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

Yes, that was very clear. Thank you. I was worried about the probe shorting something out. But I like your idea about the hook probe. I will feel comfortable trying it with one of those. That way, I can attach it before I power it on.

On Thursday, November 30, 2017 at 6:22:17 PM UTC-8, compu_85 wrote:
>
> 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, <austj..._at_email.domain.hidden <javascript:>>
> 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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