A month ago, I bought an old 1970s B&W PYE 12G13 from an antique shop, where it was dusty and buried under a pile of junk. It possibly hadn't been used in a long time. I, however, frequently use it to watch movies now, in conjunction with an RF output Altech UEC DT3900RF HD set-top box.

I have noticed, in particular during advertisements, that the speaker will start making a crackling sound as the ad progressess. It is most noticeable at the end of the ad, and then it goes back into complete silence between the ads.

Adjusting the UHF control can eliminate some of it, but diagonal lines faintly appear sweeping across the screen. When i'm watching a show or movie, it doesn't crackle, but it does when I open a menu (eg. EPG, Info, Guide etc.) on the set-top box, and gets louder the further I progress into the menu.

Is this something to be worried about, a sign of old age or just a characteristic of this particular set? Could it be a capacitor or IC chip in the audio section? I'll open it up tomorrow and give it a visual inspection.

All thoughts and comments greatly appreciated!

Cheers,

Chris

Haven't worked on TV for decades but at that age it is highly probable it has paper caps & tired electrolytic caps, meaning it needs a birthday.

That could be a horizontal sync issue bearing in mind that a lot of these things took the sync from the mains and that was not particularly stable, or brilliant idea.

Crackling in the audio could be anything from a cap leaking to a mechanical issue like a bad joint or dirty valve pins.

Marc

Thanks Marcc! I highly doubt this would have paper caps. I don't remember seeing any in it when I last opened it up.

It may have a generation of caps in plastic tubes, some of those were still paper, or the early cream / blue polyester.

I have noticed some of the cream type polyester cracking their casing. Electrolytics drying, still applies.

Marc

Do the ads have very white lettering or other graphics? Peak white in most modulated video occurs at minimum RF carrier level, and with the use of an intercarrier TV set (a set that uses an IF sound subcarrier picked off the video detector (in the USA it's 4.5MHz, Australia I think used 5.5MHz) you can get a sound buzz if the TV set's video IF cuts off the carrier at peak white in the video (when the RF carrier is at its minimum, and if the circuits are not biased correctly). Thus the sound IF subcarrier disappears momentarily. And you get the buzz from that.

The image can get very white, but bearing in mind that it's a black & white set, it's hard to tell what colour the writing is supposed to be. I suppose that could be the issue. I couldn't see any issues when I opened it up today.

Chris

Wa2ise, is there any way to fix the IF intereference, or am I best off to just 'grin and bear it'?

Cheers,

Chris

And just after reading some of the posts again, it doesn't have any valves. It's competely solid state (well, except for the CRT). It'd be from the mid-late 1970's. I'm still not sure what part of a televisions serial number/model number tells you the year of mfg. Any thoughts?

Chris

Sounds like intercarrier sound buzz. If it normally happens with white text on a background picture but not with normal video then I would tend to not worry too much.

B&W TV's struggle with text on video for the reason Wa2ise explained and generate a buzzing sound. It may be a fault but it is something that happened with many sets even in the 1980's. I'd just live with it for now and if it gets worse then start looking for a problem.

Ah, okay, thanks! It's not that much of an issue / annoyance any more, so I'll leave it as is.

Thank you everyone for your help!

Chris