Dear Rodents,
Are there safety issues regarding separate PS? I read somewhere ( maybe in
r.a.t.) that it may be difficult to sell tube equipment with HV in an
umbilical cord because of NEC rules. The only NEC book I have is very old.
How about other countries? I can not remember off hand brand names, but
hasn't there been a plethora of amps with separate PS sold in the US? I
recall way back warning some families with children about computer monitors.
This was before the safety features regarding minimal radiation emission
standards from Sweden took hold in the US. Some thought I was a Jeremiad
type. I suppose with a cheaply made home brew umbilical cord, after several
twists and kinks, the situation can become potentially hazardous. Perhaps
someone versed in this issue can write a proper way to design a safe
umbilical cord. Oh well, it's always something, ain't it? Thanks.
Cordially,
west

"west" wrote in message
. ..
Dear Rodents,
Are there safety issues regarding separate PS? I read somewhere ( maybe
in
r.a.t.) that it may be difficult to sell tube equipment with HV in an
umbilical cord because of NEC rules. The only NEC book I have is very old.
How about other countries? I can not remember off hand brand names, but
hasn't there been a plethora of amps with separate PS sold in the US? I
recall way back warning some families with children about computer
monitors.
This was before the safety features regarding minimal radiation emission
standards from Sweden took hold in the US. Some thought I was a Jeremiad
type. I suppose with a cheaply made home brew umbilical cord, after
several
twists and kinks, the situation can become potentially hazardous. Perhaps
someone versed in this issue can write a proper way to design a safe
umbilical cord. Oh well, it's always something, ain't it? Thanks.
Cordially,
west



If you can lay your hands on a copy of EN60950 or EN60065, they will give
you some idea of what might be expected. Bear in mind that HT is effectively
mains and that the rules regarding mains cables and connectors will almost
certainly apply to equipment assembled now. I don't think that the rules
apply to older (older than 20 years or so) equipment. Put this query on
sci.electronics.design and you might get a reply from John Woodgate who
knows a lot more than me about these things.


Graham Holloway

west wrote:
Dear Rodents,
Are there safety issues regarding separate PS? I read somewhere ( maybe in
r.a.t.) that it may be difficult to sell tube equipment with HV in an
umbilical cord because of NEC rules. The only NEC book I have is very old.
How about other countries? I can not remember off hand brand names, but
hasn't there been a plethora of amps with separate PS sold in the US? I
recall way back warning some families with children about computer monitors.
This was before the safety features regarding minimal radiation emission
standards from Sweden took hold in the US. Some thought I was a Jeremiad
type. I suppose with a cheaply made home brew umbilical cord, after several
twists and kinks, the situation can become potentially hazardous. Perhaps
someone versed in this issue can write a proper way to design a safe
umbilical cord. Oh well, it's always something, ain't it? Thanks.
Cordially,
west


The NEC has nothing to say on the issue, as it is concerned with fixed
building wiring, not the internal wiring of "appliances and equipment".
The NEC essentially stops at the outlet the amp is plugged into.

As far as designing gear for sale, what you want are UL specifications,
not the NEC. But getting a copy of a UL spec will cost $$$, even before
the required testing to assure compliance.

FWIW, many older amateur radio RF power amplifiers used an external HV
power supply, which operated at voltages much higher than a typical
audio amp would. So do many neon signs. The problems of HV interconnects
are not insurmountable, but in today's world, lawyers tend to dictate
design as much as engineers do.


73,
Bob Weiss N2IXK

west wrote:

Dear Rodents,
Are there safety issues regarding separate PS? I read somewhere ( maybe in
r.a.t.) that it may be difficult to sell tube equipment with HV in an
umbilical cord because of NEC rules. The only NEC book I have is very old.
How about other countries? I can not remember off hand brand names, but
hasn't there been a plethora of amps with separate PS sold in the US? I
recall way back warning some families with children about computer monitors.
This was before the safety features regarding minimal radiation emission
standards from Sweden took hold in the US. Some thought I was a Jeremiad
type. I suppose with a cheaply made home brew umbilical cord, after several
twists and kinks, the situation can become potentially hazardous. Perhaps
someone versed in this issue can write a proper way to design a safe
umbilical cord. Oh well, it's always something, ain't it? Thanks.
Cordially,
west

The 300 watt amps of mine weigh 50Kg per channel.

The greatest risk in their use is that of an owner
gaining a case of backache when he moves them incorrectly.

The next risk is that of when they might fall from a bench.
Do I have to cover the risk of using these things on a bench?

The power amp is separtae from the PSU, and both weigh
25 Kg each.

I use two umbilical cords, both are mobile gantry crane flexible
cable with 5 individual cables with very tough insulation.
Current rating is 10 and 15 amps for each of five wires
in each, and should a PSU fall off a table and dangle over the edge
swinging from the amp, the cable won't damage,
and the specially reinforced octal sockets and plugs can pull awy
from the amp well before the wire deforms and stretches apart,
which would need a tonne+ of pull.


A very keen hound would attempt to chew through the cable,
but only until he got to the one which carries the +500V,
and then you'd see a dog leaving the room fast.

But such a cable could indeed become damaged, and thus expose
an owner to some voltage, but I believe the risk less than that
of using any other electrical equipments in a house such as an iron, toaster,
hair drier in a bathroom, and so far in Oz there has not been a court case where

an amp cable has killed anyone.
Plenty of other things have.

If somebody complies with all the known safety rules invented by
zealous governments on behalf of relatives of the perished,
then one is still liable if you have supplied the gear and it kills, maims,
or hurts someone who can afford better lawyers than you can.

Bob Sugden, a guy in Sydney used to make SE amps with 211
for awhile while that was the big flavour for SET amps.
He worried so much about what ppl and lawyers might do
he was careful to set his business in his own name, and make sure
his house and assets was in his wife's name.
For a young man, this is perilous, because a wife might want a divorce,
and a guy could loose his house.

We all stand to be ruined one way or another at some time in our lives.

Nobody is going to run after me if I supply *one* amp with
offending umbilical cords. But if I build a batch
of 1,000 I might indeed attract a lot of attention.
Obviously, if one uses a flimsy bundle of lampflex
cables to join two heavy electricals, then one asks for trouble.

One reason kit suppliers operated freely was because there
was no risk; if somebody gets a shock, then its the owners fault
because he assembled the parts after purchasing them.
But a smart lawyer might convince a jury
that a parts supplier supplied potentially dangerous goods to a
gullible innocent customer, and therefore be liable.
Anything that can be argued, is argued, but fortunately
some injustice of application of the law is
restrained by the record of precedents.

Patrick Turner.

"Bob Weiss" wrote in message
news:PPMce.4738$Ab.1270@trndny04...
west wrote:
Dear Rodents,
Are there safety issues regarding separate PS? I read somewhere ( maybe
in
r.a.t.) that it may be difficult to sell tube equipment with HV in an
umbilical cord because of NEC rules. The only NEC book I have is very
old.
How about other countries? I can not remember off hand brand names, but
hasn't there been a plethora of amps with separate PS sold in the US? I
recall way back warning some families with children about computer
monitors.
This was before the safety features regarding minimal radiation emission
standards from Sweden took hold in the US. Some thought I was a Jeremiad
type. I suppose with a cheaply made home brew umbilical cord, after
several
twists and kinks, the situation can become potentially hazardous.
Perhaps
someone versed in this issue can write a proper way to design a safe
umbilical cord. Oh well, it's always something, ain't it? Thanks.
Cordially,
west


The NEC has nothing to say on the issue, as it is concerned with fixed
building wiring, not the internal wiring of "appliances and equipment".
The NEC essentially stops at the outlet the amp is plugged into.

As far as designing gear for sale, what you want are UL specifications,
not the NEC. But getting a copy of a UL spec will cost $$$, even before
the required testing to assure compliance.

FWIW, many older amateur radio RF power amplifiers used an external HV
power supply, which operated at voltages much higher than a typical
audio amp would. So do many neon signs. The problems of HV interconnects
are not insurmountable, but in today's world, lawyers tend to dictate
design as much as engineers do.


73,
Bob Weiss N2IXK

Bob,
I think you are correct up to a point. The NEC addresses many issues
regarding, for instance, equipment and their minimum current leakage. There
is especially a good portion of the book devoted to hospital equipment. Even
the mechanical integrity of an ac plug, of course the receptacle too. Next
time you're in a hospital, look at all the equipment. You will see small
stickers verifying the passing of the periodical leakage test.
Cordially,
west

"west" wrote in message
. ..
Dear Rodents,
Are there safety issues regarding separate PS? I read somewhere ( maybe
in
r.a.t.) that it may be difficult to sell tube equipment with HV in an
umbilical cord because of NEC rules. The only NEC book I have is very old.
How about other countries? I can not remember off hand brand names, but
hasn't there been a plethora of amps with separate PS sold in the US? I
recall way back warning some families with children about computer
monitors.
This was before the safety features regarding minimal radiation emission
standards from Sweden took hold in the US. Some thought I was a Jeremiad
type. I suppose with a cheaply made home brew umbilical cord, after
several
twists and kinks, the situation can become potentially hazardous. Perhaps
someone versed in this issue can write a proper way to design a safe
umbilical cord. Oh well, it's always something, ain't it? Thanks.
Cordially,
west


It seems to be very difficult to get a firm answer
from any source. In addition there is the complication
that solutions used in professional application,
i.e on amps or equipment in studios or broadcasting,
are not acceptable in the domestic environment.

Connectors that have HV ratings for industrial use
are often rated at 70V AC/DC for domestic use.

In addition, trying to convince an insurance company
that an amplifier with a separate psu and 600VDC
on an umbilical cord is safe, is not an easy task.
This applies especially here in Scandinavia from
whence much safety legislation seems to
originate.

Like you, I would be very happy to see a post
in this NG from an authoritative source stating
chapter and verse.

To use an amplifier which does not have
specific acceptance on a domestic insurance
policy is total folly.

Cordially,

Iain