[sdiy] speaking of tantalums...

Adam Inglis 21pointy at tpg.com.au
Mon Nov 26 04:33:50 CET 2018

> On 26 Nov 2018, at 12:36 PM, MTG <grant at musictechnologiesgroup.com> wrote:
> What was the original voltage value on the caps (and which rail)?  Just trying to see how much "headroom" SCI had on their tant cap voltage spec, in light of the recent discussions.

From the SM, these are all the tants in a rev 3

0.22 uF  35 v     x1
2.2         25v      x16
10         10v       x5
10         25v       x7
10          3v       x5

not all these will be decouplers, apparently some are in the audio path. (Grant, I’m not sure yet which is which)

I’m inclined to go with Greg’s numbers - they’re pretty compelling!
Sure, normally, I agree with the “aint broke” philosophy, however it appears that tant failure tends to take out valuable and hard to find chips. (A couple of years ago, I had to replace the DAC. Very expensive process, and the first one I bought was a dud/fake. These are getting very thin on the ground…)

Brian, I do take your point, however, I’m careful and my Hakko desoldering gun works quickly.

> On 11/25/2018 4:12 PM, gm wrote:
>> While I agree that unnecessary work should be avoided, in the case of P5s (and P10s, and ARPs and Oberheims from the eighties) the tantalum bypass caps are the most common failure points.
>> I've got over 500 P5s in my repair database, and a good half of them came in with one or more tantalums shorted out.  Replacing them with high-temp modern electrolytics is part of my routine service.
>> The P5 (whatever rev) has tantalum power bypass caps on the power supply, front panel, CPU and voice boards, all of which should be replaced to ensure longer life of the instrument.
>> ~GMM
>> On 11/25/2018 3:50 PM, rsdio at audiobanshee.com <mailto:rsdio at audiobanshee.com> wrote:
>>> As someone who would consider purchasing a P5 r3.3, I say No.
>>> There’s no need to replace capacitors that have not failed. The copper traces on these PCBs can be fragile, and any desoldering heat could cause damage. It’s best to avoid unnecessary surgery.
>>> If you restrict yourself to the power supply PCB only, then perhaps, but I still don’t see it as an advantage. The more work that is done on these ancient beasts, the more fragile they become.
>>> Brian Willoughby
>>> On Nov 25, 2018, at 2:39 PM, Adam Inglis <21pointy at tpg.com.au> <mailto:21pointy at tpg.com.au> 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:
>>>> Anyone experienced with these machines care to comment?
>>>> Adam
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