datasheetcatalog.com/datasheets2/87/8710049_1.pdf , which has the pinout of the chip on page 7.

First check that pin 1 is actually connected to ground - there should be little resistance between this pin and the metal chassis. Next, you can check for +5 when the Lisa is plugged in on pin 9 (VCC), and the voltage on pin 14.

Clear as mud?

On Thu, Nov 30, 2017 at 8:25 PM, <austjeremy_at_email.domain.hidden> wrote:

> Comput_85 thank you for your comment, and previous ones also. I'm having a
> hard time figuring out how to actually check for voltage. I have a simple
> multimeter. Do you use both the red and black lead? Sorry for my ignorance.
> I'm still learning.
>
>
> On Thursday, November 30, 2017 at 4:35:55 PM UTC-8, austj..._at_email.domain.hidden
> wrote:
>>
>> My Apple Lisa 2/5 I/O board gives me a COPS chip error. I tested the chip
>> in another I/O board it works just fine. I switched out the socket. I
>> checked for continuity on each pin in the new socket. I have checked every
>> single tracing that connects to every pin of the COPS socket, all test fine.
>>
>> The computer starts just fine with another I/O board.
>>
>> Symptoms, the computer powers on the second power is turned on. I don't
>> have to push the power button. It just double beeps and gives I/O board
>> error 52.
>>
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-- 
Jason Perkins
313 355 0085

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