Re: checking electrolytic caps

On 05/30/2017 04:44 PM, Terry Raymond wrote:
> Hi Clockmeister,
> 
> This power source has a pigtail for powering the C64 works fine doesn't 
> blow it's fuse
> Just when powering up the C128.
> 
> This is helpful enough to find what regulator I need.

You might want to check the bridge rectifier in the C128. If one of the 
4 diodes in it has a short it will blow the fuse. It's the black square 
next to the power switch.

  Gerrit





> 
> Terry
> 
> On May 28, 2017 6:06 PM, "Clockmeister" <clockmeister@internode.on.net 
> <mailto:clockmeister@internode.on.net>> wrote:
> 
> 
> 
>     On 29/05/2017 7:50 AM, Terry Raymond wrote:
> 
>         Hi
>         Im needing to check all Caps on my C128
>         to check these would I read the caps in OHM's readings?
> 
>         Im going to desolder them one at a time just to know what ones
>         are failing
>         and if the
>         Electrolytic is leaking out or the CAP has a bulge on the top.
> 
> 
>     If you are going to the trouble of desoldering them, just replace
>     them but do so with quality caps.
> 
>         This C128 is blowing the fuse in the power source, and this
>         power source
>         has been built from scratch from Ray Carlsen in the U.S.A. I
>         trust Ray's
>         work so it must be something on the
>         C128's MB circuit.
> 
> 
>     I trust Ray's work too, but that is not to say something hasn't
>     failed in the supply. Does the fuse blow as soon as you power up the
>     C128?
>     If there is a dead short in Ray's supply I would suggest that the
>     supply fuse will blow even if the C128 isn't turned on.
> 
>         I was also told isnt there a power regulator component that has
>         3 solder
>         legs that could possibly
>         cause power problems, Should this regulator read 12VDC?   What
>         legs do I
>         probe when I read the voltages on this regulator?
> 
> 
> 
>     If it's a 78xx Voltage regulator then see here:
>     https://www.engineersgarage.com/electronic-components/7805-voltage-regulator-ic
>     <https://www.engineersgarage.com/electronic-components/7805-voltage-regulator-ic>
> 
>     Pin 1 is input voltage, 2 is ground and 3 will be the regulated
>     output voltage which should match the last two digits after the 78
>     part number. IE 7805 = 5V, 7812 = 12V.
> 
> 
> 
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> 


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