Electrical Debugging
- confirm that all LED's are on LD1, LD2 LD9, and LD10
- measure voltages at TP23 - TP28 (they should be within +/- 10%)
- if voltages are OK -> most likely the short is on the "signal path"
- if one or more voltages are out of spec (usually lower voltage) -> most likely a short on power pins (os power inputs of one of the chips)
- debugging signal paths
- switch to IV mode
- select channel 0
- for channel 0 resistance between switching card input (left-hand side of the protection resistor) and ground should be high >> MOhms
- for channel 1 (or any other) resistance between switching card input (left-hand side of the protection resistor) and ground should be around 10kOhm
- check the impedance between the selected input (S1..S8) and the output (D)
- debugging multiplexers
- switch to CV mode
- measure C for all channels, the result should be a step structure with periods of 8 and absolute values around 100 pF.
What to do if some cells do not have contact
How to check if all cells have contact
- A useful way to ensure all cells have a good contact is to measure their current at in forward bias.
- The current you see in each cell should be close to the bias voltage divided by the HV resistors (40k default) plus the series resistance of MUXes (around 6k) and protection resistor (1k, except in older models).
Obtaining a uniform and good electrical contact can be tricky and requires some practise:
- Make sure the chuck and platen/cards are as parallel as possible.
- Make sure there are a sufficient number of standoffs in between frame and probe card. They distribute the pressure uniformly unto the pins and avoid bending.
- Measure the weight you apply while contracting the pins by contacting a scale. Make sure you have enough weight to fully contract the pins.
- Try to clean the pins from time to time, e.g. by putting an isopropanol soaked sheet of clean room paper on the chuck and contact multiple times. Alternatively, use clean room q-tips and clean each pin manually (this takes a bit more time).
- Try to contract the individual pins e.g. with q-tips. You will notice that some are stiff and contract less easily than others. If nothing else helps, exchange these pins (better yet, test them before assembly!).
Communication
Some useful instructions and command list to test the firmware.