SparkFun Forums 

Where electronics enthusiasts find answers.

General project discussion / help
Did you make a robotic coffee pot which implements HTCPCP and decafs unauthorized users? Show it off here!
By wose
Well hey,

First time forum poster, long time product user. I recently picked up a Lipower board (the TPS61200 boost converter) for the express purpose of something that will involve removing the UVLO – all the Googling in the world has only produced 2 pictures of the final mod and lots of descriptions of how it's done.. I like to visually verify before bringing a soldering iron to a fresh board though.

Problem is, I think the board components have changed layout a bit since the photos I saw were taken – can anyone confirm for me, have the positions of R3 and C2 rotated?

The clearest shot of the mod I could find (the one I'm sure we've all seen, at ... e-lockout/ ) seems to have them parallel to the board edge, and what I think are R3 and C2 on the board I got are perpendicular. Also, the author of that article admits to purposefully "[trying] to produce as sloppy a soldering job" as he could for demo purposes. Kinda obscures the details.

Am I totally overthinking this? Thanks for any help.
By Valen
Yes, R3 and C2 seem to have been rotated. But in the current configuration this is easier to mod. In the old configuration it was easier to accidentally unsolder the other components. Just unsolder R3 (or both for that matter as C2 useless anyway) and fill it as a solder jumper. Then UVLO never even comes close to 0.25 volt. (Well, it will when the input power goes below 0.25 volt) Or replace it with a different value resistor based on the formulas in the datasheet.

Like in the older model, the light brown component is the capacitor (C2). The black one is the resistor R3. The one nearest the negative terminal of the JST connector. However, I can't make heads or tails out of why they used those '30E' resistors on the product image: ... 55-03a.jpg

[Edit: Solved it, according to this table 30E is indeed a 2 Mega ohm resistor. EIA-96 number coding is weird! ... istors.php]
By Valen
One last edit the forum doesn't allow me to make anymore:
"Just unsolder R3 and fill it as a solder jumper. (or both for that matter as C2 will be useless anyway if R3 is shorted)"