advice or parts source
Dave
performance, sometimes good, sometimes not so good. I'm going to replace
all of the ancient electrolytic caps but there is one I cannot source:
0.15uF 100V polar electrolytic
Not being so wise in the ways of electronic componentry and being perplexed
by all of the different variants of capacitors in particular, can I use a
non-electrolytic in this app? Say, a metallized polyester or polypropylene
film? They appear to have tighter specs (+/-5% vs. +/-20%) than comparable
electrolytics. These particular caps are coupling caps on the outputs of
the MPX decoder chips in series with the output jacks of the tuner... the
last cap the signal goes through. What are the ramifications of using a
0.1uF or a 0.22uF cap (both available from DigiKey) in this application?
I'm also having a tough time finding some electrolytic caps for an
amplifier:
0.47uF 50V, +75/-10% tolerance
22uF 16V, +50/-10% tolerance
47uF 25V, +50/-10% tolerance
100uF 25V, +50/-10% tolerance
Any advice greatly appreciated.
Dave
Dave Platt
Dave <dspea...@yahoo.delete.com> wrote:
>I recently picked up a Sansui T-80 tuner (circa 1981)... it's got some flaky
>performance, sometimes good, sometimes not so good. I'm going to replace
>all of the ancient electrolytic caps but there is one I cannot source:
>
>0.15uF 100V polar electrolytic
That's an odd one for sure! I'm not used to seeing 'lytics with so
low a capacity.
>Not being so wise in the ways of electronic componentry and being perplexed
>by all of the different variants of capacitors in particular, can I use a
>non-electrolytic in this app? Say, a metallized polyester or polypropylene
>film? They appear to have tighter specs (+/-5% vs. +/-20%) than comparable
>electrolytics. These particular caps are coupling caps on the outputs of
>the MPX decoder chips in series with the output jacks of the tuner... the
>last cap the signal goes through. What are the ramifications of using a
>0.1uF or a 0.22uF cap (both available from DigiKey) in this application?
Lower distortion, longer lifetime. Unless you feel that those are bad
things, go right ahead and stick in the 0.22 filmcap.
>I'm also having a tough time finding some electrolytic caps for an
>amplifier:
>
>0.47uF 50V, +75/-10% tolerance
Here, also, I'd suggest using a plastic-film capacitor.
>22uF 16V, +50/-10% tolerance
>47uF 25V, +50/-10% tolerance
>100uF 25V, +50/-10% tolerance
These are almost certainly filtering/smoothing caps. As you can see,
the tolerance is extremely loose. You can safely move up to the next
working-voltage rating and to the next-higher standard capacity, with
no worries at all. Modern caps are generally more compact than the
older ones and so you shouldn't have a problem finding a fit.
If possible, source 105-degree-C caps rather than 85-degree-C caps.
They may have a longer lifetime.
Do you need radial-lead caps, or the nowadays-less-common axial-lead
caps? If radial, the Panasonic NHG or FC series caps from Digi-Key
ought to work out fine for you - they're available in the capacities
and voltage specs you cite above, with tighter tolerances, and you
could move up to the next capacity in the series to improve the
filtering a bit if you want.
If you need axial-lead caps, Digi-Key has the BC Components ASM 021
and AHT 118 and AML 138 series - the latter are long-life parts which
are available in exactly the values you want.
--
Dave Platt <dpl...@radagast.org> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Dave
"Dave Platt" <dpl...@radagast.org> wrote in message
news:121bkag...@corp.supernews.com...
> >
> >0.15uF 100V polar electrolytic
>
> That's an odd one for sure! I'm not used to seeing 'lytics with so
> low a capacity.
>
> >Not being so wise in the ways of electronic componentry and being
perplexed
> >by all of the different variants of capacitors in particular, can I use a
> >non-electrolytic in this app? Say, a metallized polyester or
polypropylene
> >film? They appear to have tighter specs (+/-5% vs. +/-20%) than
comparable
> >electrolytics. These particular caps are coupling caps on the outputs of
> >the MPX decoder chips in series with the output jacks of the tuner... the
> >last cap the signal goes through. What are the ramifications of using a
> >0.1uF or a 0.22uF cap (both available from DigiKey) in this application?
>
> Lower distortion, longer lifetime. Unless you feel that those are bad
> things, go right ahead and stick in the 0.22 filmcap.
>
voltage, film caps are a better choice if they are available. The
electrolytics are used (in general) where higher capacitance is needed.
Why, then, is my board liberally sprinkled with 1uF, 2.2uF, and 3.3uF
electrolytics if film caps last longer and create less distortion? I'm
talking about the FM signal path caps, decoupling caps, etc. Was it not
possible in 1981 to get a 1uF 50V non-electrolytic capacitor?
What would be the drawback(s) to replacing the electrolytics with their
1000-5000h life with film caps of identical rating with a 200,000h MTBF?
Thanks a lot for your insight.
Dave
Dave
> >0.1uF or a 0.22uF cap (both available from DigiKey) in this application?
>
> Lower distortion, longer lifetime. Unless you feel that those are bad
> things, go right ahead and stick in the 0.22 filmcap.
>
ramifications of replacing the 0.15uF electrolytic with a 0.1uF or 0.22uF
ELECTROLYTIC?
Dave
"Dave" <dspea...@yahoo.delete.com> wrote in message
news:iVkRf.27832$M52.6029@edtnps89...
>
> So, what you appear to be saying is that for a given capacitance and rated
> voltage, film caps are a better choice if they are available. The
> electrolytics are used (in general) where higher capacitance is needed.
> Why, then, is my board liberally sprinkled with 1uF, 2.2uF, and 3.3uF
> electrolytics if film caps last longer and create less distortion? I'm
> talking about the FM signal path caps, decoupling caps, etc. Was it not
> possible in 1981 to get a 1uF 50V non-electrolytic capacitor?
>
> What would be the drawback(s) to replacing the electrolytics with their
> 1000-5000h life with film caps of identical rating with a 200,000h MTBF?
>
about $0.30.
Dave Platt
Dave <dspea...@yahoo.delete.com> wrote:
>So, what you appear to be saying is that for a given capacitance and rated
>voltage, film caps are a better choice if they are available.
For signal-coupling applications, I believe that this is an accurate
statement.
> The
>electrolytics are used (in general) where higher capacitance is needed.
>Why, then, is my board liberally sprinkled with 1uF, 2.2uF, and 3.3uF
>electrolytics if film caps last longer and create less distortion?
I $uppo$e that it ha$ to do mo$tly with the relative co$t of the
different type$ of capacitor$.
Electrolytics are cheap, and physically small for their capacity.
Filmcaps are expensive (relatively speaking) and are physically larger
per capacity.
As a crude example: using Digi-Key single-quantity prices, small
electrolytics suitable for signal coupling purposes might run in the
$.20 range and would be quite small (under 1/2" long and maybe 1/4" in
diameter?). Metallized-polyester caps of similar capacity cost about
a dollar and are at least twice as large in each dimension. The
compact "stacked metallized film" capacitors can rival electrolytics
in physical size, but a 1 uF 50-volt part will cost you $3.63.
> I'm
>talking about the FM signal path caps, decoupling caps, etc. Was it not
>possible in 1981 to get a 1uF 50V non-electrolytic capacitor?
Certainly. However, they were physically a good deal larger than
electrolytics of similar capacity, and quite a bit more expensive.
The small stacked-film caps available today compare favorably in size
to the small 'lytics, but they're probably ten times the price.
>What would be the drawback(s) to replacing the electrolytics with their
>1000-5000h life with film caps of identical rating with a 200,000h MTBF?
The only technical drawback I can see, would be that you'd need to
make sure you're buying filmcaps which can fit into the physical space
available.
The filmcaps are significant more expensive than 'lytics.
Note that all of the above applies to signal-path caps. I would *not*
recommend replacing electrolytics with filmcaps in power-supply
bypassing applications. Power supply traces which are bypassed only
using low-ESR, high-Q caps (e.g. stacked film) can suffer from some
nasty resonance effects - the inductance of the traces interacts with
the high-Q capacitance to form a tank circuit - and this can result in
oscillation, ineffective bypassing at certain frequencies, and other
nasty effects.
Dave Platt
Dave <dspea...@yahoo.delete.com> wrote:
>> Lower distortion, longer lifetime. Unless you feel that those are bad
>> things, go right ahead and stick in the 0.22 filmcap.
>>
>Sorry, I should have been more clear. I mean what would be the
>ramifications of replacing the 0.15uF electrolytic with a 0.1uF or 0.22uF
>ELECTROLYTIC?
Little to none. Depending on the source and load impedances, it's
possible that going down from 0.15 to 0.10 _might_ result in a
premature rolloff of the low frequencies. I doubt it, but it's
possible. Going _up_ to a 0.22 should ensure that this does not happen.
Given the loose tolerances of most 'lytics, it's unlikely to matter,
but I'd recommend usign the 0.22 uF anyhow.
to...@fullnet.com
Having also read your subsequent posts in this thread:
At http://www.mouser.com , you can find some nice metallized polyester
caps by AVX, such as the 0.15 uF 63V 10% for $0.08, qty 1 (or 5% for
$0.18). They are SMALL, too: 2.5mm D x 7.5mm W x 6.5mm H, with
0.2-inch lead spacing. They go up to 2.2uF, although the size at 2.2uF
rises to 6mm D x 7.5mm W x 12mm H.
The Mouser.com part number for the 0.15 uF 10% one is 581-BQ014D0154K.
The 5% version's part number is the same, except for a J instead of K,
at the end.
The 0.47uF 63V 5% and 10% metallized polyester AVX caps in the same
series have Mouser.com part numbers 581-BQ074D047J and ...K, and go for
$0.25 and $0.23, qty 1.
For the 0.15uF cap, I would tend to prefer the WIMA MKP2-series
metallized polypropylene, especially if small size is important: The
Mouser.com part number 505-MKP20.15/100/5 is rated 100vdc/63vac, 5%,
and sells for $0.87 for qty 1. It's SMALL, too, at 7.2mm D x 7.2mm W x
13mm H, with 5mm lead spacing.
If you can tolerate a slightly-larger size, you can get some metallized
polypropylene caps with "< 0.1% dissipation factor (DF)": Mouser.com
part number 1429-1474 is 0.47uF 100v 10%, for %0.70 qty 1, and measures
10mm D x 18.5mm W x 15.5mm H. And there's also the 1429-2475, 4.7uF
250v 10% for $3.49 qty 1, measuring 37mm W x 18mm D x 27mm H.
And once you get up to sizes that large, there are quite a few
alternatives available, in film caps.
There are film caps in the larger capacitance values, at Mouser.com,
too, although they tend to get a bit pricey, in most cases. For
example, check out the ones in the AVX "FFB" series (which seem to be
intended for DC filtering).
Note that you may have to solder wires onto the leads, if you are
replacing physically-larger caps with some of the very small ones that
I mentioned above.
Regarding whether you can always replace electrolytics with
similarly-rated film caps (and then get better performance and
reliability), the answer might be "usually". But note that, sometimes,
maybe especially in power-supply bypass/decoupling applications near
ICs (or, e.g., similarly, on a per-board basis), the designer might
have relied on the higher ESR (equivalent series resistance) of an
el-cheapo electrolytic (or a tantalum) cap to be a necessary part of
the circuit (maybe, e.g., for damping). If I ever had to guess, then I
would guess that, for an audio signal path cap, a film cap would almost
always be better than an electrolytic (and I would then almost always
prefer polypropylene over polyester).
Sorry for the long post. Gotta run. Have fun.
Tom