Hi
One of the attractions for manufacturers to buy in 'standard' units is
that they carry UL accreditation, taking some of the cost of the
certification procedure allowing them to be sold worldwide.
One problem AMEK had with one of the standard units was that they don't
like starting up into almost a short circuit (lots of capacitance), so a
'slow start' mod was applied.
They also do not manage 'tracking' between pos and neg supplies (split
rail situation) although this is not often much of an issue as op amps
in particular are not so fussy about exact rail voltages as long as they
are between about 4 and 18 Volts. Obviously the overall system would
produce asymmetrical clipping of audio if they were more than about 1 or
2 volts 'out'.
There is an obvious 'hiccup' in that 17.5 - 18 volts is not in the usual
range of supply voltage in which case modding a 15 Volt UP to 17 or 18
is in a way preferable to taking a 24 Volt down because if it fails the
overvoltage produced may be survivable whereas from a 24 volt (upwards)
module it would not.
At Christmas time I went out to fix an 'International Power module which
had failed and was putting out 24 Volts (rather than 18). The whole desk
had been running at this for a month or so but there were no circuit
failures. I previously saw a different supply which had failed to about
26 Volts where again only 1 lightmeter circuit had failed. The desk had
been running for about 5 months like this with the main complaint being
the hum as it was DC but not 'regulated'.
While regulator failures are quite rare, it is possibly worth
investigating the OVP option set to say 20 Volts. The other thing is
that the desk circuitry should be protected against having one rail
'missing' meaning that it should ALL go off if either of the audio rails
is above 20 or below say 4 Volts (4 being about the minimum where all
common op amps have definitely 'woken up' and can act in the proper
mode). Adding this extra circuitry starts to make things messy again
unfortunately.
Matt S
Brian Roth wrote:
Dear Matt,
I tend to build power supplies "from scratch" using industry-standard
"open frame linear" modules from Power-One, International Power,
Condor, etc. See:
http://www.internationalpower.com/
http://www.power-one.com/resources/products/datasheet/lin.pdf
http://www.slpower.com/Upload/Technical/20070209014693243081780_International%20Linears_G.pdf
(And, there are other companies making the same interchangeable modules.)
The Upside is that the modules are "industry standard" items with
identical specs for a given voltage/current rating, and hence are
readily available from multiple manufacturers. Those companies
manufacturing the modules are specialists in ONLY power supplies and
sell the modules through multiple parts houses (Mouser, Digikey,
Allied, Newark, etc). Hence, if a module fails at some point in the
future (which is somewhat unlikely..these are VERY solid modules),
another "industry standard" module can be easily retrofitted, even
from a different module manufacturer. IOW, a Power-One module can be
swapped in place of a International or Condor...etc. The metal work,
mounting holes, etc are identical from one company to the next.
The Downside is that the modules have to be initially installed into
some sort of metal enclosure with fuses, power cord, switch, etc.
That metal enclosure can be a "fancy" rack mounted box, or a "homely"
steel box (less expensive) that sits beside/underneath the desk.
Console companies such as Amek, Otari, Allen-Heath and others shipped
their large desks with "open frame linears" stuffed into nifty rack
mounted boxes carrying the console company's logo, so this isn't
something I concocted on my own..LOL!
My Two Cents! <grin>
Best,
Bri
Matt Boynton wrote:
Hello list. I have a Series 1E. Who out there can
rebuild/refurbush/overhaul my power supply? It works, but it has a
pretty significant hum. I have a back up supply that is in better
condition however, I would like to get one of them in top shape.
Thanks everyone.
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