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Any ideas on repairing a (slightly!) blown motor board ?


Astro-Geek
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8 hours ago, chaotic-one said:

 

Okay replaced the ferrite beads, still no go, looks like I lost the programming on the chip maybe

 

If that didn't work, take a look at the 1N4148 diodes on the TX lines of the PICs - If replacing those (see previous posts in this thread where I replaced some using through hole parts) you still get the "no response" message on the handset, or a time out using EQMOD and a EQDIR cable then yes I would agree, the UARTs on one or both 16F886's will have been blown, and replacing them with a reprogrammed PIC would be my recommendation.  Hopefully you'll have more luck than I have at sourcing replacements at non inflated prices due to the global shortage.  I had to resort to contacting Microchip in order to get the last pair of controllers, which took 6 weeks to get to me from the UK.

Quote

also do we know the pinout for the hand controller programming cable, which we did not receive with our purchase?

The RJ11 port is a normal standard serial (RS232) port.  The TX/RX pins are given as 

pinout.png.b9ce5824f286222dddf924fba738dde3.png 

Note that you will need a standard RS232 to USB adapter if your computer lacks an old style serial port - If you use a 5v TTL serial to USB adapter it may not work as the handset is expecting +/- 12v rather than 0-5 signals

A little googling found the pinouts for the Skywatcher serial cable that normally gets shipped with the mount

spacer.png

 

More info

Edited by malc-c
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On 08/11/2021 at 16:28, malc-c said:

If that didn't work, take a look at the 1N4148 diodes on the TX lines of the PICs - If replacing those (see previous posts in this thread where I replaced some using through hole parts) you still get the "no response" message on the handset, or a time out using EQMOD and a EQDIR cable then yes I would agree, the UARTs on one or both 16F886's will have been blown, and replacing them with a reprogrammed PIC would be my recommendation.  Hopefully you'll have more luck than I have at sourcing replacements at non inflated prices due to the global shortage.  I had to resort to contacting Microchip in order to get the last pair of controllers, which took 6 weeks to get to me from the UK.

The RJ11 port is a normal standard serial (RS232) port.  The TX/RX pins are given as 

pinout.png.b9ce5824f286222dddf924fba738dde3.png 

Note that you will need a standard RS232 to USB adapter if your computer lacks an old style serial port - If you use a 5v TTL serial to USB adapter it may not work as the handset is expecting +/- 12v rather than 0-5 signals

A little googling found the pinouts for the Skywatcher serial cable that normally gets shipped with the mount

spacer.png

 

More info

Thanks for all the info Malcom

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