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recapping a tr909 advice

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selfpreservation:
hi i plan to recap my tr909 and would like to know were to start really

do i need to replace all the caps or just electrolytic ?
do i just need to do the voice board ?

any advice would be welcome

cheers ciaran

Gordonjcp:
If it's working properly, leave it the hell alone.

I wish I knew who came up with the ridiculous idea of "recapping" equipment so I can kick them up the arse so hard their teeth go on fire.

So far I've scrapped a Prophet 600 and a JX-8P because of this "recapping" thing - both of them had been wrecked beyond all hope of repair by someone who had attempted to replace every capacitor on every board and had done an extremely bad job of it.  The *really* annoying thing is that the JX was working to begin with and the P600 had a really, really simple fault - and nothing to do with capacitors!

Capacitors pretty much never fail.  Where you do see failed capacitors, they are either cheap underspecified smoothing capacitors in switched-mode power supplies, or small ceramic capacitors that have had a DC bias across them (they turn into resistors, gradually).

Once again, if it's working, leave it alone.  If it's *not* working, find out what's wrong with it and fix it.  Don't just go blundering in replacing parts at random.

Circuitbenders:

--- Quote from: Gordonjcp on April 22, 2011, 08:04:21 AM ---I wish I knew who came up with the ridiculous idea of "recapping" equipment so I can kick them up the arse so hard their teeth go on fire.

--- End quote ---

You wouldn't be saying that if you'd seen the inside of the Bentley Rhythm Ace i was working on recently. 40 year old caps probably shouldn't be that shape, or that colour come to think of it. Recapping the whole thing certainly lowered the noise floor a fair amount, but then that thing is a noise magnet anyway, and the power supply was buggered meaning everything was running higher than the intended capacitor ratings.

I'd only recap something if a few of the caps were discoloured or bulging ominously, or if there was that unpleasant fishy smell of leaking electrolyte. Doing it just for the sake of it is just inviting trouble, and you've got to wonder why the capacitor problems are there in the first place.

I got a brilliant Zoom 9200 reverb recently that sounded 'not quite right' and the switched mode supply absolutely stank of fish. Replaced all the caps in the PSU and it works fine. Certain companies do seem to have an annoying habit of sticking power supply caps right next to heatsinks or power resistors that get incredibly hot.

selfpreservation:
i guess im definatley in the leave it alone camp , theres that many caps im bound to make a mistake , but i do have noisy outputs on the main which can be fixed by adding caps according to the service notes for my serial and the snare doesnt sound right it the envelope on the tom portion of the sound doesnt kick in so it rings  which i guess is a cap in the envelope , i was thinking just do the lot while i had it open but i wont bother now , cheers for the advice ill probably check the power is ok do a visual on the rest and replace any dodgy looking ones

Gordonjcp:
If it's in the real genuine Roland service notes and it hasn't been done, then go right ahead - they issued ECOs for all their instruments for various things.  Back then, bugfixes involved hardware changes, not a quick reflash...

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