• Third Tube's a Charm

    Blaine Murphy08/13/2018 at 01:16 0 comments

    In the previous log I broke down the RCA TV that I chose to use for a display. I incorrectly assumed the TV was functional and proceeded to dismantle it without testing it. It turns out that when powered up it had some serious issues. At first the tube appeared lifeless while the high voltage transformer emitted high pitch clicks at random intervals. Each click was infrequent, but as time went on the rate increased so much that it almost sounded like white noise. After about 20 seconds the tube began to glow, but was interrupted and flickered during some loud pops. I was only brave enough to test the TV once and I turned it off when it started flickering because I feared it would be damaged if left on any longer. What little picture that was on the screen was out of focus and almost entirely white.

    I decided to put the RCA aside and try out a different display that I had handy: a Coby CX-TV1. The Coby is a small combination TV/radio that operates on 12V DC. Like the RCA TV the Coby has a video input, but unlike it the display is black and white.

    I found the Coby TV for about $8 while thrifting. I'm happy I didn't have plans to use battery power because the compartment was left with batteries in it for quite some time.

    Every battery was heavily damaged by rust.

    The contacts were completely destroyed.

    Before dismantling the display I did a test to see if it was operational. To my delight the TV powered on, started relatively quickly, and showed sharp details in static.

    The back of the Coby TV has a 3.5mm jack labeled "video in". I plugged a TS pigtail into this jack and a TRRS pigtail into the Pi's AV jack and proceeded to poke around. My initial guess of tip=video, sleeve=ground yielded a bouncy and bright picture on the tube. I played with the sync and brightness controls on the back until everything looked fairly clean.

    I packaged up the video cable by soldering the video wires and installing shrink tubing on each wire. I sliced a scrap cable sleeve and zip tied it to the sleeves of the joined cables for strain relief.

    After verifying the screen was good to use I did a test fit in the cabinet. The entire TV fit without an issue, but the angle of the tube didn't match the angle of the panel removed from the cabinet.

    I looked at the TV for a long bit contemplating whether I should tear it apart like I did with the RCA. I decided to keep the TV in tact so that it would be safer to work around and be more shielded to the environment. I did want to change the angle of the screen so I took a hacksaw to the battery compartment to adjust the TV's sitting angle.

    The change isn't extreme, but it's enough to make the screen feel much more natural. The hacksaw cuts weren't perfectly aligned on both sides, but this was easily fixed with some 40 grit sand paper.

    I also removed a small bit of wood from the bottom of the opening in the cabinet. This made it possible to push the TV against the opening in the cabinet without interference from any of the front-panel controls.

    I think this new display will better help me achieve the retro-futuristic feel I want in this jukebox. I was excited for the color capability of the RCA TV, but I think the Coby's black and white, visibly rounded tube is a better fit. I am happy to be working on this project for the first time in a long while. Next log I'll be assembling all of the hardware modules and testing the assembled system.

  • A Less Mysterious Display

    Blaine Murphy06/22/2017 at 00:58 0 comments

    My recent trip to the local thrift shop yielded a new display for the radio. I have decided not to use the MDA monitor and instead use a small RCA color TV/monitor. This is an easy decision since the monitor will accept the Pi's composite output without the need for an adapter.

    I have never seen a color tube this small before. There is a speaker grille and a control panel mounted on the side of the unit.

    On the back there are inputs for audio and video. I will only be using the video input as the radio cabinet already contains speakers.

    The TV is powered by a 12V DC adapter or by a "D" cell battery sled.

    The TV is too big to fit in the radio with the casing installed. The casing was a bit dificult to remove, but I managed to get past the outer shell that with a couple pairs of vice grips.

    Inside the casing there was the following label:

    I should probably find a good way to shield the tube and board once I get it installed in the cabinet. Hopefully something lightweight like aluminum or copper tape will do the trick.

  • Now In Stereo

    Blaine Murphy05/25/2017 at 05:14 0 comments

    This past week I had a couple days off work, so I decided to make use of this time to mount new speakers in the radio cabinet. I picked up some 1/4" plywood to act as a adapter to fit the two new speakers into the hole left by the old one.

    I used the old speaker as a guide to mark where mounting holes needed to be drilled.

    I then drilled mounting holes to match the oval ones on the old speaker. These greatly eased mounting the plywood in the cabinet because the existing posts were angled outward from the center of the speaker cutout.

    I'm not sure why, but the old speaker was mounted off-center to the vertical bars on the front of the radio. I compensated for this by drawing guides on the plywood that were square and centered with respect to the piece of wood the old speaker was mounted on -- not the hole left by the old speaker. This also compensated for the misalignment of the mounting holes on the plywood (I should have tried harder to align the old speaker before tracing it).

    The car speakers came with mounting brackets that made great guides for cutting holes in the plywood.

    I used a bandsaw to cut holes to mount the new speakers. These holes were slightly larger than the ones in the plastic brackets

    Here are the speakers mounted in the plywood adapter. I used screws from a recent microwave oven tear-down to secure them in place.

    I picked up some rubber washers to install between the plywood and wood of the cabinet to prevent vibration noise.

    I re-used the original nuts with some new washers to secure the plywood on the posts in the cabinet.

    Admittedly this isn't the first hack at making an adapter for these speakers. Two previous incarnations had various flaws that prevented them from being used. I used the top (attempted) adapter as scrap wood to mount the AC power inlet in the cabinet.

    I cut a small piece off of this scrap to hold the AC inlet. I used a bandsaw to cut the hole in the middle.

    I sourced two more screws from the microwave oven pile and used them to secure the inlet in place.

    I soldered on wire leads to the inlet and covered the exposed bits with heat-shrink tubing.

    Two screws hold the inlet assembly to the shelf in the cabinet that previously held the radio circuitry.

    Here's what the cabinet looks like after the new parts were installed.

    A big thanks to my friend Kai who was nice enough to let me take up space in his workshop and use his collection of power tools.

  • Mystery Meat Monitor

    Blaine Murphy12/18/2016 at 04:12 1 comment

    In order to use the Carry-I's monitor with a Raspberry Pi I needed to learn a little more about the beast. The most direct route would be to run a diagnostic program to discover the graphics hardware, but that isn't an option. I can't power on the computer because I lost the power supply brick at some point in the last couple years (oops).

    The computer is very small, only occupying a footprint the length and width of the monitor. It seems like the model would have made a good candidate for a POS or cataloging computer.

    The 9 pin video connector is on the right side near the power connector. The label "display" isn't very descriptive; time to go inside.

    Two screws hold the outer casing to an inner frame. The outer casing slides off the rear of the computer after the screws are removed. Inside there are two 3.5" bays. The left bay holds a 40-pin ATA device; the right holds a 34-pin floppy device.

    Four screws fix the inner chassis to the motherboard. The inner frame slides off of the front of the board after the screws are removed.

    I looked at the area of the board near the video port for ICs that appeared to be connected to the port. After coming up empty on a few searches I found a chip that looked promising. The identifier TM6310 hit on an archive of a 4chan technology ... err, discussion. The part seems to be a combination MDA/Hercules video driver and parallel port driver.

    One mystery solved, but more questions emerge. It looks like I'll be looking for a way to drive a monochrome display from the Raspberry Pi.

  • The Lightning and Thunder Arrives

    Blaine Murphy12/18/2016 at 02:24 0 comments

    Back in July I ordered power and audio components from Amazon. While taking pictures for another log I decided to post some pictures of goodies I received.

    The original driver in the radio is a bit rusted up and has a busted cone, so I'm replacing it with modern car audio drivers. Two 4x6 Pioneer TSG4645R speakers will fill the left and right sides of the hole left by the original driver. A DROK TPA 3116 amplifier (far right) will recieve input from a Raspberry Pi and drive the new speakers. Also pictured is wire that came with the new drivers and a 3.5mm audio jumper.

    A DMiotech 24V DC power supply (top right) will accept mains power and provide power to the audio amplifier and Icstation DC to DC 5V USB buck converter (bottom right) that will power the Raspberry Pi. Also pictured is an AC power cable, an AC socket, A USB micro B cable, and some terminal strips

  • A Cool Looking Radio

    Blaine Murphy07/02/2016 at 08:20 0 comments

    Recently I spotted a cool looking Philco radio at a local junk store and snagged it for $40. I awkwardly loaded the spiderweb filled wooden box into my car and drove it home to my apartment. The label inside has the part number 42-390; a nice radio for its time in 1942. The wooden cabinet shows a lot of water damage and aging so it's a perfect donor for a Fallout themed project.

    The original circuitry was trashed, so I decided to start from the ground up and only recycle the cabinet. I removed the circuitry, faceplate, and speaker from the cabinet eaving only the wood and some mounting bolts behind.

    I think the radio may have served as a part donor at some point as all the tubes and many of the components have been removed.

    I recruited my friend Kai to help and we managed to procure an air compressor from a kind stranger in town (small communities rock). After blowing 74 years of dust, spiderwebs, and dead bugs out with the compressor I wiped the remaining dirt out with a dry cloth. After all of this cleaning I glued the loose bits of wood and veneer down and threw a coat of furniture polish on.

    My scrap computer pile yielded a display that fits perfectly into the hole left by the removed radio unit. The donor unit is a Carry-I computer. I can find little information about this particular model, so I may have to perform some exploratory surgery to determine how to drive the display.