Page 3
Front Panel Board Assembly
Assembly of the front panel board is not a beginner’s project and these instructions won’t teach you
how to solder components on a PCB, solder connectors, or show you the difference between a resistor
and a diode. If you have any concerns about building this board, please contact me first.
Many assembly details are illustrated in photographs that follow. Rather than print this manual, you
may want to view this document on your tablet while you work. A tablet makes it especially easy to
zoom into the photos to see the details you may need.
Parts List
Designator
Description
Part Number
Distributor
C1-C5
0.1uf, 50v
2146302
Jameco
C6
100uf, 16v electrolytic
647-TVX1C101MAD
Mouser
D1-D36
Red LED
Everlite HLMPD150A
Digi-Key 1080-1064-ND
J1
50 pin, dual row IDC straight header
517-D3433-6302-AR
Mouser
J2
5-pin, 0.156 locking header
B5P-VH-B-LFSN
Digi-Key 455-1642-ND
Female Housing
VHR-5N
Digi-Key 455-1186-ND
Crimp Pins
SVH-21T-P1.1
Digi-Key 455-1133-1-ND
IC-A,B,C,D,E
74LS165 Parallel In Shift Register
595-SN74LS165AN
Mouser
R1-R36
2K, 1/4w, 5%
291-2K-RC
Mouser
R37-R52
4.3K,1/4w, 5%
291-4.3K-RC
Mouser
S1
Toggle Switch On-None-On (Silver)
APEM 5236AB
Search for best deal
S10-S25
Toggle Switch On-None-On (Gold)
APEM 5236CDB
Search for best deal
S2-S9
Toggle Switch (On)-Off-(On) (Gold)
APEM 5237CDB
Search for best deal
Switches
If at all possible, do not use C&K switches for the front panel
. The C&K switches have an erratic and stiff
feel – especially the momentary switches – compared to the American Switch brand used in the original
Altair. In addition, I’ve had several C&K switches break while gently tightening the bushing nut as well as
during normal use. The APEM switch part numbers listed above are much closer to the original American
Switch brand. In fact, APEM purchased American Switch a number of years ago.
The power switch must have silver contacts as noted for S1. Ideally, use gold contacts for all remaining
switches. Do not mix switch brands as most have slightly different body heights and this causes prob-
lems when mounting the front panel to the mounting plate/bracket.
The APEM switches can be expensive. I may be able to help with a bulk buy. Contact me if interested.
Additional Part Notes
Use only LS-TTL parts
. Some IC inputs are tied directly to Vcc. Multi-emitter TTL inputs do not tolerate
this well (e.g., 74xxx and 74Sxxx).
The specified LEDs provide an appropriate brightness with the 2K resistors specified for R1-R36. You may
need to choose a different resistor value if a different LED is used.
