Is there any way to adjust this?

My friend gave me an digital VOM, and DC voltages in the 2 volt range read 14% high.

Is there any way to adjust this?

Or, is there ever a way to adjust this?

No schematic is available, I'm pretty sure but its guts look like most of them. .

Reply to
micky
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** So all the other ranges are OK ?

If so, it sounds like manufacturing error.

.... Phil

Reply to
Phil Allison

Some few types have an internal adjustment process. Short the leads, push a sequence of buttons, it zeros out for ohms. For DCV, it will require a battery of known voltage within the range required.

Peter Wieck Melrose Park, PA

Reply to
pfjw

The Peter Fuckwit Wieck Troll spewed:

** Fuck off, you retarded pile of bat manure.

No-one needs to see your brain dead, autistic crap.

.... Phil

Reply to
Phil Allison

Off your meds again?

Fluke 73III True RMS meter. Set to ohms. Cross leads. Hold Down Yellow (ran ge) Button. Meter adjusts to 0 ohms. Proceed from there. I have been using this meter for almost 20 years now, and go through this when either switch ing leads or changing the battery, or if it has been sitting for a while.

I guess quality equipment (along with quality meds) is not available in you r cave?

Reply to
pfjw

It seems to me, the cheaper it is, the higher the chance of finding a calibration pot inside.

But the calibration is only for the voltage reference, so, as Phil comments, if only one range is off, then it is not a calibration problem.

--
RoRo
Reply to
Robert Roland

Or, the rest of the range is OK, with the error only at the lowest end of t he scale (and how Fluke does it in my case for Volts) as noted by the OP. I f measuring in dozens or hundreds of volts. a 0.5 V error ain't much. 0-2 V , quite a bit. About anyone can make a meter that is +/-1% at 500V. Not so many at 2% at 2V.

Peter Wieck Melrose Park, PA

Reply to
pfjw

calibration pot inside."

Your theory is blown out of the water, sorry. Those $0.000 ones from Harbor Freight have no pot.

comments, if only one range is off, then it is not a calibration problem.

--
RoRo " 

Kinda is and kinda ain't. Seriously, I only recently learned how these thin 
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Reply to
jurb6006

I hae opened up 3 of the 'free'or about $ 6 if just bought ones and they all have an adjustment pot. They all seem to be close enough compaired to my Fluke that I did not do any adjustment to that pot.

Have you actully opened up any ?

Reply to
Ralph Mowery

The Peter Wieck Fuckwit Troll spewed

** Fuck off, you retarded pile of bat manure.

No-one needs to see your brain dead, autistic crap.

** ROTFL - wot brain dead crap. ** Fuck off, you retarded pile of bat manure.

No-one needs to see your brain dead, autistic crap.

.... Phil

Proceed from there. I have been using this meter for almost 20 years now, and go through this when either switching leads or changing the battery, or if it has been sitting for a while.

Reply to
Phil Allison

** Of course not, have to be brain dead to think that.

.... Phil

Reply to
Phil Allison

The Peter Wieck Fuckwit Troll spewed:

** Complete CRAP !!!

Fuck off, you retarded pile of bat manure.

No-one needs to see your brain dead, autistic crap.

.... Phil

Reply to
Phil Allison

I checked since I first posted and the 20 and 200 volt DC scales have the same problem. They give the same reading of 1.7 on a AA battery, a battery that is probably dead since it's 3 years old and the camera two of them are in was dead, and isn't now that I replaced the batteries.

And the AC volts is good, I don't have a handy way to messure milliamps The continuity buzzer is dead (and I checked both leads). And none of the resistance scales work.

So it's probably not worth keeping a battery in it with ohms scales, but I am still interested in calibration so I'm glad I asked.

The story is more complicated than it was yesterday. Yesterday I replaced some other battery and measured the old one and it was 1.4. then I measured the two from yesterday and instead of 1.74, it said

0.6!! But later today I measured again and it was up to 1.7!!! A dirty pot?

Hmmm.

Hmmm.

Okay, my final paragraph today: I figured that out, but only by fildding with it. How many of you figured it out from a distance? (It's another serious problem.)

It may have worked well at one time. Actually my friend died and this was among his things. So eEven though I have other, better, and similar meters, I'm reluctant to throw it out.

The fuse had been blown and was missing, so he took it apart. The shine is off a tiny bit of circuit board by the fuse, so it was a big blowout. And there are two holes in the PCB with nothing in them right near the burned spot, but the first two times I looked there, I thought they were just extra holes, since there is no evidence of a part, and I though there was no copper trace. There were parts in the way so I couldn't see everything.

But now I see that there is a trace headed in the direction of each hole. I guess the blowout took the part and part of the traces with it, that there was nothing holding the part to the PCB but the solder attachment to the traces. That's why the holes are so empty and clean.

With this added knowledge, I'll look it up again. (I looked it up yesterday and found how big the fuse should be.)

Just $15 at Amazon.

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And manualslib.com has the manual but it's only 9 pages and has no schematic.

The missing part seems to be connected to the ground on one side and one pin of an 8-pin IC at the other. I suppose it's either a cap or resistor. Since the ohms scales don't work, is it reasonable to guess it's a resistor???

I have a resistor-substitution box, bought at a hamfest and only used once. Wait, that time I decided it was easier to use a pot. I could do that now too.

Unless one of you knows what the part would be, or where to get a schematic for a Vellaman DVM850BL

the only other idea is to buy a second one and see what part is in that spot. Then I could give away the new one.

Reply to
micky

So give it back to him

Reply to
Phoena Greene

You did not read what I wrote, did you?

I spoke of chance, and you refute my claim based on one single sample?

Not exactly solid statistics.

--
RoRo
Reply to
Robert Roland

Did you try a new battery in the meter? Weak batteries will give odd readings...

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup) 
John's  Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 
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Reply to
John Robertson

all have an adjustment pot. They all seem to be close enough compaired to my Fluke that I did not do any adjustment to that pot.

Have you actully opened up any ? "

About three of them, no pots.

Of course that does not mean they're all the same, I have encountered two d istinct types at least, one has a power switch and the other simply has an "off" position on the range switch. (which I do not prefer)

Perhaps they were well hidden. At any rate, one pot for the whole thing wou ld adjust all the ranges, so if only certain ranges are off then something else is wrong.

There are probably many different versions of these things. At work I stumb led across a Craftsman meter which is about the spitting image of one of th ese, but then we know Sears stuff is built by the lowest bidder. However I haven't taken that one apart, it works, I will see the inside when the batt ery dies I guess. It could be totally different but really I do not see the reason why. When they work right they seem to really work right, they agre e with my decent Fluke and they agree with my buddy's even better Fluke.

I had one that would not zero on any range, they said don't even bother to send it back, they just sent a new one. Throwaway test equipment, ever thou ght you'd see it ?

But then a $300 guitar can be throwaway as well, really. My buddy bought an Ibanez acoustic with the electronic pickups. Sounded great actually, like a miced guitar and not much feedback. But the electronics quite. He calls a nd they gave him a full refund and said not to even bother sending it back. I bought it thinking maybe I would fix the pickup but never got to it, so I have me a decent acoustic. And that prick made $100 off of me. It does pl ay really well though. He should have sold it to me for $50 though. But rea lly, I started taking that guitar apart and the way they put the pickup in pretty much precluded any type of repairs. I swear, it should be illegal fo r electronics manufacturers to be in possession of any type of glue, and I mean death by slow torture for thee board of directors.

Reply to
jurb6006

No, several. Unless the pot is well hidden somewhere.

I have changed the batteries in a few, and one I wanted to somehow revamp a nd make it read like a benchtop DVM but once I saw the ubiquitous zebra str ip I figured the chances of that were slim and none and slim has a bulletho le in his head.

Thing about these tings is it is almost not worth changing the battery, dep ending on where you go it might cost you more than the whole meter.

But anyway, using this Google groups is getting to be a drag, no tree view so you have a hard time seeinf where your post goes, as in who it appears y ou are responding to. And now it doesn't like my old Firefox so I am in IE again. I used to have Thunderbird set up opn this thing but lost it somehow due to a system restore or something. I might just shoot the thing and be done with it.

Reply to
jurb6006

prick made $100 off of me. It does play really well though. He should have sold it to me for $50 though. But really, I started taking that guitar apart and the way they put the pickup in pretty much precluded any type of repairs. I swear, it should be illegal for electronics manufacturers to be in possession of any type of glue, and I mean death by slow torture for thee board of directors.

Most anything under $ 500 is a throw away now unless you can fix it yourself. With companies charging $ 50 to $ 100 per hour labor, the cost to ship it back, especially if it is big or heavy, all tht ammounts up fast. Sort of like the socket sets from 40 years ago with the lifetime warrenty. The whole set was about $ 5. If you sent the broken part back and $ 4.50 for retrun postage and handling, they would send you a replacement for the broken part.

Reply to
Ralph Mowery

I was born in 1950 and remember much from those days. I would not want to go back . Things were inexpensive that people had to have, other things not so much.

YOU should remember the TV sets. Many homes had a black and white, but few color sets. Now many have one in most of the bed rooms and a very large one in the main room. Cars always needed something done to it. now a oil change every 5000 miles is about all to 50,000 or 100,000 miles. Many only had one car and as you said it was almost a junker. Most now have a car for almost every driver in the family and no junkers either. Cloths dryers were not in many homes to around the late 60's. Homes had a telephone and some were even on party lines. Now many people have their own cell phone.

Only thing I relly can think of back in the good old days that was better was there was very little crime.

Reply to
Ralph Mowery

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