SMPS
- Thread starter DP
- Start date
Yes
What scope, multimeter and any mains isolation? If yes, what spec
What do you repair
Multimeter is the mainstay for voltage measurements but how do you check the waveforms
Do you use isolating transformer?
Oscilloscope. Mostly used for checking IC drive signals (in my case)
Always. (Well, most of the times yes. ) The isolation transformer is there to protect you just as much as your scope. It doesn't make working on mains voltage equipment entirely safe, but it does help significantly.
Beware, if you are testing your SMPS using an isolation transformer and a scope - when you connect up the probe ground on a traditional scope, you will lose isolation - the circuit won't be floating anymore, as the scope references to earth.
There are some interesting scope meters appearing on Amazon etc. some for less than £100 (one is on my Christmas list!). Being battery powered, you wouldn't lose isolation.
Personally, I haven't used an isolation transformer for troubleshooting, but most of the problems I've found, could be discovered with the circuit dead - i.e. the usual suspects: caps, resistors, diodes, MOSFETs, etc.
Yeah that why I mentioned that my £7 multimeter normally finds the fault.
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I've got a KeySight diff probe/amp which calls itself "high voltage" but it's not all that high, 100V common mode iirc. Some are rather low. I've used it for some inverters & motor drivers and some high speed serial comms where it reduces the common mode noise problem. It's around here - somewhere, haven't seen it for years.
You should be able to use differential mode on a scope with two normal single ended probes - no need to be concerned with the common mode voltage range, as long as the signal doesn't exceed the general input voltage range.
It's not really needed if you have a handheld/battery type scope though. My Fluke Scopemeter was a few quid but often one of these <£40 ones off ebay would be fine for little stuff. Remarkable for what you can get now for the price of a tank of fuel. Well, £100 - £120.
You should be able to use differential mode on a scope with two normal single ended probes - no need to be concerned with the common mode voltage range, as long as the signal doesn't exceed the general input voltage range.
It's not really needed if you have a handheld/battery type scope though. My Fluke Scopemeter was a few quid but often one of these <£40 ones off ebay would be fine for little stuff. Remarkable for what you can get now for the price of a tank of fuel. Well, £100 - £120.
To date have done repairs where cap checks showed faulty components.
Am aware about earth connection of scope and applying the scope to SMPS where input and output are isolated. For this have differential probes
Have been reading up about different component functions etc