Hardware Modifications

62 18. Hardware Modifications 18.1. Accessing the Internals {ToDo: Explain how to get at the insides - remove binding posts)

63 18.2. External LED - Modification This modification adds a red LED under the “ON/OFF” Button. In combination with the existing green LED, 3 colors become possible, allowing the button to respond in a variety of ways using the ‘External LED’ setting. Here is a YouTube video showing one of the options available with this modification: RD60xx 'External LED' Mod In Action Here is the link to the Original Posting about this modification on EEVBlog Materials Needed: Insulated Hook-up Wire 30 Gauge, or smallest available suggested. LED Red, 0603 or 0805 package. Resistor 470 Ω, surface mount package suggested. 1) Access the Front side of the Front PCB. (See: Accessing the Internals ) Area of Work - beside LED marked D4

64 2) Mask off around the area of work. Not required, but helps prevent accidental damage to the surrounding area. 3) Drill hole at the location shown. Use the smallest practical drill size to create a hole hook-up wire can pass through. (0.4mm or next smallest available suggested) Try to position the hole near the bottom of the copper area. Be cautious to NOT break the trace running below 4) Clean up the hole on the rear of the PCB. Using a larger diameter drill bit, remove any burrs left over from the drilling done in the previous step.

65 5) Cut the track and prepare pads. Cut as shown in the image above. Scrape off some of the solder mask to expose bare copper. Use a continuity checker to confirm the new island of copper is not shorted to ground. Tin both pads in preparation for soldering. (As shown to right) 6) Solder in a new Red LED. Ensure the new LED is in the same orientation as the existing LED. (This image also shows the next step completed, as seen from the front of the PCB.)

66 7) Connect hook-up wire from back side of PCB. Connect wire to the LED through the newly drilled hole. Ensure the wire is fully insulated from the ground plane on the back of the PCB. (The wire’s insulation should be passing through the hole.) 8) Connect the other end of the hook-up wire to the pad shown, through the 470 Ω Resistor. The pad is located between the 2x8 header and the crystal Wire connected to pad ‘Below’ R38 through a (0605 package) 470 Ω Resistor.

67 9) Test / Reassemble Unit. Here is the result… As an alternative solution... Illuminate the button from the side by installing a Bright LED inside the case. For example:

68 18.3. Front Power Switch - Modification {To Do: Insert instructions for adding a front power switch} {Reference from Change logs:

• Added option "Power Switch" to turn On/Off the primary PSU. (5V standby power supply required). (Note: Adds a 3 second power-on delay). The control output is routed to the PA14 port (pin 4 of the J2 connector). High level - turn on, floating or low level - turn off. Note: the maximum load on the port is 20mA !!! (it is better to use an optocoupler).}

69 18.4. Improve Internal Thermal Measurement Accuracy Apply thermal paste between the thermistor and heatsink to more accurately display the temperature. 18.5. Using the TTL Interface User example from EEVBlog forum. Communication Protocol: From EEVBlog post: Protocol reverse engineering HERE.

70 18.6. Output Surge Problem - Hardware Bug, With Fix Some RD60xx have a small hardware problem… Depending on your version and your primary supply, there may be a surge at the output when the primary power supply is turned on. This occurs regardless of the ‘Boot Output’ setting. For further technical info, see the original EEVBlog Forum post HERE. Below is an oscilloscope screenshot showing the problem on a RD6012: RD6012 output (RED Binding Post) when Primary Power Supply energized. This is a hardware problem that occurs when the RD60xx’s on-board TL594 Integrated Circuit (IC) is first powered, but before the RD60xx unit has entered a stable operating mode. 18.6.1. How to get rid of the problem Replace R22 with a resistor value between 68K - 100K. This will increase the turn-on delay time, reducing or eliminating the problem.

71 Schematic view of the part to replace Exact location of R22 on the PCB inside the RD60xx. (With 56K Resistor installed.)