Hey guys, yes, two scopes are cool and I bought the 2235 back in 1989. I was working at HP at that time and I was perceived as an heretic to buy scopes from a competitor : ) But HP oscilloscopes, in my opinion, could never compete with the TEKs. I had to replace the flyback transformer on this one after 15 years of service and it was not fun to fix the self-relaxing supply: a cleverly-designed type but a mess to troubleshoot. Then I had the opportunity to obtain a TEK 2465B which was not working properly and I fixed it, good for another decade : )
Now, without a scope, I could not fix most of the instruments or equipment I have been repairing for years. You truly need to observe the waveforms - especially in a switching converter, my specialty - to learn from it and infer what the issue it. I agree, a multimeter is also needed, but, in most cases, the lack of scope would have been an impeding factor.
Regarding the PFC design, I agree with nomaka, it must be a fail-safe design. But these guys usually won't invest in an extra relay to short the front-end NTC and prefer to insert it in series with the diode as it minimizes the ac ripple and the rms component. A bad approach, I agree. I have also sometimes seen it in series with the bulk cap. and later shorted by a ground-referenced MOSFET. Again, not the best approach.
Cheers, Christophe
Now, without a scope, I could not fix most of the instruments or equipment I have been repairing for years. You truly need to observe the waveforms - especially in a switching converter, my specialty - to learn from it and infer what the issue it. I agree, a multimeter is also needed, but, in most cases, the lack of scope would have been an impeding factor.
Regarding the PFC design, I agree with nomaka, it must be a fail-safe design. But these guys usually won't invest in an extra relay to short the front-end NTC and prefer to insert it in series with the diode as it minimizes the ac ripple and the rms component. A bad approach, I agree. I have also sometimes seen it in series with the bulk cap. and later shorted by a ground-referenced MOSFET. Again, not the best approach.
Cheers, Christophe
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