How did you come up with the 33,000 uF number, Perry, and is it one big
capacitor or lots of little ones tied together? The big cap will also
filter out some of the remaining ripple in the power supply that may
have been managed by the ni-cad battery.

Jeremy

On 9/17/2016 3:50 PM, Perry Sandeen via time-nuts wrote:

That NiCad pack is part of the power supply and as Jeremy points out is part of the filter system.    And so one needs to restore it as part of the instrument as even the 28V external power supply floats these cells and trips power interruption indicator if lost

Power supply is not terribly hard to fix and the small signal transistors can be replaced with  2N 2222,3904 and 3906'es depending on rating.  You don't even need a extender a Huntron tracker or similar current limited lissajous bridge will identify failed or leaky caps and semiconductors

Remember HP did nothing without a good engineering reason and that plate is there for RF shielding to prevent stray sources coupling with the outputs

If a proper rebuild is too expensive I'd suggest selling it on the well known auction site rather than hacking it up as 105's have been selling in the hundreds regardless of condition

As an experiment, I bought an AIMS sine-wave inverter for the 105B
Quartz Oscillator. The inverter has a built-in transfer switch that is
supposed to allow the load to operate from the AC line and automatically
switch to battery/inverter should the AC power line fail.

In fact the thing seems to work—the output is a nice 118 VAC sine wave
measuring 60.189 ± 0.003 Hz and the transfer switch is fast enough that
the 105B doesn't seem to notice the change. The "AC Interruption" light
doesn't light and I don't see a flicker of the 5 MHz output on my scope.

Just for the fun of it, I connected a filament transformer and ran the
low voltage into my distortion analyzer. The result was about 5%
distortion for the inverter and 1.5% for the AC line. This got me to
wondering, we've discussed the AC power line frequency at length but not
other "qualities" of that "signal.' I was surprised that the AC line had
so much distortion but it's a subject I've never considered. Has anyone
in this group looked at this? [Yes, this is perilously close to not
being appropriate Time-Nuts discussion matter—sorry!]

Jeremy

Regards,
Jeremy

On 9/18/2016 4:33 AM, Scott McGrath wrote:

Yes,
I did intensive measurements of power line quality. If the voltage THD of your AC line is only 1.5%, then your area is supplied by veeeery good quality energy.
Mine exceeds 10% :(.
Not only the THD as number is important, for certain applications the shape is important, too [how you got to that average THD]. If you live at the end of distribution line[s] the max of the "sine" voltage is delayed few ms from the middle of zero crossings.
For sensitive [AC] measurements I use a dual loop inverter experiencing 2% THD [mainly due to quantisation errors].

But I believe the THD is of no importance for DC supplied things as the AC is rectified and stabilised. In that particular case, I would not bother about the AC energy quality at all.
Best,
Adrian

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Jeremy Nichols
Sent: Tuesday, October 4, 2016 3:52 AM
To: time-nuts@febo.com
Subject: [time-nuts] AC line distortion [Was: HP 105B Battery, the saga continues]

As an experiment, I bought an AIMS sine-wave inverter for the 105B Quartz Oscillator. The inverter has a built-in transfer switch that is supposed to allow the load to operate from the AC line and automatically switch to battery/inverter should the AC power line fail.

In fact the thing seems to work—the output is a nice 118 VAC sine wave measuring 60.189 ± 0.003 Hz and the transfer switch is fast enough that the 105B doesn't seem to notice the change. The "AC Interruption" light doesn't light and I don't see a flicker of the 5 MHz output on my scope.

Just for the fun of it, I connected a filament transformer and ran the low voltage into my distortion analyzer. The result was about 5% distortion for the inverter and 1.5% for the AC line. This got me to wondering, we've discussed the AC power line frequency at length but not other "qualities" of that "signal.' I was surprised that the AC line had so much distortion but it's a subject I've never considered. Has anyone in this group looked at this? [Yes, this is perilously close to not being appropriate Time-Nuts discussion matter—sorry!]

Jeremy

Regards,
Jeremy

On 9/18/2016 4:33 AM, Scott McGrath wrote:

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Jeremy wrote:

The attached image shows the AC mains at my location (orange trace), and
the distortion residual from a THD analyzer (cyan trace).  I think the
distortion was significantly higher than 1.5%, but I don't have the
specific figure handy.  Viewing the mains voltage on a spectrum
analyzer, the harmonics up through and beyond the 20th are all above -50dBc.

Best regards,

Charles

Hi

A lot of the distortion on the AC line is locally produced. Consider a very normal
bridge rectifier running into a capacitor. It draws “all” the current in narrow spikes
near the peaks of the sine wave. A half wave rectifier would be even worse (only
one spike per cycle). That highly non-linear load will work against the impedance
of the distribution system to distort the AC voltage.

It’s hardly a “electronics only” sort of problem. If you attach a motor to the line, it
likely is driving something. If that something is imbalanced (think of a fan) or has
a cycle (think of a compressor), that non-linear power demand reflects back on the
AC line.

Needless to say none of this makes the power company very happy. They would
much prefer to drive nice zero phase angle linear loads ….. Their generators are
essentially giant sine wave generators. Load mismatch wears them out quicker
than a “proper” load.

Bob

Considering some signal generators will have 1% (-40dBc) distortion with a
5k - 10k price tag, your 1% is not to bad.

On Mon, Oct 3, 2016 at 8:52 PM, Jeremy Nichols jn6wfo@gmail.com wrote:

Thank you all for the inputs. In the present case, the location is my home
about an hour north of San Francisco, California. We are in a rural
location with other homes and some small businesses (legal or otherwise).
There could be many things hung on the 60 Hz power lines adding noise to
the "signal;" whether a "city" location would be better or worse is a
question I've never asked.

To understand the situation a little better, I put my HP-5489A Low Pass
Filter on the inverter's AC output, again through the filament transformer,
and watched the oscilloscope while I dialed down the frequency response. A
filter setting of 300 Hz was enough to visually clean up the noise while
not affecting the amplitude of the 'fundamental.' I was pleased that the
noise was manageable with such a simple tool.

Continuing, I tried a Corcom 10SP1 AC line filter from my junk box. This is
a fairly large filter, weighing about one kilo. I haven't been able to find
any specs on this thing, which is somewhere between 20 and 50 years old. It
has stamped on it a code "8003," which might mean the 3rd week/month of
1980, or it might not. Anyway, the line filter took care of the noise,
reducing both the AC power line and inverter output distortion to 0.35%,
better than I expected.

With the fundamental filtered out by the distortion analyzer, the remaining
noise consists of a rather dirty-looking 180 Hz sine wave, obviously a
harmonic of the 60 Hz fundamental, source unknown. Much of the local
electric energy comes from "The Geysers," an area of thermal springs and
steam at the north end of our county (Sonoma). The steam drives turbines
(of course), which spin generators. Since electricity is 'fungible' and (as
the old joke goes) "few people examine their electricity closely," the
noise could be coming from anywhere. A local source is most likely, as
others have already suggested.

Jeremy

On Tue, Oct 4, 2016 at 6:26 AM, Scott Stobbe scott.j.stobbe@gmail.com
wrote: