This topic was migrated from the BotBlox ticketing system after being summarized and anonymized.
Question
While replacing U1 on a GigaBlox BB-GGB-C-3, I lost resistor R4 and damaged the PCB pad for pin 3 of U1.
Could you confirm R4’s value and specifications so I can replace it? Also, where does U1 pin 3 connect? The connection is not visually clear, and I would like to restore it if possible.
Answer
We checked the BB-GGB-C-3 design files and confirmed the following component and connection details.
What replacement should I use for R4?
R4 has the following specifications:
| Parameter | Specification |
|---|---|
| Resistance | 10 kΩ |
| Package | 0402 |
| Tolerance | 1% |
| Part used by BotBlox | RC0402FR-0710KL |
You can use the listed part or a suitable equivalent matching these specifications.
What does U1 pin 3 connect to?
Pin 3 of U1 is the EN (enable) pin. On BB-GGB-C-3, it connects to a junction shared by three components:
| Component | Value | Connection from the shared EN junction |
|---|---|---|
| R51 | 120 kΩ | To VIN |
| R52 | 47 kΩ | To GND |
| D3 | 4.7 V Zener diode | To GND |
How can I restore the connection if the pad has lifted?
Electrically, the connection can be restored by connecting U1 pin 3 to the shared junction of R51, R52 and D3.
Use the side of those components connected to the EN junction—not their opposite connections to VIN or GND. This restores the original electrical connection even if the pin 3 pad is no longer usable.
These details apply specifically to GigaBlox BB-GGB-C-3.