MS8268 multimeter repair

[red5kenny]

hello,
I'm a novice hobbyist who is really interested in electronics but I am at the bottom of the skill ladder.
So I recently purchased a Mastech MS8268 Multimeter off ebay that was in need of repair. (nothing like diving in at the deep end for my first repair)
It was boxed and looks brand new but the digital read out screen just will not work nor do the terminal warning led's for test probes
I've give it a thorough visual inspection and there's no signs of any damage at all.
Can any body help to advise on where to look or how to fix

 

[pc1966]

Repairing something like a meter, in particular if you don't have a working meter already, is not a job I would attempt as a start!

Even if you do get it working, it will be difficult to know if it is accurate, and if you make any physical modifications to get it working you would be well advised not to use it on high energy systems (e.g. mains supply) in case you have compromised its fault containment capabilities.

If you want a basic meter that can be used fairly safely then it must be (honestly) rated at CAT-III or CAT-IV and this is a possible choice for £33:

RS PRO RS14 Handheld Digital Multimeter, 10A ac Max, 10A dc Max, 600V ac Max | RS

uk.rs-online.com

If you have a bit more money to spend then one that is highly rated on this forum is the Testo 760-2 meter at around £102 on tester.co.uk (there is a cheaper -1 and more expensive -3 but the -2 seems the sweet spot in terms of ability versus cost). It has a good auto-range system so you are less likely to make an expensive of potentially fatal mistake.

Finally if you have money to burn, say around £400, then the likes of the Fluke 179 (my own meter) or the Fluke 87 which is slightly better. But few actually need the sort of range & accuracy they offer.

Beyond that you get in to bench meters and they quickly go to the £1k region, but are not so usable at hand held meter, just a lot more accurate. The Aim-TTi 1908 is good value though.

 

[telectrix]

hello,
I'm a novice hobbyist who is really interested in electronics but I am at the bottom of the skill ladder.
So I recently purchased a Mastech MS8268 Multimeter off ebay that was in need of repair. (nothing like diving in at the deep end for my first repair)
It was boxed and looks brand new but the digital read out screen just will not work nor do the terminal warning led's for test probes
I've give it a thorough visual inspection and there's no signs of any damage at all.
Can any body help to advise on where to look or how to fix

had similar fault on a megger. was the lead inside broke off the terminal for the probes. 10 minute soldering repair.

 

[red5kenny]

Repairing something like a meter, in particular if you don't have a working meter already, is not a job I would attempt as a start!

Even if you do get it working, it will be difficult to know if it is accurate, and if you make any physical modifications to get it working you would be well advised not to use it on high energy systems (e.g. mains supply) in case you have compromised its fault containment capabilities.

If you want a basic meter that can be used fairly safely then it must be (honestly) rated at CAT-III or CAT-IV and this is a possible choice for £33:

RS PRO RS14 Handheld Digital Multimeter, 10A ac Max, 10A dc Max, 600V ac Max | RS

uk.rs-online.com

If you have a bit more money to spend then one that is highly rated on this forum is the Testo 760-2 meter at around £102 on tester.co.uk (there is a cheaper -1 and more expensive -3 but the -2 seems the sweet spot in terms of ability versus cost). It has a good auto-range system so you are less likely to make an expensive of potentially fatal mistake.

Finally if you have money to burn, say around £400, then the likes of the Fluke 179 (my own meter) or the Fluke 87 which is slightly better. But few actually need the sort of range & accuracy they offer.

Beyond that you get in to bench meters and they quickly go to the £1k region, but are not so usable at hand held meter, just a lot more accurate. The Aim-TTi 1908 is good value though.

thanks for you response very much appreciated and information within taken on board.

 

[red5kenny]

thanks for you response very much appreciated and information within taken on board.

Sorry I forgot to mention I have got a working multimeter

 

[Lucien Nunes]

If appears completely dead it might be simple. Check battery contacts and power switch contacts for continuity, any voltage regulator for correct output and make sure the power rail is getting to the main IC(s)
If it is, the most likely culprit will be the main IC and the unit is junk. As a last resort it might be worth pulling the selector switch apart as is is a weak spot on cheaper meters and everything might be blank if no valid range is selected, even though the LSI is alive and kicking. You can look for waveforms around it if you have a scope but by this time you will have expended more time that the unit is worth.

The only digital multimeter I have ever considered worth repairing is my trusty Fluke that followed me around the world for over 20 years, and that only for sentimental reasons as it was my 6th sense for 1/4 of my lifespan. But the main IC is dead and I will have to find one with a broken case etc to cannibalise.

As PC1966 says, repairing a multimeter is an odd place to start. Traditionally, measuring instruments are not forgiving of mistakes and less-than-ideal work. As he also points out, when used on high energy systems such as the 230V mains, a seemingly innocent repair such as replacing a resistor with one of the same value and power rating but subtly different construction, could turn the meter into a fireball.

Post your findings though...

 

[Moley]

Have you checked the internal fuse ? I'm sure (but could be wrong) that model uses 3 AA (or AAA, I can't remember) batteries. These are in the back panel which comes away when you open up the meter. Check that the contacts are making between the board and the back panel.

 

[red5kenny]

If appears completely dead it might be simple. Check battery contacts and power switch contacts for continuity, any voltage regulator for correct output and make sure the power rail is getting to the main IC(s)
If it is, the most likely culprit will be the main IC and the unit is junk. As a last resort it might be worth pulling the selector switch apart as is is a weak spot on cheaper meters and everything might be blank if no valid range is selected, even though the LSI is alive and kicking. You can look for waveforms around it if you have a scope but by this time you will have expended more time that the unit is worth.

The only digital multimeter I have ever considered worth repairing is my trusty Fluke that followed me around the world for over 20 years, and that only for sentimental reasons as it was my 6th sense for 1/4 of my lifespan. But the main IC is dead and I will have to find one with a broken case etc to cannibalise.

As PC1966 says, repairing a multimeter is an odd place to start. Traditionally, measuring instruments are not forgiving of mistakes and less-than-ideal work. As he also points out, when used on high energy systems such as the 230V mains, a seemingly innocent repair such as replacing a resistor with one of the same value and power rating but subtly different construction, could turn the meter into a fireball.

Post your findings though...

ok I'll try and have at look at all what you said but I've got to be honest most of the stuff you mentioned to investigate was like reading Klingon so I will have to do some research on the interweb to find out what you were talking about ...lol
Like I said in my original post my skill set is bottom of the ladder as I'm just starting out in electronics but I find it so very interesting I want to get better at it and no better place than diving in at the deep end and speaking to you top guys... every day's a school day, if you don't learn something new a day then you've wasted a day.
thanks for your all your suggestions and help I get on it right away