SC127, v1.0, Assembly Guide

Click here for a list of the parts required to build an SC127, v1.0, Compact Flash interface.

Experienced builders READ THIS.

Power is supplied to the IDE header via JP2. Thise does not need to be fitted if you are using the recommended Compact Flash adapter module as there is a track between the jumper pads. If you wish to fit a jumper then cut the track first. After that, go ahead and populate the board. There shouldn’t be any further surprises to catch you out.

This guide assumes you are familiar with assembling circuit boards, soldering, and cleaning. If not, it is recommended you read some of the guides on the internet before continuing.

First check you have all the required components, as listed in the parts list.

Before assembling it is worth visually inspecting the circuit board for anything that looks out of place, such as mechanical damage or apparent manufacturing defects.

If you have a multimeter that measures resistance or has a continuity test function, check there is not a short on the power supply tracks. Connect the probes to each terminal of one of the capacitors, such as C1. This should be an open circuit, not a short.

The picture below shows what a completed SC127 should look like, depending on your choice of assembly options.

IDE header

Fit and solder the IDE header pins in the position indicated below in yellow.

Press the connector firmly against the edge of the PCB and ensure the pins are in the centre of the pads. Solder one of the middle pins on one side of the board and then check the connector is still in the correct place and the pins are parallel to the board’s surface.

Solder one of the middle pins on the other side of the board and repeat the checks. It is important the pins are parallel to the PCB so the adapter card site vertically and is neatly aligned with the PCB.

Solder one pin at each end of the connector and on each side of the board. Repeat the alignment checks. Now solder all the remaining pins.

Resistors (1k)

Fit and solder the 1k resistors, R1 to R4.

IC socket

Fit and solder the IC socket for U1.

Be sure to fit it with the notch matching the legend on the circuit board, so you do not end up fitting the IC the wrong way around too.

Capacitors (100 nF)

Fir and solder the 100 nF cacacitors, C1, C2 and C4.

Z50Bus header

Fit and solder the Z50Bus header, P2.

Ensure the pins are parallel to the PCB’s surface so that the card will stand vertical in the backplane socket.

Jumper header pins

Fit and solder the jumper header pins, JP1.

Jumper header pins (optional)

Fitting header pins, JP2, is optional. This jumper allows power to be optionally provided to the IDE header. If you are only intending using the recommended Compact Flash adapter module then there is not need to fit the header pins – the PCB has been made with a track between the pads so that power is supplied to the IDE header.

IMPORTANT: If you want to fit the jumper option it is vital you first cut the track between the pads of JP2 on the component side of the PCB, as indicated below.


Fit and solder yellow LED (LED1) in the position shown below.

It is important to fit the LED the correct way around. LEDs usually have a small flat side to indicate the cathode (the negative end). This should be positioned to match the flat side shown on the circuit board (illustrated to the right). Also, the cathode pin on the LED is usually shorter than the other pin (the Anode).

Capacitor (100 µF)

Fit and solder capacitor C3 (shown below in yellow).

It is important to fit this capacitor the right way around. The negative terminal is indicated with a ‘minus’ sign, as illustrated to the right. The negative terminal also has a shorter lead.

To make the board as low profile as possible, this capacitor can be fitted laying flat, in the position shown below.

Quick Tests

Visually inspect the soldering for bad joints and shorts. Clean and inspect again.

Check for a short on the power supply tracks by measuring the resistance between IC U1 pin 20 and U1 pin 10 (indicated below in red). This should be an open circuit, not a short. If you are using a digital meter set to measure resistance it will likely take a few seconds for the reading to stabilise as there are now capacitors on the power lines. A reading of more than 100k Ω (100000 ohms) is acceptable.

Integrated circuit

Insert IC U1 into its socket, taking care to insert it the right way around, as illustrated below. Be careful not to bend any legs over.

Jumper shunts

Fit jumper shunts in the positions indicated below. Remember, JP2 is optional so the header pins may not be fitted here.

JP1 sets the device address. Currently, this should be 0x10 to 0x17.

Adapter module and CF card

Fit the adapter module and Compact Flash card as shown below.

You are now ready to give it a try.

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