Spare BS170

[Darren C.]

Anyone have any idea where I can scavenge a BS170 MOSFET N-Channel. I soldered one a little crooked and snapped it trying to straighten it. I've got one from Mouser in my cart. But, I can't help thinking I can rob one off of something I have lying around the house. Probably not, but I thought it was worth asking. Not only does Mouser charge $5 to ship a $.40 part, I have to wait several days to get it. We have a radio shack in town (think they are still open) but not sure if they would have anything. I couldn't see that they carried it online.

It's not a total FU because it goes on the button board. Looks like I can still use the HM without it while I'm waiting.

 

[Bryan Mayland]

Radio shack only carries a big-ole TO-220 as their only MOSFET so it's a no-go there. You use a MPS2222A which they do have, but you'd need to add a 1K-3.3K resistor on the base leg (collector to pin 16 of the LCD, emitter to GND) which starts to get a little messy. I checked MicroCenter because they have a lot of electronic stuff but they only have transistors as well. I can't think of anywhere else you might get one.

If you can't find one I can ship you one. I could put it in a first class envelope but it might be crushed along the way and adding something to support it might not make the minimum bend radius of the postal machines. Still, I can give it a try if you want. The other option is to put it in a padded envelope but that would cost $3.

EDIT: Oh but yes, you can use the HeaterMeter without it, but the LCD backlight won't work. The other option is to just solder the drain and source pin holes together in the MOSFET footprint, which will give you 100% backlight all the time. If you want to do that let me know and I can show you which two holes to connect.

 

[Darren C.]

Well, that's generous of you to offer to send me one. But, I don't want to put you out. I might go with the 100% backlight option. I could solder something removable and still have the option to order the part later, if I choose to. I don't think I ever changed the brightness on my HM 4.1. So, I don't think I'd miss not having the option to change the backlight later.