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Tantalums acquire microscopic defects due to soldering. These greatly reduc e voltacity (or some similar word). Lack of any flexibility in the connecti ons also causes this problem. To correct this, tants need a healing process after soldering. This consists of slowly ramping up voltage in series with a resistor. Do that & your tants should be reliable & nonexplosive at full rated voltage.
NT
No kidding? ;)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
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uce voltacity (or some similar word). Lack of any flexibility in the connec tions also causes this problem. To correct this, tants need a healing proce ss after soldering. This consists of slowly ramping up voltage in series wi th a resistor. Do that & your tants should be reliable & nonexplosive at fu ll rated voltage.
How slow is slow? What size resistor? I was thinking of incorporating thi s into the test procedure for a board using a tant cap that fails on first test far more often than other components. On second thought, without havi ng a way to properly analyze the problem, maybe it's better to let the cap fail and be replaced. Fixing one short on a part may be setting it up for a later failure in the field???
Rick C.
Tesla referral code ++++
I tend to not trust L or C meters, especially cheap ones. I connect a
50 ohm sine wave generator to a cap or inductor and spin the knob and watch the frequency response, which tells me a lot in a few seconds.If the voltage across the cap is small compared to the generator open-circuit voltage, you can pretend that the generator is shorted, calculate the current, and use the frequency and current to calculate C. Ignore phase.
Or Spice it to be accurate!
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
That's absolutely something we don't want to do in production.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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educe voltacity (or some similar word). Lack of any flexibility in the conn ections also causes this problem. To correct this, tants need a healing pro cess after soldering. This consists of slowly ramping up voltage in series with a resistor. Do that & your tants should be reliable & nonexplosive at full rated voltage.
those I don't know. I saw others had beaten me to it. You could find out wi th a bad batch.
using a tant cap that fails on first test far more often than other compone nts. On second thought, without having a way to properly analyze the probl em, maybe it's better to let the cap fail and be replaced. Fixing one shor t on a part may be setting it up for a later failure in the field???
AIUI the reforming type process makes sure they're fully upto the job, untr eated ones tend not to be.
NT
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duce voltacity (or some similar word). Lack of any flexibility in the conne ctions also causes this problem. To correct this, tants need a healing proc ess after soldering. This consists of slowly ramping up voltage in series w ith a resistor. Do that & your tants should be reliable & nonexplosive at f ull rated voltage.
I was just wondering whether an instrument could do it itself as part of 1s t boot. Perhaps in some cases.
NT
I only use tantalums for their ESR, at the outputs of linear regulators, derated at least 3:1 on voltage. That seems reliable.
Otherwise, I'd use ceramics or polymers and add ESR resistors or something to keep the regs happy. I recently did a 48-to-32 volt reg with an LM317HV, and did my ADJ node trick to stabilize that with ceramic output caps; otherwise I'd need a 100 volt tantalum.
Regular aluminums are OK, just a bit big.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
There is a thing that works for 1.25V out, but it takes several parts. At 1.25v, a tantalum is fine.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
tabbypurr wrote
I often test new circuit prototypes on the lab supply with current limit set low by slowly turning up the voltage. Maybe that fixes the tantalums too.
John Larkin wrote
My very cheap LC meter simply is a frequency meter that uses a reference C for L measurement and a reference L for C measurement, the counter is xtal based.
Although my reference L is just junk box inductors, the reference C is quite precise. Nothing wrong with that. And for measuring changes the absolute value is not so important anyways.
Temperature. We can't use X5R because they're only good to 85C.
Has someone tested the 10uF caps. 0.47 and 0.1 can be substituted with polyester or something but 10uF is harder to replace without electrolytics.
My AADE meter works like that. It's great for small caps and small inductors, terrible for large values.
Last week I measured the inductance of a winding on a biggish toroid. The AADE read low by about a factor of 4.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
p and I want to place an order to support production for a while. In perfo rming a Digikey/Mouser search I see there are now X7R devices in the same f ootprint. I know the X7R will be more stable under DC voltage which is an advantage *if* there is much DC on the input. The amplifier circuit has a
6 volt DC bias on the input (half way to the +12 volt rail). The caps prev ent the input from seeing this bias. The design passes all functional test s in production (including frequency response) with the X5R devices.are only four devices on the board, so a small increase in price is not so significant. I'm just wondering if there is any technical downside to usi ng the X7R formulation in place of the X5R. Or is the X7R formulation all upside relative to the X5R?
make good use of your pcb planes :)
Yes, the smiley indicates a joke for anyone not functional enough to realis e that.
Most boards can also tolerate a drop in quantity of dewhatsitting. Decoupli ng caps.
NT
John Larkin wrote
Indeed, best for small inductors like for RF. Usually I just calculate toroids from number of turns and core material Seems to work so far, and measure temperature.... scope it..
See that fan? My latest invention, old computah fan, blowing away from where I am soldering, creates a low pressure behind the soldering area, so no more solder smoke in my nose, smoke flows away from you.
I think it uses a relay to switch in and out an extra capacitor, which allows it to calibrate out most of the tolerances.
At what frequency? These meters use an oscillator that varies over a very wide spread, and they don't tell you what the actual test frequency was. My guess: it was accurate, but not at the frequency your other gear measured it at. Or it was affected by the additional capacitance of the toroid.
Clifford Heath.
PS I have used my LC meter to get the Al of toroids from a given number of turns, seems to work OK. Lots of unknown cores from old computah power supplies etc.
Well, it's just a poor little LM311 inside. ;)
Blech.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
If that is so, then it is quite a different thing from what I was referring to as 'My very cheap LC meter', scroll down here for accuracy and description:
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