Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Tubes and Hybrids => Topic started by: Hawk on June 03, 2015, 09:24:44 AM

Title: Capacitance Meter
Post by: Hawk on June 03, 2015, 09:24:44 AM
I'm using a blue ESR meter for caps 1uf and above and I love this meter! But what about those little tiny caps? What are techs using to measure these little guys? Can anyone recommend a cap meter? I'm currently using a cheap Mastercraft Meter but I question the cap readings. I also know these little caps need to come out of the PCB in order to test properly. So, I'm putting it out there, what do people recommend? What works for you?

Thanks.
Title: Re: Capacitance Meter
Post by: g1 on June 03, 2015, 11:59:40 AM
Not sure if you mean little caps, or maybe SMT caps.
I don't often measure little caps, or any other for that matter.  More likely to find bad ones from fault symptoms and in circuit measurements.
But they do have their uses, and having the right tools for the job is very valuable when required.
I have a DE-5000 LCR meter that is well regarded and relatively inexpensive.  But you need to make sure you get the clips, or SMT tweezers if you need them.  I made the mistake of thinking I could use regular probes and ended up having to buy the right ones.  Would have been cheaper to get them all together.
Title: Re: Capacitance Meter
Post by: Enzo on June 03, 2015, 12:14:24 PM
Agree^^^

I do have a cap meter, an old B&K 820
http://www.scribd.com/doc/100751619/b-k-Precision-820-Capacitance-Meter-Service-Manual#scribd

I rarely get it out, and mostly just to identify some mystery part.   ESR matters more to electrolytic caps, because they can dry out,  Film caps don't really do that, and while they can get leaky, that usually occurs at voltage, and hand meters do not apply more than a volt or two.  They cannot detect a cap that is leaky over say 200v.

I am not concerned that a film cap or a ceramic is going to be way off value. So I rarely measure them.  And for the vast majority of cases, I will find the cap is bad or not by its performance in the circuit.  For example that leaky film cap when coupling a plate to a grid will result in a voltage on that grid.

I do have an old Eico 950B
http://www.ohio.edu/people/postr/bapix/capchkr2.htm

Its measurement feature is not all that precise, though if you wanted to match caps for some reason, it is a bridge which can do that.  But its main feature is the leakage test, which can apply up to 500v across the test cap.  But I don't get that out much either.

But mainly I prefer to use the circuit operation to determine cap quality.