Problem Solved !!!!
Must remember that if testing a circuit designed to work from mains with
a 10v pk/pk signal than the ammount of time the positive peak is > 5v is
none hence the power supply aint working properly ! In future will
engage brain before makin self look fool !
Steve...

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Alan B. Pearce
Sent: 14 December 2002 15:17
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: 508 external rc osc


>I am having a couple of minor problems with a 508 and ext rc osc
>
>What values of r and C do you guys use to get 4mhz (the internal osc
>aint adjustable and the spae is too barn door ish) I have tried 2k2 and

>33p and it aint stable also seems to drag powersupply down until res
>gets to about 4.5 k then freq is miles off
>
>Any sugestions ???

As you are prepared to go for an external clock input why not use an
external oscillator with a resonator or crystal? This will give you much
more accuracy than you can hope to achieve with RC, and that seems to be
what you are looking for.

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