rumpfy
25-10-2014, 07:33 PM
I've done some work on my RKE for the TW Magna. Before I put my file away, I thought to record the info here.
My problem was intermittent operation and I did buy another new RKE fob from Mr. Minnit. It cost $130 but it is an OEM with Mitsubishi logo. Design wise, it is identical to my old unit.
1. Have drawn the circuit diagram and identified the test points which are available on the underside of the PCB (printed circuit board).
2. The manufacturing method of soldering the components to the PCB is OK for the electronic parts but I believe the soldering of the battery holder is more problematic. The plating of the battery holder terminals, their size, and shape, suggests the the solder paste system used for the assembly will not give a good bond to the PCB. I noted that the plastic feet moulded into the battery holder MUST BE pressed against the PCB during soldering; The manufacturing method doesnt seem to guarantee this. Over time, the feet come clear of the PCB and this slight gap allows the holder to wobble when pressing the buttons and this wobble allows the solder joints to fail. I was able to remove the battery holder, clean the lugs and finally to resolder the holder to the PCB.
3. Some members observe 'goo' on the PCB. I have seen this goo on other types of remote control and in these cases there appears to be something exhuding out of the silicon rubber push button pad on to the PCB. I find that washing the rubber pad in soapy water is the best way to clean it.
4. The push buttons themselves are filled with silicon grease and the contact is made as a clicker plate arrangement. There are no springs. The design of the clicker plate is inherently spring loaded. The design appears to be good.
5. The logic IC (integrated circuit), is made by Freescale semiconductor. The code number is SC428996CDW. This item is available but I was unable to locate ANY technical information about it. It seems that this device is a pre-programmed micro processor based unit, but I have no idea what the unprogrammed base device is. Freescale is a competent microprocessor manufacturer. My guess is that any RKE with this SC428996 will operate the TW.
6. The system operates as a OOK system. This means 'ON OFF KEYING'. The device is designed so that if more than one button is pressed, the the unit will NOT generate a code. The design of the switch circuit is slightly deficient in that if there is a small leakage across a push button switch, then it is possible that the unit may send a signal without the button being pressed. Therefore, if there is conductive gunk on the PCB, the unit may be shutdown. So a clean dry PCB is imperative.
7. The PCB shows the Bosch copyright, and the unit would appear to be a genuine unit where the BOSCH logo is present.
8. The transmitter is a single transistor (BFR505) tuned to around 305 mHz by a surface accoustic wave filter (SAW). The output power is limited by the transistor oscillator design and would be difficult to increase this power. The time required to start the oscillator and get the receiver to register the transmitted code seems to be at least half to one second. So patience is needed when pressing the buttons to open/close doors.
Hope this helps,
rumpfy
My problem was intermittent operation and I did buy another new RKE fob from Mr. Minnit. It cost $130 but it is an OEM with Mitsubishi logo. Design wise, it is identical to my old unit.
1. Have drawn the circuit diagram and identified the test points which are available on the underside of the PCB (printed circuit board).
2. The manufacturing method of soldering the components to the PCB is OK for the electronic parts but I believe the soldering of the battery holder is more problematic. The plating of the battery holder terminals, their size, and shape, suggests the the solder paste system used for the assembly will not give a good bond to the PCB. I noted that the plastic feet moulded into the battery holder MUST BE pressed against the PCB during soldering; The manufacturing method doesnt seem to guarantee this. Over time, the feet come clear of the PCB and this slight gap allows the holder to wobble when pressing the buttons and this wobble allows the solder joints to fail. I was able to remove the battery holder, clean the lugs and finally to resolder the holder to the PCB.
3. Some members observe 'goo' on the PCB. I have seen this goo on other types of remote control and in these cases there appears to be something exhuding out of the silicon rubber push button pad on to the PCB. I find that washing the rubber pad in soapy water is the best way to clean it.
4. The push buttons themselves are filled with silicon grease and the contact is made as a clicker plate arrangement. There are no springs. The design of the clicker plate is inherently spring loaded. The design appears to be good.
5. The logic IC (integrated circuit), is made by Freescale semiconductor. The code number is SC428996CDW. This item is available but I was unable to locate ANY technical information about it. It seems that this device is a pre-programmed micro processor based unit, but I have no idea what the unprogrammed base device is. Freescale is a competent microprocessor manufacturer. My guess is that any RKE with this SC428996 will operate the TW.
6. The system operates as a OOK system. This means 'ON OFF KEYING'. The device is designed so that if more than one button is pressed, the the unit will NOT generate a code. The design of the switch circuit is slightly deficient in that if there is a small leakage across a push button switch, then it is possible that the unit may send a signal without the button being pressed. Therefore, if there is conductive gunk on the PCB, the unit may be shutdown. So a clean dry PCB is imperative.
7. The PCB shows the Bosch copyright, and the unit would appear to be a genuine unit where the BOSCH logo is present.
8. The transmitter is a single transistor (BFR505) tuned to around 305 mHz by a surface accoustic wave filter (SAW). The output power is limited by the transistor oscillator design and would be difficult to increase this power. The time required to start the oscillator and get the receiver to register the transmitted code seems to be at least half to one second. So patience is needed when pressing the buttons to open/close doors.
Hope this helps,
rumpfy