my bad prom

[Ken Kelly]

Mike,

	This is from an email last year when I was doing the same thing.

> Easy.  Just get a 555 and connect it up as follows:
> 
> Pin 1 is Ground. Pin 8 is +12V. Connect a 0.1 uF ceramic cap between these
> pins, with short leads, for bypassing. Otherwise it may misbehave.
> 
> Tie pin 4 to pin 8.
> 
> Tie pin 6 to pin 2.
> 
> Add a 3.9K resistor from pin 7 to pin 8. (A 3.3K will be close enough)
> 
> Add a 22K resistor from pin 6 to pin 7. (You could adjust this one for
> precision setting, but it's not needed for this application)
> 
> Add a 1 uf capacitor (electrolytic OK) + side to pin 6, - side to pin 1.
> 
> Add a 0.1uf cap from pin 5 to pin 1.
> 
> Output is on pin 3. It will be approx.
> -----------------------------------------------------------------
> Have fun...

		Ken


Mike Rolica wrote:
> 
> OK so I know my prom is junk.  It's a hypertech (no It is not the piggy
> back type-165ecm)now my OEM prom needs a signal from the vats module
> (5v at 30hz square wave) I have the OEM service manual from gm (it is the one
> that the mechanics use at the dealership, it's about 4"thick) I have access
> to allot of them (86-96 and EFI gm car/truck) If anybody is interested just
> email me. I can scan what you need and send it to you.  Anywayz,  the signal
> the vat needs, is the amplitude of the wave from 0-5v or is it -5v - +5v?
> How can I build something to bypass this?
> Mike  Rolica :)
> mrolica at meridian-mag.com
> (519)-245-4040
> EXT: 260