Rapitest DM25 multimeter - UK Vintage Radio Repair and Restoration Discussion Forum

skamanuk · 30th Apr 2015, 11:14 am

Hi I'm very much a novice with electrics however I have managed to refurbish a number of valve amplified record players. I have been given the Rapitest DM25 multimeter but no instruction manual. My questions are can I use this particular meter to check capacitors? If yes how do I go about it and where should I set the dial to. I am aware of the high voltages involved with these machines and all safety precautions are taken. Thanks Gary

Station X · 30th Apr 2015, 11:23 am

There doesn't seem to be much information available for these meters.

If you could post a clear picture of it I'm sure we can help.

However it is unlikely that a normal multi-meter will be able to directly test capacitors at the full working voltage.

skamanuk · 30th Apr 2015, 2:27 pm

Here's a picture of the meter

Station X · 30th Apr 2015, 2:42 pm

That's a useful looking meter, but it has no facility to test capacitors.

The manual for any non-auto ranging DMM should get you going, but try this for starters.

http://www.ece.vt.edu/cel/docs/MY-64...ter-Manual.pdf

Points to remember.

Use the correct input sockets.

Resistance measurements are taken with equipment powered off.

When measuring voltage remember to select AC or DC and connect the meter in parallel with the circuit under test.

When measuring current remember to select AC or DC and connect the meter in series with the circuit under test. If you connect it in parallel there may be a big bang!

If unsure of the expected reading start on the highest range and work down until you get a sensible reading.

AC/HL · 5th Nov 2017, 4:38 pm

For further information see here: https://www.vintage-radio.net/forum/...d.php?t=141094

paulsherwin · 5th Nov 2017, 5:18 pm

As Graham says, that appears to be a perfectly decent cheap multimeter. It is very suitable for the sort of vintage radio and record player work likely to be done by a beginner, though not some of the more esoteric stuff that some members get up to.

Testing capacitors is a complex business, which is why lots of people advocate just changing any suspect ones without trying to identify those that have actually failed. You need to test them at their actual working voltages, and distinguish between changes in value and leakage. There is also the question of ESR when testing electrolytic caps.

30th Apr 2015, 11:14 am	#1
skamanuk Retired Dormant Member Join Date: Apr 2013 Location: London, UK. Posts: 245	Rapitest DM25 multimeter Hi I'm very much a novice with electrics however I have managed to refurbish a number of valve amplified record players. I have been given the Rapitest DM25 multimeter but no instruction manual. My questions are can I use this particular meter to check capacitors? If yes how do I go about it and where should I set the dial to. I am aware of the high voltages involved with these machines and all safety precautions are taken. Thanks Gary

30th Apr 2015, 11:23 am	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,286	Re: Rapitest DM25 multimeter There doesn't seem to be much information available for these meters. If you could post a clear picture of it I'm sure we can help. However it is unlikely that a normal multi-meter will be able to directly test capacitors at the full working voltage. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

30th Apr 2015, 2:27 pm	#3
skamanuk Retired Dormant Member Join Date: Apr 2013 Location: London, UK. Posts: 245	Re: Rapitest DM25 multimeter Here's a picture of the meter Attached Thumbnails

30th Apr 2015, 2:42 pm	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,286	Re: Rapitest DM25 multimeter That's a useful looking meter, but it has no facility to test capacitors. The manual for any non-auto ranging DMM should get you going, but try this for starters. http://www.ece.vt.edu/cel/docs/MY-64...ter-Manual.pdf Points to remember. Use the correct input sockets. Resistance measurements are taken with equipment powered off. When measuring voltage remember to select AC or DC and connect the meter in parallel with the circuit under test. When measuring current remember to select AC or DC and connect the meter in series with the circuit under test. If you connect it in parallel there may be a big bang! If unsure of the expected reading start on the highest range and work down until you get a sensible reading. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

5th Nov 2017, 4:38 pm	#5
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Rapitest DM25 multimeter For further information see here: https://www.vintage-radio.net/forum/...d.php?t=141094

5th Nov 2017, 5:18 pm	#6
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,927	Re: Rapitest DM25 multimeter As Graham says, that appears to be a perfectly decent cheap multimeter. It is very suitable for the sort of vintage radio and record player work likely to be done by a beginner, though not some of the more esoteric stuff that some members get up to. Testing capacitors is a complex business, which is why lots of people advocate just changing any suspect ones without trying to identify those that have actually failed. You need to test them at their actual working voltages, and distinguish between changes in value and leakage. There is also the question of ESR when testing electrolytic caps.