EEVblog

Dave looks through the documentation for the vintage 1980 NEC PCN-1205AH 5kW Analog TV Transmitter that used to transmit the CH7 TV frequency in Sydney
He then tears down the HPA-3696 IF Modulator used in the system.
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[@whitcwa]

Dave, you mention someone using the TV signal as a frequency reference. The TV station I work at once got a call from NASA asking what had happened to our signal. They were measuring the color subcarrier frequency (3.579545Mhz), not the RF carrier frequency. It turned out that they had been using our signal to check calibration on field equipment. We had been using a rubidium standard, but it had recently failed so we went back to a normal ovenized oscillator. It was well within tolerance for broadcast, but not nearly good enough for their purposes. They gave us an HP cesium standard to restore our stability.

[@0xbenedikt]

Very interesting!

[@TankR]

"...So NASA just gave us a cesium clock." Some engineers have all the luck... Also I like that NASA has enough cesium clocks laying around to give them to the odd broadcaster to fix the signal their piggybacking off of instead of rolling their own transmitter

[@moldyoldie7888]

Your tax dollars at work. Oh well.

[@whitcwa]

@@moldyoldie7888 Wise spending compared to equiping each location with its own cesium clock.

[@moldyoldie7888]

@@whitcwa Touche`

[@scotshabalam2432]

The thing i love about this piece of equipment is that it's clearly intended for the owner to be their own service technician.

[@mycosys]

*employ their own technical division

[@CH_Pechiar]

Analogue TV is an outstanding engineering development. One of the design specifications being that on the transmitter side all the complex (thus expensive) processes should be done to the signals so that the TV sets would be really simple (thus inexpensive), in order to achieve the widest audience possible. The gamma pre-equalization to match the nonlinearity of the CRTs, the number of frames and timings to use the line frequency as the reference, the use of POV and the concept of interlaced lines in order to reduce required bandwidth, etc. Moreover, when colour was introduced it had to be done in such a way that B&W sets will still work (backwards compatibility). Colour was added to a signal that was not design for that and this by itself is a great achievement.

[@mycosys]

none of that is done in any of that gear though XD

[@taylorschuller8386]

"If you have to ask for the price, you can't afford it." That is the most true statement i have heard all day.

[@ClosetYeti]

For anyone interested (not that there's anything wrong with the manuals), the physical teardown starts at 0:32:05

[@RadioChief52]

I maintained a higher powered version of a very similar model NEC transmitter on channel 6 over here in the states. Two 30 kW transmitters paralleled for 60 kW into a circular polarized antenna. It was a very well behaved transmitter. Well thought out design. Sadly at the end of the analog era it was unceremoniously removed and sold for scrap.

[@sumatoborukiSaru]

37:15 "Some weird-ass, old style lamp" IS a lamp. It's a tattle-tale neon that glows when the fuse is blown. 1:02:40 to 1:04:25 Looks like they recapped the entire PSU. The main filters are very modern, non NEC brand & the control PCB is filled with Hitano EXR caps from WES. 1:09:12 The 'sha' in Kinsekisha is dervived from kaisha, meaning 'company' in Japanese. So, to a Japanese person, it would read as Kinseki Co. Lab. Somebody within NEC obviously thought it was a gross error to exclude the honorific 'sha' from the name & 'pencilled it in' just before printing. :))

[@oriole8789]

I always make time for Dave's vids even when I'm busy. ;) An important thing to realize is that even though construction techniques may change with time, the laws of physics do not. This type of gear gives a comparatively clear idea of how different system requirements were painstakingly addressed. Modern gear is all simulated with $250k RF & EM software, but this gear is basically manufactured from the combined engineering experience of that time. Whatever needed to be calculated, was done manually.. and RF & EM math is no walk in the park. NEC probably lost a lot of their "vertical integration" (when a company manufactures many of their own components for their products) when China and Taiwan became prominent in their industry. Same deal happened with Sony and others. Sony used to be all made in Japan. Then a mix of Japan & Taiwan. And today, basically whatever country is cheapest.. which isn't even China anymore. :)

[@themainproblem]

At a former employer, they had a communications hub for communications to all stores. It was built with NEC gear and it was just amazingly nice in construction quality. Even the electrical service panels were just gorgeous! Beautifully designed and executed. First rate all the way around. NEC rocks!

[@CookingWithCows]

So now Dave is going to run his own pirate TV channel to bring EEVblog over all of Baulkham Hills :D

[@robina.jensen6114]

No, he is going out to all of Australia. So all Aussies with bad internet connection, can now see EEVblog in color! :-D

[@usoppbarbosa981]

when i see the amount of work put into getting a clean TV signal out.. it makes me think.. if TV channels did put the same effort for content creativity, i'd still own a TV today :)

[@docdaneeka3424]

I havn't owned a TV for nearly 4 years! And I don't miss it!

[@usoppbarbosa981]

ah.. 9 years for me :p

[@willrobbinson]

These days i watch virtually NO tv maybe 1or2 hrs week at most because most of it is just garbage now

[@mycosys]

Is it still a TV if it isnt connected to an aerial? XD

[@paulstubbs7678]

Dave, the TV derived frequency standard idea you referred to was NOT done from the RF carrier frequency, but from the video sync frequency of 15.625KHz, which was usually derived from a Caesium etc atomic reference back at the TV station, not at the transmitter site. As the transmitter bandwidth is about 5.5MHz, a TCXO is fine.

[@MrCapacitator]

The oscillator was not invented at the same time, Gouriet actually invented it 10 year before Clapp. Gouriet in 1938 and Clapp in 1948. Due to wartime security Gouriet's oscillator design was kept secret until after WWII, the same circuit was then independently discovered by Clapp and published by him.

[@dawson345]

I love it when 'future dave' sends a message about component names.

[@0xbenedikt]

One day we will get a warning from him from the future ;-)

[@hankus253]

I've been looking for the gizmo the cranks the audio up several DBs when a commercial is being aired, but haven't seen it yet.

[@michaelterrell]

That is done in the studio. At one time Broadcast Engineers were allowed to do their jobs, not be mandated to by the Marketing Department.

[@ersonthemesa]

I can almost smell that vintage. Great video and I loved the TV Xmitter tour too. Cheers !

[@Maxxarcade]

That thing has some beautiful construction. I had to LOL at the replacement Jamicon cap that someone put in there. Looks like that may have been done in the 90's. This makes me want to dig out my 1950's military signal generator and do a video about it. It's all tube based with big oil caps, and has the same immaculate construction.

[@fuzzybobbles]

Please do. I for one would like to see it. :-D

[@sprybug]

Brohoof.

[@ianc4901]

Do it Maxx, it's been a long time since you uploaded any in-depth vids !

[@torcs10]

If you do it than I will do a Video about My Old Russian Radiotehnika S90 speaker. I will disassemble it. It has Oil caps and big resistors in it :)

[@sprybug]

BTW, so far +6 for a highly disparaging comment? People can be so cruel.

[@WarpRadio]

seeing this, even now, today, still makes me drool- in awe and give me that "warm fuzzy feeling" that makes me want to break out some old RF equipment and start playing with it again :)

[@johncrunk8038]

These TV videos stirred memories from the past. Although the stuff I worked with in the military in the 60's packed a bit more power, the quality and heft of the equipment was about the same. Good job!

[@terrywilson4118]

The SAW filter at 1:01 in your video is the vestigual side band filter (VSBF). It would be used to filter out the upper(higher frequencies)of the lower sideband from the video modulator output to create the final "vestigual sideband signal", which is quite a critical requirement to keep things within the correct bandwidth before it's fed to the IF mixer and then RF amplifiers hence it has to be in a temperature regulated oven. in otherwords only the full upper sideband is transmitted and the low frequency portion of the lower sideband so everything thats needed fits within the 7Mhz TV channel bandwidth.

[@josugambee3701]

If that documentation is hand-typed, I really hope it's a photocopy for the sake of the poor guy who would've had do produce over 1000 copies...

[@kilrahvp]

Beautiful stuff. Seeing all the discrete stuff just has so much more "charm" than... basically having the whole thing in a single chip like everything nowadays.

[@vk6xre]

This takes me back... I used to maintain the NEC txs back in the early 80s for ABC (Telecom Australia). Great gear.

[@mannys4539]

thank you for opening up things i would normally never get a chance to disassemble ive been stuck watching ur vids for like 2 days strait its like getting a free electrics 101 lesson just watching you

[@pulesjet]

Walking down Memory Lane here. Worked on NEC Line of Sight (LOS) Microwave radio's for more then a few years. Our stuff looked remarkably similar to this type equipment. Some of the most dependable equipment I've ever dealt with. Always gave you hints before a fail. You had more then enough time to correct the situation before things went DEAD BUG. Those NEC service manuals would lead you down the rabbet hole rather easy. Our radio's employed the same Quadrature amplitude modulation (QAM) modulation . Top shelf equipment for the time. Nothing like the Dated Rubbish we had to use in the Military. LOL

[@pulesjet]

Those NEC Radios had some crazily stable frequency outputs. Something like 0.000,0001 PPM over a years time.

[@yaidontknowwhattoput]

Bit late on the comments here but now I work on these. A video for everything. Good on ya.

[@fuzzybobbles]

YAY!!! I discover this at 1-25am. Time to get more beer out of the fridge and hope I'm not too tired for work at 6am tomorrow morning.

[@yaghiyahbrenner8902]

Hats off to the engineering / documentation team.electronic craft at its best. good tear down.

[@JimTheZombieHunter]

@22:19 - I used to meticulously align the optics of Minolta copiers (and later MFPs) - skew, slew, trapezoidal distortion .. to within 1/2 of a pencil line of the original document. Until the day that I watched a customer toss a pile of paper into the document feeder tray. lol. Yup, they didn't care.

[@Samsgarden]

I like the sense of nostalgia and feel for the "qualitative", you bring to clinical logical devices.

[@morelenmir]

Did they just GIVE you these devices Dave? Wow!!! It is very strange. Just from watching these videos I can smell the electronics! When I was very young - 3-4 - I would sit quietly and watch my father repair televisions. This was back in the late seventies and, while no doubt hugely inferior in build quality the various internal panels were made up of the same incongruous mixture of half-solid-state, half-valve design and ALL through-hole discrete components. All the bright colours and interesting shapes used to leave me spell bound. The smell of solder and hum of a big pistol soldering iron are massively evocative for me and lodged permanently in my brain. I just wish I had actually LEARNED electronics rather than watched it!

[@krisraps]

Woow, This Is Pure History You Holding, Wow !

[@aserta]

The most nostalgic thing in this whole video for me has to be the type writer ink that smudged on the other page. I'm only 26 but i still remember (and have) those pesky type writers and all the damn quirks you had to put up with in order to use them properly.

[@TheChipmunk2008]

Dave, take a closer look at the fuseholder, it MIGHT be the type RS used to sell that has a neon or LED across the fuse to light up when the fuse blows maybe?

[@alpcns]

Exactly. I have seen the exact same types on military radar equipment. When the fuse blows, the neon (or LED) lights up. Very nice construction.

[@hugoromeyn4582]

Not cost saving as in consumer gear... I Love that. That's the reason why it has been in service for over a 30 years.

[@sammiejansen981]

One and a half minutes into this video, and I feel this is going to be a great video! Thanks mate!

[@CH_Pechiar]

It is unbelievable how clean everything is. Also on the previous video of the tour. The output valve with its massive airflow around it and perfectly clean. Was the air inside the whole building treated, in some way, like purified?

[@gglovato]

Dave, don't you want to test the capacitance of those big caps to see how much they drifted over time and what their current ESR is?

[@batsali99]

Beautiful. I'd really like to see a teardown of the power amp of a TV transmitter. Keep up the good work, Dave. Love your channel.

[@theLuigiFan0007Productions]

Best. Teardown. Ever... And I still have 30m26s left to go! I loved the first part, no need to skip. The documentation is as important as the teardown. Question, If it has EVERY schematic, is it possible to hack one up if you have lots of free time? LOL That sounds like something I would try haha. PoLoMoTo2534 No dust? WHAT? TAKE MY MONEY!!!! That amazed me too, actually it nearly scared me, considering the inside of my PC after cleaning it only 3 months ago....... and this thing, spotless. This thing is truly overengineered, which is what I call true engineering. Such attention to detail, so much care put into the construction. I want one! Old electronics were so reliable, what happened. I cant wait untill he posts the manual, I will download it even if its 2GB+. I want to put it on my PC and read it untill I understand everything (I do this with anything I get, download the service manual and read till it makes sense). I wonder if I could find it already on the internet. In my opinion, analog signals are FAR more reliable and travel much further compared to digital. You can get just as good quality with analog as digital also. What truly made me think was the card slots, they are very similar to something I have drawn diagrams for and want to make someday. +1 to the people who made this thing happen! I cant believe I watch both videos without doing anything else. I guess I could label it education...

[@whitcwa]

A TCXO was certainly sufficient for broadcast purposes. The carrier tolerance in the US was 1KHZ. .Our RCA transmitter had an OCXO. In addition to automated in-house frequency measurement and logging, my station hired a frequency monitoring service which sent us monthly reports.

[@willrobbinson]

Its an end of an era of great tube transmitters, ps the pa tubes typically lasted 2-3 years, those racks had rear fan cooling via an air intake filter hence little dust . NEC did make some great stuff back then hence 30year life ect only to be replaced by silicon filled multiple plug in pa modules that have no interesting values ect, but thats progress what ever that is. I too appreciate the amount of work that went into these transmitters & other equipment truly amazing

[@video99couk]

Your T-shirt got me thinking about the 555 reset circuit. It is not well defined, did you know that? On some 555 timers, reset makes the output stop. Others it holds it high, and others again it holds the output low. I know this because I was making a modification to a car alarm some years ago, where the reset condition actually mattered.

[@cdigames]

That Oven Controller board at 56:00 looked absolutely TOASTY! I haven't seen a PCB that burnt looking since I had a multimeter blow up on me!

[@mq1991]

Yeah I was very surprised he didn't comment on that. If anything, he seemed perplexed where the soot was coming from.

[@JohannaMueller57]

10:30 funny how "seal level" actually still makes kinda sense. xD

[@TomStorey96]

+JohannaMueller57 haha I noticed this too.

[@maxsnts]

I work on IT with data-center and stuff... and the lack of dust on these after 30 years is still stunning.

[@blabby102]

In Japanese, sha (社) can mean "company". When company names are translated into English, sometimes they include it and sometimes they don't. They must have changed their mind about their English name.

[@trangotowergmail]

Amazing how dust free the instrument stayed for 3 decades. The cooling air must have gotten excellent dust filtering.

[@jaryH3]

Hexacapacitors are awesome idea. I bet they are hexa-shaped to fill the space well. Like the bees honeycomb.

[@BAMBAM5476]

No dust there would be filters on the vents for dust and bugs. Love these video's Dave keep it up.

[@ayrendraganas8686]

server rooms are pretty much cleanrooms

[@pelor92]

my guess for the spacers is that they put them there has to do with capacitive coupling between pins putting a dielectric material in there other then air changes the capacitance between pins to alter their frequency characteristic in some way...

[@AureliusR]

Awesome video Dave!! These are the videos I look forward to and watch in rapture.

[@radial9202]

The large blue hexagon electrolytic capacitors are toroidal, you will note that the centre core is offsets the connecting screws. Not really sure why the are manufactured or what the advantage is for a hex case though? You mentioned input as being 5 KW, That would be amazingly efficient, I think the input would be more like 15 KW with 10 KW lost in heat and just 5 KW available at the RF output terminal, this does not include any losses in the external feeder lines. Great manuals, glad you showed us those, real masterpieces.

[@whitcwa]

You're very close. The spec sheet said 16 KW.

[@K7AGE]

I think people used the color subcarrier frequency as a reference and not the channel frequency. It was common at the TV networks to lock their sync generators to a rubidium standard. So, if you could grab the 4.43 or 3.58 MHz out of a TV set that was locked to the station, you could get an accurate reference.

[@BryGuy2001]

I am surprised my firewall "porn filter" didn't block this video. Another great video. Thank you for sharing!

[@casperhito]

I've been super excited about this one!

[@petersage5157]

Looks like more than a few people have had a go at those JIS screws with Phillips screwdrivers and chowdered them up a bit.

[@ronaldlijs]

Great video Dave, amazing that most chips are NEC, BLIMEY! Keep them up!

[@pedrocordebello]

Great teardown video, Dave! Such a nice piece of gear!! =D

[@wel97459]

The Shielding on the audio is a big deal, you don't want to have video signals on the audio. FYI that audio transform is worth a penny on ebay don't trash it.

[@geoffclulow8632]

Fantastic stuff. Show me more!! I am into analogue broadcast equipment.

[@HDXFH]

man i would love to use this at home beautifully made bit of kit!!

[@RiaRadioFMHD773]

Gotta love the "Hot Snot". It holds everything down.

[@michaelterrell]

A TCXO has no oven, it is Temperature Compensated, not oven controlled like an OCXO.

[@andrewagner9212]

Michael Terrell The tolerances for the wide band TV signal , a TCXO is fine.

[@fordprefect2735]

@@andrewagner9212 In Europe big transmitters sharing the same channel used précision offset to minimise interference. The précision had to be on the order of frame frequency.

[@alfonsoflorio]

smelling the 30 years old electronic.... I am in tears

[@Abhishek-C92]

NEC is a no joke company who builds serious things with care so much it will run forever.Still NEC Soc and decoder chips are used for set top boxes, pci tv card and in many other applications.

[@RobertBardos]

dave i recognise that soot, thats magic smoke soot. someome somehow at somepoint released some magic smoke from that machine. maybe a lightening strike? was that at the power input?

[@rib180]

That VESTIGIAL SIDE BAND filter (heated SAW filter) would be interesting to see the exact precision passband. I think that strips off the upper sideband so it does not interfere with color subcarrier or audio FM.

[@XOIIOXOIIO]

That's a neat power switch design, never seen that. I haven't watched much of this yet but I do hope dearly he tries to power some of this stuff up.

[@uzaiyaro]

I haven't watched the whole thing yet, but just the documentation alone is really interesting. I suppose a lot of people would say "you don't get it like this anymore", but I'd imagine for something like a TV or radio transmitter, you still would. Though it'd probably be quite modularised now, you'd still have to have reams of documentation in order to run something like this...

[@strangersound]

The documentation is definitely.art. Beautiful stuff. I'm not even to the innards yet. ;) Is the FET attenuator a limiter circuit?

[@roystonrichards3368]

I remember some of the safety info for high power transmitters, “because of this, whilst the broadcaster is in operation..."

[@alexhartman4447]

I work in broadcast, cost (today) for a 500w Digital transmitter in the states is around $40k. That scale is pretty linear based on output.

[@alexhartman4447]

Best guess for this particular box would've been in the $700k USD range, before shipping from Japan of course.

[@matthiasBdot]

thanks for reading the f**king manual! :)

[@Trusten-rw2st]

Very funny to see. I´m born in Oct 15 1981, quality product from the early 80´s !

[@NeverTalkToCops1]

63 engineers worked on that box and died early. Black magic analog design.

[@ryans413]

There is no dust because the rooms these things are held in are well ventilated. Dust ruins the life span of electronics.

[@theLuigiFan0007Productions]

HDXFH I agree that is the definition of a proper power supply. I dont think a review could do it justice. It obviously has some amps, I wonder what the max current is! Those are some weird capacitors though, never seen any like it. Iv seen flattened ones, but not hexagonal. I doubt the PSU had ever gone over 30%-40% load the way it looks.

[@TheBas1984]

Very interesting!! I really like broadcast stuff, its build like a tank, and very reliable. I am also a radio amateur (PA1BJS). Is there a chance that you test the transmitter on a dummyload or something, to explain a little more how it works? Groeten! ("greetings from" in Dutch) Bas

[@donpalmera]

Got to love that Japlish documentation.. at least it's not really recent and doesn't have loads of "born in Japan English".. so other than the weird grammar and fruity selection of adjectives it should be readable. I was working with a company that was making some units to go into apartments and all the documentation said "mansion" instead of apartment because that's what they call apartments over here.. I kept telling them that mansion is something very different in real English but I'm pretty sure they shipped out uncorrected manuals.

[@Seansmit23]

Been waiting for this. Yay!

[@wdavem]

BIG thumbs up!!! BEAUTIFUL and historic piece you have there. I'm very into all things analog video. I'm watching your vid as I'm up late working on a difficult fix on a BVU 950 Umatic VTR. Likely this model transmitted over your gear there often in the 90's if they ever used 3/4" @ your channel 7 though maybe they had bigger better stuff. I need all the info and background I can get as I never 'worked' in the industry or learned this in school. I don't care what others say, perhaps they get bored easily and it's not hard to skip ahead so what's not to like? I don't know, maybe separate the service manual into another vid but please include as much as you like and Thank You!!

[@andrewhellershanks8315]

At 1:09:59, the manual shows the oscillator was designed for "maximam" efficiency. :)

[@legomaniac150]

Could you scan all of that manual for us to read online? Much love if you do :P

[@VenturiLife]

I'd say the typewritten areas of the manual were done with a teleprinter or on an impact line printer of some kind.

[@haraldlindohf4032]

Would you be able to smell what vintage a device is?

[@zaprodk]

1:04:25 All new caps!

[@HDXFH]

That is a Proper PSU!!!!

[@BlueSkyScholar]

I had care of a pair of PCN1430AL's 30KW Low VHF that ran in tandem for 50KW output (see my older vids) It was a little more modern ~1987 with PLL exciters. The only major servicing problem in its later years was NEC was not only an equipment mfgr they were a component mfgr and there are alot of single purpose IC's that were pure unobtanium.

[@redtails]

8:29 looks like there's a typo in this documentation? The PCN-1213 is available in 10kW and 13kW, and the PCN-1225 is also available in 20 and 25kW..? The last two digits seem to tell something about wattage, but not in all models

[@sysmatt]

That fuse holder probably has a neon blow indicator bulb

[@dedskin1]

As you listen to him you can feel knowledge draining out of your brain

[@andiyladdie3188]

Finnaly done! Thnanks Dave!!!

[@senorjp21]

A foreign concept these days: make sure the documentation is sufficient for someone who can't get any more documentation.

[@rsattahip]

Digital Dave is lost in the analog era. My first oscilloscope (at age 14) was primarily for doing IF alignments on old analog TV's and radios.

[@euniceokoth8070]

Otley of my favourite place in the UK to offer

[@PA2OLD]

Ah... I was right on twitter, it is some sort of heating panel. If you have more riddles, then also give the answer after a while on twitter... Nice and interesting video !!

[@94Gidge]

did you end up tearing down the other gear?.

[@redtails]

22:29 MENTAL CRISIS XD, electrical engineers spend tens of thousands of hours over-engineering an industrial product, greatly focusing on quality and people still get crappy picture quality on their PoS TV

[@Murphistic]

This 5kW puppy is really awesome. Now I'm wondering how big is the 2 megawatt MW radio transmitter I know about :) .