VFE Choral reef - small mistake in shopping list

[kaydonna]

Hey all,

Just wanted to post this here so no one gets caught in the same trap as me.

On the Choral reef shopping list it calls for a 65k resistor, while on the pcb there is no spot for a 65k resistor. There is however a 68k resistor on the pcb and not the shopping list so I'm just assuming there was a typo.

Can anyone else confirm this? Spent far too long looking for 65k resistors, couldnt even find them on Mouser.

Thanks,
kaydonna

[benny_profane]

Hey kaydonna, welcome to the forum!

See the attached image. If you look at the schematic, pin 6 of LM358 goes to 82k and 65k. Follow the traces on the board image to the 68k resistor. That's where the 65k is supposed to be (per the schematic). Mouser has 64.9k Xicon 1% metal film resistors. I used that and worked for me. Hope that helps.

[kaydonna]

Thanks for the reply benny_profane!

I do see that on the schematic. Does that mean that there is an error on the PCB then?

I was able to find 64.9k resistors on Mouser, I figured that since 65k are far less common that 68k was the intended value. But if you said you built it and it worked with a 64.9k, thats good enough. 

[madbean]

For some reason, I forgot to include this text on the Choral Reef project doc (but it should be in all of them):

Note: Use the values listed on the image above – not the values indicated on the silk-screen of the PCB.  Some values changed over time in the VFE product cycles.

IOW, use the layout image of the board on page 1, not the values listed on the PCB. The Shopping List corresponds to the layout image. Peter did not update his PCBs for different values when he tweaked them.

[kaydonna]

Ah! Ok.

Thanks for clarifying. First VFE build.

[benny_profane]

For some reason, I forgot to include this text on the Choral Reef project doc (but it should be in all of them):

Note: Use the values listed on the image above – not the values indicated on the silk-screen of the PCB.  Some values changed over time in the VFE product cycles.

IOW, use the layout image of the board on page 1, not the values listed on the PCB. The Shopping List corresponds to the layout image. Peter did not update his PCBs for different values when he tweaked them.

That leaves a discrepancy between the image (68k) and the BOM/schematic (65k). I built from the schematic and just assumed the PCB image had a misprint.

[zgrav]

If you think about it, it makes sense that if you see a discrepancy it is more likely that the build document was updated to work with an existing PCB, than it would be if a new version of a PCB was issued without updating the build document.    Odds are pretty good, though, that either part will work in the build even though someone decided a different part might work a bit better.