MicroSquirt.com read only forum (Jan.15,2018)

Is there a difference between using a 1k pullup on pin 4, to swapping out R51 for a 1k?

Only if you also had R50 jumpered. With R50 in the way, you'd only pull the voltage on pin 4 down to 4.5 volts if you ground pin 4.

What if i remove R51, use the top pad (towards vcc/D6) from R51 and put a 1k resistor to vr2 in side of R50? Leaving r50 intact. Or should i still short r50? Or how else could I accomplish this? I don't want to use any external resistors for a project.

Is there any downfall or issues with doing this internal mod? -Or 100% good to go? Or would it be safer just to add the 1k across the pins between the ampseal and pcb.

Externally, Pin 4 biased to 5v actually makes a cleaner signal for me than going to 12v. With this in mind, will just swapping r51 as i mentioned be the fix?

(your statement confuses me a little, as if your saying- as in production form, when pin 4 is grounded, the voltage is pulled down to 1.8v. If the resistor R51 is changed to a 1k, then the voltage will be pulled down to 4.5v. ) If this is the case, i understand the circuit a little better and you already answered my question in the first post.

So to get this straight, i can bias the input circuit to either 5v or 12v with R50 & R51 mods. And there is no downfall or risk in doing so.

I meant to say that if you had swapped R51 for a 1K resistor, and made no other changes, grounding pin 4 would only pull the voltage on the input of the VR conditioner down to 4.5 volts.

If you want to add an internal pull up, why not solder a through hole resistor to the pins on the AMPSEAL itself?

Yes, i can solder across the ampseal pins.

I was just looking at doing the mod on pcb as I have 3 version 1's that i am updating/ swapping smt diode and resistor for through hole. (D5 & R26) I figured another resistor swap on pcb was easy enough at the same time. And a little cleaner. The version 1's i have are just test units kinda and not critical. Any version 2's will be across the pins.