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!

"gareth" wrote in
:

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?

There's still a significant market for valve-based guitar amplifiers, so
somebody must be making the HT capacitors for them.


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

Don't forget to include a suitable voltage divider chain.

On Tue, 27 Jan 2015 14:49:49 +0000 (UTC), Custos Custodum
wrote:

"gareth" wrote in
:

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?

There's still a significant market for valve-based guitar amplifiers, so
somebody must be making the HT capacitors for them.


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

Don't forget to include a suitable voltage divider chain.
Whats wrong with a 450volt rated cap?

In rec.radio.amateur.homebrew Rambo wrote:
On Tue, 27 Jan 2015 14:49:49 +0000 (UTC), Custos Custodum
wrote:

"gareth" wrote in
:

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?

There's still a significant market for valve-based guitar amplifiers, so
somebody must be making the HT capacitors for them.


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

Don't forget to include a suitable voltage divider chain.
Whats wrong with a 450volt rated cap?

Nothing; he is starting out with the false premise that high voltage
capacitors are difficult to obtain, which they are not.



--
Jim Pennino

"Rambo" wrote in message
...
On Tue, 27 Jan 2015 14:49:49 +0000 (UTC), Custos Custodum
wrote:

"gareth" wrote in
:

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?

There's still a significant market for valve-based guitar amplifiers, so
somebody must be making the HT capacitors for them.


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

Don't forget to include a suitable voltage divider chain.
Whats wrong with a 450volt rated cap?

Are they readily available?

On 1/27/2015 12:41 PM, gareth wrote:
"Rambo" wrote in message
...
On Tue, 27 Jan 2015 14:49:49 +0000 (UTC), Custos Custodum
wrote:

"gareth" wrote in
:

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?

There's still a significant market for valve-based guitar amplifiers, so
somebody must be making the HT capacitors for them.


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

Don't forget to include a suitable voltage divider chain.
Whats wrong with a 450volt rated cap?

Are they readily available?

Yes. Did you even look for them?

--

Rick

On Tue, 27 Jan 2015 17:41:21 -0000, "gareth"
wrote:


Don't forget to include a suitable voltage divider chain.
Whats wrong with a 450volt rated cap?

Are they readily available?

How about:

http://uk.rs-online.com/web/p/alumin...itors/7441896/



http://uk.rs-online.com/web/generalD...ile=conditions
" All prices exclude VAT, which RS will add at the rate applicable at
the date of order despatch. RS reserves the right to change prices
without prior notice at any time."

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.