HP Clock

Friday, August 12, 2011

More Utah Teapot

Until recently I had access to a copy of Maya, but unfortunately it had expired.  I occasionally like to make 3D models of objects, and until now have been using old versions of CAD programs.  With my access to Maya gone I decided to try the open source 3D program Blender.  I had looked at it in the past, and found the interface difficult to use.  Additionally the program was very buggy and crashed a lot.

That has all changed with this newer version.  Version 2.58.1 is awesome and very easy to use.  3D programs in general are very deep and difficult to learn, but with the help of the on line tutorial videos I was able to get results very quickly.  It was very easy to build a table and room with lighting for my Utah Teapot.

In this view you can see the camera, lights and room I created in Blender

I can highly recommend Blender as a free and easy way for anyone to experiment in 3D modeling.

Thursday, August 4, 2011

Who remembers the Utah Teapot?

I was lucky enough to be in Mountain View with enough time to burn to see the Computer History Museum.  It was wonderful, containing everything from an IMP from the earliest days of the DARPA Internet to large portions of ENIAC.  One of the unexpected treats was the original Utah Teapot used by Martin Newell to create one of the most iconic 3D models that is used by just about anybody who even has a passing interest in 3D modeling.

The first time I tried rendering it in the late 90s was using Autocad R14.  When I went back to look at the rendering I noticed that the model I was using was missing the lid.  Also, not a great job of rendering...

After seeing the original I was inspired to create and place a Utah Teapot on my desk.  Rendering the teapot is much easier now than it has ever been.  This image was created with a Wave Front object found on the web, a picture of my desk, and Photoshop CS4.

After doing a little reading it’s no surprise to me that the teapot makes a few cameo appearances.  Most notably in the Pixar movie ‘Toy Story’, and in the NT release of the ‘Pipes’ screen saver.  Here are a couple of great reads telling the story of the Utah Teapot.

Sunday, July 24, 2011

8656 Up and Running

I finished up repairs on the signal generator this weekend and did a brief performance check.  I was unable to easily find an axial equivalent for the shorted filter cap so I came up with this arrangement for mounting a nice radial style with screw terminals.  I also ordered the R712 diode pack in a TO-3 package, but until they arrive I’m using an NTE diode pack in a TO-220 package.

After confirming that everything was running nice and cool and at the correct voltages I let the generator burn in for a day before looking at the ovenized 10 MHz crystal time base.

After 24 hours I took my 10 MHz rubidium frequency source and compared then trimmed the 8656A oscillator to match.  The rubidium source is mounted in an old hard drive enclosure.  I added a meter and leds to indicate the status and when the rubidium cell is locked.  To keep the operating conditions as true as possible I set the fan back in place after each adjustment.  I waited an hour in between each adjustment.

Letting it sit for a few more hours I checked in with my HP 8566.  This generator looks to be very accurate in both frequency and amplitude accuracy.

Tuesday, July 19, 2011

HP 8656A Progress

I’ve started to clean up and identify the parts that are bad or damaged.  Not only was the Molex J5 on the A10 board melted, but also the far end connector J2 on the A14 board in a compartment in the back of the generator.  I was lucky that the ground return wire did not damage adjacent wires in the bundle.  Here is a simplified schematic of the unregulated portion of the +5 volt logic supply detailing the parts that were damaged.

Here is the HP 8656A pulled apart so that the molex connectors and ground wire can be replaced.

This picture shows one of the Molex shells after repair.  Note that Pin one had to be replaced with a non-HP pin.

New ground return wire is back in place and the wire harness is all bundled back together.

Monday, July 18, 2011

Who let the smoke out?

All the smoke was let out of an HP 8656A RF generator, and I’m currently in the process of trying to get it back into the box.  This picture is of J5 on the A10 power supply board where the most significant damage is.

This next photo is the underside of the A10 board near the J5 connector.  It’s interesting to note that at the topside Pin 1 (GND) had the melted wire while on the bottom of the board Pin 2 (+5V) has the crispy trace.

Wednesday, July 13, 2011

Why do we have 29.97 frame rates, and not just 30??

I get this question quite often, so I thought I would provide the best answer I could including some historical perspective.

The short answer is that it is due to making a less expensive and more reliable sound recovery circuit in black and white televisions in the 50s.
Here’s why.  Radios typically recover information by the nonlinear mixing of the radio frequency energy from the transmitter with that of a local oscillator.  The combination of the two signals will produce sum and difference frequencies, also known as high side and low side conversion.  The output of that mixer is applied to an IF amplifier that has a tuned bandpass for a single frequency. (IF = Intermediate Frequency).  Tuning in the radio is accomplished by changing the frequency of the local oscillator such that the combination of local oscillator plus the transmitting station or local oscillator minus the transmitting station matches the tuned response of the IF amplifier.  That way depending on the frequency of the local oscillator, only a single frequency or station can pass though the key-hole that is the IF filter and amplifier.
As specified in the early 40s, the NTSC originally had a frame rate of 30 and a line rate of 15,750.  Also early in the specification of television it was decided that the picture would be amplitude modulated on one carrier and the sound would be frequency modulated on a second higher frequency carrier separated enough to prevent the two signals from interfering with each other.  What this means is that a television essentially needed two radio receivers comprised of two mixers, two local oscillators, two IF amplifiers, and two detectors. One set of circuits for picture, and one set for sound.  The difficulty in this scheme is getting the two local oscillators to change frequency exactly the right amount every time the user changed channels.  This is further exacerbated by the inherent lack of stability of oscillators at these high frequencies.  There were no inexpensive phased lock loops and digital synthesizers in the 50s.  To eliminate the difficulty and expense of building two oscillators that would track each other and not drift apart it was decided that the tolerance of frequency separation could be held more precisely at a single location, the TV transmitter.  It was further decided to separate the visual and audio signals by exactly 4.5 MHz.  This allowed set manufacturers to design TV sets with inter-carrier sound detection, or a carrier within a carrier.  The system worked by using a single local oscillator, mixer and IF amplifier to detect the entire audio/video signal.  This means that the ‘baseband video’ at the output of the detector contained the audio at 4.5 MHz as well as the picture.  The detected signal was split with one side going to a 4.5 MHz tuned circuit called the ‘sound trap’ to remove the sound carrier from the picture. The other side went directly to a 4.5 MHz IF amplifier where it could be amplified to a usable level, no secondary local oscillator needed.  The output of this second IF amplifier could now be fed to an FM discriminator to extract the audio.
With the advent of color a third carrier needed to be added to the scheme.  This third carrier literally needed to be shoe-horned in between the visual signal and the audio signal.  If the frequency of the color carrier were to high it would interfere with the 4.5 MHz sound carrier.  If the frequency of the color carrier were to low artifacts would be seen in the picture.  Add to this that the color information added to the video signal could not obsolete the installed base of black and white televisions.  The decision was made to place the color carrier below the sound carrier and inband of the picture carrier.  This is illustrated in figure 1 below.

Fig. 1 Relationship between the luminance signal, sound signal and the color subcarrier.
  • fs = Frequency of sound carrier
  • fc = Frequency of chrominance or color carrier
  • fh = Frequency of horizontal line rate

Since the frequency of the sound carrier could not change without making the legacy black and white TVs obsolete 4.5 MHz was made to be the 286th harmonic of the horizontal line rate.
286 = fs /fh
Using this equation the horizontal rate will be equal to the sound carrier divided by 286.  286 is the closest even number harmonic that will provide a ratio close to the original line rate of 15,750 KHz.
fh = fs/286
The color sub carrier frequency will need to be in the range of approximately 3.6 Mhz and an odd harmonic of the half horizontal line rate.  An odd harmonic that is half of the line frequency is desirable because the color subcarrier is ‘inband’ of the luminance signal, and because an odd harmonic half line rate will have opposite voltage polarities for the picture information on odd and even lines.  This method of reducing the interference of the color and luminance signal is known as frequency interlace.  The odd harmonic of the half line frequency closest to the original line rate of 15, 750 KHz would be 457/2.  However 457 is a prime number, making it difficult to derive other frequencies such as the horizontal and vertical rate.  The next best choice and the harmonic that was ultimately chosen was 455/2.  455 has the prime factors of 5, 7 and 13 making it easier to create frequency divider chains.
fc = (455/2)* fh
Again, the equation can be solved for the horizontal rate, but this time as it relates to the color carrier, and the selected harmonic of that carrier.
fh = 2*fc /455
Setting the two equations for the horizontal frequency equal to each other, one in terms of the sound carrier and the other in terms of the color carrier, the yet unknown horizontal rate drops out. Now the color carrier can be solved for and calculated exclusively in terms of the selected harmonics and the implacable 4.5 MHz sound carrier.
2*fc /455 = fs/286 = 4.5 MHz/286
fc = (455*4.5 MHz)/(2*286) = 3,579,545.4546 Hz
The Horizontal line rate can now be calculated based on the calculated color rate.
fh = 2*fc /455 = 15,734.2657 Hz
Dividing this new line rate into the original line rate gives the ratio of frequency reduction from the original black and white system to the NTSC color standard.
15,750 Hz/15,734.2657 Hz = 1.001
Ratio of Frequency Change = 1.001 : 1
Dividing the 1.001 frequency reduction coefficient into the original black and white 30 frames per second gives the color frame rate we are now familiar with.
30 fps/1.001 = 29.97
Donald G. Fink, Editor, Television Standards and Practice – NTSC, First Edition, New York, McGraw-Hill Book Company., 1943. (Appendix I)

Donald G. Fink, Editor, Television Engineering Handbook, First Edition, New York, McGraw-Hill Book Company., 1957. (Pg. 7-3 to Pg. 7-4, sec 7.103 Timing Relationships)

Bernard Grob, Basic Television, Principles and Servicing, New York, McGraw-Hill Book Company., 1964. (Pg. 523-524, sec 22.16 Intercarrier sound), (Pg. 580-582, sec 24.15 Color subcarrier frequency)

Howard W. Sams & Co., Reference Data For Radio Engineers, Sixth Edition, New York, McGraw-Hill Book Company., 1977.  (Pg. 30-31 Transmission Standards)

Friday, April 22, 2011

Tuning Duplexers in the Geek Lab

One of the duplexers that had been pronounced as 'misbehaving' from the mountain top repeater was pulled down and delivered to the lab.  The first order of business was to take a look at it using the VNA (Vector Network Analyzer).

Initial findings for the duplexer were not great as can be seen in the response plot.  The bugs on the plot represent the receive and transmit frequencies for the repeater.

Tuning each section individually and then reconnecting them to view an over all plot produced a somewhat better response.  This particular duplexer includes a notch capacitor with each cavity. The bug for the receive frequency on the left is off by 200 Khz.  I'll let you know how the duplexer works when it is reinstalled back on the mountain.

Monday, April 4, 2011

First Shop Science Project

My friend Jake cam over with his Dad on Sunday and we worked together to make a steam turbine as a science project.  Jake's design was based on a published design in the May 1960 issue of Mechanix Illustrated.  The original article can be found on Scribd at this link:

After testing on the kitchen stove and making a few small adjustments the turbine worked very well.  Here is a picture of Jake's turbine showing the various parts.

Here is a picture of the young inventor with his completed turbine after testing.

Internet in the Shop

During construction I included a length of fiber optic cable that could be used to interconnect Cisco Catalyst 2900 switches that I picked up for $20 apiece at a swap meet.  In this picture you can see where the fiber optic cable terminates next to the shop electrical sub panel.  The hooks inside the electrical box used to coil the excess fiber optic cable and prevent it from bending and breaking the glass filament were made from a cheap plastic hooks designed to hang from the top of a door.

Sunday, March 27, 2011

Artifacts found in the shop.

Much of the material that was moved out of the shop in haste is now being sorted.  No explanation is being offered for this image.....

Thursday, March 24, 2011

Shop is Operational

One of the final steps in making the shop operational was the replacement of the original 1961 bench tops with new maple bench tops.  The original bench tops were made from discarded wood.  In this picture the walls of the shop see daylight for the first time since the shop was built.

Next, it was necessary to construct new level bases for the maple tops.  All of the support lumber was four by four redwood, making for a sturdy base.

Here is the completed results.  One bench is at a sitting height while the second bench works well when standing.  In the second photo you can see the original front door that I saved from the house when it was demolished.

Monday, March 7, 2011

Motorola Mystery

While trying to restore an older analog bench supply I discovered that the series pass transistor in all of the regulating circuits used a Motorola 1700G transistor.  The mystery is I can find no record of this device either on the Internet, or in the large collection of Motorola data books that I have.  The part is clearly marked with the famous Motorola logo and the number 1700G.  I’ve even gone so far as to dig through boxes of used books at OpAmp Labs Book Store. (http://opamp.com) By the way one of the best technical book stores in Los Angeles.

I was able to get a sense of what the device was from looking at the schematic and putting it on my Tek 575 curve tracer.  ( fixed up discard from a friend who found it at a ham-fest in Santa Barbara.)  Here is plot from the curve tracer that I labeled using Photoshop.

One of the handiest pieces of hardware that I have, other than the curve tracer, is an old scope camera that I modified by removing all of the Polaroid dependent parts from and replacing it with a shelf and baffle that accommodates a small digital camera. 

Here is a picture of the camera in use on a Tek 556 dual beam scope.

The good news is that all the series pass transistors appear to be good.  I am, however, still surprised that I can find no record of this device.  If anyone knows anything about this mystery device, let me know.

Tuesday, February 22, 2011

Shop Update

Some of this is a little delayed, but I finally had a chance to load a few pictures of the shop re-build into my lap top.  This picture shows the floor removed and the dirt being prepared to receive the rebar for the pylons and grade beams.

This view is looking out of the shop toward the door of the shop.  All of the iron work is in place and ready for the pouring of the concrete.

At last the new floor is in place.  The next step will be to remove the rotted wood in preparation of framing, and roofing.

Now the fun begins.  Here is the roof that I helped to build when I was 9 years old being removed.

Thursday, February 10, 2011

Lab Clock Near Completion

A precision time source for the lab is up and running.  I'm using a surplus GPSDO (Global Positioning Satellite Disciplined Oscillator).  These units came out of cell sites and were used to keep the cell sites in step with each other.  The GPSDO is monitored by a surplus DL360 server picked up at a swap-meet for $40.

The server uploads the status to my web site so that I can monitor the GPSDO from a web address. The uploaded data shows the position of the satellites as well as the crystal aging.

The next step will be to put a distribution amplifier with built in divider chain.  This will take the 10 MHz from the GPSDO and feed it to multiple instruments.  I've built the distribution amplifier by modifying an old video distribution amp.  I replaced the 75 ohm build out resistors with 50 ohm resistors.  I also added a 50 ohm one to one transformer on each output so that I can eliminate ground loops when feeding multiple devices.  The divider chain gives me precision frequency outputs at 1 MHz, 100 KHz,
10 KHz, and 1 KHz.

The final piece of this project will be to derive 60 Hz from the 10 MHz master output. (Useful for monitoring the power grid, and driving conventional clock circuits.)  I plan to do this by extracting the third harmonic from the 100 KHz square wave, and then dividing the resultant 300 Khz signal down to 60 Hz.

Monday, January 31, 2011

Shop progress

The rebuilding of my Dad's shop is progressing nicely. The shop was originally built in 1961, and had a dirt floor. Here is how the shop appeared in the 70s. It's remained pretty much unchanged until recently. This picture is featured in the book about my Dad and uncle "The Legendary Lydecker Brothers".

Here it is being lifted off of the foundation so that the plywood floor and dirt can be removed and replaced by concrete.

Wednesday, January 19, 2011

Clock Wiget for the blog

After finding my way around setting up the blog I felt inspired to create my own wiget in the form of a Nixie clock.  I used this HP 5512A Electronic Counter as the model for my clock.
I found the counter in the junk yard at Apex electronics for $20.00 (http://www.apexelectronic.com) .  For anyone who lives in the San Fernando Valley, Apex is geek heaven.  After cleaning, fixing and painting I used pictures of the counter to create the images that I then animated using Java script, CSS, and HTML.  I seems to render on everything but Microsoft IE, so this is still a work in progress.

Saturday, January 8, 2011

Let there be electrons

Solar panel system is installed inspected and waiting for DWP to upload new firmware into our meeter that will let us tie to the grid.