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Why does my TV get clear video, but only static as sound?
December 20, 2009 9:24 PM   Subscribe

Why does my TV get clear video, but only static as sound?

My wife, despite knowing absolutely nothing about any kind of electronics, purchased a used TV from a garage sale. The TV was from a company I had never heard of, PRIMA, and looks to be in good condition. My basic setup is a standard coax cable from the wall to an adapter at the other end of the coax, the connector looks similar to that of an RCA connection...a thicker dongle basically, which goes into the back of the TV. I've tested it on two connections, one of which is for my normal TV, but both times I get a good picture with only static as sound.

The TV's menu options allow me to set the input type from UHF, VLF-H, VLF-L...do any of these matter? Also, the audio can be from M, BG, or I...not sure what any of these mean.

Someone please tell me I too know nothing about electronics, and the TV isn't a worthless piece of junk? If it matters, I'm in Singapore...thanks!
posted by jimdanger to Technology (7 answers total)
 
The audio carrier in (analogue) TV broadcasts is offset from the nominal frequency by a certain (fixed, & dependent on the standard used locally) amount. If that offset is wrong, then the set will tune to the nominal frequency, 'pull in' to lock to the video signal (oversimplification there!), but not be tuned to the audio. In that case, you'll get picture + audio static.

According to this list of world TV standards, Singapore should be PAL B/G audio (i.e. 5.5MHz offset). If you can't get audio when set to that, then it's probable the set is faulty. If they set is manually tuneable, then you may be able to tune in to the audio, but you'll probably lose the video.
posted by Pinback at 10:04 PM on December 20, 2009


Are you getting your TV via antenna, cable or other?

Singapore TV uses the PAL system, which is common outside the US. This page says it's PAL-B, so that tells you to set the audio to "B"and the frequency band to "VHF".

Are you getting video when you set it to the other (UHF) frequency bands?

Note to US readers: this is all in contrast to the NTSC system used in the US until recently. As of June 12, 2009, all analog NTSC TV carriers are shut down and only digital is left. yes, I'm simplifying
posted by intermod at 10:05 PM on December 20, 2009


drat!
posted by intermod at 10:05 PM on December 20, 2009


;-)

Afterthought: PAL-L is sometimes used in MATV systems (i.e. hotels, apartment blocks, etc). This uses a different audio subcarrier offset again (6.5MHz), and is sometimes AM rather than FM modulated (though IIRC, AM is only used in SECAM countries).

It's essentially designed to provide vendor lock-in for MATV installers, and also so people can't pinch sets from hotels ;-). It's also sometimes used by Hams for Amateur TV broadcasts to prevent casual viewers from watching / listening.

Are you in an apartment block where the TV signal may be rebroadcast through an MATV system? Is your current set configured for PAL-L?
posted by Pinback at 10:36 PM on December 20, 2009


Thanks for the replies. I'm in an apartment building, but I'm not sure how the cable is dispersed. There are only 6 apartments in the building, so I doubt it's being strained or anything. My TV is connected via a coax cable...nothing else.

After changing the sound to BG, I was able to get clear sound for about 4 seconds before it was slowly drowned out by static. The only option I see for PAL/NTSC, is for "Color Setting." If I select PAL, everything is in black & white, and there's no improvement for the audio. When I set it to auto, it's in color.

I should have mentioned this, but our cable was recently upgraded. Not sure if it was digital or not, but assuming it was, how could I tell if my TV was incompatible? I don't think it's the case because I can see clear video, but who knows?
posted by jimdanger at 5:15 AM on December 21, 2009


Here is the entire TV menu, with all currently set options:

Picture
- Brightness: 0
- Contrast: 75
- Colour: 50
- Sharpness: 50
- Tint: 0

Soung
- Volume: 13
- AVL: ON (Can also be set to OFF)

Setup
- Language: English
- Blue Back: ON (Can also be set to OFF)
- Colour System: AUTO (Can also be PAL/SECAM/NTSC4.43/NTSC)
- Sound System: BG (Can also be DK or I)
- Black Stretch: OFF (Can also be set to ON)
- Tone: Normal (Can also be Warm, Cool)
- TXT Language: PAN-Europe
- TXT East/West: WEST (Can also be East)

Tuning
- Program NO: 6
- Skip: OFF
- Lock: OFF
- Band: VHF-L (Can also be VHF-L or UHF)
- Auto Search: (Appears to be auto-tuning, without fixing issue)
- Search: Same as above, but by channel.
- Fine Tune: Manual tuning...doesn't fix.
- AFT: ON (Can also be set to OFF)
- Exchange: Goes to a sub-menu
Something else I noticed, is that each channel appears to have its own setting. When I go to channel 5, it'll show AUTO, BG. When I go to channel 6, it'll show PAL, I, etc.
posted by jimdanger at 5:36 AM on December 21, 2009


Without going into further technical details, your extra info suggests that the reason the TV was in a garage sale is that it was faulty ;-).

OTOH, it sounds like it's just the tuner that's the problem, so it'll probably still work OK if hooked up to a VCR, DVD, or digital STB* via composite (RCA), S-video (4 pin mini-DIN), or component RGB or YUV (3 x RCA, or SCART) connection (i.e. not the usual wall->tv antenna connection you noted in your original post). These don't carry audio; if the set has any of these video inputs (most made in the last 20~30 years do), it'll also have separate mono or stereo audio inputs.

(* with the caveat that I know nothing about digital TV in Singapore, save that it uses the DVB-T standard and apparently broadcasts only 1080i HD. You'll need a STB that downconverts that to 576i SD, which most in Europe / Aus do, but I have no idea what's on the market in Singapore).
posted by Pinback at 5:59 PM on December 21, 2009


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