ESR meter, a useful tool.

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ESR meter, a useful tool.

Post by ShowMaster » Tue Nov 22, 2016 3:49 pm

I recently had my 2008 series 3HD TiVo switcher ps die. A common over time failure to expect. Many ended up with counterfeit caps that would be easy to find because of the name, domed top, or leaking. Mine unfortunately, showed none of these issues!
The fix most use is to shotgun replace all the caps for maybe $20+. I thought being that I had a digital cap checker, I'd just replace the bad ones. I own a vacuum desoldering iron so removing the caps is so easy without damaging the board. Sadly all caps read normal value wise. Honestly not being up on switchers and how important a ESR value is, I had to try another approach. That was read up on switchers and ESR and buy a ESR meter. eBay, 3 days and $13 later, I owned a digital ESR, cap, diode, and transistor/fet tester. This time I started with the caps (3) on the primary side of the switcher transformer. The first 2 caps read a normal cap value with an ESR of 1 or less milliohm, normal. The 3rd a 100 ufd at 25v read low, 80ufd but the ESR read 23! Something my original cap meter couldn't! So I replaced the 100ufd with s new one that read 100 with a ESR of .34 and the ps fired right up!
All the other caps checked out perfect, and are a good brand name, so I didn't replace them.
So, I learned about SW ps, ESR and why you measure it. I own a ESR meter now, all for under the original $20 shotgun cap price.
Being that SW ps are so common now, it was worth the effort to educate myself instead of a quick fix. A used TiVo ps goes for $100 range. I have a lifetime on my TiVo so I'm good to go and maintain it.

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Re: ESR meter, a useful tool.

Post by jtroutt19 » Thu Nov 24, 2016 2:47 pm

Yip I use one everday! They are awesome because you dont have to remove the cap from the circuit to test it. I also have a capacitance meter as well. Those are good for testing new caps to make sure they are good before installation!

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