Adding composite video and sound inputs to a 1976 TV (Panasonic TR-525)

We modify a cute Panasonic TR-525 portable TV to accept video and sound inputs, so we can use it as a retro computer monitor.
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Theme song: Festive Dinner by Pony Music

[@CuriousMarc]

Pinning some answers to the most frequent comments: - the filter is indeed for the sound subcarrier, not the color subcarrier (dumb me, the color subcarrier is already suppressed). Good catch commenters! - don't do this on a TV that has a live chassis (duh). Actually, if you have a live chassis TV, you should toss it. It's bad stuff that has been banned long ago. - shorting the high voltage anode capacitance to the TV chassis ground/tube ring discharges said capacitance, regardless of the set being connected to earth or not. You do that so it discharges into itself, instead of discharging into you… - the theme song name is in the doodly-doo, aka the description below the video.

[@carpetbomberz]

I'm always look for an enjoying any/all mentions and references to the Doodly-doo. I love hearing it's name as much as referring back to it on the actual YT page 👍

[@MagisterHamid]

We need more CRT videos!

[@lesliespeaker668]

This reassuring shade of brown color adds to the structural stability of the case.

[@TheFleetz]

I use to modify domestic Panasonic TVs for video and audio inputs for commercial, educational institutes and industrial applications back in the early 80’s. Use to design a basic interface board which had an 8 pin monitor plug and BNC and RCA connectors. The board had transistor buffers for impedance matching. Had also to fit mains isolation transformer as they were hot chassis’s. I probably did +300 over 3-4 years. Most of the monitors were used with U-Matic 3/4” Panasonic, Sony or JVC industrial video recorders. You video brought back memories…😀👍

[@michaelcalvin42]

Whether it's Apollo equipment, fancy test gear, or consumer electronics, your channel is always a joy to watch, and I usually learn something along the way. Keep up the good work!

[@trevorvanbremen4718]

Such memories!!! I did basically the SAME thing about 50 years ago... I needed a B&W monitor for the computer I'd just built, so I grabbed our old B&W TV and 'modded' it... The main difference between your version and my old one is that my 'donor unit' was built using 'FETs with pilot lights' (a.k.a. tubes). From memory, it was a Pye T-20 chassis (Pye was a common brand here in NZ) I took a slightly different approach to squelch the incoming noise from the final IF... I installed a switch for the filament of that final IF tube (I think it was an ECF80 triode + pentode?)

[@RingingResonance]

'FETs with pilot lights' I'm stealing this.

[@Nukle0n]

PSA to not attempt this on a "hot-chassis" TV, lots of black and white TVs use the null wire from the AC power as a common ground, which means they would be incredibly dangerous if modified with a composite jack. This one is not such a model luckily.

[@tekvax01]

I smoked a very expensive S-VHS machine this way... I'm still salty about it 28 years later...

[@compu85]

Finding an AC/DC set makes it easier to find one that's not hot chassis. Plus, wouldn't the cap block any AC? Hmm, unless the line cord was backwards...

[@Nukle0n]

@@compu85 or the outlet is wired backwards. or the extension cable/power strip. It's just too risky.

[@connerlabs]

Yup been there, done that, got zapped trying to add a headphone jack

[@Anthonytheredneck]

​@@compu85AC can travel though a capacitor, it is DC that is blocked by a capacitor

[@MVVblog]

In my latest video, I converted a small CRT TV into a portable Commodore emulator. It's always fun to play with these little marvels of days gone by.

[@CuriousMarc]

Love your videos. Such fun to listen to your beautiful Italian!

[@m.j.morshead]

I found one of these at a garage sale for $5 about ten years ago in immaculate condition when everyone was getting rid of crt television's,I never purchased it but when I drove past the property that evening it was on the curb, naturally I stopped and collected it.

[@Dennis-uc2gm]

I have a handful of different branded 5 inch portable B&W sets. I never could part with them even in their late useless state. I always thought about doing this exact thing which would make them rather usable again. There have been times when a portable NTSC monitor would of aided in some video signal troubleshooting. Nice project !

[@neilbarnes3557]

Nicely done, Marc - and kudos for selecting one with an isolated supply. As others have pointed out, live-chassis TVs can - and frequently were - lethal. I worked as a broadcast engineer with the BBC for over thirty years, and so I've seen inside an awful lot of TVs/monitors, but I still remember the TV my godfather built using an old green radar screen tube; electrostatic deflection in both directions and a green and black experience. Wonderful for a ten-year-old.

[@alexlandherr]

The first TV my family had that I remember was a CRT (I was born in June 2000). I also watched my first home media on VHS and later early DVD. Good memories…

[@ptonpc]

As a student I had a Black and White portable. Always felt weird to come home and see colour.

[@drstrangelove09]

I once used an FGPA on an Altera dev board to create a digital clock that displayed on a monitor and so I had to create the VGA signal with the D to As provided on the board. It was doable and quite nice, and accurate and adjustable with the push buttons on the board. Created digits using reverse engineering of fonts with gimp. I still have the VHDL somewhere.

[@gertebert]

Big shoutout to Ernst, HB9RXQ for supplying these schematics to the world!

[@CuriousMarc]

Thanks Ernst!

[@juergenschimmer960]

The 5.5MHz Filter is to supress the audio carrier ( For Mono Audio the sound carrier is 5.5MHz above the video carrier and gets mixed down with the video carrier to 5.5MHz IF at the demodulation Diode) The color subcarrier for PAL and NTSC was ( almost everywhere ) 4.43361875MHz. Long forgotten memorys

[@gertebert]

I still have a box full of 4.43361875 MHz crystals I harvested from old TV's. Never used one of them!

[@mrnmrn1]

Correct, but only PAL is 4.43MHz, NTSC is 3.58. There is a special PAL standard in South America which also uses 3.58MHz subcarrier. Usually, there is a color subcarrier filter in the video path of newer BW TVs to eliminate dot crawl during color program reception, seems like this one doesn't have it.

[@acmefixer1]

In the US, the audio FM subcarrier is 4.5 MHz above the video carrier.

[@Rob2]

@@acmefixer1 The schematic likely was for a European version of the same TV...

[@mrnmrn1]

​@@acmefixer1 Yes, and that's why removing the filter made such huge difference in horizontal resolution. Oddly enough, East-Europe had the best quality SD broadcast until the mid '90s. Here, the audio subcarrier was at 6.5MHz, therefore this (OIRT) standard limited the video bandwith the least. Combined with the SECAM color standard, which lacks the dot crawl effect that was an issue both with PAL and NTSC, and also lacks the susceptibility to phase distortions of NTSC, made probably the best quality SD broadcast standard. At least during live broadcast, because studio recordings were made in PAL, and transcoded to SECAM before the transmitter, so it cancelled some benefits of SECAM. SECAM (even MESECAM) recordings on VHS look a lot better compared both to PAL and NTSC, although tape droupouts are often emphasized by bright red and blue flashing lines.

[@carpetbomberz]

This is just the thing you need for the Apollo vhf video feed, especially if you go on a road show. 👍 The right tool, reversibly modified, for the right job. Analog Rulz!

[@zebop917]

The Bench of Healing and Modification - I love it 😀

[@Toby_Q]

You know... I wasn't really in the mood for a B&W TV repair, but I said to myself that I really wanted to hear Marc's intro song today. So I started it up, got interested, and then the audio portion DID NOT DISAPPOINT! Thanks, I needed that tonight!

[@MLX1401]

Always glad to see some vintage Tek AV test gear action 👀

[@richardkaz2336]

Back in the days when Australia used to actually manufacture and when schematics were available and allowed repairs to be carried out. Back in 1980 I picked up from the tip a 10"Audiosonic b/w portable TV with schematic inside. I was able to identify the problem, because they had voltages and expected CRO traces to fault find. I replace the vertical sync driver transistor and patch in a video feed via a large cap directly in to run my just built 4k MicroAce (Sinclair copy). My introduction into computing and 4k Basic.

[@Rory-jk9us]

The NTSC American standard color subcarrier frequency is 3.579545 MHz. 5.5 MHz would be the beat frequency created by the FM audio transmitter in Europe which was 5.5 MHz higher in frequency than the amplitude modulated video transmitter carrier. In the US the FM audio transmitter was 4.5 MHz above the video carrier. Digital over the air television still exists in the united states on RF channels 2 though 36. The frequencies above channel 37 are now allocated to cell phones. The digital television broadcast signals look like noise when viewed on an old analog TV. If you feed a spectrum analyzer with a TV antenna you will see the digital signals. If you connect an antenna to a digital TV set you can watch free over the air digital TV.

[@CuriousMarc]

You are right. Thus must be the 4.5 MHz filter for the audio carrier then.

[@AndyGoth111]

Now you've done your magic on two kinds of AGC!

[@erwin-1660]

Brings back memories! In the late 70s, electronics magazine Elektor had published a Ceefax/teletext decoder project. Installation in my then brand new Sony Trinitron involved interrupting the composite video signal and feeding it through the decoder. With the tv chassis being live, it was quite a risky operation... I was only 15 back then and getting things to work first time was such a confidence booster!

[@phuzz00]

The design of the case is interesting. With the brown colour, the rounded corners, and the grooves, I wonder if the designer was taking inspiration from an old Bakelite radio set?

[@acmefixer1]

At about 1:53 Marc said "There is no such thing as over the air TV..." Here in LA, we can receive all the TV stations over the air, with an antenna on the roof. It should be the same up there in Silicon Valley. Of course the person can pay for cable TV or a satellite dish, etc. But none of this has stopped over the air TV. Thanks for bring back old times, Marc. Your channel is the best. 👍 BTW this TV is isolated from the AC line by the power transformer. Viewers are cautioned that not all TVs have a transformer. Some TVs have the chassis connected to the AC line and doing this modification can result in a serious shock and safety hazard.

[@eDoc2020]

Yes but you need a DTV converter box.

[@EmmanuelRAYMOND69]

Qu'il est agréable de travailler sur des composants où l'on a pas besoin d'une loupe binoculaire pour les souder ... :)

[@Peter_S_]

Anybody looking for cute little CRT monitors for retro us should check out studio camera viewfinders like the Sony DXF-50. These little monitors are often super cheap and they produce beautiful images with only 12V power necessary. There are a lot of them out there which got very, very little on time during their lives and they generally lived in very clean studios. The only non-standard thing is that they want the video a little hotter at 1.4vpp rather than 1.0vpp.

[@KallePihlajasaari]

Even the eyepiece viewfinders were cool monitors. Many were wired to scan Right to left as they had a mirror to let the tube sit sideways across the top of the handycam.

[@soranuareane]

My granddad had one of those 505s that I looked at in the early 2000s. We had a full-sized CRT television and a motorized roof-mounted antenna, but the tiny TV was just so fascinating. The picture was too small to be useful to little me, but I was astonished they could fit a full television in such a small package.

[@michaelcherry8952]

Somebody get this man a Panasonic TR-005! He NEEDS one! He DESERVES one!🤣

[@skfalpink123]

I really miss CRT displays. Sure they were big and heavy, but as a kid I used to love turning the TV off at night, and then holding a fluorescent tube against CRT, see it glow away like a light sabre! Kids today will miss the awe and magic of doing that.

[@bayareapianist]

There was a time we could open up a tv ajd fix it. I did exactly the same thing back in mid 80s to my Sony B&W TV. I had planned to build a Z80 computer. But by year 87, i had saved enough money to buy a commodore 64. Then I used the TV's composite and audio which were better than channels 3 or 4.

[@jagmarc]

That's very useful modification because it future-proofs the TV a bit more

[@Hamporkchop]

I just converted a TRG-511T to accept a raspberry pi running Kodi, love watching old tv shows on it!

[@AmiPurple]

Some of the best stuff on KZbin! Thank you

[@ajjr1228]

Did a similar conversion to a 1980s portable black and white, no schematics and the video IC didn't have any markings, so I ended up having to look through NECs '80s catalog to find similar looking chips as the sound IC was using NEC.

[@DavePKW]

I think it was in the early 80s RadioShack sold a small, portable television/monitor. I used it with my VHS video camera. Good memories.

[@gertebert]

I once ordered some VHS videotapes in the States. Must have been 1990 or something. I just put enough cash dollars in an envelope and after 3 months the tapes arrived overhere in The Netherlands. In the good old nineties you could do that. I watched them a few times and forgot about them. After a decade has passed i thought it might be a good idea to make a copy. But that failed miserably. Could not make it work? How is that? Turned out I was very lucky and didn't know it: both my Sony VHS player and my Sony Trinitron could play NTSC.

[@hymermobiler]

Thanks Mac enjoyed that!

[@GordonjSmith1]

How great is that!

[@parkerlreed]

I've done that with a few of my old sets that just had an aerial but no inputs. Added in my own coaxial jack.

[@MoparStephen]

Awesome - I have a very clean Sony Trinitron KV-8000. It's an 8 inch colour from November 1977 and I would love to do a similar modification. I'm afraid to break the set though.

[@Runco990]

Hah! That was my teenage set! My eyes were much better then. Definitely one of your most technically challenging videos to date! 😄

[@bigsarge2085]

So cool.

[@MarcelHuguenin]

Nice distraction from the very complicated projects we love to see. I think most of us did projects similar to this one back in the days. Props for the professional execution as always Marc!

[@RobSchofield]

That was fun - great!

[@loganjorgensen]

That's cute you made it reversible, maybe just maybe the analog broadcasting will start up again.😆

[@gcewing]

Good job! I'm sure this is a totally authentic recreation of how they received video from the moon. :-)

[@BaconbuttywithCheese]

Very nice. I first saw the movie Alien in black and white!

[@Novous]

I always wondered as a kid what the different was between a CRT "TV" and a CRT "monitor" were other than presumably inputs and the ability to cycle at higher ("monitor") refresh rates. For the longest time as a kid, I assumed a monitor had way more circuitry or was completely different.

[@zyeborm]

Higher resolution, no interlacing (generally) basically a (decent) monitor is a really really high quality TV.

[@FindLiberty]

APPROVED

[@funkykoval2099]

I can recommend atarii 2600 with circus game or river raid. T-rex demo from PSX is also good. You can also made colour overlays like in vectrex console. Enjoy!

[@RA-II]

We love your show!!

[@sanches2]

My uncle did that for me on our first bw home tv so i can use it as a monitor for my apple II clone computer but he put a switch at the back. (Ca.1986) we got our color tv in 1990.

[@jeremiefaucher-goulet3365]

Perfect test music 😉😎

[@SeanBZA]

Have an equally small colour JVC television, which probably still is working. Has both battery option, and composite video input as well. PAL, NTSC and SECAM systems, with both NTSC colour burst frequencies as well.

[@cambridgemart2075]

We owned a lovely old Sanyo 5" monochrome TV, modl TC5 possibly? 12V plus internal rechargeable cells and featured in one of the Bond films fitted in the dash of a car as a 'radar' screen (ours was actually the original prop from the film!)

[@CuriousMarc]

Most valuable mini TV ever…

[@joelalain]

18:25 Marc missed the chance to say: "Mom i told you one day i'd be on TV!" ;-)

[@Wizardess]

Ah, memories. This brought to mind the venerable universal manual source, Sam's Photofacts. And I am completely gobsmacked that the still exist in essentially the same business. They are expensive and very accurate. But, then, "expensive" is relative. And my mental mind set is their prices from many many decades ago. {^_^}

[@williefleete]

Word of warning from experience, DO NOT do these mods on hot chassis style sets, did something like this on a small mains powered colour TV by removing the tuner and injecting composite (and audio) into the relevant points, blew out a camera and tripped an RCD as well as getting a bit of a shock when my foot touched one of the leads. Only do these mods on TV’s that use a mains transformer and/or are battery powered and otherwise aren’t referenced to mains neutral in any way

[@subject_5056h]

i see a video of Marc making a video of a video of him in which he makes a video of it.

[@kevinsmith3854]

Way cool!

[@KallePihlajasaari]

I would investigate complete removal of POWER to the IF amplifier circuit and injecting the video after the emitter follower transistor if that cannot be powered on its own.

[@jlwilliams]

“…the bench of healing and modification…” 😂🎉❤😊

[@andymouse]

CRT will always mean 'Cathode Ray Tube' to me....cheers.

[@RickBaconsAdventures]

the only PC allowed in the workshop is the one we look up datasheets on

[@woodturnerfran]

Hey Marc, I love your videos.... But every time you move the camera there's a load of low frequency rumble that hammers the subwoofer.... Would you consider adding a low frequency cut when you are processing the video?

[@frogz]

havnt watched this yet but this sounds useful!! i have a 2 inch crt i want to use as a monitor

[@darrenerickson1288]

I've seen similar work before, but yours (and the experimentation) is absolutely awesome. I have no need for a composite CRT monitor.... and still want to do this just to have done it. 😂

[@Xsiondu]

Oh man that's awesome

[@edgeeffect]

With all your restoring of Apollo Hardware, Vintage HP test equipment and Xerox Alto's and such like... You're finally "playing in my league" with cheap E. Bay junk. ;)

[@chrissavage5966]

Ah, nostalgia. Ain't what it used to be....

[@RobertKunzman]

I have a couple of tv transmitters I can send you. I had them setup on a few channel system. You can pick any channels you want.

[@ronjohnson9690]

Those speakers have a crisp and clear sound output! Please tell me you are the accompanying pianist on the score. It is a great jingle.

[@natebender4740]

Marc Please! We need to know what your title track is! Its such a jam.

[@swedenfrommycam]

Ah, zee curious Marc, 'e 'as zis dungeon grand, Sparks fly, arks soar, zee evolution's hand, Eets smells of times, moments past, oui oui, From caves to dungeons, a wondrous spree! In 'is 'oly dungeon, secrets abound, Master Ken, 'is weapon, always around, With a flick and a twist, 'e wields wit' flair, Mon dieu! Zee sparks fly, electrifying zee air! From cavemen's days, to dungeons so tight, Marc's journey's a tale of zee curious light, Evolution's dance, in zee flicker and flash, Sacré bleu! 'Tis a sight, a story en cache! So raise zee glass, let's toast to Marc's quest, In 'is 'oly dungeon, where moments jest, Zee smell of adventure, a symphony divine, Curious Marc, oui oui, a treasure of zee vine!

[@SubTroppo]

Never being one for splatter action movies, black and white (or monochrome as I was taught to say) was good enough for me for a long time - especially as colour TV watching in the UK was charged for at a much higher rate. If the writing is good enough the nature of the watching experience has no import. Seemingly, better technology has not overall engendered good programmes on a few channels - quite the reverse.

[@station240]

Maybe you could add a switch to add/remove a trimpot from the h-hold pot, so you can just switch between NTSC and PAL without wearing the pot out.

[@rastersoft]

I remember that my aunt gave me an old B&W tv when I was 16, and it had the internal schematics, so I tried to add a composite input too. It worked... for about a couple of hours, until something burnt inside and the tv died. I suspect that having connected it directly, without a decoupling capacitor, would have something to do.

[@markgreco1962]

Are we being led into another journey???? Does Marc have another long haul project coming? Can’t wait.

[@CuriousMarc]

Yes, the Teletypes will be returning with a vengeance…

[@minty_Joe]

Tune in next time, same channel for more details.

[@mumiemonstret]

I am surprised that there is a color subcarrier rejection filter. Weren't NTSC and PAL backwards compatible with monochrome TV sets?

[@Nukle0n]

They were but you'd get dot crawl and shimmers from the color carrier signal being interpreted as luminance. Having that filter there cleans up the image by rejecting that.

[@Rob2]

It is not for color subcarrier rejection but rather for sound subcarrier rejection, and it would work in Europe. I think the schematic is for a European version.

[@Nukle0n]

@@Rob2 There's both in the video, you'd know if you watched it.

[@PaulHuininken]

Nice!

[@TheTeflonTranny]

1975 goodness..Just like me..

[@hapskie]

It doesn't seem to be from Europe as it's 120v/60hz?

[@craigrenwick9132]

I use to have one !

[@HeffeJeffe78]

We grew up with a TR-555 in our house. I vividly recall watching the Tiananmen Square protests on that tiny screen.

[@thebiggerbyte5991]

A great modification! It would mean another hole in the casing, but couldn’t the mods be made switchable? Just a thought :)

[@ptonpc]

Very cool mods :)

[@CliveBagley]

Magnifique 👍🏼👍🏼

[@sp00fman1]

Always wondered how tondonthis...... but not found the need anymore with modern electronics

[@bzotto]

Can someone clarify what the purpose of the 47uF capacitor inline with the entering video signal is?

[@CuriousMarc]

It’s for feeding the video signal in without affecting the bias of the emitter follower stage nor the black level clamping diodes.

[@pete3897]

I don't mean to be rude, but you really have to work on re-perfecting those outro audio timings! I just can't handle it when I don't get a perfect finish those beautiful last 8 high-hat chits ;-)

[@2packs4sure]

What is the name of the piece of music that you end these videos with ?? I love it

[@frankhughes_vk6fh]

curious marc tune: The song is "Field, O My Field" 1933, Composer: Lev Knipper, Lyrics: Viktor Gusev.

[@2packs4sure]

@@frankhughes_vk6fh Thanks but I was hoping for the exact recording he uses..

[@CommodoreGreg]

​​@@2packs4sure I would see if that song is in the KZbin music library. Most likely if it's there then it's the version he's using.

[@2packs4sure]

@@CommodoreGreg I went down that road about a year ago and I've posted that question in the comments on several videos over the years.. I've gotten nowhere...

[@CommodoreGreg]

@@2packs4sure That's definitely frustrating. Hopefully someone figures it out.

[@alectrona6400]

I have a Panasonic TR-515A which is rather similar to this model and it shows no signs of life. Do I need a battery plugged in or something for it to work? I do know there were some bad caps which I had to replace for sure, but maybe there are more that I missed.

[@CuriousMarc]

No, no battery needed, but check the sense switch on the power plug insert at the back. That's the one that switches between battery and AC power. On my unit it did not work and made it appear as if the device was not working.

[@alectrona6400]

@@CuriousMarc Yep, it was the sense pin! I'm using a different power cable which didn't hit the sense pin so after pushing that in with a small object it works. I will definitely look into composite modding mine, thanks!

[@tron3entertainment]

I like what you did, but why not a portable color TV, instead?

[@Bedfford]

Maybe a dumb question, why discharge the CRT to the ground with the power cord unplugged? the ground wire are disconnected from the outlet and you don't have any reference to 0v to discharge. Thanks!

[@johnopalko5223]

The zero-volt (ground) reference for the circuit is the chassis. The line cord has nothing to do with it.

[@CuriousMarc]

I’m just discharging the high voltage cap (which includes the capacitance of the tube). Into itself. So it does not discharge on me.

[@unmanaged]

Marc what is the song you use in your videos?

[@averystablegenius]

How might the one of these be modified for X and Y inputs? I would like to use my old mini TVs to display Lissajous figures and otherwise function as an analog oscilloscope.

[@rocketman221projects]

It would need a different deflection yoke and a suitable driver if you want any vertical bandwidth. You would be better off looking for a cheap scope at a hamfest. It's not easy to make a vector display with magnetic deflection, but they were used in some arcade games. There are some articles online that show how to modify a TV for use with those games.

[@anthonybrunotheodd]

Could you add rgb component? Just curious?

[@drstrangelove09]

Might you have been in danger of a shock when discharging with that thinly insulated wire?

[@minty_Joe]

There may have been a bleeder resistor installed somewhere in the HV section or the insulation has a high tolerance to voltage. "You have a good point there, Herr Doctor..."

[@VitaliiKovalev-xb3tq]

Круто уважуха телевизор лайк жирный блеск

[@Lunchpacked180]

Does anyone know the song? It's not the "le thu" song that shazam and similar recognizes it at, or atleast it's none of the songs with that name when i search for it.

[@gustavnorbacker3313]

Yes please someone tell us! Got addicted to it through the years here at the channel.

[@Petertronic]

Do people not think to look at the video description?

[@MarkMcCluney]

I suppose folks ask this all the time so please forgive me, but does anyone what Marc's theme tune is called?