petSD+ - Assembly

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20-25W

Fine (conical) tip

No temperature control

In this case, the most sensitive components, i.e., the ICs, should all be mounted in sockets. With care, the passive components can be soldered using a very basic iron with little risk.

NO !

You need a good quality, electronics grade, solder. I use 0.7mm diameter, 60% Tin/40% Lead solder with integral flux.

Due to the potential health risks associated with lead, in recent years, the use of lead based solder in manufacturing has been phased out (see RoHS). Lead-free solders are available, but, are a bit more difficult to work with as they have higher melting points and don't flow as easily.

When using lead based solder, take sensible precautions, such as having adequate ventilation. not breathing in the fumes (that applies to all solders), etc.

Continuity tester

Preferably with an audible alert (buzzer)

The minimum requirement is for a basic continuity tester, but a basic multi-meter than can measure voltage and resistance is recommended, particularly if you need to fault-find a non-working board.

The parts list includes a suggested order for mounting the components, with the exception of the SD card slot, it isn't essential that you follow the sequence indicated, but the sequence follows a logical order that has been shown to work and allows the parts to be installed without obstructing the installation of components to be mounted later in the sequence.

The instructions and most of the photos below were provided by Nils based on his work when he created the first of the petSD+ prototype boards. The medium sized images on this page should be adequate to help you identify the location of the components, but for more detail, click on the image to open up the full size photo.

Seq. No.

As you can see, the contacts, particularly those for, Signal Common (Sc), Write Protect (Wp) and Card Detect (Cd) are a bit on the small side, with Sc and Wp very close together !

For maximum stability, the slot should be placed with the two locating pins near the front of the slot set into the holes provided. 

The slot should be positioned as far to the left as the solder pad positions will allow to ensure that there is enough room for the spacer bolt to the right.

Here, an unsoldered DIP-20 socket has been been placed in the IC4 position to ensure that there is acceptable clearance on both sides.

The solder that you applied before should melt and give a good connection without shorts. The remaining terminals at the rear of the SD card slot should now be soldered to the PCB.

Verify your work with a continuity tester and an SD card

Provided that your continuity tester comes with a buzzer:

If the card is completely inserted with write protect on, there will be silence. If it is removed half the way, it will beep. If this is not the case, either the Wp, the common connection Sc or both are bad.

Measure between ground and pin 19 of the MCU as shown

If the card is pushed in completely, it will beep, if it is removed (half way), there will be silence.

Make sure, both switches are working NOW! It will be almost impossible to fix them later!

*** TIP ***     Bending the component legs

This photo shows how the component legs should be bent prior to soldering. The component on the left has its legs bent outwards and can easily product shorts to adjacent components.

The one on the right has its legs bent inwards and is the safer method to follow.

(Required for LCD only)

Check the orientation of the diode to ensure correct polarity

(Required for RTC only)

(Required for LCD only)

Ensure that the "dot" on the package is aligned with the index mark on the PCB (the square box at one end of the RR1 stencil)

The default (preferred) location for these switches is on the PCB, if petSD+ is to be mounted internally to the PET, these switches and LCD display can be mounted remotely. 

Ensure that the polarity is correct

Cut off the original leads and use a couple of the off-cuts from other components that you have already mounted to make some new, thinner, leads and solder them to the vari-cap.

Note that one leg must be bent to match the PCB hole pitch.

Take care to not short the crystal's case with one of the two connections, make sure that there is some clearance between the can and the PCB. Verify that there are no shorts with the continuity tester. To ground the case, apply some extra solder at the top end of the can and bridge between the can and the reset switch ground connection.

Take care to make sure that the positive and negative terminals are placed correctly - the "+" connection should be towards the centre of the PCB.

To reduce the stress on the battery connections to the PCB, you could apply a little glue to the battery holder prior to soldering.

To plug in the battery, place it so that it lays under the two golden fingers at the right side, then press and move the battery to the right until it snaps in.

The screw driver / lever should move the battery to the right and upwards at the same time.

The cathode (shorter lead, flattened side of the LED) goes into the square box on the PCB, both on the left side.

The next step is to fit the ICs into their sockets.

The legs on new chips have their legs slightly splayed, they need to be bent slightly so that they fit into the sockets (or directly into a PCB)  Images from RS-Components

(Photo from instructables.com)

Check that every pin on each IC has been properly inserted into its socket.

Seq. No.

Interconnection between the PCB and the display uses a 10-way ribbon cable, fitted with an IDC connector at the PCB end, and soldered directly to the back of the display at the other.

When it has been fitted, the cable is not subjected to any significant strain, so a low profile connector, i.e., one with no strain relief clip fitted, is preferred, since there is limited clearance between the PCB and the display.

Note the orientation of the cable with respect to the key on the plug

Obviously, you need to make sure that the cable is long enough to mate with the petSD+ PCB header, but leaving it too long will make it difficult to fit the display on top of the PCB.

(See the hardware page for how to determine the correct value of R2, it should normally be in the 3R to 6R range.)

Seq. No.

Power

When viewed from the rear, the cassette port power terminals are at the left hand side of the connector.

Although the PET edge connector has a key slot in it, the connector plug does not include one, either fit one yourself, or mark the connector to ensure that you know how to connect it.

I obtained a very small number of cassette port connector covers from Nils, these have now been allocated to a few of the folks who have requested a petSD+. Unfortunately, although the connectors themselves are still available, I have not been able to source additional covers. As the first power cable photo shows, without the cover, there would be no strain relief for the cable and I am not happy with the relatively heavy power cable just hanging off the solder tags so I am proposing alternative options for powering petSD+. . . . .

I can supply these if required, but you can probably source them as cheaply as I can.

(A cable like this would be a little difficult to disconnect from the PET without pulling on the wires soldered to the connector.)

Seq. No.

Note, to allow a programmer to be connected, the connector will protrude beyond the edge of the board and should be mounted orientated as shown.

If the ISP connector is added, you will need to cut the track from IC4 pin 12 and connect pin 12 to pin 1 on the ISP connector via a 680 ohm resistor (R10) on the underside of the board as shown in the photo.

The serial line shares the port with the green LED and debug output is enabled by setting CONFIG_UART_DEBUG=y in configs/config-petSD+ (a compile-time option).

One example, and the one used by Nils , is shown here, it uses a PL-2303HX USB to Serial Bridge Controller. It is available from ebay sellers for as little as £1-£2

If petSD+ is to be mounted internally, the LCD and image selection switches would not be required and a 2-way piano dip switch can (optionally) be installed to configure the IEEE-488 device address from 8-11 in the same way as was done with a Commodore 1541-II drive

On the PCB in my machine shown here, the header position is not populated, so a 2x12, 0.1" pitch, pin-header would need to be installed to allow the internal petSD+ to be connected internally.

As is it highly unlikely that you will be moving your machine around a lot, it may be acceptable to just place the petSD+ board in the empty space at the front left of the case - suitably insulated from the metal base of the computer.