YARDSTICK power supply

How to extirpate that recapping-insanity

Problem

As the majority of our 1982 QRS devices can attest: QUANTEC audio devices are being operated over 30 years and more. This is also true for some other legends of professional audio, e.g. from our competitors LEXICON, EVENTIDE, or URSA MAJOR. Although somewhat older date, this gang of bearded fellows, immortalized on this photo, has one common problem today: we all have completely underestimated the massively overstretched service life of our creations that is demanded by today’s users.

Four guys with beards
79th AES Convention New York, Oct 1985 – Left to right: Christopher Moore (Ursa Major), Anthony Agnello (Eventide), Wolfgang Schwarz (Quantec), David Griesinger (Lexicon)

Unlike that time, it is now common knowledge that electrolytics have a tendency to dry up after a couple of years. It so happens that all studio-bolides every now and then get their niggles, and then need to log off towards the workshop. For the user of such a continuous runner, this means to account that once every 7-10 years (depending on temperature), all electrolytics need to be replaced as a precaution (»recapping«).

This service is extremely time-consuming, since often several hundred electrolytics must be manually unsoldered and replaced. An additional cost driver is the need for a generous stock of parts, as the abundance of different capacity and voltage values ​​economically cannot be ordered as single pieces (»packing units«).

Budget for “a serving of recapping” is therefore an amount in the high 3-digit $ area – as long as no additional parts are found defective. If in doubt, you can find a few web links to recapping service companies and their price lists on the QUANTEC website. You may save, if you go with a provider whose business model consists in making-up of device-specific “recapping kits”.

Bursted Electrolytic Cans
A typical picture: electrolytic capacitors burst at predetermined breaking point
Who is affected?

This affects all users of devices that normally run in continuous operation, and either themselves generate heat, or which are operated near heat sources. Particularly at risk are densely stacked devices in power amp, effect, and server racks without forced air cooling.

At the recording studio are among the risk candidates: power amplifiers, equalizers, audio effect processors, and in particular all devices with tubes. Previously, tape machines were affected, today, the risk has shifted to servers and monitors.

In workshops and laboratories, measurement instruments are constantly held in standby mode, being turned on in the morning, and (maybe) turned off at night – especially laboratory power supplies, signal generators, multimeters and oscilloscopes. Not to mention those months-long endurance tests, in which not only the test object, but also the monitoring instruments remain on – in order to signal an occasional critical state immediately.

At the office, especially monitors (regardless of CRT or TFT), servers in continuous operation, and laser printers are affected. At network nodes, mainly those switches are affected that supply a multitude of attached devices via Power-over-Ethernet.

At home there are televisions and stereo systems in continuous operation, and wall wart power supplies and battery chargers for mobile phones, that hang out of a wall socket for years with their dangling low-voltage cables.

The previously well-meant advice, particularly not turn off PC monitors and the expensive power amp bolides of your classy stereo set at night, to avoid stress caused by inrush, from today’s perspective is a very bad recommendation.

Solution

As the former QRS developer, I dutifully accepted the problem, then listened into myself for a few decades (rather than into new algorithms), and finally came to the conclusion that prevention is better than soldering. Moreover: it’s better to pick, place and solder 5000 tiny pieces of “chicken feed” with a robot, instead of manually removing and re-soldering 100 electrolytic capacitors in the field, repetitively every couple of years. By mid-2004, as the first one in our industry, I was able to present a prototype of a smart, albeit highly unconventional alternative to that recapping-insanity:

  • whether SD card or TFT display – nowadays you build in the plane
  • 2D is hot, 3D is yuck
  • rather 10-50 SMD solid state capacitors instead of one electrolytic capacitor

For several years now, electrolytic capacitors are completely banished from the entire QUANTEC development department – exceptions are not permitted. If there really seems no other way, go and take an extra circuit board with a few hundred tiny solid state capacitors – picked, placed and soldered by machine. Then pack that board into your device – an additional benefit will certainly be found in no time flat …

Zerolytics

Once hooked, the idea of “massive passive” no longer let me go. It was just the right time to advance the upcoming 249x project to a position ready for production start. After various unexpectedly severe setbacks, not only because of hairline cracks or buzzing capacitors, this goal was indeed achieved until years later. But today, the following applies: whether AD, DA, or power supply – when opening a YARDSTICK, those countless “electrolytic time bombs”, otherwise ubiquitous within any other audio device of any other make, can absolutely not be discovered within that unit

YARDSTICK Power Supply
Power supply with planar transformer (bottom left) and 19 of 50 smoothing caps (center)

Since the name of “massive passive” is already occupied elsewhere in the recording industry (“Hi EveAnna”), I finally called my approach “Zerolytics”. Taking the YARDSTICK power supply as a real-world example, 50 high-voltage ceramic capacitors are being used for smoothing, instead of the usual single or two electrolytic capacitors – distributed on both sides of two power supply printed circuit boards (i.e. a total of 4 surfaces). Similar solutions exist for the replacement of electrolytic capacitors as coupling or decoupling capacitor in the analog circuits of the 2493 AD/DA converters.

YARDSTICK Power Supply
Power supply dismantled – front view with 9 additional smoothing caps

Due to excessive costs, Ceramic Capacitor Array technology is being used predominantly in power supplies of satellites and transatlantic cables, where reliability plays a paramount role. But, and that’s the crucial point, as long as soldering is well controlled, and the boards are not physically stressed by flexing or even buckling, ceramic capacitors show no aging at all. Their lifetime is said to be at least 100 years.

Isn’t outer space tech astronomically expensive?

Well it is. The cost of those 50 ceramic capacitors alone is four times greater than an entire off-the-shelf power supply. The multi-layer board for a planar transformer also adds cost. All in all, our Zerolytic power supplies cost us about 10 times more than generic ones. But QUANTEC devices are located in a price range that allows technical highlights in critical situations very well.

However, compared with the above mentioned costs for recapping procedures, Zerolytics is a bargain – this should be precisely taken into account.


Related links
  • Lifetime of electrolytic capacitors
    as a funcion of temperature
    Wikipedia
  • What is Recap (or Recapping)
    Sweetwater – US music shop
    Sweetwater
  • The full story on “re-capping” a Naim power amp
    Minutes of a professional recap session with lots of photos
    AVoptions
  • Naim Service and Accessories Price List
    What you should know about effort and cost of recapping
    AVoptions
  • Q10 temperature coefficient
    Rate of change of a chemical system according to temperature
    Wikipedia
  • Svante Arrhenius
    1859-1927
    Wikipedia

Picture Credits
  1. Courtesy of Quantec (header image)
  2. Unknown (please submit comment below if you know more)
  3. Rainer Knäpper (wikimedia)
  4. Courtesy of Quantec
  5. Courtesy of Quantec

One thought on “How to extirpate that recapping-insanity”

  1. Even if a developer originally has specified a high quality electrolytic capacitor, there’s considerable risk that, years later, a brainless buyer will purchase “reportedly identically constructed” second-source electrolytics from an untrustworthy manufacturer, which will then poison our OEM’s next production run.

    In particular, a manufacturer of “off the shelf” power supplies, suffering from price pressure, will be an easy victim of sales representatives wooing with “lower-cost equivalent”, but in reality inferior electrolytics.

    In this way, previously acceptable power supply modules suddenly mutate to “time bombs”, not detected by an unsuspecting OEM until it’s already too late.

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