# GigaBlox BB-GGB-C-3: What is R4’s value, and where does U1 pin 3 connect?

**URL:** <https://forum.botblox.org/t/gigablox-bb-ggb-c-3-what-is-r4-s-value-and-where-does-u1-pin-3-connect/651>\
**Category:** BotBlox Hardware\
**Tags:** gigablox\
**Created:** [September 19, 2026, 12:52pm UTC](https://forum.botblox.org/t/gigablox-bb-ggb-c-3-what-is-r4-s-value-and-where-does-u1-pin-3-connect/651 "2026-09-19T12:52:40Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ElsieMichaelson](https://avatars.discourse-cdn.com/v4/letter/e/b5ac83/32.png) [@ElsieMichaelson](https://forum.botblox.org/u/ElsieMichaelson)\
**Post date:** [September 19, 2026, 12:52pm UTC](https://forum.botblox.org/t/gigablox-bb-ggb-c-3-what-is-r4-s-value-and-where-does-u1-pin-3-connect/651/1 "2026-09-19T12:52:40Z")

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_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**.