Very interesting ;-)
----- Mail d'origine -----
De: Richard
À: Simmons Drums
Envoyé: Mon, 11 Jul 2011 15:39:42 +0200 (CEST)
Objet: [Simmons Drums] Re: still Unreal ...
I'm a retired Electronics Engineer / tech and spent 30+ years in design and service of all sorts of equipment. Most of the service side was looking after test equipment for a University. The synth side of things has always been a labor of love. When ever I get a piece of gear where the owner states "it's had little use and has been in storage for years" I always do the following;
1) disconnect the PSU from the main circuit.
2) plug the device into the AC via a varistat (like a big variable transformer) and slowly run the device up to it's normal rated AC operating voltage over an hour or so. This allows the Electrolytic caps in the PSU "reform" themselves.
3) reconnect the main circuit to the PSU and repeat the process of step 2. This time though the Electro's in the main device to reform.
In general, this process works most of the time. Just occasionally I'll get a cap that breaks through it's dialectric and pop.
Again like an old car that's been sitting all the oil seals etc will have gone hard, shrunk etc. Sometimes with a bit of TLC they can be massaged back into perfect order. Other times it will require a strip down and replacement.
--- In Simmons_Drums@yahoogroups.com, Jacquot.Patrice@... wrote:
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> I hear you guys !
> I'm not electronician myself but working a lot with one guy restoring my units...Fairlight, Simmons, Lexicon, Quantec, Studer etc ...He keeps explaining things that I'm not always able to understand but he's claiming that the Caps are the priorty suspicion to check today on 20 years old (or more) units like mine, as they are in the end of their life time.
> But it's interesting to hear different advice.
> The last unit I bought is a QRS quantec from the early 80's, & when I went to the studio to test it it was doing a lot of unexpected things & quite some numeric noise... I know that this reverb was coming from a famous studio , which means that it has been powered up 24hours a day for many years...I told the guy that I would buy it only if he fully recapped it.
> So he did...
> Today the unit is very stable , the noise disappeared. so I think that was a huge need doing it .
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> I suppose that the age of the concerned machines is making all relative...10 years unit don't probably need that yet... but 20 or 30 years machines...I have a doubt...
> There's also the fact that caps have a life time linked to some special temperatures use... so that's making it quite uncertain...
> Therefore I also Noticed that some still new old stock machines that had never been powered on for more than a few minutes can also have some faulty caps, dryed just by sands of time...
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> I wish I was an electronician with more competences and test equipment & skills...
> To maintain & prevent all that beloved machines from "catastrophes" ...
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> Thanks for your advices,
> Best
> Patrice.
>
> ----- Mail d'origine -----
> De: Richard
> À: Simmons Drums
> Envoyé: Mon, 11 Jul 2011 05:47:41 +0200 (CEST)
> Objet: [Simmons Drums] Re: still Unreal ...
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> I'd like to throw my hat into the ring.
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> All of what has been said above is true. If a piece of "vintage gear" "aint broke" there's no need to fix it. Ceramics and Tants are notorious for giving problems as they age. Tants simply give up the ghost and go bang, no warning, no drifting values. Ceramics will begin to drift from there stated value till they simply become resistive. Here's an example, I received a Drumulator that suddenly refused to power up. The start up is triggered by a voltage sensing arrangement that requires the 5v line to be at 5v and stable. I measured all the PSU voltages and all was good except the 5v line., it was only at 3.94 v. I lifted the output leg from the board and found it to now be a stable 5.0v. The Drumulator is chock full of TTL logic and as such each chip has a 0.01uf ceramic cap associated. I removed ALL said ceramics and replaced with new. Problem solved, nice running Drumulator. Overall the vast number of leaky ceramics had become a resistive load, dragging
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> As to Electrolytics, I agree, replace only if they show signs of fault. BUT if I am undertaking a full restoration of a piece of gear and wish to return it to it's original spec, every component gets a full "once over" and replaced if a even suspect it's not to spec.
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> If I did not do this, it would be akin to restoring a classic vehicle but not rebuilding the engine....doesn't make sense.
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> With this in mind though, restoration work carried out by someone not experienced in the field will certainly create more problems than what it was worth.
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> "Simply cutting down the weeds with a lawn mower may remove the immediate problem, but the weeds WILL grow back"
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> cheers
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> Richard
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> --- In Simmons_Drums@yahoogroups.com, "gordonjcp" wrote:
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> > --- In Simmons_Drums@yahoogroups.com, Jacquot.Patrice@ wrote:
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> > > What about when the condensators are dead or progressively faulty ?
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> > > don't they involve other componants damages & breakdowns by not regulating anymore tensions ?
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> > That's a bit of a myth. If you run gear in seriously hot conditions more-or-less continuously you will eventually start to dry out the electrolytic capacitors. This will make the supply voltage drop and go all ripply, and you'll hear that as a hum on the output. Other than that, they just don't seem to fail, much.
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> > Disc ceramic capacitors fail by going leaky - that is, the ceramic stops being an insulator and they slowly become resistors. This happens quite a lot - in one particular kind of radio I work on, I often change three surface-mount ceramic capacitors because if they haven't failed yet, they will soon. Once they start to go leaky the decline is rapid - before long they will become a dead short and cause all sorts of mayhem.
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> > Tantalum bead capacitors which are used in computer equipment to decouple noise from power supplies fail by going dead short ∗instantly∗. You know when this happens because of the thick smoke and horrible smell. In an emergency you can often just cut them off the board until you get a chance to replace them. It might be noisier, but it won't break anything.
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> > Gordon MM0YEQ
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