Difference between revisions of "Original XT/IDE PCB Construction"
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Latest revision as of 11:11, 21 April 2021
PCB Construction instructions for the 'original' XTIDE card. Originally published via the Vintage Computer Forum Wiki (but content damaged during wiki engine transfer); this version is revised and updated to include note of R6 substitution and a few pointers on soldering in general.
Materials Required
- XTIDE kit (pcb and components)
- Soldering iron (10-15w iron from radio shack will do, but a temperature controlled soldering station is highly recommended)
- Solder (preferably fine guage, for example 0.7mm, tin-lead 60:40)
- Isopropynol (i.e. tape-head cleaner)
- Wire cutters and fine thin-nose pliers
The board can be difficult to solder; a flux pen will help greatly.
Soldering Guide
There are numerous guides on soldering - for example How To Solder on YouTube.
But a few general pointers:
- Wash your hands and avoid touching things any more than absolutely necessary - grease will stop the solder flowing properly
- Clean the PCB using isopropynol before you start
- If using a flux pen, mark over the pads on the PCB immediately before fitting the components and soldering
- If the solder isn't flowing on a joint properly, remove (by sucker) any solder globs, clean up the area with cotton-bud and isopropynol, then apply more flux to the pad and the pin, and try again
- Tin the soldering iron bit, press it gently against the pin and the pad, then apply solder to the other side of the pin after 1-2 seconds. The solder should flow easily into the joint and the flux will bubble off
- Set a temperature controlled soldering station to about 260*C when using tin-lead solder
Assembly
In general it is easiest to start with the smallest components and work up to the largest, since this way the components being soldered are held in place by virtue of them resting on the work surface whilst soldering. Hence the order of works is something like:
- Resistors
- IC Sockets (where being used) and/or directly soldered ICs
- Tantylum capacitors and resistor networks
- Pin-headers
- LED and Electrolytic capacitor
Resistors
First install the seven resistors (R1..R7) in the board, all 10k.
Bend the legs into a U shape, with the resistor in the middle of the U and slide the legs through the holes. On the other side of the PCB, bend the legs out so the resistors are held in place when you flip the card.
Solder everything down and trim the legs off.
Note: Since production, a design error has been identified and R6 should be zero-ohms and jumper K1 only ever at potition 'L'. Hence, when assembling the board, either use a zero-ohm (single black-band) resistor at R6 or a thin piece of wire in its place.
IC Sockets and ICs
The use of sockets is highly recommended if not using a temperature controlled soldering iron, to avoid damaging an IC when soldering. It is also highly recommended regardless for the EEPROM, since these components are relatively expensive and the ROM may well be useful for something else in the future.
If the board is being constructed using sockets for the various ICs, fit these into the mounting holes first, noting the direction tab/indent on the left side of each socket (if present) should match the silkscreen on the PCB.
Next solder every pin of every socket or chip to the PCB.
Tantylum Capacitors, Resistor Networks and DIP Switch
Install the resistor packs, RR1 and RR2. Be sure of the orientation of the packs; the printing on the device should face down toward the ISA connector.
Next install the ten capacitors next to each socket. It doesn't matter which direction they are mounted; just mount them all the same direction for consistency. Push the legs of the caps all the way through the holes, and bend them out on the other side to hold the capacitor in place for soldering, just as with the resistors earlier.
Next mount the DIP switch and solder.
Pin-Headers
Most vaguely recent IDE cables, and certainly all 80-wire varients, will have pin-20 blocked in the host connector to prevent the cable being connected other than in the correct orientation. Hence, the corresponding pin should be removed from the 40-pin header prior to soldering - it can be simply leavered out against the plastic former using a fine pair of thin-nose plyers. For reference, note the pin to remove from this view of a motherboard connector:
IDE connector with key-pin missing. Note pin-1 is bottom-left.
Once done, place the 40 pin header onto the board, with the longer side of the pins facing up out of the card - this is where the IDE cable will go - and solder.
If required, solder in the 14-pin header too (note it can be omited since no available BIOS uses any IRQ).
Then install the 2-pin connector just above U10, and finally the 3-pin header to the right of the IRQ select block.
LED and Electrolytic Capacitor
Install the large barrel capacitor in C0. Note that this device is polarity sensitive and must be installed with the positive (+) side of the capacitor closest to the silkscreened C0 (and the negative side on the "47uF" side of the silkscreen). The stripe on the capacitor itself denotes the negative leg.
Install the LED, noting also that LEDs too are polarity sensitive. The round base of the LED itself is slightly flattened on one side - that flattened side goes up (near the "D" in LED printed on the silkscreen).
Installing the ICs
The IC numbers are printed on the PCB at the appropriate positions, and note the small tab/indent on one side of the IC denoting orientation - make sure that tab matches the printed similar markings on the board. All the tabs should be on the left side as you are facing the card.
It is likely that the IC pins will need to be bent inwards a little to line up properly with the sockets. Lay the edge of each IC on the table and try to slightly bend the entire row of pins at the same time. Once correct, press each IC fully into the socket, being careful that all the legs are going in properly and not bending underneath the IC itself or outwards.
Installation and Configuration
Install jumpers on pins JP1 and JP2 to enable the ROM, and K1 should be jumpered into the L position.
Set the DIP switch accordingly - usually the defaults will work, being DUUU UDUU for default port 0x300 for IO and address 0xD000 for the BIOS.
Attach the bracket to the board, using two pan-head machine screws.
Attach a hard drive cable to the IDE connector (note pin 1 of the cable is typically denoted with a RED stripe on the cable) and then carefully install the board in the computer.
The next step is to flash the EEPROM BIOS, for example using the XT-IDE Universal BIOS v1.1.5.