Vintage Synth Repair

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
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin