[Dr_C]

Looking across the main distributors of Scalextric products it appears that stock of the C7042 Advanced Power Base (APB) has run low.

Also, we now know that when throttle ports fail this can also lead to wider reliability issues with the APB - so it is often not as simple as avoiding using the dead ports.

This brings consideration of whether the microcontroller can be removed and replaced, back into scope.

Over the next few posts I will share a step-by-step guide covering the removal and replacement of the microcontroller.

This is not something that everyone can try. However there are likely to be a few members across the digital slot car community who will have the skills and equipment to successfully carry out the procedures involved.

What will follow is a high-level outline guide.

I hope this thread generates some interest and proves useful too.

c

[Dr_C]

PREPARATION

Step 1: Disassemble the APB including removing the power connections tonthe track-piece and the connections to the ID sensors and slot sensors.

Once this has been done the mother board and the top board (LEDs and buttons) can be laid out as per the photo below.

   

Step 2: Cut the 16-way ribbon cable as shown below. This cable is very short and makes the repair too difficult if left in place.

   

Step 3: remove the remains of the ribbon cable from the main board and use a solder-sucker to open up the 16 holes. Later we will fit a 16 way header. The main board is now ready for the microcontroller removal and replacement. At this point it should appear as per the photo below.

   

c

[Dr_C]

MICROCONTROLLER REMOVAL AND REPLACEMENT

The microcontroller used in the C7042 Advanced Power Base (APB) is the:

PIC24HJ64GP206

From here on we will refer to it as the PIC24. It is a fine pitch 64 pin microcontroller.

First two points of caution:

1/ When removing the PIC24 ensure the solder on all 64 pins is molten. If any pin remains soldered to its underlying pad when lifting the PIC24 the underlying pad will be damaged.

2/ When soldering the new PIC24 in place take the greatest of care to ensure that no solder bridging occurs between adjacent pins. If this happens it is extremely difficult or even impossible to correct.

Now to return to the procedure…

The photo below shows the PIC24 prior to removal.

   

Step 4: Flood all four sides of the PIC with fresh solder using a fine tipped soldering iron.

Step 5: Create a frame around the PIC24 on three sides using 8mm Kapton tape to protect nearby components from excess heat. The aluminium heatsink acts as the forth side of the frame.

Step 6: Heat the PIC24 using a hot air gun with an 8mm diameter nozzle and an air temperature of 285 degrees C.

Once all four sides of solder surrounding the PIC24 have become molten extremely gently tap the PIC24 to see if it is free to move. If so, carefully lift away the PIC24 with fine tweezers. If it is not free to move, continue to heat for a few more seconds.

Step 7: Clean the 64 solder pads and then add fresh solder to each pad using a fine tipped soldering iron. This step is critical as this is the solder which will form the electrical connections with the PIC24.

The photo below shows the cleaned and fresh solder prepared pads.

   

Step 8: Extremely carefully position the new PIC correctly aligned over the solder pads then ‘tack’ solder each of the 64 pins to the underlying pad using a clean tipped fine solder iron. No solder is added at this stage as this would risk bridging between pins. Then repeat the tack soldering again for each of the 64 pins to ensure 100% success.

The photo below shows the replacement PIC24 correctly soldered in place using the above procedure.

   

Step 9: Use a continuity tester to double check that all 64 pins are electrically connected to their underlying pad. This is carried out for each pin by testing continuity between the top of the pin and a known track connection point on the main board.

Step 10: Solder into place a 5 pin header at the ICSP interface and then connect a PICKIT programmer. Then load APB HEX firmware that includes a suitable bootloader. We will require this bootloader to be present when later we use standard procedures to upgrade the firmware to version 1.009.

The photo below shows the APB main board connected to a PICKIT4 using the ICSP interface. Power at this stage is provided via the PICKIT only. The required voltage is 3.3V.

   

At this stage the hard work is done. Just the LED/button interface to replace, firmware to be upgraded to v1.009, then full system testing.

This will be covered next :)

Hope you enjoyed the journey so far?

c

[Dr_C]

BTW, after step 10 a simple electrical test can be carried out to ensure all so far has gone well…

Step 11:

- Fit the tower.

- Fit a wired controller to one of the ports and connect a digital car (with corresponding ID) to the track power output of the APB.

- Connect DC power.

The tower should display the firmware version. If so this confirms the serial link is running correctly.

The throttle controller should control the motor of the connected digital car. Motor and brakes should function as normal.

This confirms core control functions of the APB and its MOSFET driver circuits.

We will test for correct function of ID sensors later.

The above repaired APB correctly demonstrated the above… so all is well :)

c

[Dr_C]

HARDWARE FINAL RE-ASSEMBLY

Step 12: Next, it’s time to replace the 16 way ribbon connection we removed earlier. This involves attaching a 16 way header to the main board. It’s standard 0.1 inch pitch (i.e. 2.54mm pitch).

I use small PCBs with FFC 8-way connectors and 8-way FFC cables to make the 16 connections to the LEDs and top panel buttons.

The FFC assembly is shown in the next photo.

   

Next, the FFC assembly is shown plugged into the 16 way header. This is now unplug-able and replug-able for future maintenance.

   

Step 13: The hardware is now re-assembled and ready for installation of firmware v1.009 and system testing.

   

c

[Dr_C]

UPGRADE TO FIRMWARE v1.009

Step 14: There are several methods to upgrade the APB firmware to the current recommended version which is v1.009. An excellent method is embedded in RCS64. Here I use the exe file from the ‘jackaments’ website. It still functions perfectly on Windoes 11 machines all these years later. Acknowledgements to the PBPro team for their excellent work on APB development all those years ago :)

The photo below shows the APB connected to my Windows 11 laptop via the RS485 opto isolator block. I prefer this to the more basic hard wired cable as it blocks static electricity and other forms of signal noise including ground loops. I describe this approach elsewhere on slotracer.online.

The simple start-up procedure is followed and firmware v1.009 downloads successfully onto the repaired APB. It is now a fully up-to-date APB!

   

Finally, the repaired APB is powered-up with the tower attached to confirm the current firmware version.

   

The final stage of the repair exercise is to connect the powerbase to a highspeed raceway, connect a favourite RMS (RCS64 in my case) and race hard with six digital cars.

This repair is not for everyone to attempt but I do hope it inspires and assists a few digital slot car ‘electronics gurus’ to give it a try. 

We know the APB has been out of production for quite a few years and it appears, finally, that new old stock has finally become exhausted (happy to be corrected if this proves to be incorrect).

This repair approach may be useful in extending the useful life of those much appreciated APBs which lie at the heart of racing clubs and home raceways.

c