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Hmm, it's a bit hard to say, definitely.? It wouldn't be my first, or even second, choice.

A 1N4004 is a silicon power rectifier diode, designed to conduct up to 1A of current; while the OA95 is a germanium small-signal diode, designed to conduct up to 50mA of current.? Since the DX7 only needs a tiny current through the diode to keep the RAM from losing its data, the current rating doesn't matter.

What *does* matter is the forward voltage drop of the diode.? This is voltage lost by the act of conducting current, and is never zero.? The drop varies with the current flowing through the diode, but is generally lower for germanium diodes than their silicon counterparts; and lower for small-signal diodes than their power equivalents.? Looking at the data sheets, an OA95 is likely to drop 0.2-0.3V at the currents required, while the 1N4004 is likely to drop 0.6-0.7V.

What does this mean to you?? In the best of circumstances, it will probably work, but the backup battery is going to read as 'bad' long before the end of its actual life.? A lithium coin-call battery is about 3V when new, and it drops to around 2.3-2.4V when it's pretty well used up.? I don't know the minimum voltage needed by the DX7's RAM chips, but let's assume that it's 2V.? If so, an OA95 can work until the battery is 2V + 0.2-0.3V = 2.2-2.3V; the 1N4004 can only work until the battery is 2V + 0.6-0.7V = 2.6-2.7V.

In the worst of circumstances, some other property of the DX7 circuitry requires a higher voltage than 2V to work properly, perhaps as high as 2.5V.? In this case, even a nearly-new battery may not be able to provide enough voltage to meet or exceed this situation, leading to data corruption.

If an OA95 isn't available, I would recommend (in rough order of preference)

1. Another small-signal germanium diode.
2. A Schottky small-signal diode, such as a BAT81S or BAT83S.
3. A silicon small-signal diode, such as a 1N914 or 1N4148.
4. A higher-power germanium diode.
5. A higher-power silicon diode, such as a 1N4001 or 1N4004.

Of course #1 through #4 are not likely to be found at the local DIY shop; one would have to order them from Mouser, Farnell, Allied, etc., or find one on eBay.

Just my $0.02USD ...