| Description |
- We replaced the concerning tray, on which the problem is visible (see video)
- The problem still exists
- Mr. Kupfer measures the voltage -20V, +20 V, 8 V, 36 V in the backplane of the tower (see Photo 1)
- But the voltage is constant and good
- We changes the cables with the edac but the problem still exists
- We recognized that the problem was visible on more trays of the concerned 4-tray-section
- We change onother tray, and suddenly the problem was gone
- That means that the problem we see on the first tray was created by another tray
- That means that one card is infecting all other tray, and make problem on the other trays
- Mr. Kupfer assumes that the defect tray influences other trays over the analog bus
- Mr. Leroux recognized that one tray was very hot at the right side
- Mr. Kupfer takes his thermal camera and we see that one voltage regulator U86 was hoter than the U85 (see photo 2,3)
- We had over 100degree!
- He assumes that U86 is overloaded!
- Now we measure the U86 Pin 3 (Output) and we see that the voltage has the right level (-18 Volt) but is switch on and off repeatedly (see photo 2 and pdf 4)
- Now we measure the U85 Pin 2 (Output) and we see that the voltage has the right level (+18 Volt) but is switch on and off repeatedly (pdf 4)
- We compare with another tray (see photo 3)
- We had 30 degree!
- He assumes that the U86 is not defect. Why? Because the voltage is -18V, and that ok. The problem is only that the -18V is switching ON an OFF
- What the cause of the switching?
- The U86 has an intern security circuit: When U86 is overloaded or too hot, than he disables the ouput
- He assumes that the U86 is overloaded because the following components needs too much power
- We recognized that U14 is cold, but U17,U19....where very hot
- He recognized on the schematics that the U17 (SSM2402), the pin 2 and pin 13 must have opposit logic states.
- We measure all ssm2402 =U14,U17,U21,U28,U34,U6,U8,U10,U12
- If we measure the pin 2 (High signal = 5 Volt) and pin 13 (Low signal = 0 Volt) or wise versa, this means that the device is ok
- Now we continue and measure now the U21
- We measure the pin 2 (High Signal = 5 Volt) and pin 13 (Low signal = 0 Volt), that the device is ok...
we measure all devices, they are all OK !!!
- But what causes the pulsating problem ?
- We measure now all pins of U14,U17,U21,U28,U34,U6,U8,U10,U12
- At Pin 7 must be "-18V" and Pin 14 must be "+18V" at all devices
- At U14 Pin 14 is "+18V", this is correct
- At U17,U21,U28,U34,U6,U8,U10,U12 on the Pin 14 = We measure -9 Volt pulsating, this is not ok !!! (see photo 4)
- Mr. Leroux ask if the voltage regulator is defect. Mr. Kupfer says no, because we have -18V.
- Mr. Kupfer says if would be defect if we would not have -18 Volt !
- Mr. Kupfer: The missing positiv supply voltage on U21 causes the increased current on the negative supply -18V which overloaded U86!!
- Mr. Kupfer realised that there is no connection between from U14 Pin 14 and U21 Pin 14 !
- Mr. Kupfer detects the problem! There is no connection betwenn U14 and U17
- Mr. Kupfer says that U14 must be connected with U21 or U28 or U34 and so on...
- Mr. Kupfer realised that there is a connection between all devices = U17,U21,U28,U34,U6,U8,U10,U12
- We take a wire and connected U14 Pin 14 and U17 Pin 14 (see photo 5)
- The problem is solved!
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