Does anyone have the circuit diagram for the early Project Speed Box?
Mine has stopped working, the platter won't turn at all and both LEDs are illuminated all the time.
I've attached an photo of the front of the unit for reference (power pulled so no LEDs on), and a photo of the circuit board.
On initial investigation the transistor circled gets very hot very quickly after power on, so my guess is that'll be the obvious place to start. But I need the schematic to get the transistor part number and see what it is exactly it does.
Thanks in advance.
Steve
Mine has stopped working, the platter won't turn at all and both LEDs are illuminated all the time.
I've attached an photo of the front of the unit for reference (power pulled so no LEDs on), and a photo of the circuit board.
On initial investigation the transistor circled gets very hot very quickly after power on, so my guess is that'll be the obvious place to start. But I need the schematic to get the transistor part number and see what it is exactly it does.
Thanks in advance.
Steve
Attachments
The µP is an Atmel AT89C2051 and given the proximity of NL1 to pin 1 of the processor (Reset), it is most likely a reset controller. If the µP is not coming out of reset, it would also explain the symptoms you describe. Transistors are marked as VTx, so I don't think this part is a transistor.
The 2051 requires an active high reset at power up so something like the Microchip MCP101-450 would work, although the pin out may differ from the part you have (if there is a PN on the device it would help to know what it is). A 3 legged part is easily rotated to orient the pins in the correct pattern. The reset controller has an input (5VDC), ground and output (connect to pin 1 of the µP). This is fairly easy to discern with a VOM.
The last 3 digits of the MCP101 PN is the reset voltage (450=4.5VDC). 460, 475 will also work. You could also dispense with a controller altogether and connect a 1µFd cap between pin 1 of the µP and 5V. This provides an active high reset pulse at power up but does not provide brown out protection or a reset if the power dips when your AC compressor turns on.
The 2051 requires an active high reset at power up so something like the Microchip MCP101-450 would work, although the pin out may differ from the part you have (if there is a PN on the device it would help to know what it is). A 3 legged part is easily rotated to orient the pins in the correct pattern. The reset controller has an input (5VDC), ground and output (connect to pin 1 of the µP). This is fairly easy to discern with a VOM.
The last 3 digits of the MCP101 PN is the reset voltage (450=4.5VDC). 460, 475 will also work. You could also dispense with a controller altogether and connect a 1µFd cap between pin 1 of the µP and 5V. This provides an active high reset pulse at power up but does not provide brown out protection or a reset if the power dips when your AC compressor turns on.