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#1
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Tantalum caps.
Over the last few years I've acquired quite a few consumer electronincs pcbs
including TVs, VCRs, stereos, etc, so when I discovered that I needed a tantalum to repair some test equipment I was going to salvage a tantalum. I couldn't find one anywhere, so I assume they're too expensive or too unrelaible for high end consumer electronics. A couple of the boards were from my personal stuff purchased new. One example is a MGA Mitsubishi rear projection TV that operated flawlessly for nearly 20 years of daily use. Most of my test equipment comes from hamfests and is surplus after becoming obsolete and non-operative in less than 20 years. That leads me to wonder what the real story is behind tantalum capacitors. What do the experts have to say? tnx hank wd5jfr |
#2
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Henry Kolesnik wrote:
Over the last few years I've acquired quite a few consumer electronincs pcbs including TVs, VCRs, stereos, etc, so when I discovered that I needed a tantalum to repair some test equipment I was going to salvage a tantalum. I couldn't find one anywhere, so I assume they're too expensive or too unrelaible for high end consumer electronics. A couple of the boards were from my personal stuff purchased new. One example is a MGA Mitsubishi rear projection TV that operated flawlessly for nearly 20 years of daily use. Most of my test equipment comes from hamfests and is surplus after becoming obsolete and non-operative in less than 20 years. That leads me to wonder what the real story is behind tantalum capacitors. What do the experts have to say? tnx hank wd5jfr They can have very good characteristics (small size, low esr, high parallel resistance and good capacitance stability) but have some strange failure modes if they are misapplied. Digikey sells a great variety of them. I can seldom justify their cost in production designs, but use them quite often in one offs. -- John Popelish |
#3
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John Popelish wrote:
Henry Kolesnik wrote: Over the last few years I've acquired quite a few consumer electronincs pcbs including TVs, VCRs, stereos, etc, so when I discovered that I needed a tantalum to repair some test equipment I was going to salvage a tantalum. I couldn't find one anywhere, so I assume they're too expensive or too unrelaible for high end consumer electronics. A couple of the boards were from my personal stuff purchased new. One example is a MGA Mitsubishi rear projection TV that operated flawlessly for nearly 20 years of daily use. Most of my test equipment comes from hamfests and is surplus after becoming obsolete and non-operative in less than 20 years. That leads me to wonder what the real story is behind tantalum capacitors. What do the experts have to say? tnx hank wd5jfr They can have very good characteristics (small size, low esr, high parallel resistance and good capacitance stability) but have some strange failure modes if they are misapplied. Digikey sells a great variety of them. I can seldom justify their cost in production designs, but use them quite often in one offs. So in a production design, what would you use to get the equivalent performance? An aluminum electrolytic in parallel with a ceramic? -- @@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@ h@e@r@e@@ ###Got a Question about ELECTRONICS? Check HERE First:### http://users.pandora.be/educypedia/e...s/databank.htm My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 at hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). http://www.everybookstore.com You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it: http://physics.nist.gov/cuu/Units/binary.html @@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@ u@e@n@t@@ F o d d e r f o r s t u p i d n o t e n o u g h i n c l u d e d t e x t m s g |
#4
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"Watson A.Name \"Watt Sun - the Dark Remover\"" wrote:
John Popelish wrote: (snip) I can seldom justify their cost in production designs, but use them quite often in one offs. So in a production design, what would you use to get the equivalent performance? An aluminum electrolytic in parallel with a ceramic? A production design usually pays for the engineering necessary to reduce the need for premium quality components. Your solution is often a cheaper alternative to a premium quality tantalum. -- John Popelish |
#5
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In article , Henry Kolesnik
writes Over the last few years I've acquired quite a few consumer electronincs pcbs including TVs, VCRs, stereos, etc, so when I discovered that I needed a tantalum to repair some test equipment I was going to salvage a tantalum. I couldn't find one anywhere, so I assume they're too expensive or too unrelaible for high end consumer electronics. A couple of the boards were from my personal stuff purchased new. One example is a MGA Mitsubishi rear projection TV that operated flawlessly for nearly 20 years of daily use. Most of my test equipment comes from hamfests and is surplus after becoming obsolete and non-operative in less than 20 years. That leads me to wonder what the real story is behind tantalum capacitors. What do the experts have to say? tnx hank wd5jfr twere always regarded as more reliable than aluminum; however there is a failure mechanism associated with the source resistance and how close the operating voltage is to the maximum specified. Modern aluminum can have very low esr and an adequate alternative to tantalum. -- ddwyer |
#6
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On Wed, 21 Jan 2004 17:26:14 -0600, "Henry Kolesnik"
wrote: Over the last few years I've acquired quite a few consumer electronincs pcbs including TVs, VCRs, stereos, etc, so when I discovered that I needed a tantalum to repair some test equipment I was going to salvage a tantalum. I couldn't find one anywhere, so I assume they're too expensive or too unrelaible for high end consumer electronics. A couple of the boards were from my personal stuff purchased new. One example is a MGA Mitsubishi rear projection TV that operated flawlessly for nearly 20 years of daily use. Most of my test equipment comes from hamfests and is surplus after becoming obsolete and non-operative in less than 20 years. That leads me to wonder what the real story is behind tantalum capacitors. What do the experts have to say? tnx hank wd5jfr We often use surface-mount tantalums on high-density, high-cost boards. They are very reliable (don't dry out like aluminums) if used carefully, but high peak currents can ignite them, so they are generally a bad idea for bypassing power rails. Polymer aluminums (don't dry out) or polymer tantalums (don't explode) seem like a good idea, but I haven't tried them yet. I think multilayer ceramics are pushing 100 uF these days. John |
#7
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I have a Racal 9301A where a tantalum must have caught on fire because all
that was left was 2 leads, some crisp blackish ash and a little hardened crust on the pcb where it burned. There's probaby 10 other tants on the board and one or more are shorted but still intact and I'm trying to find the bads one/ones with least effort without a schematic. The other unit is a Wavetek 188-S1257 where a tantalum had a dead short but was intact. I repalced it with an electrolytic. The cap is on a 15 volt rail where I think it shorted and took out the regulator. Ireplace the regulator with what I assumed was a good one out of a new box but it was bad and it put 23 volts on the rail that had a 20 volt rating but no more failed. Sometime I have good luck. 73 hank wd5jfr "John Larkin" wrote in message ... On Wed, 21 Jan 2004 17:26:14 -0600, "Henry Kolesnik" wrote: Over the last few years I've acquired quite a few consumer electronincs pcbs including TVs, VCRs, stereos, etc, so when I discovered that I needed a tantalum to repair some test equipment I was going to salvage a tantalum. I couldn't find one anywhere, so I assume they're too expensive or too unrelaible for high end consumer electronics. A couple of the boards were from my personal stuff purchased new. One example is a MGA Mitsubishi rear projection TV that operated flawlessly for nearly 20 years of daily use. Most of my test equipment comes from hamfests and is surplus after becoming obsolete and non-operative in less than 20 years. That leads me to wonder what the real story is behind tantalum capacitors. What do the experts have to say? tnx hank wd5jfr We often use surface-mount tantalums on high-density, high-cost boards. They are very reliable (don't dry out like aluminums) if used carefully, but high peak currents can ignite them, so they are generally a bad idea for bypassing power rails. Polymer aluminums (don't dry out) or polymer tantalums (don't explode) seem like a good idea, but I haven't tried them yet. I think multilayer ceramics are pushing 100 uF these days. John |
#8
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John Larkin wrote:
I think multilayer ceramics are pushing 100 uF these days. Yes, but alas, only with zero volts across them. Capacitance drops precipitously with DC bias. For a cap with Y5V dielectric, at half the rated DC voltage, there's only 10% of the initial capacitance left. Most manufacturers don't tell you. |
#9
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"Jeroen" wrote in message ... John Larkin wrote: I think multilayer ceramics are pushing 100 uF these days. Yes, but alas, only with zero volts across them. Capacitance drops precipitously with DC bias. For a cap with Y5V dielectric, at half the rated DC voltage, there's only 10% of the initial capacitance left. Most manufacturers don't tell you. I didn't think it was quite as bad as that. Also very temperature dependent. These type of ceramics are also pyroelectric as well as being piezoelectric! |
#10
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In article , Fred
writes "Jeroen" wrote in message ... John Larkin wrote: I think multilayer ceramics are pushing 100 uF these days. Yes, but alas, only with zero volts across them. Capacitance drops precipitously with DC bias. For a cap with Y5V dielectric, at half the rated DC voltage, there's only 10% of the initial capacitance left. Most manufacturers don't tell you. The high k types vary to +-10% and +20-80% from memory if full temp is allowed for. High K doped with piezo material, they can be heard to click if hit with a square wave. |
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