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Dear Malcolm and Archie, I found this topic with Google when my HEQ5 failed after a Comet NEOWISE expedition up in the mountains. With the help of your posts, I was able to repair my mount and I would like to shortly summarize how I did it. So, it started when I turned on the mount one week later, and the hand controller said: "No response both axles" I like to build my own PCBs and Arduino / ESP projects, so I am a bit familiar with electronics. I took the mount apart and after I traced the power supply, checked the capacitors and it was all OK, I suspected, that the serial communication of the microcontrollers should be faulty. But the mount was still under the 5 year warranty, so I decided to return it before I take out my soldering iron. Unfortunately the shop told me, that the warranty is void, because I installed a belt kit earlier what I purchased from them. (Nice...) So, I had the option to buy a new panel for ~180 EUR or fix it. I ordered the PICs and the motor controller ICs for about 20EUR total, plus a PICkit3 clone and a SOIP28 to DIP28 adapter for a few euros. I never programmed PICs earlier, so I had to found out, that the PICKit alone is not enough to load the .HEX, I needed to supply external 5V to the PIC. I downloaded from here the different HEQ5.hex files, which turned out to be different than what I created with bin2hex. I made a "test environment" on a breadboard, the PIC, the RX/TX, 5V supply and the HC. Pin 21 tells to the PIC on the HEQ5 PCB, that which PIC is DEC (GND) and which is RA (5V) With this I was able to test the PICs before soldering them on the board. The only .HEX worked was the original HEQ5.HEX uoloaded by Malcolm on 27th of May. The test schematic is here: https://easyeda.com/Higany/synscan-esp8266 I supplied the HC from USB 5V, because it works from 5V as well, but this needs extreme caution, don't connect 12V while testing. (Pictures: https://photos.app.goo.gl/DFYHGF5gYhKZSGPw8 ) All the parts on the PIC side of the HEQ5 PCB are glued onto the PCB, which makes the removal of the PICs difficult, the best is to cut the legs next to the package and pry them off with a prier. This will help save the delicate PCB traces. Unfortunately I somehow fried one PIC and all 4pcs. A3959SLBT stepper drivers. I wanted to test them without the motors connected, and while I was checked for not properly soldered legs, they got very hot and developed short circuits inside. The situation at this point semmed hopeless and it was very difficult to find out what happened, but luckily I could locate this new problem. After replacing the faulty PIC and the stepper drivers, I connected the motors. The HC initialized OK, but the DEC motor only vibrated and missed the steps, and one of the stepper driver ICs started getting hot. I quickly turned the power off, reworked the hot IC's output pins, which solved the problem. After testing I assembled the mount and it works fine again. Another interesting finding, which may help others to locate problems with this board: The LED on the mount is driven by the DEC PIC. So, if the LED lights, the PIC works. I read somewhere, that this "No response both axles" of HEQ5 / EQ6 failure can happen when dew gets in the mount through the polar scope hole. That hole was uncovered on my mount as well during its last night. So, always cover that hole after using the polar scope. If the cover was lost, a standard 1,25" tube end cap is a perfect replacement, because the hole diameter is 1,25" as well. I added TVS diodes on the RX / TX lines and to the 12V input. And I also designed a small protection PCB to protect the mount from reverse polarity, overcurrent, overvoltage and transients, but it is not delivered yet. So, thank you again guys for this topic!