LabGuy's World: RCA CRV-59AAE Iconoscope TV Camera Restoration - Part 3
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Establishing second order goals - 20150603

REMAINING RESTORATION GOALS:

  • 1. Repair the poor low frequency response of the video amplifier. This is the cause of the horizontal smearing following dark to light, and light to dark, transitions in the image. I will replace all of the interstage coupling capacitors in the video amplifier with brand new high tech parts. The old tubular paper capacitors are far past their due dates. It is amazing they work as well as they do.

  • 2. Add sync drive to the scan oscillators. At least get the oscillators running at true 525/30i frequencies of 15,750Hz and 60Hz (EIA) OR 15,734Hz and 59.94Hz (NTSC). This will start with a dedicated sync generator. But, I will also add an LM1881 IC sync stripper and glue logic to allow the selection of external sync in the form of a composite input video signal. That should allow locking this camera easily to house sync if it ever ends up in a proper video studio. A simple toggle switch selects the mode in which to operate.

  • 3. Third goal is to add a process amplifier to the video output. This will take care of summing the new sync and blanking signals into the video signal as well as allowing for adjusting the signals to their proper levels..

  • 4. Mount a viewfinder to the camera. I have many to choose from.

  • 5. On going goal for now. That is to finalize the power supply. If you recall, I replaced the 28 volt supply with a newer unit. That unit does not fit within the original cabinet. Another 28 volt power supply has been ordered that will fit inside the existing cabinet.

  • 6. Locate the intermittant source of smoke. Sometimes, when the camera has been running for about 15 minutes with the covers on, it begins to smoke. With the covers off, I have not been able to duplicate the problem. I'm too chicken to just let the part go ahead and burn out, making it easy to locate. But, what if it is a part I can not replace?


Schematic: RCA CRV-59AAE Miniature Airborne TV Camera - 20150603

       Running along the top of the schematic, please locate the following capacitors: C113, C133, C154, C145, C148, and C149. Note how theses capacitors connect from the plate of the tube on the left to the grid of the tube on the right. These are called coupling capacitors, because they couple the AC component of the signal between the amplifer stages while blocking the DC voltages. The new parts were ordered this evening directly from [Antique Electronic Supply]. If you are restoring vacuum tube equipment, this is the place to find your replacement parts.

       As the original coupling capacitors aged over the past 60 years, their rated capacitance value decreased as the paper dialectric decayed and dried out. These get replaced with Sprague brand orange drop capacitors which are lunar modules to ox carts in comparison. This should clear up the distracting horizontal streaking in the picture.

       Stay tuned. Updates on this part when the new components arrive.


We say goodbye to the gnarly selenium rectifier and big iron transformer- 20150607

       They don't make them like this any more! That [antique selenium rectifier] is still the most fascinating component in the system. Not counting the iconoscope tube, of course. The full wave bridge version, such as this example, are very rare today. It has that retro-futuristic Jetsons look about it. Sadly, it is no longer performing up to par. It has got to go!


New 28 volt power supply installed on the left - 20150607

       Seen here, on the left, is the new 28 volt power supply installed in place of the above components. This is a modern high efficiency switching power supply and is much more compact than the previous analog power supply. Unfortunately, it is not as quiet. There is about 20mV of 60Hz hum on this power supply's output. Probably because it is operating at full load or there is a ground loop within the enclosure. Fortunately, I discovered that the voltage adjustment can go well over thirty volts. So, a common mode choke and post filtering capacitor should fix the hum and any resulting voltage drop, if any, can be dialed out.

       Despite the short coming in noise performance, this power supply is an excellent bargain. A product of modern China, it cost me less than $40 installed. You can't beat that. To replicate the original iron transformer circuit today would certainly cost several hundred dollars. This unit is manufactued by Hengfu, model number HF150W-SF-28, available at [MPJA Online, Power Supply Depot].

       A thorough wipe down, with a damp towel, and the chassis cleaned up nicely. The high voltage sticker hides a huge ugly hole where the original 28 volt filtering capacitor was installed. I have reinserted the two vacuum tubes in the center. Though they no longer perform any active function, they look better than the empty tube sockets.


Iconoscope TV Camera Power Supply - 20150611

       Video explaining the major sections of the original DC power supply constructed 59 years ago by Mr. H.E. Fisher. Essentially a video of the previous few paragraphs. I describe the replacement of the +28 volt DC power supply section with the modern switching mode power supply. Enjoy!

       This is an on going project. Check back occasionally to follow my progress.

REFERENCES:

       1. Harjo Sales [CRV-59 television camera conversion] instructions.

       2. Mr. Fisher's original [CRV-59AAE conversion notes] in no particular order. I received them shuffled. I was not the person who scanned this material either. It is what it is. But, it is rich in info if you take the time to study it.

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BIBLIOGRAPHY:

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Created: June 3, 2015 Last updated: June 12, 2015