trinityamps.com

The 5R 2 watt resistor that came with my VRM kit has the correct markings for 5 ohms but actually reads 2.9. Is that too far out of spec to use with the VRM? My local RS doesn't carry these so if I have to order one, am I good to move the 1M resistor off the input jacks and add the DC blocking caps and add the VRM later?

Thanks!

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~fredster

That's too far out and won't protect your MOSFET under extreme overload. Though that is unlikely to happen. But, Email me and remind me to send you a replacement.

I would not move the 1M until you add the 0.1uf blocking caps.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks Stephen, no worries, I'll get one coming. Probably faster that way Just to be clear - I already have the blocking caps in place, so I should be ok to move the 1M and run with stock power until the VRM is together?

Thanks!

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~fredster

Yes

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Well, this is frustrating. I ordered one of these at 5.1 ohms but it reads 3.4. Is that too far out also?

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~fredster

Hmm two brand new out of spec resistors. Very odd

I'd wager that your DMM might not be very accurate or might not be calibrated properly (how is the battery?).

New production electronic components usually have pretty tight tolerances.

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http://pdfelectronics.com

Wow, good call! I swapped the batteries and both resistors were in spec. Put the old batteries back in and they test bad again. Funny thing though, I tested all the other components in the kit and they looked good. Even the old (AA) batteries both test at 1.4v. Oh well. Thanks KL, I'm going ahead with the original parts .

edit: I should pay attention to who's talking to me...

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~fredster

Lower values are harder to measure then bigger values.

All good!

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http://pdfelectronics.com

Old batteries can't supply enough current for an accurate low ohms reading on a DMM.

Batteries should be tested with a load, say a 100 ohm resistor, to get a valid reading. An old battery might read an acceptable voltage with no load, but its internal resistance has become too high for it to be able to supply enough current for most applications.

Good luck with your VRM.

Thanks Mitch, I did not know that. Learnin' all kinds of stuff here, way cool!

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~fredster

Good call and lesson learned!!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps