Film cameras
Pentax Spotmatic F battery
1 × 1.35V mercury (legacy) button cell
The Pentax Spotmatic F meter was designed for a 1.35V mercury Mallory PX-625 / Eveready E-625N. Modern options include Wein MRB625 or an MR-9 adapter path. Alkaline 1.5V lookalikes can meter wrongly. This is not the ME Super’s two LR44 cells — and earlier Spotmatic SP bodies used a different mercury cell. The shutter is mechanical — only the meter needs a cell.
How to replace it
| Compartment | Battery chamber in the camera base |
|---|---|
| How to open | Open the battery-chamber cover with a coin; insert the cell with the (+) side facing outward. |
| Orientation | + side facing outward |
| Low battery indicator | Battery check: shutter to B, ASA 100 — viewfinder needle should stay in the up/steady position |
| Notes | Keep the lens cap on when stored — Spotmatic F meter drain differs from earlier Spotmatics. Not an ME Super LR44×2 answer. |
| Access | Coin or simple twist |
Important
- Spotmatic F meter was designed for 1.35V mercury PX625 / E-625N — not ME Super’s 2× LR44.
- Earlier Spotmatic SP (non-F) used a different mercury cell — identify F vs SP before buying.
- Alkaline 1.5V lookalikes can fit and still meter wrongly as they discharge.
- Common modern paths: Wein MRB625 zinc-air or MR-9 adapter with silver-oxide 386.
- Mechanical shutter works without a battery; only the meter needs power.
- Keep button cells away from children.
Sources
Helpful for this device
Optional tools for opening, testing or charging — separate from the battery answer.
- iFixit Opening Picks
Non-marring opening for tool-free / clip housings
- Fluke 101 Digital Multimeter
Accurate open-circuit voltage and basic electrical checks
- Digital multimeter
Measure open-circuit voltage and general electronics checks
New battery but still not working?
A fresh 1 × PX625 should restore Pentax Spotmatic F if the battery was the problem. Work through the checks below before replacing the device.
- Check orientation
Confirm the cell is seated correctly: + side facing outward
- Check the battery type
This device needs 1 × PX625 (mercury_oxide_legacy). Rechargeable cells are not supported for this device. Same size does not always mean the same battery.
- Check known model-specific issues
Spotmatic F meter was designed for 1.35V mercury PX625 / E-625N — not ME Super’s 2× LR44. Earlier Spotmatic SP (non-F) used a different mercury cell — identify F vs SP before buying. Alkaline 1.5V lookalikes can fit and still meter wrongly as they discharge.
- Confirm the battery itself
Try a known-good fresh cell of the exact code listed above.
- Still not responding?
If a correct, fresh battery installed properly does not restore the device, the fault may be elsewhere — the device may need service or replacement.