How to test an IC voltage regulator with a DVM

Is there a way to test an IC voltage regulator with a digital volt meter? I have a three pin adjustable voltage regulator and I need to know if it is bad.

Thanks!

Milkman

Reply to
LVMilkman
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On May 12, 9:23 pm, LVMilkman wrote: > Is there a way to test an IC voltage regulator with a digital volt > meter? I have a three pin adjustable voltage regulator and I need to > know if it is bad. >

If there are no shorts between pins (totally trashed), the usual method is to connect it up with the proper resistors and measure the actual output under varying loads. Is there any other way?

GG

Reply to
stratus46

Not that I know of, and that is certainly the way that I do it. They are pretty reliable though, if we're talking something like an LM317T. I repair about 6 or 7 hundred per year of a particular board that uses one. I would guess that I get perhaps 10 regulator problems in that number, and amongst those, probably only 3 or 4 are the device itself. The rest are o/c resistors in the output voltage set chain, or short circuit caps at the set or output pins.

Arfa

Reply to
Arfa Daily

LOL pretty reliable and you repair that many?

:)

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Reply to
Meat Plow

I repaired over 10,000 CATV converters for United Video's Cincinnati, Ohio system in the early '80s, along with commercial C-band microwave receivers and other headend equipment for over a dozen CATV systems in a four year period. I processed the converters 100 at a time, unless the total spare stock was below that number and ran a production line repair, kicking out the few dogs to finish last.

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Reply to
Michael A. Terrell

Hey Meat, how's it going? Perhaps you misunderstood what I said. I stated that I repaired 6 or 7 hundred a year of a particular board that happens to *use* an LM317T. I then went on to explain that of those several hundred, *very few* of the faults that the boards had, were related to that '317.

Actually, I've just looked at the figures, and I do about 100 every 6 weeks, so it's actually nearer 800 a year. This board has an LM317T and a 7805 on it, neither of which are heatsunk by anything other than being screwed down ( and often not very well ) to the PCB. Both of these regs run too hot to touch in normal use. I have a separate spares drawer cabinet for the repair of these, and in it, I keep a running stock of 5 LM317's, which I replenish perhaps once a year. The very occasional power supply faults that these boards suffer on their 12v rail, which the '317 is used to derive from the raw 24v supply, are almost invariably o/c surface mount R's in the voltage set network, or s/c tantalum surface mount caps.

Considering that these devices are s/c, thermal, and SOA protected, this pretty much puts them outside being damaged by external conditions, so any failures have to be random chance. Semicon manufacturers have got random chance failures, after the bottom of the bathtub, licked these days, so I don't see why you find the fact that I don't have very much trouble with the

317's, given the number that pass by me, funny ??

Do you have some other experience of them ? Am I alone in not seeing a big reliability problem ? Just interested ... d;~}

Arfa

Reply to
Arfa Daily

Guys: Thanks for the help and I really appreciate the advice of the down stream resisitors. I will check all components, I just was not sure how to check a voltage regulator, but it seems that there is no easy way to do that with a DVM.

Thanks again,

Milkman

Reply to
LVMilkman

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