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MR-9 Adapter - Voltage Reducing Converter

Type: Voltage reducing adapter kit

Contents: Kit contains 1 x MR-9 Adapter, 1 x 386 cell. Output Voltage: 1.35 V.

Diameter: 15.6 mm. Height: 5.95 mm. 

Price: 29.43 each. Postage and packing included.

Emulates: PX625 / PX13 / EPX625 / V625PX / MR09 / MR9 / H-D / HD / RPX625 / RM625 / KX625 / HD1560 / 1124MP / Mallory RM-625R / Eveready E625N / Burgess HG-625R / 4370 / 4371 / V13PX / EPX13 / V625PX / HD625 / PN625 / RM625 / 4625 / 625 / H1560 / HD-D / M01 / M20 / 8930.

The "Rolls Royce" solution to problem of the discontinued Mercuric Oxide MR9, PX13 and PX625. Our MR-9 Adapter has the outer dimensions of the PX625  mercury cell with a recess that takes the inexpensive and easily obtained silver oxide 386 cell. Buried within the MR-9 Adapter are micro electronics that drop the voltage from the 1.55 Volts put out by the silver oxide cell to the 1.35 Volts that your  camera was designed for.

No adjustment or modification to your camera is required. The MR-9 Adapter does not require activation or a supply of air. The MR-9 Adapter and silver oxide 386 cell has a significantly longer battery life than the zinc air WeinCELL MRB625 batteries.

MR-9 Adapters are a one time purchase, and will last a lifetime. Simply replace the expired silver oxide 386 cell with a fresh one.



The MR-9 Adapter is designed for low current and cannot be used in applications that exceed 200 micro amps. The only known examples are the Canonet GIII 17 and 19 where the metering and exposure system function perfectly, but the battery check lamp will not illuminate.

If you wish to measure the voltage from the MR-9 Adapter and silver oxide cell with a digital voltmeter, put a 10 KiloOhm resistance between the measurement terminals. This will allow sufficient current to flow to activate the voltage reducing circuitry. An analogue voltmeter will draw sufficient voltage to activate the voltage reducing circuitry.

Some of our customers use the slightly deeper SR44 or 357 silver oxide cell in our MR-9 adapter. The deeper battery has a greater electrical capacity and so lasts longer. The short coming of this arrangement is that the combination of MR-9 Adapter and SR44  is 0.35 mm thicker than the original PX625, PX13, MR9 cell. Most cameras have spring contacts that can accommodate this fatter unit, but some battery compartments with screw down lids might not be able to screw down fully. If in doubt, stick to the 386 cell that gives the exact dimensions of the original battery. 

Click here to purchase extra 386 cells.

Click here to purchase the deeper SR44/357 cells.

There are other possible mercury free replacements for a PX625, PX13 or MR9 cell, click on the links to find out more:

The least expensive PX625 replacement is the alkaline cell, the LR9 or V625U. They fit perfectly but, as with all alkaline cells the voltage is not stable, it drifts down from 1.5V towards 1.35V (the voltage of the original Mercury cell) and then lower still. If you use the cell in a camera that needs a steady reference voltage, as the voltage is not steady throughout the useful life of the cells,  you need to constantly adjust how you compensate.

Because the S625PX silver oxide cell produces a steady 1.55V, you are able to compensate for the higher voltage by a  fixed number of stops or by adjusting the ASA setting. There may be as many as two f-stops underexposure by a camera that uses 1.55v instead of the original 1.35v, but the compensation you require is constant.

Another PX625 replacement is a zinc air battery. The WeinCELL MRB625 is a custom zinc/air battery designed to replace banned mercury batteries.  WeinCELLs deliver the same 1.35 V voltage and stability of output as did the mercury PX625 batteries so there is no need to adjust your exposure. The WeinCELL MRB625 batteries last much longer than hearing aid batteries, some times up to a year. To achieve this longer life, the MRB625 used a proprietary electrolyte and has only two small air holes, instead of the 7 larger holes found in standard hearing aid batteries.

Some devices such as the Gossen Linasix 3 light meter and Gossen Lunasix 3/S light meter and many others take a stack of two PX625 cells. These can be replaced by two MR9 Adapters, but a more cost effective solution is a single PX14 Adapter which takes two silver oxide cells and contains micro electronics that drop the voltage from the silver oxide cells to the 2.70 Volts that your light meter or camera was designed for. No adjustment or modification to your device is required. 

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