Tantalum Capacitor Warning

[Chuck D. Bones]

Last year, I bought 120 AVX 10uF 16V tantalum caps from Electronic Goldmine. After experiencing several failures in pedals during bench testing, I pulled the remaining 106 out of the bag and tested them all for leakage. The result was that 77 out of 106 had leakage that was out of spec. Spec is 1.2uA at 16V and 85C. I tested them at 9.3V and 22C. Anything over 1uA was rejected. Most were at least 10x out of spec and many were over 100x out of spec. If you have any of these caps, I advise you to test before installing them. I have other value AVX tantalums from them that work fine, but now I'm going to test more of them. I have purchased many different parts from EG and had no problems until now. The test procedure is simple: a 9V pedal power supply, a 10K resistor and the capacitor under test are connected in series. Measure the voltage drop across the 10K resistor with a DMM. Make sure to observe the correct polarity when connecting the capacitor. Give the current a few seconds to stabilize. The voltage, in mV, divided by 10 is the leakage in uA. Anything below 10mV (1uA) is acceptable. Most of the good ones read below 2mV (0.2uA).

 

[bengarland]

Is it these?

https://www.mouser.jp/ProductDetail/avx/tap106k016gsb/?qs=haOJH97oC3eigepEVuhRiA==&countrycode=US&currencycode=USD

I just put some of those in a few of my synthesizer builds last week. Didn't even think to test them as my assumption is that new parts are all tested at the factory. Guess I'll make a note to pull them if I have any weird problems once I get everything hooked up.

Thanks for the reminder... and the "how to"... I definitely need to improve my testing knowledge and skills.

 

[zgrav]

You are probably OK with caps from Mouser. CDBones was talking about what was likely a specially priced value bundle from Electronic Goldmine.

 

[Chuck D. Bones]

The ones that caused trouble for me were probably that part number, but most likely a different mfg lot. Electronic Goldmine sells surplus parts. I have no idea when my parts were manufactured, but it was probably many years ago. Like zgrav said, you're fine. You can trust Mouser to sell good parts. This warning is about that part value sold by EG and only those parts sold by EG. The evidence is pretty strong that they have a bad lot. I informed them yesterday by email and have not yet heard back.

Just to provide some background info: commercial grade capacitors are usually sample tested by the mfgr. They don't test every part in a batch. Only a small number of parts are tested from each batch and if the number of test failures is too high, something like 5% of the parts sampled, then the entire lot is scrapped. Mouser gets their parts directly from the manufacturer, or from an authorized distributor. The parts can be traced directly back to the mfgr and to the production lot. There's no telling where EG gets their parts. I expect the majority of them come from equipment manufacturers who have leftover parts from a production run. EG sells parts at a discount and rightly so because they have no traceability to who owned them previously or what they did with them. IMO it's lower risk than buying parts on eBay, but the risk is far from zero.