EEVblog - 2014-01-29
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. Facility tour: http://www.youtube.com/watch?v=mR_wJkxKSXU Forum: http://www.eevblog.com/forum/blog/eevblog-574-nec-analog-tv-if-modulator-teardown/ EEVblog Main Web Site: http://www.eevblog.com EEVblog Amazon Store: http://astore.amazon.com/eevblogstore-20 Donations: http://www.eevblog.com/donations/ Projects: http://www.eevblog.com/projects/ Electronics Info Wiki: http://www.eevblog.com/wiki/
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.
Very interesting!
"...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
For anyone interested (not that there's anything wrong with the manuals), the physical teardown starts at 0:32:05
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. :))
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.
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.
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 :)
I havn't owned a TV for nearly 4 years! And I don't miss it!
ah.. 9 years for me :p
These days i watch virtually NO tv maybe 1or2 hrs week at most because most of it is just garbage now
Is it still a TV if it isnt connected to an aerial? XD
The thing i love about this piece of equipment is that it's clearly intended for the owner to be their own service technician.
*employ their own technical division
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.
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...
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?
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?
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.
10:30 funny how "seal level" actually still makes kinda sense. xD
+JohannaMueller57 haha I noticed this too.
I love it when 'future dave' sends a message about component names.
One day we will get a warning from him from the future ;-)
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.
none of that is done in any of that gear though XD
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.
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. :)
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.
Brohoof.
Do it Maxx, it's been a long time since you uploaded any in-depth vids !
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 :)
BTW, so far +6 for a highly disparaging comment? People can be so cruel.
@sprybug
Anyone who knows Maxx's channel will know what the pony is about, nobody else matters
No dust? WHAT? TAKE MY MONEY!!!!
how much you got - its a clean room like a server farm ;)
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.
where can i find the scanned documentation?
1:04:25 All new caps!
A foreign concept these days: make sure the documentation is sufficient for someone who can't get any more documentation.
A TCXO has no oven, it is Temperature Compensated, not oven controlled like an OCXO.
Michael Terrell The tolerances for the wide band TV signal , a TCXO is fine.
so much for going to sleep :)
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.
Fantastic stuff. Show me more!! I am into analogue broadcast equipment.
1:04:22 AHAHAH Awesome Only You Dave can do this things
This was operational in Iraq for 30 years? :P
+fungunfanatic I'm glad I'm not the only one to make that terrible pun.
Awesome video Dave!! These are the videos I look forward to and watch in rapture.
Would you be able to smell what vintage a device is?
WAIT. i just got the reference :warning will robinson, form lost in space ! ive been watching your videos for year haha..
I can almost smell that vintage. Great video and I loved the TV Xmitter tour too. Cheers !
2:50 if you have to ask the price, then you can't afford it!
"If you have to ask for the price, you can't afford it." That is the most true statement i have heard all day.
4:15 well that's a not-so-nice way of starting a manual XD DEATH ON CONTACT
0:00 Bracing for epic HF voodoo stuff!
I just found this and the TX site tour vid - great work
wondering about the other components you have and where there teardown vid is ???
sniff
38:07
:)
Great video Dave, amazing that most chips are NEC, BLIMEY! Keep them up!
I remember some of the safety info for high power transmitters, “because of this, whilst the broadcaster is in operation..."
Above seal level lol
I like your tshirt :)
Could you digitize and upload the schematics so we can gawk at them?
man i would love to use this at home beautifully made bit of kit!!
I've been super excited about this one!
Maximam Efficiency!
Power it up- :)
32:12 well god damn finally get your screwdriver already
Been waiting for this. Yay!
Gotta love the "Hot Snot". It holds everything down.
Cooking With Cows - 2014-01-29
So now Dave is going to run his own pirate TV channel to bring EEVblog over all of Baulkham Hills :D
Robin A. Jensen - 2020-01-27
No, he is going out to all of Australia. So all Aussies with bad internet connection, can now see EEVblog in color! :-D