Thanks for your input Olin,

Olin wrote
> Perhaps you could replace the second resistor and zener with a 7805.  Then
> everything would run off the regulated 5V.

That was my first thought too  ...  and easy enough to implement on the 
original pcb, though I did wonder if I could fit a 5 volt zener ... or 
equivalent two terminal device of some sort ..  to clamp the 5.6 down to 5 
volts  ...  and fit that to the new daughter board (or is that just too 
crude)  :)

Olin wrote
> Does the micro need to perform accurate timing?  If it's just implementing
> some logic, then use a PIC with a internal oscillator.

No, definitely not accuarte  ...  so internal oscillator is starting to 
sound the way to go.

Olin wrote
> What does the rest of the board do?

Not much. Has the four output fets which are good for 13 amps each 
(TO220's).
Has four leds which flash nicely to show the pulsation rate.
Monitors the current on each o/p in case of overload and will shut down if 
it occurs.
Has a plug in header with four links that sets the 'cycles per minute' and 
also their ratio (on-off time)


>Why does it cost $1200?  Is this the
> artifically inflated end user replacement price or include the cost of
> sending someone out to do the replacement?

Good question  ... and yes  ...  definitely inflated. It's what the dairy 
farmer pays for a replacement board !!!
In fact I've heard prices quoted as high as $1500. A s/h one will set them 
back $900.

I mentioned earlier, one guy voluteered that he'd be very happy if I cherged 
him $500 to repair a board  ...  who knows what he'll charge the farmer.

Doesn't include going out to fit!!

Believe it or not  ... these things are all of 200mm x 150mm.


>A lot of things are not clear
> from your post, but it could possibly be cheaper, and certainly more
> reliable, to create a new functionally identical board with a PIC on it 
> than
> a daughter board.  In case of failed processor, swap the whole board with
> the new one instead of swapping the processor with a daughter board.

I had also considered this too  ...  though for me personally would have 
been a bigger job than I would like to tackle. I'd probably still favour 
retrofitting a daughter board.

> Either way, this is the kind of thing we do.  Give me a call if you want 
> to
> kick this around.  (978) 742-9014.

I appreciate your help, thanks. I'll see if I can get through.

Regards,  Roger 

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