The Bus Isolation extender basically isolates the power and the signals from the motherboard to the I/O boards under test (UUT). It serves two purposes, one is to protect the motherboard from being damaged and the other is to allow repeated board test without having to power the whole system up and down. However, the user I/O board under test should be inserted or removed from the extender only while the extender is switched off. The extender could be switched on and off by either the toggle switch on the extender or by external TTL signal issued from external sources under software control.
The bus isolation extender itself, should be secured firmly onto the motherboard in either open or in-chassis test environment. This will prevent it from being accidentally lifted while the system power is still on. If this happens, the extender and the motherboard will be severely damaged.
The AGPIX32-E and the AGPROIX-C share the same printed circuit board. The only difference is the connector on the top and the keys being cut around the gold finger area.
1. Read the AGP specification (version 3.0), to understand the gold finger pin out, A side (solder side), B side (component side), VDDq (1.5V for 4X, 8X; 3.3V for 1X,2X), gold finger key cut definitions and etc. Some information is also available on the FAQ section of Adex's web pages.
2. Read the AGPIX32-E user's manual for proper understanding of the theory of operation. Be familiar with the location of jumpers, MOSFETs, buffer ICs, switch operation, buzzer and LED operations, and etc.
3. POWER CHECK
Static Check (without applying power to the AGPIX32-E
Dynamic Check (with power on, but without UUT on top of the extender):
R9 (15K), R6 (430) and C4 (1uf) are used for the biasing of the Q1 (
R11 (820), R12 (43K) and C3 (1uf) are used for the biasing of the Q2 and Q3 (12V).
R7 (420), R10 (22K) and C2 (1uf) are used for the biasing of the Q4, Q5 (3.3V) and Q6 (VDDq)
If still not correctable, then contact Adex with symptoms for further assistance.
If the above conditions are correct then proceed to check the buffers.
4. BUFFER IC CHECK
A simple way is described in the following text to check out the buffer ICs without having to power up the extender board. Even though this is not a fool-proof method, it will capture most of the damaged buffer ICs.
We strongly suggest you replace any of the buffer ICs that have visible physical cracks or do not have the right reading, and then try the extender in your system again. One could also use logic probe or scope to check the buffers. The signal on one side should travel to the other side, when the buffers are turned on (except the pins that should read zero). If not, replace the buffers. Please see the buffer pinout below for the input/output signal pair. Note: Not all signals are active at all times, during any particular bus cycle.
Usually the buffers at the corners, on both sides, are most likely to be damaged. This happens, when user forgets to turn off the extender while removing the user I/O boards. There are voltage pins close to the signal pins, near the corners, and when pulling the board up, the I/O board gold finger may short them out, causing damages to the corner buffers, if extender is not switched off. .
The isolation buffer ICs are very sensitive CMOS analog switches. Sparking or over current are usually the major causes that damage the buffers. When these buffers are damaged, they may short to VCC, Gnd, and become very resistive or overheat. We strongly suggest you be aware of ESD and handle the extender with care.
Please see the AGPIX32-E parts list and the QS3245 pin out for buffer pairs. Update your board with the component values on the parts list if necessary. User can download the AGPIX32-E user manual, AGPIX32EMAN.PDF, in pdf format . The file size is about 1,498Kbyte.
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