On Tue, 27 Jan 2015, gareth wrote:

The problems associated with replacing (or even obtaining) the HT reservoir
capacitors in valve projects might be replace with a series / parallel
arrangement of those dinky 100uF 35V SMD ones?

Probably could be rolled up and placed inside the original aluminium can,
too!

You didn't specify what voltage you need.

For "average" high voltage, there are all those line side capacitors in
switching supplies. I thought they were about 450volts, but it's been a
while since I checked. So one can extract from a scrap computer supply,
or likely buy those as replacement parts. If they aren't high enough
voltage, then they are a better start for combining than 35v ones.

I was actually surprised 20 years ago when I discovered ripple in my
Tektronix scope. I found which of the many supplies was the problem by
using the scope itself, touching each of the high voltage lines until I
found one where the ripple increased. The needed capacitor wsa much larger
than "average" value in the days of electrolytics, I figured it would be
hard to find. Yet I checked the bins at the local surplus store, and
easily found a replacement, high enough voltage, and some large value like
100uF (which is large for tube power supplies).

If you're talking about high voltage for power amplifiers, I thought a lot
of those oil-filled capacitors from the old days were still viable. They
were sealed and hence don't dry out. The relatively small capacitance
ones but which have ceramic insulators for the leads to come through. They
were useful fifty years ago, they are apparently still good now. All you
have to do is dig deep enough to find them under more recent items.

If this is for a receiver, run it at a lower voltage. I gather the
Collins 75S line of receivers used "relatively low" voltage on the plates,
not real low but low relative to what other companies put on the plates.
I remember an article in CQ by Fred Brown where he updated his HRO for
subminiature tubes, and he followed this line about lower plate voltage,
though I can't remember the benefits he mentioned.

Michael

Michael Black wrote:

On Tue, 27 Jan 2015, gareth wrote:

The problems associated with replacing (or even obtaining) the HT reservoir
capacitors in valve projects might be replace with a series / parallel
arrangement of those dinky 100uF 35V SMD ones?

Probably could be rolled up and placed inside the original aluminium can,
too!

You didn't specify what voltage you need.

For "average" high voltage, there are all those line side capacitors in
switching supplies. I thought they were about 450volts, but it's been a
while since I checked. So one can extract from a scrap computer supply,
or likely buy those as replacement parts. If they aren't high enough
voltage, then they are a better start for combining than 35v ones.

I was actually surprised 20 years ago when I discovered ripple in my
Tektronix scope. I found which of the many supplies was the problem by
using the scope itself, touching each of the high voltage lines until I
found one where the ripple increased. The needed capacitor wsa much larger
than "average" value in the days of electrolytics, I figured it would be
hard to find. Yet I checked the bins at the local surplus store, and
easily found a replacement, high enough voltage, and some large value like
100uF (which is large for tube power supplies).

If you're talking about high voltage for power amplifiers, I thought a lot
of those oil-filled capacitors from the old days were still viable. They
were sealed and hence don't dry out. The relatively small capacitance
ones but which have ceramic insulators for the leads to come through. They
were useful fifty years ago, they are apparently still good now. All you
have to do is dig deep enough to find them under more recent items.

The oils in these old capacitors are often PCBs (polychlorinated
bi-phenyls) which are quite toxic. And they can leak slightly even if
not visibly. So I wouldn't have them in a house occupied by any non-old
non-amateurs. (A bit late for me to take up H & S on my own behalf.)





If this is for a receiver, run it at a lower voltage. I gather the
Collins 75S line of receivers used "relatively low" voltage on the plates,
not real low but low relative to what other companies put on the plates.
I remember an article in CQ by Fred Brown where he updated his HRO for
subminiature tubes, and he followed this line about lower plate voltage,
though I can't remember the benefits he mentioned.

Michael


--
Roger Hayter

"Roger Hayter" wrote in message
...
The oils in these old capacitors are often PCBs (polychlorinated
bi-phenyls) which are quite toxic. And they can leak slightly even if
not visibly. So I wouldn't have them in a house occupied by any non-old
non-amateurs. (A bit late for me to take up H & S on my own behalf.)


The PCB is not really that toxic. The problem is that it almost does not
break down and gets into the food chain. You can touch it and even get a
small ammount in your mouth without any harm to you. I don't mean drink it,
but say you get some on your hand and lick a drop or two off your finger.

On 1/27/2015 7:59 PM, Ralph Mowery wrote:
"Roger Hayter" wrote in message
...
The oils in these old capacitors are often PCBs (polychlorinated
bi-phenyls) which are quite toxic. And they can leak slightly even if
not visibly. So I wouldn't have them in a house occupied by any non-old
non-amateurs. (A bit late for me to take up H & S on my own behalf.)


The PCB is not really that toxic. The problem is that it almost does not
break down and gets into the food chain. You can touch it and even get a
small ammount in your mouth without any harm to you. I don't mean drink it,
but say you get some on your hand and lick a drop or two off your finger.

Wow! What is your basis for saying that? Are you trying to say if it
doesn't kill you outright there is no danger?

--

Rick

On 1/27/2015 9:47 PM, rickman wrote:
On 1/27/2015 7:59 PM, Ralph Mowery wrote:
"Roger Hayter" wrote in message
...
The oils in these old capacitors are often PCBs (polychlorinated
bi-phenyls) which are quite toxic. And they can leak slightly even if
not visibly. So I wouldn't have them in a house occupied by any non-old
non-amateurs. (A bit late for me to take up H & S on my own behalf.)


The PCB is not really that toxic. The problem is that it almost does not
break down and gets into the food chain. You can touch it and even get a
small ammount in your mouth without any harm to you. I don't mean
drink it,
but say you get some on your hand and lick a drop or two off your finger.

Wow! What is your basis for saying that? Are you trying to say if it
doesn't kill you outright there is no danger?


He's right - it isn't really that toxic. It takes multiple exposures
over a long time to do any harm; getting some on your hands won't hurt
you. And even when it does harm you, it's not fatal. But it does cause
nervous system disorders.

There are a lot of things much more toxic you can easily find, even at
the grocery store. Drain cleaner comes to mind...

--
==================
Remove the "x" from my email address
Jerry Stuckle

==================

On 1/27/2015 10:37 PM, Jerry Stuckle wrote:
On 1/27/2015 9:47 PM, rickman wrote:
On 1/27/2015 7:59 PM, Ralph Mowery wrote:
"Roger Hayter" wrote in message
...
The oils in these old capacitors are often PCBs (polychlorinated
bi-phenyls) which are quite toxic. And they can leak slightly even if
not visibly. So I wouldn't have them in a house occupied by any non-old
non-amateurs. (A bit late for me to take up H & S on my own behalf.)


The PCB is not really that toxic. The problem is that it almost does not
break down and gets into the food chain. You can touch it and even get a
small ammount in your mouth without any harm to you. I don't mean
drink it,
but say you get some on your hand and lick a drop or two off your finger.

Wow! What is your basis for saying that? Are you trying to say if it
doesn't kill you outright there is no danger?


He's right - it isn't really that toxic. It takes multiple exposures
over a long time to do any harm; getting some on your hands won't hurt
you. And even when it does harm you, it's not fatal. But it does cause
nervous system disorders.

There are a lot of things much more toxic you can easily find, even at
the grocery store. Drain cleaner comes to mind...

I asked what the source of this "fact" is. PCBs cause cancer. I have
never heard exposure to a carcinogen is safe as long as it is only for a
"short time" or "just once". Scientists have tried to establish
exposure thresholds, but this is speculation. The issue is how much
risk are you willing to accept rather than there being a threshold of harm.

Just in the last few years I learned that we have so extensively
polluted our environment that it is not recommended to eat the fish from
nearly any river in the several US states where I live. This pollution
is largely in the form of PCBs. It is not from point sources that can
be cleaned up. It is widespread from small sources. Essentially, we
integrated this stuff into our lives to the extent that we are regularly
bathed in it.

It seems people believe our persistent destruction of the environment is
something that happens somewhere else or the harm is overblown or that
it is something that we will have to deal with in the future. But this
is not true. The future is here and we are all living in the results of
our own ignorance.

BTW, unlike carcinogens, I can eat drain cleaner every day in adequately
small amounts. NaOH, Sodium Hydroxide. I have sodium in my diet as an
essential nutrient and hydroxide exists in all water solutions. NaOH is
not actually a poison, it is a corrosive. If you come into contact with
it in high concentrations it is harmful. In low concentrations it is
harmless in the true sense. I know this for a fact. Without harm, I
have handled NaOH in concentrations high enough that I can feel the
soapiness. So your analogy is poor.

--

Rick

On 1/27/2015 11:18 PM, rickman wrote:
On 1/27/2015 10:37 PM, Jerry Stuckle wrote:
On 1/27/2015 9:47 PM, rickman wrote:
On 1/27/2015 7:59 PM, Ralph Mowery wrote:
"Roger Hayter" wrote in message
...
The oils in these old capacitors are often PCBs (polychlorinated
bi-phenyls) which are quite toxic. And they can leak slightly
even if
not visibly. So I wouldn't have them in a house occupied by any
non-old
non-amateurs. (A bit late for me to take up H & S on my own behalf.)


The PCB is not really that toxic. The problem is that it almost
does not
break down and gets into the food chain. You can touch it and even
get a
small ammount in your mouth without any harm to you. I don't mean
drink it,
but say you get some on your hand and lick a drop or two off your
finger.

Wow! What is your basis for saying that? Are you trying to say if it
doesn't kill you outright there is no danger?


He's right - it isn't really that toxic. It takes multiple exposures
over a long time to do any harm; getting some on your hands won't hurt
you. And even when it does harm you, it's not fatal. But it does cause
nervous system disorders.

There are a lot of things much more toxic you can easily find, even at
the grocery store. Drain cleaner comes to mind...

I asked what the source of this "fact" is. PCBs cause cancer. I have
never heard exposure to a carcinogen is safe as long as it is only for a
"short time" or "just once". Scientists have tried to establish
exposure thresholds, but this is speculation. The issue is how much
risk are you willing to accept rather than there being a threshold of harm.


Exactly. There are no thresholds because scientists cannot determine
how much is required to cause a problem. Unlike drain cleaner, for
instance.

And there are a lot of things which cause cancer. Even artificial sugar
has been blamed for causing cancer. So are you going to stop using
anything containing artificial sugar?

Just in the last few years I learned that we have so extensively
polluted our environment that it is not recommended to eat the fish from
nearly any river in the several US states where I live. This pollution
is largely in the form of PCBs. It is not from point sources that can
be cleaned up. It is widespread from small sources. Essentially, we
integrated this stuff into our lives to the extent that we are regularly
bathed in it.


More scare tactics. Pollution from medications (especially hormones)
being flushed down the drain is a much bigger problem. So I guess we
should stop taking any medications.

It seems people believe our persistent destruction of the environment is
something that happens somewhere else or the harm is overblown or that
it is something that we will have to deal with in the future. But this
is not true. The future is here and we are all living in the results of
our own ignorance.


Which still has nothing to do with PCBs - except for scare tactics.


BTW, unlike carcinogens, I can eat drain cleaner every day in adequately
small amounts. NaOH, Sodium Hydroxide. I have sodium in my diet as an
essential nutrient and hydroxide exists in all water solutions. NaOH is
not actually a poison, it is a corrosive. If you come into contact with
it in high concentrations it is harmful. In low concentrations it is
harmless in the true sense. I know this for a fact. Without harm, I
have handled NaOH in concentrations high enough that I can feel the
soapiness. So your analogy is poor.


No, you have sodium chloride (NaCl) in your diet, not NaOH. And even
small amounts of NaOH have been shown to be harmful - it is considered a
poison.

--
==================
Remove the "x" from my email address
Jerry Stuckle

==================

"rickman" wrote in message
...

The PCB is not really that toxic. The problem is that it almost does not
break down and gets into the food chain. You can touch it and even get a
small ammount in your mouth without any harm to you. I don't mean drink
it,
but say you get some on your hand and lick a drop or two off your finger.

Wow! What is your basis for saying that? Are you trying to say if it
doesn't kill you outright there is no danger?

PCB is often talked about like a few drops will kill you. Many things
around the house are much more toxic. Look at all the dangers listed on the
drugs they advertise on the TV.
While we don't want the PCP oil to get into the food chain, some tree
huggers just jumped on that and tried to make it sound like it would kill
you or cause brain damage or some such junk as that. While it will do that,
it takes more than a few drops and not many people are going to just drink a
glass of it.

"Ralph Mowery" wrote in message
...
"rickman" wrote in message
...

The PCB is not really that toxic. The problem is that it almost does
not
break down and gets into the food chain. You can touch it and even get
a
small ammount in your mouth without any harm to you. I don't mean drink
it, but say you get some on your hand and lick a drop or two off your
finger.

Wow! What is your basis for saying that? Are you trying to say if it
doesn't kill you outright there is no danger?

PCB is often talked about like a few drops will kill you. Many things
around the house are much more toxic. Look at all the dangers listed on
the drugs they advertise on the TV.
While we don't want the PCP oil to get into the food chain, some tree
huggers just jumped on that and tried to make it sound like it would kill
you or cause brain damage or some such junk as that. While it will do
that, it takes more than a few drops and not many people are going to just
drink a glass of it.

I'll stick to beer, thanks.
--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk

Ralph Mowery wrote:

"rickman" wrote in message
...

The PCB is not really that toxic. The problem is that it almost does not
break down and gets into the food chain. You can touch it and even get a
small ammount in your mouth without any harm to you. I don't mean drink
it,
but say you get some on your hand and lick a drop or two off your finger.

Wow! What is your basis for saying that? Are you trying to say if it
doesn't kill you outright there is no danger?

PCB is often talked about like a few drops will kill you. Many things
around the house are much more toxic. Look at all the dangers listed on the
drugs they advertise on the TV.
While we don't want the PCP oil to get into the food chain, some tree
huggers just jumped on that and tried to make it sound like it would kill
you or cause brain damage or some such junk as that. While it will do that,
it takes more than a few drops and not many people are going to just drink a
glass of it.

Yes. It is not very poisonous, but it adds long term to the burden of
toxins the body has to deal with. If you have children or
grandchildren in the house you might want to avoid even a 1% increase in
the chance of them getting cancer or neurological damage in 50 years
time just so you can use a 70 year old capacitor. Or you might decide
it is a negligible risk. At a population level, it is probably sensible
to try to keep PCBs out of the environment. A hundred little things may
add up to a significant improvement in health in the next century. Why
not do them if the cost is not too great now?

--
Roger Hayter