Re: Remote Power Supply Connection

On Tue, 20 May 2008 06:56:50 +1000, "Trevor Wilson"
<trevor@[EMAIL PROTECTED]
> wrote:

>
>
>"flipper" <flipper@[EMAIL PROTECTED]
> wrote in message 
>news:otr234tvk9aflrt4p3etfpsjlqjc5617kh@[EMAIL PROTECTED]
>> On Mon, 19 May 2008 08:33:56 +1000, "keithr" <keithr@[EMAIL PROTECTED]
>
>> wrote:
>>
>>>
>>>"Patrick Turner" <info@[EMAIL PROTECTED]
> wrote in message
>>>news:48303804.A765B189@[EMAIL PROTECTED]
>>>>
>>>>
>>>> Trevor Wilson wrote:
>>>>>
>>>>> "flipper" <flipper@[EMAIL PROTECTED]
> wrote in message
>>>>> news:2e1v24tp96nb7n7dopacuig5rv7hubtiru@[EMAIL PROTECTED]
>>>>> > On Sun, 18 May 2008 09:04:49 +1000, "Trevor Wilson"
>>>>> > <trevor@[EMAIL PROTECTED]
> wrote:
>>>>> >
>>>>> >>
>>>>> >>"flipper" <flipper@[EMAIL PROTECTED]
> wrote in message
>>>>> >>news:oolu249l2p19arj95g2it4fhjag238ajfl@[EMAIL PROTECTED]
>>>>> >>> On Sun, 18 May 2008 07:36:56 +1000, "Trevor Wilson"
>>>>> >>> <trevor@[EMAIL PROTECTED]
> wrote:
>>>>> >>>
>>>>> >>>>
>>>>> >>>>"Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message
>>>>> >>>>news:g0mu6g$2vgp$1@[EMAIL PROTECTED]
>>>>> >>>>> Trevor Wilson wrote:
>>>>> >>>>>> **Asked and answered. Use AC. Do not use DC.
>>>>> >>>>>>
>>>>> >>>>>
>>>>> >>>>> In practice that is perhaps not such a good idea as it sounds.
It
>>>>> >>>>> means
>>>>> >>>>> the rectifiers will be at the end of a fairly long piece of 
>>>>> >>>>> cable.
>>>>> >>>>> The
>>>>> >>>>> large rate of changes of current caused by rectifiers
(especially
>>>>> >>>>> the
>>>>> >>>>> semiconductor type) combined with the series inductance of the
>>>>> >>>>> cable
>>>>> >>>>> is
>>>>> >>>>> a
>>>>> >>>>> recipe for noise, interference and possibly stability
problems.
>>>>> >>>>
>>>>> >>>>**I fail to see how. In practice rectifiers are already at the
end 
>>>>> >>>>of
>>>>> >>>>very
>>>>> >>>>long cables and are supplied by devices with prodigious
inductance.
>>>>> >>>>In
>>>>> >>>>any
>>>>> >>>>case, there are measures that can be taken to reduce the
problems
>>>>> >>>>associated
>>>>> >>>>with noise from diodes. There are even (easy) measures which can
be
>>>>> >>>>taken
>>>>> >>>>to
>>>>> >>>>reduce the inductance of those connecting cables. What I am very
>>>>> >>>>concerned
>>>>> >>>>about is the extreme ignorance displayed about the dangers 
>>>>> >>>>associated
>>>>> >>>>with
>>>>> >>>>DC arcs and connectors. This, as opposed to your hypothetical,
is a
>>>>> >>>>very
>>>>> >>>>real possibility. Read this:
>>>>> >>>>
>>>>> >>>>http://www.arcadvisor.com/faq/dc_direct_current_arc.html
>>>>> >>>>
>>>>> >>>>Trevor Wilson
>>>>> >>>>
>>>>> >>>
>>>>> >>> The connector isn't a switch, relay, or fuse.
>>>>> >>
>>>>> >>**Indeed. If it is unplugged, whilst 'hot' a disaster could
result.
>>>>> >
>>>>> > While I'm not particularly enamored with the idea of HVDC
umbilicals
>>>>> > it doesn't take too much thought to come up with at least one
means 
>>>>> > to
>>>>> > prevent manual disconnect while hot and I'm sure a few minutes
more
>>>>> > could produce others.
>>>>>
>>>>> **I've not seen any solutions proferred yet. However, the use of AC
>>>>> eliminates any problems. There is no downside.
>>>>>
>>>>> >
>>>>> >> Using AC
>>>>> >>eliminates any possibility of such a disaster.
>>>>> >
>>>>> > So does preventing disconnect while hot and you seem to have
>>>>> > completely missed the entire discussion about how to ensure 'no 
>>>>> > touchy
>>>>> > hot pins'. And, if done right,  no 'touchy hot' could also mean no
>>>>> > 'arcy disaster hot'.
>>>>>
>>>>> **Then present your solution and explain why is is better than using

>>>>> AC.
>>>>>
>>>>> >
>>>>> >> Using DC is just dumb.
>>>>> >
>>>>> > You really should look for a more congenial means to salve your
ego.
>>>>>
>>>>> **Just dealing in the facts. Inconvenient that they are. Using AC is

>>>>> much
>>>>> smarter, safer and simpler. Using DC is dumb, unsafe and
inconveniently
>>>>> complex.
>>>>>
>>>>> Trevor Wilson
>>>>
>>>> Trevor, you wouldn't know a fact even if one bit you on the arse.
>>>>
>>>> Thr trouble is you are unaware of solutions because you've never
>>>> had to find solutions.
>>>>
>>>> AC is fine where possible, but what us tubies like to keep
>>>> OFF THE AUDIO CHASSIS is the whole PSU, ie, mains PT, diodes, first
>>>> electro filter caps, and
>>>> chokes, and second electro filter caps.
>>>>
>>>> The sensible thing is to transfer the Vdc by cable, but on the
>>>> audio chassis the Vdc has a small amount of C between say the OPT CT
and
>>>> 0V, say about 2uF only, plastic type.
>>>> This will shunt the inductance of the cable, and it is 5Amp rated
wire,
>>>> its dc resistance is totally insignificant.
>>>> One can have a diode in series with the Vdc input at the amp to
prevent
>>>> say +600V causing current flow from the live pin to something earthy.
>>>> One can also rig up the feeds so that if the cable becomes unplugged
>>>> from the
>>>> PSU a relay closes and a resistance is connected to the
>>>> Vdc rail and 0V. Because only 2uF is present, the decline in Vdc to
safe
>>>> levels
>>>> can be very fast even without tubes drawing current.
>>>>
>>>> Patrick Turner.
>>>
>>>Lets face it the whole safety thing can be fixed.
>>
>> Of course. Trevor is just dedicated to not finding a solution, which
>> is always a self fulfilling prophecy.
>
>**I've already provided a solution - use AC, not DC.

That's not a solution to the design requirement.

>
>>
>>> You put the connectors at
>>>each end under covers. The covers can only be lifted by removing a
screw 
>>>(or
>>>two), under the cover is a micro switch. Long before anybody can access

>>>the
>>>actual connectors, the power is switched off by the microswitch.
>>
>> That's the 'a few minutes of thought' solution I mentioned but I'd
>> probably kill AC and use Patrick's reservoir discharge rather than
>> beak live B+.
>
>**All of which can be dispensed with, when using AC.

That violates the design requirement.