Now I have a decent lens setup I thought I'd see how I go focusing an image onto the Iconoscope tube itself, so I pulled out the tube and carefully rigged it up and positioned the lens for distant focus onto the tube and got a nice image of the front yard focused onto the Iconoscope's mosaic. I can see however that the size of the focused image being much bigger than the mosaic will make the angle of the viewable area narrower so for close ups I won't get much viewing area and for head/shoulder shots one would have to stand I guess at least 2 metres away from the camera. So whilst not a perfect lens for the camera, it will do for now till I get the camera completed and functional or come across/make a better lens sometime down the track.
Next step now is to make the lens secure and rackable on the aluminum railing. Giving the nature of the railing having an inner rail overhanging on the inside I decided to make a little chipwood platform that the lens can be secured to and the platform slides inside the railings, so that's what I did. I also needed something to push and pull the lens back and forth and going through my junk collection I found a car oil dipstick and thought it would be great for the task. So I cut the dipstick down to size and bent it to fit snugly on the platform and I nailed another piece of chipwood over the dipstick to secure it to the platform. I then nailed and hot glued the lens to the platform and then drilled and pop riveted the railing to the inside of the camera enclosure. I also added a couple of rivets to the back of the rails so the platform doesn't slide off at the back. It worked out beautifully and I now have a rackable lens system! :D
So that wraps up the lens system, at least for now anyways.
Now it's time to get into the electronics territory which is where things get really hard and it becomes a vertical mountain climb without rope and harness from here! As mentioned I can construct electronic circuits, fault find circuits with the help of a service manual and to a certain extent modify circuits, but when it comes to designing circuits from scratch, that goes beyond my scope of knowledge and so I need lots of help from those who are knowledgeable in that area!
Anyways at present I need to tackle the power supply, head amp and deflection yoke as I have gathered up a good amount of info in those three categories to work with but of course am missing bits to actually start construction.
For the power supply, I have Yoshio Ozaki's drawn schematic which he kindly provided me which is great, however the transformer's input and output voltages are not labeled and there are some components without values given and some of the transistors are odd values which are unobtainium so I cannot yet construct the power supply until I get all those issues addressed.
For the head amp, as mentioned earlier I can use a head amp from a plumbicon tube colour camera so I went searching for uploaded plumbicon camera service manuals and to my luck I found a complete manual for a 1970s Norelco/Philips LDH1 camera on the "Museum of the Broadcast Television Camera" site which can be downloaded from this page . Also on that site on this page is a schematic for an original 1936 EMI emitron Iconoscope tube TV camera which is great to have and might come in handy. Looking at the preamp and video circuit, the circuit is very constructable and the transistors whilst not available at Jaycar Electronics or Futurlec can be found on Ebay so I believe I can build this head amp. The preamp is straight forward but the video circuit I need to know how much of it is part of the head amp and what to leave out so will be asking my expert friends.
For the deflection yoke, I have a good amount of data from Yoshio Ozaki's memo notes he kindly provided me so I know the resistance and inductance of the horizontal and vertical coils, plus some of the dimensions of the yoke assembly, all this being of great help to me! I also have some info from other sources as well that have been of extra help. The resistances/inductances for the coils are as follows:
Horizontal: R=4-4.8 ohms approx L=68-69uH approx
Vertical: R=36-39 ohms approx L=417-420uH approx
Now I don't know the SWG gauge of wire to use for the coils nor the amount of turns for the horizontal and vertical coils to make up the inductance values and there's still missing info for the dimensions of each coil in terms of thickness, width and height so I will be needing help on filling in those details. Here below is my sketches of the yoke and some of its dimensions based off the info provided so far:
Since I last updated my site I have made progress on the electronic side of things with my Iconoscope camera project with the help from my good mate Richard Diehl of Labguysworld.com who has kindly sent me parts and tech info and Maurice Schechter who has kindly sent me tech on the WWII 1846 Iconoscope bomber camera.
So after getting a lens system happening I started on thinking where to go next with the project. I ended up being geared towards two things, building a preamp for the tube's output due to the fact I can use a plumbicon camera preamp and also building the high tension power supply for the tube's high voltages as Richard Diehl kindly sent me a couple of -1KV DC power supply units which easily got me started on it.
First thing the high tension power supply. To begin with I tried making the high tension power supply using a high voltage microwave transformer that was over 2KV which I supplied it with a low AC input to ouput 1KV and with some diodes and high voltage capacitors made 1KV DC out. The microwave transformer was quite bulky and I would have to another transformer to step down mains 240VAC to a much lower voltage for the microwave transformer's input to make 1KV. Luckily my mate Richard Diehl had acquired some -1KV power supplies and he kindly donate a couple to me for the project and all I needed to do was make a +/-12V DC power supply to input +/-12V into the -1KV power unit to make it operate. One important thing I learned with the Iconoscope tube, the voltage must never be positive so just as well I didn't make a +1KV power supply!
So here below is the -1KV power supply driven by my home built +/-12V regulated power supply which is driven by a centre tapped 240V-15V-15V transformer:
So that's my basic -1KV high tension supply down pat. Next with that I need to tap off that high tension supply the necessary voltages for the tube with the use of resistors.
Next thing I decided to do was to build the pre-amp for the tube and have learned that a plumbicon camera preamp will work for the Iconoscope. I went looking for a plumbicon preamp schematic and found one on the TV Camera Museum website in the service manual for an early 1970s Norelco LDH-1 plumbicon colour camera which can be found here. I decided to copy the circuit to the tee and so I shopped on Ebay for the rare old transistors required for the circuit. Once I got all the parts I constructed the circuit and made a makeshift +/-12V regulated power supply on breadboard to test it out:
Now time to test the preamp. To do this I have the output connected to the scope and touch the input terminals with my finger to induce noise into the preamp and see if it amplifies an output noise. On powering up the preamp I could see a waveform on the scope indicating that the preamp is oscillating badly but reacting with a smeared waveform when I touch the input terminals:
So this preamp has some very nasty oscillation! The cause of it was likely due to inadequate grounding which I guess the ground floated in an oscillation manner and hence the oscillation waveform.
I discussed with Richard Diehl about my preamp issue, he kindly sent me a kit of micro sized surface mount parts and prototype boards and tools so I could build a smaller neater tighter and well grounded preamp for the tube. The components were so tiny I had to use the eye magnifying monocle to see them properly! Anyhow I constructed the preamp using mostly the micro sized parts but using those original transistors from the first version of the preamp. It certainly looked more neater and tighter and the prototype board had loads of grounding on it! Here below are pics of my "Mach II" preamp:
Now it was time to test it and see if it worked. Once again connected the preamp to my +/-12V power supply and the output to the scope. Fired up the scope and was happy to see there was no oscillation at all and then I touched the input terminals and I got amplified noise which was perfect, so my preamp works! :D
So that's the preamp 1st stage video amplification completed! I have been looking over the WWII 1846 iconoscope bomber camera circuit and can see that the video amp stages look very much similar so it looks like I can pretty much duplicate the preamp for the stages and add in the little necessary extras after.
Now it's pretty much up in the air what to work on next with this camera. Richard suggested I start with the power supplies then the deflection stage and then the video amplification. So that gives me some direction of where to go next with this project.
So that's about it for now, when I make further progress with this project I will post the updates.
I have been exchanging further emails with Richard Diehl on this project in regards of what I can do next with this project and he has suggested for the purpose of testing the Iconoscope tube I try testing it in a 1 inch vidicon tube yoke and use the deflection board from my homemade vidicon camera to drive it. I don't have a spare 1 inch yoke but I do have in possession three RCA 30mm vidicon camera tube yokes the same as this one Richard has which I think will be good enough for the task. Also I thought perhaps use the video board as well from my homemade camera and add the preamp as well to it for extra video amplification. So it looks like now I am going to use the video board and deflection board from my homemade camera and adapt them to the Iconoscope project. So looks like I will get this Iconoscope camera rigged up ready for testing in the very near future yaaaay! :D So I have began with drawing a rough block diagram of how this camera is going to be laid out:
The first thing I decided to tackle is to modify and adapt one of the three RCA 30mm vidicon yokes so it can be used with the Iconoscope tube. I removed the yoke's preamp and cut the wires from the plug that connects to the yoke so I'm left with just the yoke assembly and wires only. Then I hammered the yoke inside the enclosure to one end so the tube can go right in.
Now the diameter of the inside of the yoke is larger than the tube's neck so I decided to wrap some cardboard paper inside the yoke so the tube neck will fit nice and snug. Well there was one problem, the base end of the neck was wider than the upper end of the neck where the yoke is positioned so I decided to wrap some cardboard paper around the neck prior to slipping it into the yoke so the base end can go through and then upper end with wrapped cardboard paper in which it fits nice and snug.
Here in Part 16 of my Iconoscope vlog series I discuss in detail my plans in constructing this Iconoscope camera using the deflection and video circuits from my homemade vidicon and a RCA 30mm plumbicon tube yoke. I also discuss the high tension power supply unit to supply the high voltages for the Iconoscope tube's anodes and grids using a voltage divider circuit, schematic provided by Richard Diehl of Labguysworld.com .
Next part of this project I decided to work on is the high tension power supply for the tube's anodes and grids. So going by Richard's voltage divider schematic I replicated it on my breadboard and tested it out and it worked but the voltages weren't quite right due to the resistors not being accurate to their given value due to the 5% tolerance factor and the total resistance worked out to be around roughly 800-850K ohms instead of 1M ohms. I added another 100K resistor to get it closer to specs and stuck it beween the 150K and 250K pot so I can get the 300V for Anode 1. On testing the voltages, the total voltage drop across the circuit is 1017V which is good but testing the voltages at each point relative to each end of the circuit there's inconsistency as they don't add up to the total voltage, I am guessing my multimeter's resistors have something to do with that. Anyhow I am still in the testing stage with the voltage divide and am yet to solder it all onto a circuit board.
Going back to the RCA plumbicon yoke I have to add some soft cushioning around the outer metallic regions of the yoke so the Iconoscope tube doesn't hit on the metal as it can scratch/break the tube. I bought some rubber foam from an arts/crafts store and cut some rings and lined them over the metallic outer area of the tube so the yoke is now well cushioned.
Now to work out which wires are what for this yoke, there are 11 of them!!! So I paired up the wires and checked the resistances across them which are as follows:
red/black - 2.3 ohms
green/white green - 53.7 ohms
brown/white brown - 103.8 ohms
orange/white orange - 2.65K ohms
purple/white purple - 2.69K ohms
grey - on its own
After discussing the yoke resistances with Richard, it looks to be that the red/black is the horizontal deflection coils and the green/white green is the vertical deflection coils and the grey wire is the shield connection. The rest are for focus and alignment coils which will not be used for the Iconoscope tube. So will be using those two pairs of wires for horizontal/vertical deflection and the grey for shielding.
So that's pretty much where I'm up to now with this project. The next thing I'm tackling is finding a way to mount this yoke assembly inside of the camera's enclosure as it has to be positioned at a slant for the slanted Iconoscope tube neck, I plan to bolt the yoke underneath the compartment housing the lens. Here is a photo showing me holding the yoke in that position.
Been a couple of months since my last update but have actually been doing further work on this camera and have made significant progress!
Firstly trying to find a way to mount the yoke underneath the lens carriage. I figured one end should be made pivotal so I can correctly position the slant of the yoke so I used a door hinge and bolted it to the lens carriage and the yoke. Now that the yoke is pivotal I needed to secure the other end of the yoke, so I used some nuts, bolts and washers and a piece of metal I bent which did the trick nicely! :) Here below is the yoke nicely secured to the bottom of the lens carriage: