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Need help to identify componet

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jpanhalt

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Unfortunately, Photobucket and other off-site image hosting services do not always work. This is one such instance. Can you upload the image and post it here.
 

jpanhalt

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That blue component looks like a ceramic resonator (oscillator) for the chip next to it. 3.58 is probably its frequency in MHz. That is a very common frequency as it divides nicely. Looks normal to me in the picture. They often look like gum drops.

Another view might show the defect you suspect.
 

X-bahamutzero

New Member
Well right next the pin on the under component looks as if it shot its guts out and removing the green coating of the board. Not sure how well you can see it in the background but the black specs on the board is its guts.
 

tomizett

Active Member
In which case it's more then likely there's other damage, unfortunately. Possibly a dead microcontroller.
 

AnalogKid

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That is a very common frequency as it divides nicely.
Off topic and picky, but -

Divides nicely into what? 3.579545 MHz is very common because it is the color subcarrier frequency in NTSC composit video, so there is a crystal oscillator in every analog color TV ever made. IBM used it as the master clock frequency in the original PC so they could get double duty out of it as the clock for their color graphics video adapter board, so there was one in every pc ever made for two decades.

But, that frequency was chosen specifically *not* to be divisible into anything, especially the US power grid frequency and its harmonics. That is why the interlace dots in analog color TV appear (intentionally) to crawl upwards, and why (consequently) the infuriating MSDOS internal time (tick) is a nice, round 18.206507 milliseconds.

I spent a couple of decades dealing with it in broadcast video, followed by decades dealing with it in computers. Grrrrrrrrrrrrrrrrrrrrrrrr

OK, I feel better now.

ak
 

MikeMl

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It looks to me that there is a missing capacitor where the silk-screened circle is... Almost certain that just replacing the missing cap will not fix the underlying problem, which is likely to be a burned trace on the pcb...

There must be '94 Camrys in car junk yards by now...
 

jpanhalt

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OK, I feel better now.
ak
I just want to feel warmer.:)

I don't know why "3.68" MHz was chosen instead of "3.69." It is a standard frequency and gives little error in baud rates, e.g.,
upload_2018-1-5_9-57-52.png

It is within about 0.2% of 60 x 60 x 2^10 (exact= 3.686400 MHz) .

Why its label is rounded down is a mystery to me and something I never lost sleep over. Maybe that was done to accommodate 60 x 60 x ((2^10) -1) too. Its next doubling is often called 7.37 MHz, which implies to me that calling it 3.68 instead of 3.69 was not done out of ignorance of the exact value.

John
 

AnalogKid

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I don't know why "3.68" MHz was chosen instead of "3.69." It is a standard frequency and gives little error in baud rates
I think you are confusing 3.58 with 3.68.

3.58 MHz was chosen specifically to interleave the color subcarrier sidebands with the horizontal sync, vertical sync, and audio subcarrier sidebands so they would not interfere and cause older TV sets with mis-aligned circuits to lose sync or have a buzz in the audio. By design it is not harmonically related to either 60 Hz or 15.75 kHz. The NTSC (Never Twice Same Color) system pulls the vertical field rate from 60.00 Hz down to 59.94 Hz. This is why, when the set is displaying a color signal, power supply hum appears on the screen as a moving bar. Before 19xx, a true monochrome signal displayed hum as a stationary bar. After 19xx, even old mono stations had to use the color standard sync timing.

This was all before the Bell 103A 300 bps standard was introduced in 1962, and way before 1200 bps (1972/76) and higher baud rates.

ak
 

jpanhalt

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You are right. The numbers on the part are 3.58 and being so accustomed to 3.68, I saw, read, and typed 3.58, but my brain was thinking 3.68.

Sorry.
 
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