This is why you don't buy cheap multimeters.

[b700029]

Re: This is why you don't buy cheap multimeters.

There is no fuse for "10A" jack. To use safely, each measurement can not last for more than 10 seconds, and the interval between each measurement must be more than 15 minutes.

[Th3_uN1Qu3]

Re: This is why you don't buy cheap multimeters.

That's what it says on all meters, including my Uni-T ones which are fused. Never respected that and i haven't gotten a shunt catch fire yet, not sure how it affects accuracy tho. I've actually put 30A fuses in my Uni-Ts instead of 10A to avoid nuisance blowing.

[retiredcaps]

Re: This is why you don't buy cheap multimeters.

My Harbor Freight $3 multimeter

Apparently, one person thinks it is worth $100 Buy It Now on ebay.

http://www.ebay.com/itm/110818056416

Obviously, it didn't sell so he relisted it for $45.

http://www.ebay.com/itm/110820886299

[severach]

Re: This is why you don't buy cheap multimeters.

YOU ARE BIDDING ON A NEW GEN-TECH DIGITAL MULTIMETER NEVER USED IN EXCELLENT SHAPE HAS ON/OFF SWITCH COMES WITH RED &BLACK METER READERS.

It's Cen-Tech. With spelling like that perhaps he went to the Verizon School of Math and his decimals are off. Could one of those meter readers be Peter the Meter Reader?

[kaboom]

Re: This is why you don't buy cheap multimeters.

...perhaps he went to the Verizon School of Math and his decimals are off...

Like this?

[ratdude747]

Re: This is why you don't buy cheap multimeters.

Apparently, one person thinks it is worth $100 Buy It Now on ebay.

http://www.ebay.com/itm/110818056416

Obviously, it didn't sell so he relisted it for $45.

http://www.ebay.com/itm/110820886299

him:

me:

they must be making crack more potent these days...

[bluto]

Re: This is why you don't buy cheap multimeters.

Like this?

At least the place didn't burn. A couple of years ago around these parts, a charter subcontractor managed to burn down a brand new $2.5 million house by drilling into the electrical panel from the outside. It took 6 fire departments to put it out! This is the best link I can find...

http://www.ksdk.com/news/story.aspx?storyid=88193

Somewhere else it said the guy worked for 'Sparx' Communications

[momaka]

Re: This is why you don't buy cheap multimeters.

After playing a bit more with the probes on my 830D yesterday, I found something very interesting.

Up until this point, a short circuit on my 830D would show as 2-3 Ohms (and very rarely 1.8). I though this was just due to my 830D being very cheap - but it's not. Yesterday, I was trying out some spare connectors to see if they can fit in the multimeter plugs so that I could make my own high-current probes (since the original probe wires are obviously too underrated for that). After inserting one of the connectors in 10A jack of the multimeter plug, I selected the 200 Ohm scale and used the red probe (still plugged in its usual place) to see if my connector actually made connection with the multimeter - it did. Not only that, but my multimeter was reading 0.5 Ohms! I though, that can't be right, so I unplugged my black probe, inserted my own connector in the COM plug and measured the resistance again. But once more, the multimeter read 0.5 Ohms. At this point, I pretty much knew what was going on. I swapped the red probe for the black probe, then tested resistance again to my connector in the COM plug... yup, back to 2.2 Ohms.

So as it turns out, the wire for my black multimeter probe does actually have about 2 Ohms of resistance. - No wonder it heats up so badly. Also explains why in the past, my multimeter would drop so much voltage when I was trying to measure current. Now I know. Time for new probes.

[Agent24]

Re: This is why you don't buy cheap multimeters.

Your original 830D probes are actually still in one piece? Wow. Mine died years ago, so they never had a chance to give me a false reading.

[Krankshaft]

Re: This is why you don't buy cheap multimeters.

Like this?

Do doubt the double insulation on that drill saved the morons life.

[momaka]

Re: This is why you don't buy cheap multimeters.

Your original 830D probes are actually still in one piece? Wow. Mine died years ago, so they never had a chance to give me a false reading.

Oh no, of course not. I did fix them (see page 1 or link below):
https://www.badcaps.net/forum/showpo...6&postcount=12

[LENOVO-A880]

Re: This is why you don't buy cheap multimeters.

Fixing DT830D UNI-T DMM

First of all, this is a hobby of mine and I'm not a pro where I depend on my equipment. So I have had this cheap and old multimeter to only check fuses, shorts (continuity), Ohm tests, and etc. For me, it doesn't make sense to buy another new multimeter just to repair a $20 residue value monitor or test a faulty transistor. Even $20 would be hard to justify unless I'm trying to fix a several thousand dollar LCD or plasma TV.

This DT830D multimeter from China died off a few years ago due to the LCD problem mainly ICL7106 ic. It doesn't work at all now so what I did was I changed 9V battery together with the 200mA fuse (only one) and same thing I get nothing on the LCD display. Finally I found out that the battery block clip +/- terminal has loose contact inside of it and when I gently pulled the negative lead, it appears to come off. I've ordered several pieces of battery block clips and need to resolder it to the UNI-T multimeter board as a replacement to the bad clip.

Questions

1. What is the suitable temperature that should be used on this kind of circuit board?
2. Can I adjust my soldering iron temperature to 250°C for this kind of soldering job?

[Per Hansson]

Re: This is why you don't buy cheap multimeters.

It does not depend on what PCB you have, it depends on what solder you use.
It's usually written in the specs or even on the roll of the solder...

[stj]

Re: This is why you don't buy cheap multimeters.

try not to go over 270 or the insulation on the wire will shrink.

[LENOVO-A880]

Re: This is why you don't buy cheap multimeters.

It does not depend on what PCB you have, it depends on what solder you use.
It's usually written in the specs or even on the roll of the solder...

Does this type of solder wire suitable for soldering on the UNI-T DT830D circuit board?

Specifications:
-Alloy Composition : Sn63PB37 (63% Tin, 37% Lead)
-Melting Point : 183 ~ 193°C
-Flux % In Core Wire : 2.0%

Solder Name:
-KEWEI Sn63Pb37 Flux Core Solder Wire (0.8mm)

Country Of Origin:
-China

[stj]

Re: This is why you don't buy cheap multimeters.

that will do,
but lead-free stuff would be better.

[mariushm]

Re: This is why you don't buy cheap multimeters.

That solder is quite good, if it is what it says.

If it's really 63/37 that means it's eutectic...solder will melt or turn to solid within a very narrow temperature range of about 1-2 degrees C around the 183c value.

To solder you actually need to set the temperature of your iron higher, because when you put the iron on the copper on the pcb and you have the wire from the connector there as well, both will pull heat away from the iron tip and the temperature may drop below that 183c temperature and you won't solder reliably.
You adjust the temperature to be hot enough to warm up everything in 2-3 seconds .

1. Strip insulation from the wires of your connector.
2. Tin the wires :
2.1 Set iron temperature to about 220-250c
2.2 Clean the tip from oxides with a paper handkerchief or some napkin, add a tiny bit of solder
2.4 Make contact between the wire and the tip and then on the opposite side, touch the wire with the solder wire. Flux from solder wire will pour and protect the wire, then solder will melt and tin the wire.
2.5 Move the iron tip back and forth on the uninsulated wire end to tin it nicely.

( this should take no more than 4-5 seconds, otherwise the insulation of the connector will start to melt)

3. Cut a part of the uninsulated wire, leave just enough to be over that copper pad on the pcb
4. Raise iron to about 250-300c , wait to reach that temperature.
5. Put wire over the pad, or shove it through the hole if there's any
6. Solder wire in one hand, iron in the other
7. Put iron tip in such a way that it touches both the connector wire and the copper pad
8. Bring solder wire to the pcb pad, wait to see enough solder flow to make the connection is made, move solder wire away than a second later remove the iron tip.

Job done.

Here's good video showing tinning of wires : https://www.youtube.com/watch?v=0SnOW2VdCTI

Same procedure as I explained it, but since you probably don't have liquid flux, you're using the actual flux in the solder wire instead so that's why I told you to have the solder wire above, to let the flux flow on wire before solder from the wire actually melts.

[selldoor]

Re: This is why you don't buy cheap multimeters.

that will do,
but lead-free stuff would be better.

Just wondering why you would say that? ecological/health view?
its more difficult for a newbie to use?

[stj]

Re: This is why you don't buy cheap multimeters.

better for health,
cheaper (because it's sold by weight, not length.)
better flux than a lot of older solders,
lower resistance.
stronger joints.

the only reason to use lead is if you have a crap iron,
but they guy asked about the temperature to set the iron - so he has decent kit.

incidentally, leaded solder from china should be dirt cheap, because THEY cant use it under the chinese regulations that are more strict than RoHS.

they are just clearing old stock.

[mariushm]

Re: This is why you don't buy cheap multimeters.

better for health,

NOT better for health : due to higher melting temperature, lead free solder has stronger fluxes, which are more toxic - the flux smoke hurts you infinitely more than the presence of lead in solder (you don't get lead in your body from soldering, the temperature is not big enough for lead to become "airborn")

cheaper (because it's sold by weight, not length.)

NOT cheaper in all cases, at least if you want to get a good lead free solder (the one with 2% silver and/or 0.5-1% copper)

better flux than a lot of older solders,

It's debatable. It's not necessarily better, but it's STRONGER, more acid, more toxic for your lungs. It has to be because due to the higher melting temperature of lead free solder, most people keep the soldering irons at much higher temperatures, which gives flux less time to activate and work before it's boiled/evaporated by the iron tip.
As I already said, the flux smokes are much worse than lead free solder fluxes, and since most people don't have a ventilator on their desk, you can safely say lead bases solders will be better.

lower resistance.
stronger joints.

I don't feel like checking, but i doubt in practice it makes a real difference.

If anyone cares to search and compare, he/she can start from here:

https://www.badcaps.net/download/?id=1a48997a