Re: C128 parts

From: Marko Mäkelä <>
Date: Thu, 29 Jun 2017 12:09:51 +0300
Message-ID: <20170629090951.2cq4fwc6ccemj76f@hp>
On Wed, Jun 28, 2017 at 03:17:00PM -0600, Terry Raymond wrote:
>What pins on the power switch can I jumper?

I think that you can use an ohm meter to measure the resistance between 
all pairs of pins, in both the ON and OFF position of the switch. This 
is obviously without any power cable connected. Ignore any readings that 
are above some tens of ohms. If the connection is good, it should be 
very close to zero ohms.

If the switch indeed is a problem (say, there is some dirt or corrosion 
inside), the resistance could vary when you are gently rocking the 
switch in the ON position.

When it comes to the power connector, I think that the only possible 
failure mode should be corrosion or mechanical damage, or a bad 
soldering on the circuit board. You could add some new solder and flux 
and then measure the resistance between the circuit board and the pins 
on the outside. I think it should be more likely that the power cord 
from the power supply is damaged, for example if the cable has been bent 
heavily. Have you checked the power supply with another machine?

>I will check all the points you mention Mike.  I did already check U59 
>Regulator it is getting 12V.

Did you measure all voltages on the power connector solder pads on the 
circuit board? Do the voltages remain stable if you gently rock the 
switch in the ON position or if you bend the power cord near the 
connector or the brick?


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Received on 2017-06-29 10:00:03

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