Tseng ET4000/W32 does not POST

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Tseng ET4000/W32 does not POST

Postby stalk3r » 2019-7-02 @ 09:14

I received this card but it does not seem to POST. The card is in good shape, although I noticed that a component is apparently missing from near the VGA chip. There are tiny remnants of solder on it so I am pretty sure something was there.

Image


I found a quality photo from a similar card on the internet which shows the missing piece. Any idea what kind of component is it? It has a brownish top, without any marking unfortunately.

Image
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Re: Tseng ET4000/W32 does not POST

Postby The Serpent Rider » 2019-7-02 @ 11:30

Typical ceramic capacitor. Most likely should work fine without one, so the problem is somewhere else.
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Re: Tseng ET4000/W32 does not POST

Postby stalk3r » 2019-7-02 @ 13:54

The Serpent Rider wrote:Typical ceramic capacitor. Most likely should work fine without one, so the problem is somewhere else.


if I follow the trace then it eventually goes back to another pin of the VGA chip, and now there is a break on the circuit, which I guess can cause troubles. I will try to have it replaced to see if it helps.
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Re: Tseng ET4000/W32 does not POST

Postby SirNickity » 2019-7-03 @ 18:28

It's almost certainly a power supply bypass cap - which is just there to filter noise and provide readily available energy for transistors switching quickly inside the IC. The cap will sit between a V+ rail and Gnd.

The chip will still be connected to V+ without it. Notice the via -- the small hole -- on the trace before the cap? That's most likely connecting to a V+ plane on the back or inner layer of PCB. Without the cap, it just won't get the benefit of shorting noise to gnd and providing a low(er)-impedance source of energy at the start of a transition. It's good design practice and will help the chip to run stable and emit less EMI, but it's not going to be a show-stopper.

I.e., "most likely should work fine without one". :-)
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Re: Tseng ET4000/W32 does not POST

Postby stalk3r » 2019-7-03 @ 20:30

^^^Thanks for the explanation. In other words, another brick in the drawer.
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