Black And White TV Was Hiding A Special Input Board

[John Floren] found a nice old black & white TV in a thrift store, and as so many of us would, he decided to take it home. He was surprised upon getting it there that it had, in addition to the VHF and UHF antenna inputs, a mysterious extra connector on the back. Naturally, he set about investigating.

On the rear was an obviously hacked-in F-type connector, paired with a toggle switch, both unlabelled. Running the output of an RF modulator to the connector didn’t net an image on the screen, even though the same method worked when hooked up to the antenna inputs. Undeterred, [John] dug deeper.

Inside, a little PCB bearing the mark “TVM.04” was inside, bearing a handful of components. The device turned out to be a Pickes and Trout TVM-04 adapter, designed in the 1970s for hooking a computer up to a television for use as a monitor. The adapter board allows the Hitachi TV to accept a composite video input. [John] was able to test the TV with a NES clone outputting composite video and voila, it worked! [John] then went further, adding an audio input and installing standard RCA jacks to make it easier to use the input with more modern electronics.

It’s a great example of how simply opening up some electronics and poking around can teach you something. Hacking on old-school TVs is a popular pastime around these parts, it seems. If you’ve been working on your own retro display hack, be sure to let us know.

71 thoughts on “Black And White TV Was Hiding A Special Input Board

  1. In the U.S. it was far more common to use a cheap composite NTSC video/audio to RF (often channel 2) modulator. You can still buy them today, see [1]. As time went on out-of-the-box more and more TVs had composite video and audio female RCA jacks on them. Today many flat screen TVs still have composite RCA jack inputs: yellow – video, white – audio left, red – audio right. Today, very similar devices exist in the form of composite NTSC video/audio to HDMI adapters.[2]

    * References:

    1. GE RF Modulator with S-Video, Convert RCA/S-Video to RF Coax Connection, for Older TV Sets, Use with Blu-ray, DVD Players, VCR, and Video Game Consoles, 35856 4.1 out of 5 stars 132 ratings $11.49

    2. HDMI to RCA, 1080p HDMI to AV 3RCA CVBs Composite Video Audio Converter Adapter Supports PAL/ NTSC for TV Stick, Roku, Chromecast, Apple TV, PC, Laptop, Xbox, HDTV, DVD-Black 4.2 out of 5 stars 5,699 ratings $10.99

    1. Yes that’s what most people did although I remember units that could switch between channels 3 and 4 being more common than ones which worked on channel 2. Maybe that’s because my experience came a little later in the 80s rather than the 70s or because we had a broadcaster on channel 2 in my area.

      In “my day” composite inputs were common on the main family tv, probably used by the VCR. But the kids’ game console or maybe computer would be connected to a smaller, less expensive tv, probably used (back to the 70s vintage as in the article) and those likely didn’t have any inputs except antenna. Likewise the family tv might have cable or at least a large outdoor antenna on the roof or mast but if anyone was watching tv on the kids’ game tv it was with rabbit ears.

      So modulators kind of sucked two ways. They never gave as clear a picture as an actual composite input that skipped the RF step. And the switch would attenuate a bit of the signal from the already crappy rabbit ears when you just wanted to watch tv. In my house that took a couple of fuzzy but watchable channels down to unwatchable.

      I modded an old TV to add a composite input as a kid and it was well worth it.

      1. Composite inputs didn’t happen until the ’80s, when VCRs became a thing. Also I can’t ever remember modulators (in the US) using anything other than a channel 3/4 switch, so that would have been in the ’70s before that became standard.

        The reason for channels 3 and 4 is that you could be sure that one of them would not be used in your area. A broadcast TV signal is just a little too wide to allow adjacent channels in the same market, so one or the other would always be available.

        1. I wondered about this. What channel was used n the very early days? There was the “Sup ‘R’ Mod” from M&R Enterprises, a side deal for the Apple II, and a check says it was on channel 33. I’m too lazy to see what Don Lancaster said on the subject.

          Definitely two channels were better than one, but you didn’t need more.

          Pong arrived in homes in 1975, so I suspect it set the tone, since it was non-technical buyers who needed to use tv sets. It was 1977 and the Apple II that really melded modulators to home computers, if yiu wanted colir, it was most likely the family tv set. The Commodore PET had a built in monitor, the TRS-80 had a monitor to match.

          There weren’t many options in the early days, you needed to add an input to a tv set unless you scrounged a surplus monitor or terminal. Even in 1980, I used a Ball Brothers surplus monitor, something like 7″ with my OSI Superboard, then had to modify my Radio Shack Color Computer in 1984 to bypass the RF modulator since it had no composite output.

          It’s true, VCRs likely drove the need for inputs more than computers, or video games.

  2. Lucky you. Our Goodwill and others won’t take tube TV’s even little portables. They also wont take flat panel TV’s more than 2 inches (5 to 6 cm) thick because of mercury tube backlights.

    1. None of my local thrift stores will take em but now and then one slips in. My best find was a beastly 32″ WEGA TV that worked for $10. Had everything but HDMI input and worked great for my gaming. But next time I find one I will get 6 pack beer and call a couple friends to help me move it for the beer, lifting that 32″ by myself into a cart was hard!!! Then I had to move it from my cart to my car. My car had white flags waving before I even started!!!

  3. There weren’t any black and white TVs made in the 1970s because that’s when color TV became standardized, and zero black & white TVs had printed circuit boards. Even early color TVs were hard wired vacuum tube circuitry at first.

    1. For those of us the grew up in the 70s, there were lots of black and white TVs at the time. For example, check out Zenith. Just like low price TVs today may not have all the smart capabilities, the cheaper TVs of the 70s tend to be black and white. The old TVs were both PCB and tube based.

      1. Interestingly, today it’s apparently more likely that cheap tvs have smart features, because they can subsidize the cost through “post-sale monetization”. But point well made: presence of a newer/fancier option doesn’t mean the old one goes away. Look at the release dates of various x86 processors: it was years before most saw any significant adoption.

    2. Color TV took forever to be adopted. They made and sold B&W TVs well into the 80s.

      The first TV I got to keep in my room was a 6 inch “portable” B&W TV that ran on DC or 9 D batteries. It was about the size of a large shoe box. My parents got it by sitting through some timeshare presentation around 1986.

    3. Wrong on many aspects like … all of them.

      B&W TVs were made much longer. Printed circuits have been all around in the 70s, including B&W TVs. There was no “standard” to color TV, because, NTSC is not a standard but the typical American joke to doing things as wrong as possible if there is a right way to do it (which would have been PAL) :-)

          1. I can confirm the above. My electronics instructor in the 1990’s also called it “Never Twice the Same Color”. It’s not unusual to leave out articles and other small works from an acronym or initialism. USA not USOA.

          1. PAL’s analog delay lines made sets more expensive than NTSC. but later in their lives the economies of scale and miniaturization made the difference for manufactures only a few dozen cents.

        1. You’re entitled to your opinion, but in Europe we could always tell (with the sound turned off) which sitcoms or soaps were from the USA, and which ones from Europe simply by how much fuzzier the NTSC pictures were. The difference between PAL’s 576 VS NTSC’s 480 visible lines of resolution was very visible.
          The difference between my high school’s 60hz refresh rate computer monitors and the TVs running at 50hz didn’t make much of a difference in my experience. Both were flickery.

          1. In the US I could tell which video games were European because the music was out tune. Also there was a lot of British programming shown in the US, and it often had aspect ratio issues.

            People paid extra for monochrome monitors that refreshed at 70 Hz+ (my multisync monochrome SVGA “paperwhite” could do 72 Hz) , the standard Monochrome monitor bundled with the IBM PC (IBM 5151) used in the US was only 50 Hz. The slower the phosphor the less painful it was to look at.

          2. Of course it was very visible, because they had to use scan conversion, probably by re-filming it with a high-persistence phosphor display tube and a video camera. NTSC wasn’t the reason for the fuzziness, the re-sampling was.

      1. Of course NTSC was standard, it may not have been perfect, but unless yiu had a standard, transmitters and receivers would never have worked. You didn’t even need a color set after the networks went color,that’s how standard things were.

        1. that bit in “Back To The Future”

          Doc Brown holding a Sony “Handicam”

          “a whole TV studio in the palm of my hand”

          it would have worked

          there has been a whole HackaDay article about the backward compatibility built into colour TV sets

          1. It was very much a formal standard, and was drawn up by committee. Heck, it literally is named after the committee that did that: National Television System Committee

          2. wtf???

            NTSC = National Television Standards Committee


            An NTSC picture is made up of 525 interlaced lines and is displayed at a rate of 29.97 frames per second
            each line is 63.5 uS, the line rate is 15.625 kHz
            with an 8 uS horizontal sync pulse, an 11 uS verticle sync pulse

            PAL is almost the same but 625 lines

            it’s a “standard”

            how do you guys not know this stuff??

    4. lol

      for a while there in the 70’s I used to get a pallet of 12″ General black and white TV sets and modify them for composite in to use with Apple II computers, I think the model was a GC – 123

      this is when Computerland were on Pirie street in Adelaide

      the “mod” was an RCA jack and a switch to kill power to the tuner

      K Mart used to sell General B&W sets rebranded as “Audiosonic”

      the last B&W set I bought was in 2008, it was a cute 4″ unit

    5. Absolute rubbish. Consumer products aren’t ‘standardized’, people buy what they want, what they can afford, or what meets their needs. Black and white CRT TVs were manufactured all the way into the 1990s (and possibly later, but 1990 is the last time I bought one new)

    6. Color sets were still expensive, which is why most small computer users had monochrome monitors/tv sets. You could get a Dazzler or an Apple II, but most people didn’t want to spend the money. So a lot of monitors were tv sets, either modified for direct inout, like this, or through an RF modulator. Apple talked a third party into making an RF modulator, since especially if you wanted color, the cost meant yiu used thefamiky tv set, so no mods.

      The SOL 20 didn’t do color, the PET’s built in monitor was monochrome, the first TRS-80 came with what amounted to a stripped down monochrome tv. My OSI Superboard from 1977 didn’t do colir.

      It was almost shocking when a computer, I think the TI 99/4, came bundled with a color monitor (and soon the computer was unbundled).

      I didn’t see color tv at home until 1979, or 80, and that was gecause of a scrounged and repaired tv set.

    7. Is that the strangest troll I ever read or do you actually believe that?

      There were black and white TVs made well into the 90s as budget portables and non-portables at least into the 80s. As a kid I used to buy them used at garage sales and use them till they died. I’ve taken several apart and they definitely used printed circuit boards and solid state tech (besides the CRT).

      1. Black and white TV sets were made and sold until the analogue switch off happened.

        Colour TV were way more expensive compared to a b&w one and especially for portable/battery use b/w TV were used like this

        And one example of b&w portable tv sold in the 2000s.

        The switch off killed the CRT sets because the expense to make a CRT TV design with the new DVB tuner and retool the factory was in the same ballpark of redesign from scratch and using a flat panel, that was going cheaper an cheaper with better quality.

        Italian TV maker MIVAR tried to design a DVB CRT TV and faield, going bankrupt. Getting a dead end like that meant that one of the supplier, Samsung had the time to sell more of their TV with their brand directly and when finally they started to sell MIVAR TV with LCD Samsung-made flat panels they were more expensive and the picture quality wasn’t better than Samsung TVs.

        1. that is the same model I bought!!!

          composite video in works really well, Arduino video circuit looks crisp

          not sure about battery power though, 6(? 8?) C cells last about 20 minutes if you are lucky!

    8. My grandparents had a TV just like this one in their basement from that era. I used to play NES games on it.

      I had a portable one that was a tiny screen, maybe 6 or 8″ that I think could run on C batteries and was also a radio. It was B&W only and that was in the late 80s or early 90s.

    9. Well, I guess the small 12 or 13 inch black and white TV I bought from Sears in 1985 (that had a composite input jack from the factory) was “new old stock” that was manufactured in the 1970s and sat around for 15 or 20 years before they decided to sell it. It had printed circuit boards and the only tube was the picture tube.

    10. I hacked a 1970’s 9″ B&W Sony TV-900U portable TV, tapping into the composite video post-demodulator, to display the video from my pre-S100-bus pre-CP/M “Digital Group” computer. It had a whopping 2Kbytes RAM until I hand-wired a protoboard with another 16 Kbytes.

  4. I have a hazy recollection of using a cheap B&W TV as a monitor for something or other many years ago. I can’t quite remember, but it may have been for an Osborne 1 luggable. I think there was an official dongle to get composite video output, and I read an article somewhere about how to feed the composite video into a TV somehow. Whatever it was that produced the signal, it was pretty fuzzy on that little TV.

        1. That very much is an F connector. The SO-239 socket and PL-259, also referred to as a UHF connector (even though they are crap for UHF), have a larger diameter barrel and a much larger center pin than the connector shown. The SO-239 / PL-259 combination are most often used on CB / Ham radio. Some light reading about the connectors –

          1. That switch would have had to be big to match the size of an SO-239 connector.would

            Besides, not only is the center pin much bigger, but the top of the connector is not flat.

            I can’t believe how much knowledge has been lost.

    1. I think I remember some mods where they got by with swamping the existing video signal, but if you look in Don Lancaster’s TV Typewriter Cookbook, I’m pretty sure in the section on modifying TVs, he shows a switch to disconnect the detector, and to switch in some level of bias.

  5. No sparks? No mention of a coupling cap on the audio. Those sets are hot chassis. Plug the AC cord the wrong way and it isn’t good. I remember installing a similar thing in a color TV in the 70s. Even if the AC cord is polarized and correctly inserted, no guarantee what the common voltage is for audio or video. Could be zero. Could be a hundred volts or more.

    1. Japanese B&W sets from that era ususally run off 12V DC and have a transformer, many of them even had an extra socket or screw terminals to connect it to a car battery. This was often a main selling point, because back then camping was a big thing and caravans and other recreational vehicles had no fancy power supplies.

    2. There’s no audio input here, and generally nobody bothrred. Not much sound in those days, and if you needed it, build a tiny audio amp, with an LM380.

      Big clunky tube “portables” were transformerless because a transformer that could handle the filament current were heavy and big. But solid state caused a shift back to transformers, much smaller.

      Of course, many made do with tube sets, cheaper when used or sitting around, and there were lots of warnings about using an isolation transformer.

      I recall the TRS-80 monitor used optocouolers to keep things safe.

    3. I saw more than a few solid state color TV’s that had hot chassis, they were cost cutting crap. I blew up the built in modulator in a friend’s C-64 because of one of these. Early 80’s.

    1. Yup. When I started college (1969) my work-study job started me and a few others off modding over 250 Sharp 12″ B&W TVs for external video and audio. Once I (thought I) knew what I was doing I added input jacks to my Packard-Bell 10″ B&W TV. The Sharps were transformer powered, the P-B wasn’t, and I learned a valuable lesson.

  6. Most if not all of the monitors in the original coin operated video games (Space Race for example) had B&W TVs with the rear case removed and direct video inputs added. This continued until the Ball Brothers and others started selling designed for application video monitors and the last version were the vector scan monitors used by Atari with “Missile Comand”. All had CRTs of course.

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