On Jul 31, 2006, at 2:41 AM, Tom W8JI wrote:
>> Also, for the price on their high end units, there really
>> is not an excuse for them to use 2,000 hour caps vice the
>> 5,000 hour caps that are not much more. Read my earlier
>> email about how you can expect 3 years before the power
>> supply is beyond it's rated life expectancy.
>
> We can read it, but we should be aware it isn't correct.
>
> I'm not sure if MFJ is buying 2000 hour MTBF caps or not,
> but the 2000 hour number is NOT the expected mean time hours
> before failure in operation. It appears to me that is what
> you are doing, and that what you are doing is absolutely
> wrong. ****Everyone needs to understand this very well.
> Whatever the raw number, 2000 or 5000 or whatever, it is NOT
> the expected life. That is a base number used in a MTBF
> formula.**** In other words a "2000 hour MTBF" in the
> component rating does not mean that is the operating MTBF.
> That is simply very wrong. Anyone who reads component data
> sheets or application notes would know that.
>
> (Those caps weren't initially speced to be 2000 hour parts,
> but that was in the early 1980's and I'm not sure what they
> are buying now.)
>
> To put it bluntly, the numbers about expected life in the
> earlier email are meaningless. They are not even correct for
> a 450 volt part operated at 85 degrees C (185F) internal
> temperature because, even if raised by a power of 1 (an 85C
> cap operated at 75C internal temperature), the life is 4000
> hours.
good point, Tom. IOW, at room temp the caps are going to be going
strong when the operator is 6-feet under.
>
> ...
R L MEASURES, AG6K. 805-386-3734
r@somis.org
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|