Trickysystems

On the subject of programmers, the PIC programmers I use are pictured. The K150 needs the config file updated to program 16F886 PICs. The PICKit 3 works better for me although the required sockets need to be purchased. There are PICKit 3.5 devices advertised on the Internet, but these weren't designed by Microchip. I'd stick with PICKit 3 and use the standalone software available free from Microchip. The latest programmer is the PICKit 4, but for our purposes, the PICKit 3 will work and is cheaper. Make sure it has the logo.

Of the two controllers I have, the earlier one has the AJ3 IC (U6) and the later one just has a resistor, at least based on when they were purchased, but the actual controller delivered may just be a question of stock on hand at the time. The controller without the tiny IC 6 has R8 omitted, R10 installed (150K), and a new position, R18 (100K) installed. Having a closer look at the circuit, PIC pin 6 (RG1/TX2/CK2) connects to pin 5 (2A) of U8 (74HCT2G125), so is an input. The output of U8 then goes via R18, which is a pull up resistor, to a through hole where small IC U6 would be mounted on the other controller. The other output from U8 (1Y) appears on another through hole next to it. As this appears to be a multi layer board, it is very hard to identify where the tracks actually end up. This could mean that the PIC is OK, and also U8. Repairing the issues on the daughter board may allow the main board to power up. The outputs from the burnt U6 would need to be identified and direct connected, so possibly fixing the controller? As for the extra diode soldered to one of my controllers, it simply replaces D4 and so is not extra, just heavier duty. Richard

The two controllers are very similar, with some rearrangement of components. The blown IC is replaced by a resistor on the other board. The only SMD device in the same package, with AJ3 marking, was 3AA02/34LC02. This is a Microchip 2K I2C Serial EEPROM. If this is what the device is, I'm not sure what it is doing. Pictures attached of each controller. R18 replaces the IC on the other controller, and some other resistors are added or omitted between the two controllers. Both controllers are version 5, yet slightly different. Both have the USB connector on the hand unit. J8 pins connect to the correct pins on the PIC to enable ICSP. It is looking like a better option is to replace the hand controller, or use a BT or WiFi adapter. Controllers seem to be available on the second hand market from time to time. Although my engineering past makes me want to know what went up. All ICs and transistors are encapsulated with smoke, so that is the indicator they have failed, at least that is what I was taught...

Malcolm, Just a little more snooping between my two hand controllers. The added diode in one simply is a replacement for D4, so maybe just an upgraded component for extra current? The IC that is vaporised on your controller has AJ3 as the marking and appears to be a DFN8 package. Without checking the tracks, I am uncertain of the actual type of device or the function. Note that the other hand controller I have does not have that IC present. I'll try and figure out the differences between the two circuits. Perhaps it might be possible to bypass it completely? J8 on the controllers appears to be the ICSP for the PIC. I'll check further to confirm if that is the case. If the controller does not prove repairable, then an alternative is to remove it and put in a wireless or BT adapter in place of it to control the motors. Richard

Malcolm, I just had a look in the latest handset I have and it has the values stamped on the ferrites and an extra diode. Picture attached. 102 ferrite is 0.15 ohm at DC and 1,000 ohms @ 100MHz and 1.5A max current. For a test, you could probably use a low ohm resistor or even short it. As this is the interface board to the rest of the hand set, it could be tested in isolation. Hope this helps. Richard

Just a few observations to go with Malcolm's detailed post. While I do have a hot air rework station, due to the small size of these boards with surface mounted components very close to the ICs, I've found the Dremel method works best for me. Once the body of the IC is removed, a quick wipe with a soldering iron and solder wick cleans the pads nicely. Tin the bottom of the IC legs, and a wipe of a flux pen on the board pads, position the IC and solder away. There is usually enough solder on the legs of the IC and the board to attach the ICs, however use a good magnifier to check and correct where needed. If the ICSP pins aren't present on the control board, install them. I found them helpful with my two failed MC004 boards to check programming and to also reprogram the PICs. I have a PICKit 3, so just plugged my repaired board in, applied power to it, and placed the PIC programmer into the correct mode. I had my config bits incorrectly set for the boards, so the ICSP pins made it easy to correct. My motor drive ICs were also toast, so if it is a good blowup, they usually will show discolouring on the surface of the chip. I was fitting my own wifi adapter and applied 12 volts where it shouldn't go. There are discrepancies with the actual pin outs for the various GoTo implementations. I've just acquired a Saxon 150/75 GoTo which is almost the same as the SW Star Discovery 2i. It had been modified by a 2 year old, so had the controller cable was destroyed, finder scope disassembled and only one eyepiece. Check the hand controller? Simple, just plug the cable from my Dob in, NO! Checked the wiring and it was different. If I'd plugged in the other cable, then I'd be trying to fix a new board, probably ARM based. I'll have to check what it is some day. The wiring gods were with me, so crimped on new connectors to the cable remains and it worked. Upgraded motor controller and handset software to the latest versions. I now have two operational GoTo scopes, one 6" and one 10", and living in a rural area, with Bortle 2 skies, I'm amazed at what is visible compared to when I lived near a city on the coast. This thread has been invaluable to get me and others up and running. I wonder how many have plugged in the wrong cables, rather than a genuine component failure? I do like the quality of the board repairs that Malcolm has posted, first class! Richard

I actually have one of these scopes, purchased on FB for a very low price last week, due to being partly disassembled by the original owner's 2 year old daughter. Her modifications included ripping out the hand controller cable, trashing one eyepiece completely , disassembling the other eye piece and the finder scope no longer has a reticle. Luckily I also have a SW 250P GoTo Dob which I recently fixed the electronics on, so a spare hand controller and eye pieces to use. The mirror on the Saxon was well out of adjustment, so much tweaking and it is now collimated. GoTo works well and had a quick look the other night at Jupiter, and thanks to the Goto, saw Uranus. The Saxon Astroseeker 15075 is almost equivalent to the Sky-Watcher AZ GoTo Star Discovery 2i, with the exception of having a finder scope and not a red dot finder. The hand controller is included and not an extra. It is the version 5 hand controller with the USB port on the controller. I used that port to upgrade the hand controller to version 4.39.21 and the motor controller to version 3.40.A6. I don't think this particular mount supports motor controller upgrade via WiFi, besides I already had the files on the laptop computer. Wifi works well from Android, although I find the hand controller good as well. The hand controller bracket is attached using velcro straps which slips down the tripod leg. I found a much better clip-on version on Thingiverse which was easy to 3D print. Also did a Cheshire from there and that worked well as an assist to the laser collimator I used to get the scope back into use. The one operational Saxon eye piece I have is a Saxon Super 25 wide angle with long eye relief. It works well with this scope. The other eye piece is supposed to be a Saxon Super 10, but that didn't survive the 2 year old. The scope is well made, dare I say, built to survive? The steel tripod is very solid. While the complete assembly is easy to shift around, I find it easier to remove the OTA from the tripod, setup the tripod in the viewing area, making sure it is level, then place the OTA back on the tripod, finding the balance point. Turn on the GoTo, do the setup, and in a few minutes you are ready to go (well after the scope has got to temperature). From the short time I have had this scope, I've found it very good. It is also easily transportable and a lot lighter than my 10" Dob. It is also a lot easier for my grandchildren to look through compared to the dob. There aren't many reviews for the Saxon scope, but most of the ones for the SW Star Discovery are good. The Saxon prices are good as well in Australia. clear skies Richard

Hi all, Just a few thoughts. While there has been success with repairing failed boards, ( thanks again Malcolm et al) the newer boards use ARM STM32F051 and other chips and the MC006 uses a PIC18F45K20, the old MC004 seems to be no longer available as a spare. The last code available for the earlier boards seems to be 2.09 as later code versions are too big to fit the PIC16F886 memory, unless I am missing something and the SW firmware loader figures out the processor and loads correct code for it. Another thought I have is that while my Dob 250 has servo motors, do the latest SW Dobsonians now have steppers or still have DC servo motors? From pictures on the net of later motherboards, they have DIP switches and ARM processors, plus embedded WiFi, but there is no information if these can be fitted to earlier Dobsonians for any possible upgrade path for earlier scopes with toasted motherboards, hence the stepper or servo question. While I have a Dob, is there enough information to compile a matrix of what motherboards go with which telescope (EQ, AZ, Bob etc), and the latest code version? This may be of use to the people who have boards that are not repairable, or seeking an upgrade path. Richard

I thought I'd add my experiences with my SW Flextube 250P Dob with Synscan MC004F mainboards. I decided to add my own WiFi adapter and used the wrong pin data and blew both boards. Used a PICKit 3 to program them but still no joy with the 'Both Axes no response' messages. Changed the motor drivers then, plus the other chips for good measure. I also added the pins to enable on board programming of the PIC. Some measure of success with no error about the AZ motor, just the ALT motor. A good look under the magnifier revealed some not great soldered joints on that board, which was the one I started on. Back into the scope, hand controller says all good, but still no action from either motor. Hmmm, more thinking and reading. I was using the Hex file, MC004Final with config bits 3FFA 0700 set. I then tried code MC004D with config bits 2FA2 0500 set, no code or data protection. Back into the Dob and I heard a slight click from the motors as I powered on. Answered the hand controller startup questions and tried the direction control buttons. You beaut, all working again. Now if the current wet weather will stop for a time and we get clear skies... I've just recently moved to a rural region about 80 kms South from Sydney (Australia) with great dark skies, so should be good to test all functions. Thanks to this Forum and especially malc-c, for his and all the others who have contributed information and solutions for these less than robust boards.