[sdiy] speaking of tantalums...

Neil Johnson neil.johnson71 at gmail.com
Mon Nov 26 13:07:11 CET 2018


Adam Inglis wrote:
> I’m getting a Prophet 5 rev 3.3. (no midi) ready for sale. I’m wondering if I should be replacing the tantalums in it.
>They seem to be considered a ticking time bomb. One site I came across suggested replacing the decoupling
> tants with low ESR electrolytics, I assume you just use identical farad values:

When tants blow they do two things:

1) They can damage nearby components with hot sharp pieces of epoxy or
hot flameouts (pro-tip: if working on circuits with tants on power
rails wear protective goggles).
For example: https://youtu.be/VknpLq7DkSM?t=92

2) They often fail shorted, and PCB power traces become fusible links
that burn out necessitating replacing damaged tracks with tinned wire
or similar.  And also sometimes they can take the associated voltage
regulators with them too.  I had a mixing desk that lost its +15V rail
- the tant had gone short, that also killed the 7815, and made me
check over every op-amp as some don't like one rail going missing.
This would be particularly bad on any circuits with unprotected
SSM2164/V2164 and the negative rail is killed by a tant.  More info
here:
http://www.njohnson.co.uk/index.php?menu=2&submenu=2&subsubmenu=3

As for replacing, the rule I tend to use is replace tants with
aluminium elect of 10x the value if you can fit them in.  Anywhere
around DC-DC converters is tricky territory so consult manufacturer's
data sheets for capacitor selection advice.

Neil
-- 
http://www.njohnson.co.uk




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