Recommend you measure right across the rectifier outputs, don't trust your ground.  It's usually a good idea to float the ground of your power cord when using a scope to measure across two points when one isn't earth ground, either with a ground adapter or by removing the ground pin from the power cord.

-----Original Message-----
From: owner-cbm-hackers@ling.gu.se [mailto:owner-cbm-hackers@ling.gu.se] On Behalf Of ruud.baltissen@apg.nl
Sent: Friday, August 07, 2009 9:30 AM
To: cbm-hackers@ling.gu.se
Subject: RE: Dead PET 2001

Hallo Phil,


Just out of my head: the 8VAC should be rectified and supply the power
for the 7805s. Instead you read 0V. My conclusion:
- dead rectifiers (BOTH are brooken ???)
- bad connection
So do me a favour and measure directly on the outputs of the diodes.


--
     ___
    / __|__
   / /  |_/     Groetjes, Ruud
   \ \__|_\
    \___|       URL: Ruud.C64.org



Bugs in my programs? Probably a lot, but none I am aware of.



-----Oorspronkelijk bericht-----
Van: owner-cbm-hackers@ling.gu.se [mailto:owner-cbm-hackers@ling.gu.se]
Namens Philip Lord
Verzonden: vrijdag 7 augustus 2009 14:26
Aan: cbm-hackers@ling.gu.se
Onderwerp: Re: Dead PET 2001

Hi again,
Sorry it took me so long to get around to measuring the voltages off my
machine...I hope you are all still here.
So here we go (All voltages are approximates):

Between the two transformer tabs that go to the monitor - 16VAC
Pin1 - 8VAC
Pin2 - 0V
Pin4 - 0V
Pin5 - 8VAC

I also took measurements on the 7805's and as they are tied to pin2,
there is no voltage read. 0V.
Pin2 and Pin4 both come from the same place off the huge blue capacitor,
so maybe I can assume this is dead?
Is there anyway to test this capacitor?

Any further advice would be greatly appreciated.

Thanks again
Phil


On Jul 30, 2009, at 11:50 AM, Ethan Dicks wrote:

> On Wed, Jul 29, 2009 at 10:39 PM, William
> Levak<wlevak@sdf.lonestar.org
> > wrote:
>> I pulled out my 2001 and took some measurememts.  On connector J8 the

>> center wire is ground. Measuring from the various pins to ground.
>>
>> Pin 1 - 8V
>> pin 2 - 20V
>> pin 4 - 20V
>> pin 5 - 8V
>>
>> Measuring between the two wires on the transformer that go to the
>> video board - 16V.
>
> That all makes sense - 8V should be enough headroom for a 7805 and
> ISTR there's a 7812 on the monitor analog board, so 16V is plenty hot
> enough to get 12V from a 7812 (+15V happens to be enough).
>
> -ethan
>
>
>       Message was sent through the cbm-hackers mailing list


       Message was sent through the cbm-hackers mailing list

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