Here is a step by step guide to service your unit. The common failed component is the TO-3 7805 5v regulator, situated on the power control board. We are not exactly sure as to what is the cause of the higher failure rate, but we suspect it’s a heat failure after prolonged high current demand.
This step by step procedure on how to disassemble and repair the unit is 7 steps, and should take no longer than 20min. In order to confirm these steps will help you, the common symptoms include dead LCDs on power, while the power indicated by the lighted power switch still lights, and no voltage from the terminals.
Step 1: Remove the screws (circled in yellow in the image) on both sides of the chassis of the PBB-272A
Step 2: Remove the screws (circled in green in the image) on the bottom of the PBB-272A. The four in the top right being the screws that hold the power board to the chassis
Step 3: Remove the screws (circled in red in the image) that clamp the casing of the 5V regulator to the heat sink and circuit board
Step 4: Desolder the faulty 5V regulator from the board ensuring the terminals are completely disconnected from the board as shown in the circled images below
Step 5: Place the new LM7805 5V voltage regulator from Circuit Specialists into the format as shown below and insert into the heatsink holes
Step 6: Mount the heat sink back to the board, while also inserting the LM7805 into the holes, and using the screws that were removed in step 3 to clamp down the new LM7805
Step 7: The last repair step is to solder the LM7805 terminal leads to the pads as shown below
Reassemble your fixed PBB-272A, and congratulations you’re finished. You’re now ready to continue prototyping, and designing awesome things with your powered breadboard from Circuit Specialists!