Bob wrote:

As I've said before, get a little desk fan (see attached photo).
Position it behind the counter, blowing straight into the heatsink from
2-3 inches away.  The ones I have are all sturdy metal, with blades 5 or
6 inches in diameter.  They spin much slower than muffin-type fans, so
they are very quiet.  (Even if you have replaced the internal fan with a
much quieter one, you will still not hear the external fan.)

I've done this with all of my 5370Bs, and the heatsinks run barely warm
to the touch.  What an improvement!

I paid about $12 each at the local hardware store, but there is probably
a wide range of asking prices.

Best regards,

Charles

You could try hooking up a transformer with a 20V secondary as an
autotransformer to reduce the line voltage.

On Fri, Dec 30, 2016, 9:09 PM Bob Stewart bob@evoria.net wrote:

On 31 Dec 2016 02:03, "Bob Stewart" bob@evoria.net wrote:

stuff than I am!  They run very hot.  It's a good idea to get a GPIB
extender so your GPIB cable can clear the heat sink.  Somebody, can't
remember who, worked up a nice looking conversion to a pair of switching
supplies.

SMPSs tend to be less clean than a linear supply. I would be somewhat
reluctant to take that route on test equipment. But I will search for the
conversion.

I have a 13 A variac sitting around that's not been used in the last 25
years. I think as a short term measure I will drop the voltage to a few
bits of the equipment with linear power supplies. The spectrum analyzer has
linear supplies and puts out a lot of heat.  As someone else said,  a 20 V
transformer would work. Adding the variac will take me 5 minutes to do,
which has an advantage over anything I need to build.

I will also log the mains voltage over a period of a few weeks and see if
it high enough to ask the electricity supply company to do something about
it.  I do know someone that measured his voltage and found it was outside
the legal limits. He advised the electricity supplier,  they agreed,  but
said that they were not going to do anything about it.  He wired his whole
house on an auto transformer.  I would be speaking to my Membrr of
Parliament (MP) if it was outside the legal limits. I don't know what legal
limits exist in the UK for voltage,  but I can find out.

It is unusual in the UK for a domestic property to have a phase supply, but
mine does.  I don't know whether any one phase is consistently lower than
any other. If so phases could be switched.  But given my close promptly to
the 11 kV transformer,  I doubt it.

I know at one point I had a dispute with the electricity supply company as
the 415 V overhead power lines used to be regularly hit by farm vehicles
down a private road where my property is. This would pull the cables away
from my house and make a mess of the house. The electricity supplier would
always repair the damage,  but after this happened a few times I
complained. I was initially told they would do nothing as it is not a road.
But I discovered that the cables needed to be a minimum height if there was
vehicular access. So whether the electricity supplier considered it a road
or not was irrelevant.  Eventually they extended a pole and raised the
cables up, which appears to have solved the problem.  Whether I can
convince them to move the transformer taps is another matter.  I suspect
that it might be hard if my supply is consistently high, but not outside
the legal limits.

Dave

Hi,

I'm not totally sure about the limits, but I have read several times
that in the UK the nominal supply voltage is 230 V +10%/−6% to
accommodate the fact that most supplies are in fact still 240 V. The
context was that a lot of test equipment failed when operated at around
250 V and many input capacitors (particularly the ones inside a know
brand IEC socket - filter) caught fire.

Wikipedia says that several areas in UK still have 250 V because this
value is withing the current limits.

I think that the governing document is British Standard BS 7697: Nominal
voltages for low voltage public electricity supply systems —
(Implementation of HD 472 S1).

Regards,

Ignacio, EB4APL

El 31/12/2016 a las 11:25, Dr. David Kirkby (Kirkby Microwave Ltd) escribió:

On 31 December 2016 at 13:03, EB4APL eb4apl@gmail.com wrote:

Hi,
I have just been on to the phone of a friend of mine who spent much of his
like working in the electricity generating industry. Working at both
Darlington (coal) and Bradwell (nuclear) power stations in the UK. Among
many other things he said

• He did not know the current specifications limits for certain, but he
  said easy to check. (What you say - 230 -6%/+10% does seem to be quoted in
  many places, but I guess I should check it out.)
• Supply voltage is likely to be highest about at 2-3 am in Summer
• Supply voltage is likely to be lowest on a cold Winter's afternoon.
• Voltages in use around the county include at the least 11, 22, 33, 66,
  132, 275 and 400 kV.
• There's not much standardization of generator voltage - Bradwell nuclear
  power station was 11.1 kV.
• There are taps on the 275 kV transformers to keep the 132 kV close to 132
  kV
• There are 6 taps on the 11 kV transformers feeding my house to adjust the
  voltage. Those can only be adjusted with the 11 kV off - they can't be done
  with it online. Essentially this means to change the taps, an area would
  need to be powered off.
• If voltage is out of spec, it should be possible to get something done
  about it.
• The electricity board can install monitor equipment.
• Since I am right by the 11 kV transformer, and other places further away,
  dropping the voltage at my place might put other places too low.

I think short-term I will put the auto transformer in line. I will monitor
the mains, and report it in the summer, when I'm told it is likely to go
higher.

It hit 250.04 V in the last hour or so, but I have not seen the magic
figure of 253 V.

I'll get my 3457A calibrated by Keysight, then look to measure this and if
appropriate make a formal request to have the voltage checked, and
hopefully the problems would occur during the time it was monitored.

Dave

----- Original Message -----
From: "Dr. David Kirkby (Kirkby Microwave Ltd)"
drkirkby@kirkbymicrowave.co.uk
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Saturday, December 31, 2016 11:01 AM
Subject: Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob
for the 5370B TI counter?

There are some devices that benefit from the higher voltage. Motors usually
run cooler and last longer due to the lower I2R losses.
Maybe just use a buck transformer in your lab for the (older) test
equipment.

David,

You're a volt-nut too, aren't you ?
Maybe motorise the variac and keep your lab at 240V +/- almost-nothing ?

On Sat, Dec 31, 2016 at 7:57 PM, Tom Miller tmiller11147@verizon.net
wrote: