Alrighty then. The 5AXP4 project shall be known as Cyclops, the one eyed monster, from this day forward. Why? I'll tell you why.

       Back in the early 1960s, our family went to [Coos Bay, Oregon] to visit Aunt Dorothy. I was 7 or 8 years old. Aunt Dorthy was no less than 400 pounds. Best cook I ever met! Like kids of that era, I asked Aunt Dorothy what we would be watching on TV that evening. She replied, "The one eyed monster". Oh boy! A scary movie!

       After dinner, we all settled down in front of a fantastic Admiral "port hole" TV with huge round screen! The room was heated with a wood burning stove in the corner. A storm was blowing off the Pacific Ocean just out back. (You could fish out the back window during high tide!) It was a dark and stormy night as well as a Rockwell moment. The viewing started. As the evening wore on, I became restless as I had not yet seen the one eyed monster, which I presumed to be a science fiction movie. We sure can be dumb as kids. When I asked about the one eyed monster it was pointed out to me, with great hilarity all around, that I'd been watching it all evening.

       People are cruel.

       But, funny.

       Sometimes.

       Since that fateful experience, I always wax nostalgic when I see an old round screen TV. I see the round TV screen. I smell the cooking. I feel the family. I remember Aunt Dorothy.

       And that, faithful followers, is why this project is called Cyclops, the one eyed monster.

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Project update - 20141020


The Cyclops Project Schematic, revision 2, for your review - 20141020

       Moving right along and returning to the topic of the project, let's review the schematic briefly. The iron core transformer provides the heater and bias voltages for the tube. Since the new potentiometers, R1 and R8, are both now 100K ohms, I had to change R2 from 2.2M to 220K. R1 was originally 1 meg ohm. I simply scaled the pair of resistors by ten. The focus circuit's original divide ratio remains unchanged. It just draws a little more power. The brightness circuit is unchanged.

       The plastic parts are on the 3D printer as I type. Should have at least one of them tomorrow. It was warping a little when I left work and had several hours yet to go. Will know how it turned out in the morning.

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Project update - 20141021


Printed Plastics Parts on the printer and on the project! - 20141021

       The top half of the CRT support frame awaited me this morning when I arrived at work. The lower half has been ready for a couple of weeks. The 3D printer works by raising the table up until it just touches the printing nozzle. Think hot glue gun. A glue gun attached to a high precision X-Y plotter. A glue gun that deposits the tiniest bead of ABS plastic as it traces a pattern as thin as a sheet of paper. When that layer is complete, the table drops down a precise tiny distance. Then the printing process repeats. Layer by layer. Until the object is complete. This one took 3 hours, 45 minutes. Thank you, Judy.

       The last two plastic parts will form a support column for the back end of the CRT. These have yet to be printed. With their addition, the CRT will be fully supported, independant of the deflection yoke.

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Top 5AXP4 Support Frame has clearence for the second anode connector - 20141021

       The two front CRT frame halves are joined together by two 7 inch long #6-32 threaded rods cut from bulk stock. Locked in place by four #6-32 kep nuts. These are nuts with an integral star washer. The top nuts sit in 10mm diameter recessed wells so as to not expose the sharp edges of the threaded rod. The stainless steel rod has a very sharp burr where it was chopped off. Eventually, I will fill the wells with black silicon rubber to hide them. I built in the arched cut out to accommodate the second anode connector. The arched part not only provides strong support, it further shelters the anode connector from casual contact.

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Project update - 20141022




Let's put this CRT second anode connector on the EMCO power supply - 20141022

       Time to put the anode connector on the new power supply. First, we take the old connector apart. The wire clip pulls out of the silicone cup easily with needle nose pliers. Cut the new wire to the same patter as the old. Put the cup on the new wire... first! Solder the anode contact clip to the new wire. Slide the silicone cover back into place. [Allen B. DuMont] would be proud.

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Anode connector safely installed and a spiffy new transparent CRT safety shield - 20141022

       Another great flea market find! A nice clear plastic face shield for the CRT. And, by coincidence, there is a nice high voltage warning sticker located right where it needs to be. It is held on by four captive screws. I simply drilled under sized holes into the plastic and threaded these screws into them. They gripped well and didn't strip out. What luck!

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HV monitor, and X, Y and Z inputs on banana jacks - 20141022

       The last bit of construction is the installation of the banana jacks that interface this unit to the outside world. The two jacks on the same panel as the brightness and focus controls are the high voltage power supply monitor. These provide a scaled voltage that represents the high voltage. When I set the anode voltage to 14,000 volts, this monitor voltage will be 9.666V. On the side panel, going left to right are X- and X+ direct yoke input jacks. Next are the Y- and Y+ direct yoke input jacks. Last pair are ground and grid drive input. This supports the input of blanking pulses and or video drive at between 30Vp-p to 60Vp-p. This input is AC coupled via a 1uF, 200 volt, non polarized mylar film capacitor. More about that as that part of the circuit continues to develop.

       While doing research about amplifiers capable of driving deflection yokes, I discovered an obsolete part made by National Semiconductor (now Texas Instruments) called the LH0101. This is a power op amp. When I say power, think 30 WATTS! According to the data sheet the most obvious use for this part is "as a deflection yoke driver". What a co-inky-dink! That's exactly what I was thinking. I ordered two of them from a vendor on Ebay. Let's see how those perform when they arrive. The sooner we pass through the scan generator design phase, the sooner we can get to the color flying spot scanner project!

       The power supply table and bias circuit board have both been attached to the base board now. They are in their permanent posititions. Once the parts are painted and reassembled, then the wiring can begin. This system is very simple and that won't take long.

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Project Nearly Completed - 20141024


It has been a long haul to this point - 20141024

       Cyclops is 99% complete and passed initial testing. During bring up, of course, I got a nasty 200 volt shock and managed to make a serious burn spot in the center of the screen. Chalk that up the continuing cost of my education. You can see the Cyclops running the stereo audio pattern from my old amplifier again. This time, the spot is highly focused. I am running the tube on 10,000 volts for now. At 14,000 volts, the focus pot would occasionally arc internally. I have no explanation for this.

       Browse the Cyclops family album up to this point:

Some misc. photos of the final assembly - 20141024

       All that is left to complete Cyclops is the addition of the CRT neck support and wiring of the two power indicator LEDs. Then Cyclops will be 100%. That leads to the development of the magnetic scan amplifiers. You can bet I will be plugging this into all kinds of amplifiers to see what happens.

       My thinking is that I want to drive the yoke in the same way an audio amplifier drives a loud speaker. I think vertical scan with its lower frequency requirements, will pass through a reasonably simple audio amplifier to drive the yoke easily. The horizontal wave forms will require a very wideband DC amplifier. Say 300KHz to 400Khz of bandwidth and some reasonable power level. I am thinking in the less than ten watts range. So, analog consumer product IC amplifiers become attractive for this purpose. Don't forget that I will also be trying some extremely expensive power op amps made for this purpose. I'd be intereted in your thoughts on this topic if you care to drop me a line via email.

       Just to remind you, deflection on this CRT is not based on a hammer and bell circuit, or a pulse driven high Q tuned circuit. In the classic television horizontal scan circuit, the deflection yoke is intimately mated to the high voltage flyback transformer. Then the whole affair is finely tuned for that particular combination of scan time and flyback time. The benefits are that this classic consumer product design uses less components, lowers power consumption and lowers waste heat. This makes it almost impossible to bend the scan frequency very much because of the tuned nature of the power supply. This project divorced the scan and power supply and should have simplified the scan yoke driving circuits. But, perhaps it only changed the nature of the complexity.

Before and after. The 5AXP4 Project is Nearly Completed - 20141024

       (8am) While investigating the strange over control effect I was observing yesterday, I discovered that two of the resistors I purchased were off value by one thousand times! Instead of 81K and 220K I was sold 81 ohms and 220 ohms in packs marked otherwise. Ooops!!! (Explatives deleted - and, OH!, can I rant!) This explains the near plasma beam that I witnessed as I destroyed the screen of the CRT and the nasty shock I took from a point that should not have had enough voltage to feel. Now we know. Will be getting replacement resistors later today.

       The second error is with the transformer. It is putting out 150V and 300V instead of the expected 125V and 250V. I don't know if the transformer is mismarked (unlikely) or if the voltage specified is at the full 45mA load on the secondary. Cyclops is using a whopping 2mA of current from T1. Rectified, the voltages are now +400V and -200V Where I was expecting +360V and -180V. I will correct the replacement resistor values to accomodate this discovery as well. That will bring the pots back into their anticipated operating ranges.

       The final significant discovery is with unmodulated beam cuttoff. Since my design has no resistor in the cathode circuit, there is nothing to limit beam current. This may be a significant design error. If G1 was actually set to zero volts, relative to cathode, the tube would form a short circuit across the power supply. There is obviously some follow up research in my immediate future!

Cyclops Bias Voltage Board - 20141025

       (1pm) Recalculated all resistor values based on the higher than expected supply voltages. Designed in a beam current limit circuit. Purchased all the new value resistors. An up dated schematic coming soon.

       Focus circuit is as follows, starting from B+ and going to ground. +400V, 50K (res), 100K (pot), 250K (res), ground. This makes the "top" of the pot +350V, the bottom +250V and the mid point is at the nominal +300V for A1.

       NOTE: The "top" of a pot is the contact at the maximum clockwise position. The bottom being the contact at maximum counter clockwise. My standardized color code, for connecting wires on potentiometers is red for the top, blue for the bottom and white for "wiper" or the center tap. You can see the two red, white and blue bundles tying to the hand wired bias board.

       Moving on to the Brightness control, G1, circuit. This one is 100K (res) in series with 100K (pot) and driven from -200 volts to ground. The pot is located on the "low" side. The top of the brightness pot is at 0 volts, ground. The bottom of the pot is at -100 volts. The mid point is -50V, the approximate cuttoff point of the CRT.

       Beam current limiting. To do this, we insert a 500K (499K, 1%) resistor in series with the cathode of the tube.This limits beam current to below 100uA. With the beam set so high it was doing damage to the phosphor, I measured about 30 volts DC across the cathode resistor. This is a beam current of 60uA. Well below the target of 100uA. There is 10uF capacitor in parallel with this resistor for AC bypass when video drive is applied to G1. The range of control, on the pots, has now become broader. The maximum brightness seting is high enough to scorch the phosphor but does not cause the phosphor to glow red hot any more. That's a sight to see!

       The final circuit to get wired was the high voltage ON indicator LED. This one is lit when the 24 volt power supply is on and driving the EMCO 15KV supply. The current limiting resistor value for this LED is 1.1K for approximately 20mA of drive. Needless to say, this LED (red) is much brighter than the yellow LED I used for standby. By lowering the series resistor from 370 ohms to 100 ohms raises the brighness of the yellow LED a lot. Next step will be to lower the red LED current until both LEDs appear the same brightness.

Cyclops Schematic Rev. C - 20141027

       The latest and greatest schematic. Note the corrected focus and brightness voltage divider networks. A 499K resistor has been added to the cathode circuit to limit current and is working well. Forgotten on this drawing is the 10uF, 250V capacitor in parallel with the 499K. As a video or blanking signal drives G1, it varies the beam current in the gun. As the cathode current changes, it develops a matching voltage across the 499K resistor. The 10uF capacitor provides a short circuit path to ground for the AC components on the cathode.

       Another shaky labguy video. Enjoy!

PROJECT UPDATE - 20141110


3D Printed 5AXP4 CRT neck support bracket - 20141110

       Received the last of the plastic today. Cut some stainless steel #4-40 threaded rod to a length of 5-1/8 inches. performed a test fittting of all the pieces.

3D Printed plastic installed and looking good - 20141110

       This completes the final mechanical assembly I had envisioned at the start of the project. The 5AXP4 is now completely supported on both sides of the deflection yoke. In fact, the CRT and deflection yoke don't touch at all. The tube is dead center in the bore. The deflection yoke has its own separate support. Just because I thought it would be cool. And it is.

       This is an active project. Book mark this page and check back every day or three to keep up with on going progress.