Bk precision 1696 software
Keep in mind that what you are looking at is what supposed to be a piece of expensive professional test equipment. Here are just a few pictures to prove the point. To the left below is the corner of the front panel processor board, take a look at the flux residue and the glob of solder on the regulator heatsink!
Signal wires are simply just hot-glued in place instead of using connectors. And the image to the right below is the output terminal board on the front panel. It almost looks like that the soldering iron was not powerful enough for the job. Although it could be true that someone had serviced this unit before but given the widespread issue we can see inside this unit, there is little doubt that the construction quality is subpar. And the bodging continues.
Here are just a couple more pictures to illustrate. In the picture to the left below, you can see bodged components on the backside of the riser board and the two thin wires from the transformer are actually connected to the riser board directly.
A wire tapping into the current shunt was simply connected in a point-to-point fashion: from the back of the riser board to the current shunt resistor coil directly. Who needs a separate solder pad for that? While it could be the case that someone repaired the unit before, the prolific signs of poor soldering is evident that many of the components were simply soldered willy-nilly without too much thought about quality.
I would certainly hope that the problems I am seeing here are just one-offs as for a brand name such as BK Precision this kind of workmanship is unacceptable. On the main board you can spot an MC power factor controller. The picture below is the board mounted on the front panel. It houses the digital control logic. Towards the bottom you can see that signals are outputted to an RS port and an RS port via opto-isolators.
And here are a couple of pictures of the broken LCD itself. The LCD has 56 pins and looks to be a custom part. At least that is a possibility. While adjusting the set voltage, the set current is fixed at 1A so the only changes in the output should correspond to the set voltage and nothing else.
And then I incremented the set voltage 1V at a time from 2 to 10V and recorded the waveforms again. Finally I captured the waveform when the set voltage is at the maximum 20V. Once I have identified the bytes that control the set voltage, I used similar technique and identified the bytes that is responsible for setting the current. Once the bytes for controlling set voltage and set current display are identified, I went on and analyzed the bytes that are responsible for the actual output voltage and output current.
Here is a screenshot showing a portion of the captured data. For those who are interested, the entire spreadsheet of the captured data can be downloaded here. The next step is to analyze the data to see if there is any pattern to it.
For instance, here are the sequence of set voltage captured and the change in data is observed in three bytes B6 B7 B8. With a little bit knowledge of how a 7 segment display works and by examining data pairs with only a single segment difference for instance 1. Because there are eight bits, one of the bits in each byte is used for other purposes. The last bit in this group B6 through B8 for instance is used for the decimal point.
So the voltage setting 1. Again, using the same technique by fixing the output set voltage at 1V and adjust the set current from 0. From the captured data, we can see that B9 B10 B11 B12 are responsible for the current setting display. When current is set to 0. This time the mapping is slightly different than what we saw with the set voltage mapping. By examining across all the captured data for current settings, we can see that the digit segment mappings remain the same but the start and stop location for the digit does not align with the byte boundary as we saw earlier for the voltage setting data.
The remain 5 bits again is used for other purposes. This gives us the current setting of 0. Now we have decoded the data for driving Vset and Iset values. For the measured output voltage and current, it is a bit more tricky as the actual measured voltage and current tend to drift a bit. Again, I first captured the output voltage readings with no load. B13 and B18 also changed, but they are not part of the display data for the output voltage. So these three bytes are for the output voltage.
The current reading is scattered a little bit. It took me quite some time to figure out how it is assembled in the bytes sent to the LCD driver. After analyzing all the relevant data captures, I figured out that the hundredth and thousandth digits are stored in B0 and B1 respectively.
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