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'Vintage' Toshiba portable no sound: searching for IC TA7176AP
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Return to top of page · Post #: 16 · Written at 11:04:23 PM on 9 September 2018.
	Brad Administrator Location: Naremburn, NSW Member since 15 November 2005 Member #: 1 Postcount: 7303
Hearing in normal healthy ears is supposed to be approx. 20Hz to 20kHz. I wonder what the frequency from this noise is. A lot of people who claim to have normal hearing have told me they can't hear it and wonder what I am talking about. ‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾ A valve a day keeps the transistor away...

Return to top of page · Post #: 17 · Written at 12:58:39 AM on 10 September 2018.
	Robbbert Location: Hill Top, NSW Member since 18 September 2015 Member #: 1801 Postcount: 2015
The frequency is 15625 Hz, derived from 625 lines x 25 frames per second. Some may say, hold on, isn't that 50 frames? It would be, except TV uses interlaced scanning, so on the first go it does the odd-numbered lines, then the next go it does the even-numbered lines. So a complete frame takes 2 goes, so it's really 25 frames. Or mathematically: (625/2) * 50, which still comes to 15625. In America, it's 15750 Hz (525 lines x 30 frames). So their picture is less detailed than ours, but there's less flicker.

Return to top of page · Post #: 18 · Written at 2:01:25 PM on 10 September 2018.
	Irext Location: Werribee South, VIC Member since 30 September 2016 Member #: 1981 Postcount: 470
Most Tech's who worked on CRT TV's for any length of time develop a built in notch filter at 15625 hz. I know I have (as well as tinitus at about 6kHz).

Return to top of page · Post #: 19 · Written at 4:49:15 PM on 10 September 2018.
	Clockmeister Location: Albany, WA Member since 20 January 2012 Member #: 1068 Postcount: 25
Interesting you say that. Using a tone generator I can hear up to 15,200Hz. Interestingly between 16kHz and 20kHz there are spots where I can still hear a faint hiss.

Return to top of page · Post #: 20 · Written at 11:08:55 PM on 26 September 2018.
	Clockmeister Location: Albany, WA Member since 20 January 2012 Member #: 1068 Postcount: 25
Well the 5 chips did arrive. They are the genuine Toshiba article but are recovered, not new. In great shape though - all pins clean and straight. Anyway, popped one in and audio is back. For just shy of $3 inc postage, I can't complain

Return to top of page · Post #: 21 · Written at 11:28:06 PM on 26 September 2018.
	GTC Location: Sydney, NSW Member since 28 January 2011 Member #: 823 Postcount: 6687
Chalk that up to a win.

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