Re: 8-bit Logic probe

From: Jim Brain <brain_at_jbrain.com>
Date: Tue, 17 Nov 2020 19:07:52 -0600
Message-ID: <c100f499-d0fb-5e6f-0459-d58d8653d603_at_jbrain.com>
On 11/17/2020 6:58 PM, Terry Raymond wrote:
>
>
> Okay there is the C64/C128 Commdore service manual does that actually 
> show the Low/High states of Logic chips and MOS chips hopefully to see 
> if the chip is good or smoked?
Most often not.  You'd need to get a copy fo teh IC datasheet online and 
probe each input and then each output, determining if the IC is working 
based on teh truth table in the datasheet.
>
> maybe this is crazy but I dont know anything about logic probes, could 
> I power this somehow from the MB itself or use some other more 
> reliable power.
You can.  Or a battery.  3 AA cells should work
> Oh yeah I do remember the Led lights have something to do with the 
> high or low states am I correct?
That I am not sure.  I don't own one.
>
> The other problem is I dont have an Oscilliscope mainly for checking 
> for the
> correct signal on the processor chips, yeah I know theres the 8502 and the
> Z80 on the c128 so Im stuck with using a logic probe and a Voltage 
> meter, but if reading a chip with a voltage meter should that be set 
> at OHMS to read resistance?
No, an ohmmeeter won't be much good in either setting for a logic IC.


Jim
Received on 2020-11-18 03:00:46

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