Hi
The main killer of power supplies in the long term is HEAT. Electronic
parts are 'happiest' at around 20 - 25 Centigrade and the closer you can
keep ALL the parts to this the better. Of course to achieve this
involves decent airflow and intelligent placing of parts so that the
ones that can tolerate a little more heat are placed in a suitable position.
Overrating of particularly the 'pass' transistors and the main rectifier
is 'cheap' insurance. In a 'power one' 13 Amp supply module they run
2N3055 transistors at about 2 Amps per device which is sensible and I
have never seen any failures of these devices out of what must be over a
thousand units. Rectifiers and occasionally transformers are a different
issue.
Remember that heatsink temperature is lower than the temperature the
transistors (and rectifiers) get to so if the heatsink feels too hot to
touch (or hold comfortably) then the transistors are probably being run
a bit hard. Here, having multiple devices helps spread the strain as the
interface between the transistor and the heatsink, using an insulating
washer can allow significant difference. Make sure you have effective
thermal compound in there and the screws are tight.
With shortage of studio space and the fact these supplies are silent it
is tempting to hide them away somewhere. They MUST have good cooling
airflow.
Matt S
Ike wrote:
Hi David
No daggers from this quarter! The only thing I would add is that
what I have found with over a dozen PS-3's that I've known is that the
failures are almost entirely due to assembly problems. IOW the parts
that fail tend to do so because they weren't soldered and/or mounted
properly at the factory. Once these things are corrected they can and
do run for years without any trouble.
Best
Ike Zimbel
Zimbel Audio Ltd
416-720-0887
www.zimbelaudio.com
Sent from my iPhone
On 2010-05-11, at 11:29 PM, David Butler <[email protected]> wrote:
As a former power supply engineer I will weigh in here, all the while
watching my back for daggers!
:-)
In general, PSU designers do NOT underrate components enough, IMNSHO.
This is why so many power supplies dies early, untimely deaths. The
capacitors in particular, tend to bake. If higher temperature caps
can be found, so much the better. In general, going up a little in
voltage rating on caps is OK, SOMETIMES going up in value is OK too,
depends on the design. The idea all around is that heavier is
GENERALLY better. You don't want to go extremely high on capacitor
voltages: they are happiest on a diet of 50% or so of their nominal
ratings.
The power transistors can sometimes benefit from having higher
voltage, power and current ratings, as long as everything else (gain
especially) is the same. Personally I like rectifiers rated at at
least double, if not triple, the PEAK voltage in the circuit. Again,
rating for higher temperature handling rarely hurts.
If the supply in question lasted a long time with no problems, there
is no fault to be placed on using exact replacements either. My own
take is to be conservative by going for heavier parts if the costs
are not excessive.
Just my 50 cents...
db
--
David 'db' Butler
AV Wizard, Audio Guru & Team Leader delivering exceptional
on-time & under-budget results with cutting edge technologies.
Quoting Mike Thompson <[email protected]>:
I have a question regarding parts replacement -
i have a tech who has looked at my Series 1E power supply and told
me he could rebuild it with no problem, but I wanted to make sure
before I handed it off to him if there were any parts that needed
to be specific values (equal to or greater), anything that should
specifically be improved upon when rebuilding, how to make it
compliant to the standard, or any other tips to make sure I get the
most out of it. I know some of you guys had rebuilt them and I
figured this was the best place to ask. Let me know.
------
View the list online at:
http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] with "unsubscribe neotek" in the
message body. If you have any difficulties, or questions --please
send an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any
message or reply sent to the list will be automatically forwarded to
all subscribers.
Vive Le Neotek!
Thanks.
------
View the list online at:
http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to
mailto:[email protected] with "unsubscribe neotek" in the
message body. If you have any difficulties, or questions --please send
an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any
message or reply sent to the list will be automatically forwarded to
all subscribers.
Vive Le Neotek!
Thanks.
------
View the list online at: http://www.mail-archive.com/[email protected]
You can unsubscribe at anytime by sending an email to mailto:[email protected] with
"unsubscribe neotek" in the message body. If you have any difficulties, or
questions --please send an email to mailto:[email protected].
The Neotek list is lovingly hosted by Catapult Web. Remember that any message
or reply sent to the list will be automatically forwarded to all subscribers.
Vive Le Neotek!
Thanks.
