Vintage Synth Repair

Would it be safe to replace all the tantalum caps in my OBXa with 
regular electrolytic caps (as long as their of the same specs of 
course) ?...

I had 3 blown tantalums on mine, so I went and replaced all 6 that are 
installed, in various positions, with new tantalums.

I know these will blown up again in 15 years or so, so would it be safe 
to replace them all with electrolytics ?

Thanks !

Please,
How did you know they were blown ??


gil_we wrote:

>Would it be safe to replace all the tantalum caps in my OBXa with 
>regular electrolytic caps (as long as their of the same specs of 
>course) ?...
>
>I had 3 blown tantalums on mine, so I went and replaced all 6 that are 
>installed, in various positions, with new tantalums.
>
>I know these will blown up again in 15 years or so, so would it be safe 
>to replace them all with electrolytics ?
>
>Thanks !
>
>
>
> 
>  
>
-- 
Tom Thornton
Cincinnatti Nbr 3  Morristown NJ USA
Madison     Nbr 93 Madison    NJ
ST Johns    Nbr 1  Mountain Lakes

--- gil_we <gil_we@...> wrote:

> Would it be safe to replace all the tantalum caps in
> my OBXa with 
> regular electrolytic caps (as long as their of the
> same specs of 
> course) ?...
> 

It would be "safe" for the limited purpose that there
would be no physical danger caused. Tantylum
capacitors are a special form of electrolytic
capacitors that are specified more closely in terms of
percentage tolerance, and particularly in considerably
reduced leakage current. If the particular circuit
requires very low leakage, the electrolytic capacitor
will not work properly even when first installed. They
were also developed as a premium capacitor with longer
mean time before failure (MTBF) for use in circuits
where early failure prevention was more important than
the incremental higher price for the capacitor (for
example - a space satellite where field repair is
ultra expensive, or a jet fighter where failure could
result in loss of life).

Briefly, standard electrolytics as a replacement for
tantylum would not be recommended (of course, in this
modern world of fast obsolencence and unobtainable
parts, at some time it may be the only thing
obtainable).

Jim Cason
Electronic & computer tech 42 years

Thanks Jim !


--- In vintagesynthrepair@yahoogroups.com, James Cason <jlcason@...> 
wrote:

>
> 
> --- gil_we <gil_we@...> wrote:
> 
> > Would it be safe to replace all the tantalum caps in
> > my OBXa with 
> > regular electrolytic caps (as long as their of the
> > same specs of 
> > course) ?...
> > 
> 
> It would be "safe" for the limited purpose that there
> would be no physical danger caused. Tantylum
> capacitors are a special form of electrolytic
> capacitors that are specified more closely in terms of
> percentage tolerance, and particularly in considerably
> reduced leakage current. If the particular circuit
> requires very low leakage, the electrolytic capacitor
> will not work properly even when first installed. They
> were also developed as a premium capacitor with longer
> mean time before failure (MTBF) for use in circuits
> where early failure prevention was more important than
> the incremental higher price for the capacitor (for
> example - a space satellite where field repair is
> ultra expensive, or a jet fighter where failure could
> result in loss of life).
> 
> Briefly, standard electrolytics as a replacement for
> tantylum would not be recommended (of course, in this
> modern world of fast obsolencence and unobtainable
> parts, at some time it may be the only thing
> obtainable).
> 
> Jim Cason
> Electronic & computer tech 42 years
>

They short...


--- In vintagesynthrepair@yahoogroups.com, Tom Thornton 
<tomthornton@...> wrote:
>
> 
> Please,
> How did you know they were blown ??
> 
> 
> gil_we wrote:
> 
> >Would it be safe to replace all the tantalum caps in my OBXa with 
> >regular electrolytic caps (as long as their of the same specs of 
> >course) ?...
> >
> >I had 3 blown tantalums on mine, so I went and replaced all 6 that 
are 
> >installed, in various positions, with new tantalums.
> >
> >I know these will blown up again in 15 years or so, so would it be 
safe 

> >to replace them all with electrolytics ?
> >
> >Thanks !
> >
> >
> >
> > 
> >  
> >
> -- 
> Tom Thornton
> Cincinnatti Nbr 3  Morristown NJ USA
> Madison     Nbr 93 Madison    NJ
> ST Johns    Nbr 1  Mountain Lakes
>

Don't do it.  Replace the components with the original type and values.

Electrolytics have both a definite shelf and operational life.  
Currently about 2000 hr.. for the new stuff.

They go bad just sitting and do not have the tolerances necessary for 
some circuits, particularly timing, clock, etc., etc. that you would 
find all over the place in a synth.

Most electrolytics are about a +/- 20% value -- generally close enough 
for power supply sections, but not sensitive electronics.

Regards;

Peter

gil_we wrote:

> They short...
>
> --- In vintagesynthrepair@yahoogroups.com 
> <mailto:vintagesynthrepair%40yahoogroups.com>, Tom Thornton
> <tomthornton@...> wrote:
> >
> >
> > Please,
> > How did you know they were blown ??
> >
> >
> > gil_we wrote:
> >
> > >Would it be safe to replace all the tantalum caps in my OBXa with
> > >regular electrolytic caps (as long as their of the same specs of
> > >course) ?...
> > >
> > >I had 3 blown tantalums on mine, so I went and replaced all 6 that
> are
> > >installed, in various positions, with new tantalums.
> > >
> > >I know these will blown up again in 15 years or so, so would it be
> safe
> > >to replace them all with electrolytics ?
> > >
> > >Thanks !
> > >
> > >
> > >
> > >
> > >
> > >
> > --
> > Tom Thornton
> > Cincinnatti Nbr 3 Morristown NJ USA
> > Madison Nbr 93 Madison NJ
> > ST Johns Nbr 1 Mountain Lakes
> >
>
>  



-- 
Best regards,

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Managing Specialist, HPC Systems;      3M Center, Bldg 42-5-E08
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Yes, you can. As far as I am concerned Tants are great if you are cramped 
for space and not using them where there is likely to be lots of ripple 
(power supplies)
I would state that I have had more tants fail, either electrically or 
mechanically (legs breaking off) than any other component.
Best regards.
John.
----- Original Message ----- 

From: "gil_we" <gil_we@...>
To: <vintagesynthrepair@yahoogroups.com>
Sent: Tuesday, June 19, 2007 11:04 AM
Subject: [vintagesynthrepair] Replacing tantalum caps with electrolytic caps


> Would it be safe to replace all the tantalum caps in my OBXa with
> regular electrolytic caps (as long as their of the same specs of
> course) ?...
>
> I had 3 blown tantalums on mine, so I went and replaced all 6 that are
> installed, in various positions, with new tantalums.
>
> I know these will blown up again in 15 years or so, so would it be safe
> to replace them all with electrolytics ?
>
> Thanks !
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
> -- 
> Internal Virus Database is out-of-date.
> Checked by AVG Free Edition.
> Version: 7.5.472 / Virus Database: 269.8.13/844 - Release Date: 11/06/2007 
> 17:10
>
>

>Would it be safe to replace all the tantalum caps in
>my OBXa with
>regular electrolytic caps (as long as their of the
>same specs of
>course) ?...

It depends on how the caps are used in the circuit.  Aluminum electrolytic 
and tantalum capacitors have different characteristics- in certain cases, it 
might adversely affect circuit performance.  If the tantalum capacitors are 
just used for decoupling (across the power supply rails at various points in 
the circuit), it shouldn't present a problem (actually it might be a good 
idea, as tantalum caps tend to fail rather spectacularly if given too much 
voltage), but if they're used anywhere in the signal path, it probably 
wouldn't be much of an "upgrade" to replace them with electrolytics.

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On Tuesday 19 June 2007 16:37, Peter Bye wrote:
> Don't do it.  Replace the components with the original type and values.
>
> Electrolytics have both a definite shelf and operational life.
> Currently about 2000 hr.. for the new stuff.
>
> They go bad just sitting and do not have the tolerances necessary for
> some circuits, particularly timing, clock, etc., etc. that you would
> find all over the place in a synth.
>
> Most electrolytics are about a +/- 20% value -- generally close enough
> for power supply sections, but not sensitive electronics.

More like -20%/+80% in many instances.  Most caps that I've checked with my 
capacitance checker read way higher than the marked values.

Also,  a lot of failures of tantalum caps are because of either getting too 
close to or exceeding the rated voltage.  A prime example is in the ARP Omni, 
where they used 25V parts for a situation where as much as 30V might end up 
being present!  Going a little bit higher in voltage won't hurt anything at 
all,  and will probably give better longevity.

Me,  I wouldn't replace tantalum caps with electrolytics either.

Look at the datasheet for your typical 3-terminal regulator parts,  like the 
7805 -- they'll specify a 1uF tantalum cap at the output,  or a 25uF (!) 
aluminum electrolyitc...

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
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-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

my understanding of the use of tants & cans in circuits was this: 

electrolytics are cheap & good in situations where you need a big
"bucket" for charge, such as 50/60Hz filtering in power supplies, but
they are pretty rubbish at high frequencies, reverse leakage & being
anywhere remotely near their stated value in uF, which can also vary
with temperature & humidity. that said, they tend to last quite a long
time before giving up the game rather spectacularly. they'd be the
first thing to change in an old power amp, for instance, or anything
with a linear (big trafo) power supply. their use in cheap audio
circuits inadvertently led to enormous differences in the performance
of otherwise identical devices, such as fuzz-boxes, which in turn has
affected the market for 2nd hand electronica almost as much as the
various kinds of utility op-amp (741, 5532) used in the same devices.

tantalums tend to crop up more where space is limited, where audio
performance is more important (i.e. the reverse voltage across the
device is likely to be equal to the forward voltage), & where the
value has to be within an order of magnitude of the circuit design's
specification. they tend to go short if they fail. this is especially
troublesome as so many of them are used in linear power supplies
(often adjacent to & in parallel with much larger electrolytics) for
noise-reduction, & especially when the power supply is for audio,
control or video purposes. they have been responsible for the abrupt
end of many series regulator devices (78xx, 79xx).
if they don't fail within six months, they tend to last as long as
their rolled-up-paper cousins, but with less variation in their
performance or capacitance.

I'd replace like with like, every time. 
especially in the early 70s, people didn't use tants just for the heck
of it or because they were smaller; they were an expensive alternative
then & tend to appear where they are the only suitable option.

duncan.