Oki 395 -- Power Supply Replacement -- Revision 'A' and 'B' Printers

[The revision level of early printers is given by the fourth character of the serial number.]


Direct replacement power supplies for revision 'A' and 'B' printers are no longer available; you'll have to use the power supply meant for revision 'C' machines. ( P/N 42312551.) That power supply has different cable connectors than those on earlier power supplies. There are two ways to deal with that wrinkle.


a) Replace the affected cables:

You'll need to order one each of P/N 41998701 (9 conductor cable) and P/N 41998801 (13 conductor cable). Those cables will fit the connectors on a revision 'C' power supply.

Or,

b) Swap the old power supply's connectors over to the new power supply.

The circuit boards are of simple, single-sided construction. It's not difficult to unsolder the connectors, and install the early-style connectors on the new power supply.

The new-style connectors don't take heat very well, and are likely to be ruined by removing them, but that's really not a problem since they won't be needed again anyway. Fortunately, the early-style connectors stand up to unsoldering and resoldering just fine.

- - -

To gain access to the power supply, proceed as follows:


1) Platen Knob

2) Ribbon Access Cover

3) Top Cover
- Two M4x10mm bright pan head screws w/captive plastic washers at the rear.
- Tip up the rear of the cover and unhook its lower front edge.
- NOTE: There are two M4 hex nuts in pockets at the rear of the machine that are unsecured once the cover has been removed. It's best to remove them and set them aside with the two cover screws. The nuts are easily dislodged and lost if compressed air is used to clean the chassis.
-RE-INSTALLATION NOTE: Mind the bail actuator when re-installing the cover. The actuator must be fully toward the rear of the printer, so it ends up behind the bail's left side arm.

4) Ribbon Cartridge

5) Control Panel w/Sheet Metal Mount
- One ZIF connector for the flat cable.
- One two-conductor cable connection at the lower right of the main logic PCA (CN13).
- Five M3x6mm washerhead screws.
- Lift away the assembly a couple of inches and disconnect one four-conductor cable (CN11).

6) Main Logic PCA
- Nine cable connections.
- One captive M4 screw securing a bracket at the lower rear of the PCA.
- NOTE: Connections CN1 and CN11 are physically identical. In later machines, CN1 is yellow to avoid mix ups. In early machines, CN1 and CN11 are both white. If you encounter a white CN1, mark the CN1 cable end so you won't transpose it with CN11.

7) Mechanism
- Two cable connections at the upper right of the interface connection PCA.
- Three M4x8mm pan head screws w/captive washers at the upper rear.
- Three M4x12mm pan head screws w/captive washers; three anchor plates low in the chassis pan.
- Lift the mechanism straight up out of the chassis pan.

8) Power Supply
- Four M4x8mm pan head screws w/captive washers.

9) Cabling

Should you have chosen to replace the cables, they're now accessible -- you just have to coax out the plastic covering pieces.

Before disturbing the old cables, take a Sharpie marker and make a reference mark on the chassis pan near the power supply end of the cables. Mark the edges of the cables correspondingly adjacent to the chassis pan mark. Once you have the old cables out of the chassis pan, use their marks to guide you in marking the new cables the same way. Then you'll be able to get the new cables in place with just the right amount of slack at the power supply end.

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