for the
TRC-50X and TRC-50IA

Richard J Kinch
May, 2012

The upper-port mirror switch provides synchronization of the digital camera to the Topcon joystick. When the Topcon mirror actuates to take a photograph with the upper port, the mirror movement also mechanically actuates this new snap-action switch. The switch contact, when connected to the remote shutter control of the digital camera optically adapted to the upper port, in turn actuates the digital camera shutter. Thus the shutter lag of the digital camera and the mirror motion proceed synchronously. When the mirror has settled to the upper-port position, the digital camera will have had time to open its shutter, and the digital camera flash synchronization signal will be appropriately timed for the Topcon instrument to fire the Topcon flash in synchrony with the digital photograph.

Installation of the switch requires that you first remove one of the covers from the upper unit of the Topcon instrument. Then you attach the switch to the instrument chassis, and solder one wire to the upper-port interface connector. This task requires some basic mechanical skills, which are appropriate for a qualified ophthalmological instrument technician.

You may alternatively remove and send us your upper unit for us to perform the upgrade. You do not need to send us the rest of the instrument. See separate instructions for removing the upper unit from the instrument base and packing the upper unit for shipment. We can also supply a suitable double-wall carton and packing for shipment of the upper unit.

Kit contents: This portion of the digital adapter kit consists of:

Topcon TRC-50X mirror switch assembly
Figure 1. The mirror switch assembly.

Tools required: The following tools are required for installation, and not supplied in the kit:

Installation and operation of the adapter lens and other components of the total upgrade package are described in separate instructions. These instructions describe only the mirror-switch installation.

In the following, left and right refer to the operator's normal point of view, facing the instrument viewfinder; front refers to the patient's side of the instrument with the objective lens, rear refers to the operator's side with the viewfinder. Screws are indicated in their metric dimensions, such as screw size M3-20 indicating a 3mm thread diameter metric screw with 20mm of thread length.



If the original Topcon upper-port mirror mechanism is sticky, the digital upgrade will work unreliably or not at all. A sticky mirror is a common situation for instruments which have been in service for many years, due to the normal aging of mechanical grease and rubber pads. Perform the following test and, if necessary, correct this problem on your system before proceeding with the switch installation.

Testing the upper-port mirror actuation: Before installing the upper-port digital adapter switch, you should check that the upper-port mirror actuates properly, since having the cover off will provide an easy opportunity to repair any stickiness due to lack of lubrication or a sticky rubber landing pad. This test is especially important if you have not been using the upper port in the recent past. To test the mirror actuation, operate the instrument with the console dial selecting the upper-port 35mm camera instead of the rear-port 35mm camera, but with nothing attached to the upper port. When you push the joystick button, as you look down into the upper port, you should see and hear the mirror flipping up and down smartly, although there will be no instrument flash. If each push of the joystick button flips the mirror, the mirror should be operating correctly. The instrument should not beep or otherwise indicate an error. If instead the instrument locks up with a continuous beeping, this is a signal that the instrument senses that the mirror is not moving reliably (turn the power off and on to reset the beeping). In some cases the mirror will operate well after being actuated a few times, until it sits again for a while and the stickiness returns. This sticky-mirror problem is easily repaired by replacing the cushion pad (a new one is supplied in your kit), and perhaps applying a drop of oil on the mirror pivots. Details on this repair are in the steps below.

If your Topcon instrument has possibly had a digital upgrade installed in the past, you may wish to inspect under the mirror for an existing retrofitted switch. If present, you will either have to determine if the old upgrade can remain in place of this switch upgrade, or whether you will have to remove the old upgrade to install the new one.


Remove left cover:

To install the upper-port mirror switch, we must first access the interior of the upper unit by removing the left-side cover, as follows. This does not require removing the upper unit from the base. The left-side cover is held on by screws which are removed from recesses in the opposite-side cover of the upper unit. It may help to have a magnetic-tip screwdriver or magnetic probe to remove these loose screws from the recesses.

Topcon TRC-50X interior view, before installation
Figure 2. Locations inside the instrument, prior to switch installation.
This view shows the top rear of the chassis.

Install the new switch mechanically:

Topcon TRC-50 interior view, after installation
Figure 3. Locations inside the instrument, after switch installation.
This view shows the top rear of the chassis.

Connect switch to upper-port connector:

Topcon TRC-50X soldering
Figure 4. DB-15 soldering arrangment.
Note routing of wire and use of optional anchor pad.

Testing the installation before reassembly:

Before replacing the upper unit cover, you should test that the installation was successful. Caution: Hazardous voltages are exposed when the cover is off the upper unit and the instrument is energized, especially around the xenon flashtube on the bottom. Do not touch any electrical contacts inside the exposed instrument while it is powered on.

Reassemble the cover: Reassembly of the left-side cover is the reverse of the disassembly above. This completes the installation.

Copyright 2009, 2010, 2011, 2012 Richard J Kinch.