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Bill Of Materials (v2.x)

Once you've got the PCB, it's time to gather all the necessary components. Make sure you decide on a particular configuration as some components differ according to the chosen option.

Also, don't forget to check the Notes below for alternative values.


If you are building Durango·R (HIRES mode only), since it generates no colour signal at all, it makes no sense to select the Component Video option. If SCART is not available, use the second video output option for a suitable monochrome signal thru an RCA jack. You may delete C5 and R30 as these provide the SCART output only.

If you want to build the older v1 PCB, check this BOM instead!


Assume all ICs are in DIP package, resistors are rated 1/4 W and capacitors 10 V or higher, unless noted otherwise.

Class Type Qty. (*) ·S ·R Component video Second video output Buzzer Notes
Piezo Buzzer passive 0 +1
Capacitor 68 pF 1 3
Capacitor 22 nF 1 1
Capacitor 100 nF 1 2
E.Capacitor 1 µF 0 13
E.Capacitor 10 µF 2 1
E.Capacitor 100 µF 1 +2 +1 1
E.Capacitor 220 µF 1 1
E.Capacitor 470 µF 1 +1 1
Diode 1N4148 6 4
LED 3 mm 2 5
Transistor BC548 7 -1 -1 +3 4
Resistor 27 (0.5 W) 0 +1 7
Resistor 75 1 +2 +1 12
Resistor 120 4 -1 -1 6, 13
Resistor 330 0 +2
Resistor 470 4 -2
Resistor 680 2 -1 5
Resistor 1 K 2 +4 9
Resistor 1.2 K 1 -1
Resistor 3.3 K 5 -2 -1 +2 8
Resistor 5.6 K 0 +2 10
Resistor 6.8 K 2 +2
Resistor 8.2 K 1 -1
Resistor 12 K 2 -1 5
Resistor 18 K 1 -1
Resistor 22 K 2 +1
Resistor 33 K 2 -1 -2 +1
Resistor 39 K 0 +1
Resistor 47 K 0 +1
Resistor 56 K 0 +1 11
Resistor 82 K 0 +1
Resistor 100 K 1 3
Resistor 220 K 0 +2 14
Res. network 8x 3.3 K 1 15
Res. network 4x 4.7 K 1 16
Variable Res. 5 K 1 -1 17
Variable Res. 10 K 2 -1 -1 17, 18
Microprocessor 65C02 1
Static RAM 62256 1
Integrated circuit 74HC00 1
Integrated circuit 74HC02 1
Integrated circuit 74HC20 1 -1
Integrated circuit 74HC21 1
Integrated circuit 74HC30 1
Integrated circuit 74HC32 1
Integrated circuit 74HC74 1
Integrated circuit 74HC85 2
Integrated circuit 74HC86 2 -1
Integrated circuit 74HC139 2
Integrated circuit 74HC157 4 -1 -2
Integrated circuit 74HC166 1 -1
Integrated circuit 74HC174 1 19
Integrated circuit 74HC175 1
Integrated circuit 74HC245 3 -1
Integrated circuit 74HC257 4 -2 -2 20
Integrated circuit 74HC367 1 19
Integrated circuit 74HC574 1 -1
Integrated circuit 74HC688 1
Integrated circuit 74AC4040 1 21
Integrated circuit 74HC4040 2 21

*) Standard build is a Durango·X v2.2 with SCART output and no second video output, piezo buzzer or any extra simplifications.


  1. Non-critical value, as long as it's kept within the same order of magnitude. Higher values are usually preferable, although component footprint might be the limiting factor.
  2. C2 works as a low pass filter for audio output. May be reduced down to 39 nF or so, if more treble is desired. Does NOT affect piezo buzzer anyway.
  3. Nominal value, may be changed in case of interrupt problems.
  4. Non-critical. Any small signal equivalent device (e.g. 1N914 diodes, or 2N3904 transistors) will do, but make sure about alternative pinouts.
  5. Colours are personal preference, of course, but the proposed resistors expect the POWER LED to be a high efficiency type (Gallium Nitride, e.g. blue) whereas the ERROR LED may use an older Gallium Arsenide-Phosphide (red) unit. Resistors R29 (POWER) and R6 (ERROR) should be adapted to the LED type and preferred brightness.
  6. If the second video output is not fitted, or never to be used simultaneously with the main one, R15 can be up to 330 ohm. SCART-equipped Durangos may reduce power consumption by upping R922 up to 220 ohm or so, although some TVs may not switch reliably into RGB mode.
  7. Change according to desired piezo buzzer volume. Could be down to a zero-ohm bridge, although that might overload Q3. Notice relatively high power dissipation!
  8. R3,R34 and, to some extent, R337 are just strong pull-ups and may be chosen from around 1 Kohm up to 10 Kohm or so.
  9. R32 is for Emilio's LED and may be suited to the desired brightness (down to 680 ohm). If you intend to use this pin as a general purpose output, you may replace this resistor with a jumper.
  10. Theoretical value is 6.2 Kohm from the E24-series, but the E12 standard 5.6 Kohm seems acceptable.
  11. Theoretical value is 62 Kohm from the E24-series, but the E12 standard 56 Kohm seems acceptable.
  12. Correct value (as per RS-170 standard) is 75 ohm from the E24-series, although the E12 standard 68 ohm is acceptable.
  13. C10 was originally 1 µF, but fitting it does actually impair NMI debouncing and should not be used. In this case, R35 can be safely replaced by a jumper as well.
  14. These are just weak pull-ups/pull-downs and may be chosen from around 1 Kohm up to 330 Kohm or so. Even if they're only needed for the Durango·S variant, fitting them won't harm in any case!
  15. Strong pull-downs in SIP-9 package. This is the nominal value but could be modified slightly without any ill effect.
  16. Strong pull-ups in SIP-5 package. Nominal value is 3.3 Kohm, but 4.7 has worked fine always.
  17. PIHER PT-6-V package.
  18. Originally specified as 5 K, the new value allows for a broader adjustment margin.
  19. Could be ommited in certain configurations, see options.
  20. Single-mode Durangos (·S, ·R) may use 74HC157 instead.
  21. Although HC versions may serve well in any case, the faster AC version is recommended for U15, while U14 may be safely replaced by a slower non-HC CD4040. In some cases, U19 could be of this slower type as well, but display may become slightly glitchy.

Logic families


Some sellers on eBay, AliExpress and the like, seem to be selling non-compliant parts -- they seem to work fine on less demanding circuits, but fail whenever they're "pushed" within spec. In the case of the Durango computers, U15 and U125 are particularly sensitive parts, thus a reputable source is recommended or, at the very least, make sure you purchase under a reasonable return policy.

The Durango·X computer is designed around high-speed CMOS (HC) technology. SRAM chips are nearly always of such type, as is the 65C02 CPU_; the rest of the circuit is made from standard 74HC parts. Some considerations have to be done:

  • Generally speaking, 74HC and 74HCT are both suitable and normally interchangeable. However, the use of an HCT for U32 (or U8 on v1 boards) may affect interrupt performance, check here for details.
  • In case of U14, a non-HC CD4040 may be used without any ill effect. In some cases, U19 can be replaced by a non-HC unit as well, although some glitches on the screen might be seen.
  • Performance of U15 is critical. v1 boards work fine with a 74HC unit but, in case of v2, a 74AC4040 is highly recommended -- some displays may become unstable with the HC part.
  • Again, U125's performance is critical for optimum display quality. Some questionable parts may not be up to the official performance level, thus beware! Any other use of the 74HC157 seems more tolerant, though.


The use of bipolar TTL logic circuits (e.g. 74LS) is NOT recommended. Neither is the use of an NMOS 6502, since the software library does not necessarily support it!

Component equivalences

  • The 74HC00 may be replaced by a 74HC132 (v1 had one of these too), but the opposite is not true.
  • In this circuit, any 74HC157 may be replaced by a 74HC257 without any problems; note that single-mode Durangos need no '257s at all, and may use '157 or '257 at any position.
  • 74HC688 has same pinout and functionality as the '521 (usually available from faster logic families) and should be interchangeable.
  • Transistors and diodes are not critical, and any small signal reference may be used instead -- as long as you keep the pinout in mind.