Identifying Small PCB Connectors: JST SH, GH, PicoBlade, and the Open-Sided Housing Explained
That Open-Sided Look Is Normal – It’s Still Probably JST
If you’re trying to identify a 2-pin or 3-pin connector on a Zigbee Fingerbot or similar small IoT PCB, you’re most likely looking at a JST SH (1.0mm pitch), JST GH (1.25mm pitch), or Molex PicoBlade (also 1.25mm). The open-sided housing that trips people up isn’t a sign of some exotic connector type. It’s just how the PCB-side header looks for all of these series.
Why the Board-Side Header Looks Open
This is the biggest source of confusion. On the JST website and in distributor photos, the product images usually show the wire-side housing: the fully-enclosed plastic plug that crimps onto your wires. That component has walls on all sides.
The other half (the male header soldered onto the PCB) is a different part with a much sparser housing. For JST SH and GH, the PCB header typically has a short shroud that wraps around three sides and is open or recessed on the remaining face. Some SMD variants are even more minimal. It’s still JST. You’re just looking at the board side instead of the wire side.
Measuring Pitch: The Only Way to Know for Sure
A digital caliper solves this fast. Measure from the center of the first pin to the center of the last, then divide by the number of gaps (pin count minus one). A 3-pin GH header measures 2.5mm across all three pins: 2.5 divided by 2 gaps equals 1.25mm pitch.
You need at least 0.01mm resolution to reliably distinguish 1.0mm from 1.25mm. Most cheap digital calipers will manage it.
Key pitch values for this size class:
- 1.0mm — JST SH
- 1.25mm — JST GH or Molex PicoBlade
- 1.5mm — JST ZH (common on micro servo leads)
JST GH vs Molex PicoBlade: Same Pitch, Not the Same Connector
At 1.25mm you’ve got two common contenders that look similar but won’t mate with each other’s counterpart. The locking mechanism is what tells them apart.
JST GH uses a positive latch: a small tab on the front face of the wire-side housing clicks into a recess on the PCB header. Molex PicoBlade uses friction retention with a small side-mounted nub at one end of the housing. Under a loupe or in a macro photo these differences are clear enough. Matt Millman’s connector reference page covers the full JST lineup with photos and dimensions if you want a quick visual comparison.
Neither is better than the other for a repair job – you just need to source the right mating half. They are not interchangeable despite sharing identical pitch.
What’s Likely on a Zigbee Fingerbot
Without measuring, the most common layout on devices in this class: the 2-pin connector handles battery power, and the 3-pin connects to the push motor or a programming/reset interface. Some Fingerbot variants wire the 3-pin to a sensor combination instead. Getting the pitch confirmed is the prerequisite for everything else.
Sourcing the Mating Connector
DigiKey and Mouser stock genuine JST and Molex parts. LCSC is the budget option with international shipping on small quantities. For JST SH, the PCB header is SM02B-SRSS-TB (2-pin) or SM03B-SRSS-TB (3-pin); the mating wire housings are SSHR-02V and SSHR-03V. For GH: SM02B-GHS-TB and SM03B-GHS-TB on the board side, with GHR-02V-S and GHR-03V-S for the wire side. Always verify part numbers against the current JST catalog before ordering.
No crimp tool? Pre-crimped pigtail leads for both SH and GH are inexpensive on AliExpress and work fine for a one-off repair without investing in tooling.
If nothing in the JST or Molex catalog matches exactly, the connector is probably a no-name OEM clone with slightly different housing geometry. In that case, replace both the PCB header and wire plug with a genuine JST or Molex part rather than hunting for an exact match on a connector that may never be publicly catalogued.
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