Hi all,

I have a Philco Predicta TV on its way from the US, and I was wondering about powering it up. I know of course about the lower voltage, but what about the frequency?

There are step down (with isolation if you want) transformers available here:

http://www.tortech.com.au/stepdown.html

but I'm curious to know if the electronics will have issues running at 50Hz instead of 60Hz. I have read that some of the TV transformers may resonate incorrectly and run hot. If anyone has a US TV that they have powered up over here with or without problems, I'd greatly appreciate the info. There are a few solutions to getting the right frequency, but they seem unwieldy or expensive. (Or both.)

Cheers,

Adam

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

Eddy current losses are proportional to the square of the frequency, so going from 60 to 50 Hz should reduce the heat generated in the power transformer, so that should be OK.

I suppose it then depends if any of the frequencies generated for the various purposes in the receiver are tied to the line frequency, or are generated internally eg crystal controlled.

Hmmm... I hadn't thought about the line frequency. With any luck, it will be internally generated otherwise I'll have to sort out an inverter. It's probably easiest to buy a 12V DC to 110V AC inverter from the states and then use a chunky power supply to run it.

In terms of supplying a 525 line video signal, there is a device called Aurora that will output to all TV standards, including 425 line. Found here:

http://www.tech-retro.com/Aurora_Design/Home.html

I'll probably end up getting one of these in time, as I think I'll need it. I remember years ago when connecting a video game console to a Philips K9 I could set the console to run at 60Hz (it had been modded). All I had to do was adjust the vertical hold and it was fine. Not sure if I can be lucky with that trick this time. When the TV comes in and I can safely power it, I'll keep you posted.

Thanks again,

Adam

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

I'm not into TVs but someone else here will know.

I suppose another source of frequency for internal use would be the actual TV signal.

The TV's internal timebase oscillators (Horizontal and Vertical) are internally generated so the 50/60 Hz supply frequency will not be an issue.

Due to the differing transmission standards between the US and Australia you will have issues trying to receive local transmissions. The difference in H Osc frequencies between the two standards in so small that it doesn't really matter. The V Osc frequencies differ by 10 Hz (Aust = 50 Hz and USA = 60 Hz). Most TV's have enough adjustment range in the Vertical Hold control to cover this difference. Sometimes component values will need adjusting if the Vertical Hold control does not have enough adjustment.

The biggest problem is sound. The USA sound carrier is 4.5 MHz offset while the Aust one is 5.5 MHz. This means you will be able to receive a picture but not the sound. If you're lucky you can readjust the sound IF transformers to the higher frequency otherwise component values will need altering.

Finally, the American TV channels are on different frequencies, some are near ours so you may be able to get 1 or 2 channels. Since analogue TV transmissions end next year, these issues are largely academic since there will be nothing to receive in around 14 months time!

If you get an Aurora to give you a 525 line signal, then you won't have any problems as the TV will be running on the frequency standards it was designed for. It will also enable you to keep using the set when analogue broadcasting ends.

"Eddy current losses are proportional to the square of the frequency, so going from 60 to 50 Hz should reduce the heat generated in the power transformer, so that should be OK."

Oh, eddy current losses will be less, but the transformer will need more turns on the primary to avoid core saturation, on a transformer designed for 60Hz that is run on 50Hz. Depends on how much design margin the manufacturer used, they may have cut it tight to keep costs down. One answer is to use a lower voltage, like 110V instead of 125V.

I have a few Aussie radios with power transforemrs, and they run quite cool on American 60Hz, and I have avaliable a pair of 120VACs, one 180 degrees out of phase, to give me 240VAC. You could say that American power companies feed most homes with 240V60Hz, with a centertap that goes to ground earth. going the other way can be more of a problem, though.

If the TV is a "hot chassis" design, then the powerline mains frequency issue goes away. But be sure your voltage reducing autoformer gives you 0 to 120VAV, ie the output measures 0V and 120V to earth ground, and not 120 to 230VAC, ie, a 120V output that measures to ground earth 120V and 230VAC. Or use a true isolating transformer 230Vin to isolated 120V out.

As for generating an RF signal to feed the TV, you could get a TV modulator intended for the USA market to modulate a video signal and audio signal from, say a DVD player that is set to produce NTSC video (there should be a menu option in the DVD player for this). These modulators will put the RF carrier on the American channel 3 or 4. The American chain Radio Shack sells such modulators, and evilbay likely has them too. Usually powered by a wall wart, so you should be able to substitute your own, or run it off the same power source the TV will have.

Thanks a lot guys, sounds like it won't be all that tricky to get this TV up and running after all. I have a feeling that the Predicta does in fact use a hot chassis, so an isolation tx will be the way to go. Hadn't thought about a US RF converter, I already have a cheap and cheerful DVD player with NTSC out, and the RF option will be way cheaper than the Aurora. A cheap set top box and I'll be able to watch anything.

Do you guys like to watch certain content on your masterpieces? I want to have a "black and white" night when I'm finished doing up my HMV, showing programs like the very original Twilight Zone, and a few other monochrome movies. I think that a film like Tron Legacy could look a little out of place!

Something a mate in the UK suggested was to ask the sellers of these international TVs was to disconnect and tie down the neck socket/board prior to shipping. Too late for my Predicta, already on its way. I have another GE brand TV on its way as well, and at least I could ask them to do this. (Don't know if they will though)


More info when I have some.

Cheers,

Adam

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

Do you guys like to watch certain content on your masterpieces?

I do this with my radios. I usually have them tuned to a station that plays older music, which I don't mind listening to.

When someone asks why I am listening to 1930's and 1940's music at work I just point to the source and say old radios play old music. Oddly enough some actually believe it!

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

If a programme was made in black-and-white, I think it looks "cleaner" on a monochrome set, but old colour programmes usually look good too. The trouble with modern colour material is it's often recorded without any thought as to what it will look like in monochrome and a standard aspect ratio. So I do use my Pye mostly for old stuff.

""I just point to the source and say old radios play old music.""

I think this makes a lot of sense. I just can't imagine Hip Hop belting out of a beautiful old time radio… it just doesn't fit.

And mono movies definitely work well on the B & W TVS. When playing around with the pic geometry on the HMV, I noticed that a colour image showed chrominance signal interference. But I realise that Susan was referring to lighting and subject composition. Just like in photography, it can actually be much harder to get a great shot in B & W as its far less forgiving. I want to start a mono library of films to show on my screens, they just look so much better than on an LCD TV of today.

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

In the early days of colour, studio control rooms had a monochrome monitor so the image could be checked in black and white. You wouldn't use red lettering on a green background, for example, because it would be nearly invisible in mono.

There's ways to avoid the chrominance pattern. Check through the older posts in this section. I use the green output only on my DVD player. This trick doesn't work on my set-top box for some reason, but I rarely watch the stuff coming down the aerial!

Thanks for that Susan, I'll have a scout round the forums.

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

One way to get B&W only video is to use the luma line of an S-video jack to feed the TV modulator, if your DVD player has an S video jack output. Otherwise, as mentioned above, you can use the green video jack of the 3 RCA jacks for "component video", Y, Pr, Pb. "Y" is the B&W luma video. But the player needs to be set to interlaced component output, not progressive scan.

In the USA, some digital TV converter boxes (ATSC DTV to NTSC) came with S-video output jacks, and that luma line will be a clean source of B&W video. The Channel Master CM7000 has an analogue filter and mixer chip that takes luma and chroma video from the DACs, filters them and makes composite video to feed its TV modulator. I've modified one of these by breaking the chroma input to this chip, thus making B&W modulatoed RF signal to feed my B&W sets. Don't buy this box, it won't work on Aussie digital TV signals. But if you have an Aussie box with S-video output, this trick may be possible. But it probably won't produce 525 lines interlaced...

Susan, check to see what the component video on your converter box is set to, it may be in progressive scan mode, and if it is, it won't work on a vintage TV set. You may have to drill deep in the menus to find this setting.

And I like to play old music on my old radios too. Sometimes I wonder who owned my radio when it was new, and what it played...

"One way to get B&W only video is to use the luma line of an S-video jack to feed the TV modulator, if your DVD player has an S video jack output."

Great! Thanks to both of you! I now have 2 options. All I need (at the very least) is a step down transformer for the mains voltage (on its way) and a 6DQ6, which was broken inside the set. Very happy with the overall condition of the Predicta after being shipped across the world... the valve was already broken in the eBay pic, so no surprises, and another valve had come out of its socket but was still OK. Quite amazing actually, now I just hope the tube works or I've just paid a lot of money for a box of junk. (Of course I'd still keep it!)

‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
"What's that big box by the back door? You didn't buy another old TV from eBay did you?"

One day I'd like to buy a 405 line set from the UK, a Pye VT4 preferably, but the expense of shipping and the risk of breakage puts me off.