DIY IC Tester — Vol 1: Why Build One

1.1 Where this started

My TSH-06F handheld tester (see the TSH-06F IC Tester dive) is good at one thing: a slow truth-table check of common 74LS, 74HC and 4000-series logic. Two jobs on my bench need more than that:

• The KENBAK-1 build. About 130 standard-TTL chips, most of them fifty-year-old new old stock. They include open-collector parts (7403, 7416) and two types, the 7451 and 7454, whose pinouts differ from the 74LS parts of the same number. On top of those are the two Intel 1404A memories, MOS dynamic shift registers that need clocks swinging about 12 V below ground.
• The Heathkit ET-3400 trainer. Its RAM is four 2112 static RAMs, 256 words × 4 bits each. The TSH-06F has no memory tests at all.

The obvious move is to buy something better. TSH-06F Vol 4 surveys what’s available. This volume asks the next question: what would a tester look like if it were designed for vintage parts from the start, and is it worth building?

1.2 What every affordable tester shares

Every tester in the survey, from the $45 TSH-06F to the roughly $200 BackBit Chip Tester Pro, works the same way. It applies a pattern of HIGH and LOW inputs, reads the outputs, and compares them with a table. The differences are in the library and the socket, not the method:

Table 1 — Every tester in the survey, from the $45 TSH-06F to the roughly $200 BackBit Chip Tester Pro, works the same way. It applies a pattern of HIGH and LOW inputs, reads the outputs, and compares them with a table. The differences are in the library and the socket, not the method

Tester	Price	Memory	Standard TTL / open collector	Can be extended?
TSH-06F	~$45	None	Unverified	No
XGecu T48 + minipro	~$55–100, needs a PC	6116, 6264, 62256	Yes: separate 7451/7454 tests; open-collector tests expect “off”	Logic tests are an editable text file
Retro Chip Tester Pro	€40–60 in parts	2102, D2112A, 2114, 6116…; 4116, 4164, 41256	Standard numbers listed; OC method unstated	Firmware updates; not open source
IKCH-55 (two Picos)	not stated	2112 named	Functional only; can’t tell a 7404 from a 7405	Open design
Vintage RAM Tester V3	$37	2114, 4116, 4164, 41256… with real memory-test patterns	No logic	Open source
BackBit Chip Tester Pro	~$200	2111, 2114, 2147…; 4116 with an adapter	MOS/Commodore-focused	Updates

Sources and dates for every row are in TSH-06F Vol 4.

None of them measures anything electrical. A TTL output that can only sink 2 mA instead of 16 mA passes, because the tester reads it through a light load. So does a gate whose delay has drifted from 10 ns to 40 ns, because the tester runs far slower than the chip. Users say as much about the professional units too: one Vintage Computer Federation thread passes on a friend’s verdict that a $700 ChipMaster “can’t be fully trusted” (VCFed forum). The B&K 575A’s adjustable output thresholds were the closest any of them came to an electrical check, and it is discontinued (Global Test Supply).

1.3 The gap

Four things no affordable tester found does together:

1. Electrical checks, not just logic. Measure a LOW output while it sinks its rated current (16 mA for standard TTL). Measure a HIGH under its rated source current. Find the voltage where an input actually switches. Check input leakage. These are the failures a static test misses.
2. Tests at speed. Run a chip at its rated speed and check that outputs settle in time. Modern microcontrollers can do this: the RP2350’s programmable I/O (PIO) blocks generate and sample pin patterns with nanosecond resolution, independent of the processor.
3. The awkward old parts. The 4116 DRAM needs −5 V and +12 V as well as 5 V. The 1404A and Signetics 2504 shift registers need two-phase clocks with large negative swings. The 1101 and 1103 of 1970 have their own quirks. Today these are handled one at a time: an adapter here, a one-off Arduino project there. The only 1404-family tester found is a single open-source Arduino Nano board built for Apple-1 replica builders (GitHub, renatasdgt).
4. A library its owner can extend. Plain text, versioned, with each test written against the data sheet of the actual part, so a 7451 is never tested against a 74LS51.

1.4 Is there a market?

A small one, and it exists. The people who buy chip testers today are retro-computer restorers and replica builders: Apple-1, KIM-1, Commodore, Atari, and kit machines like the KENBAK-1. Some data points:

• The Vintage RAM Tester reports “over 200 units sold worldwide” at about $37, and its listing calls it a “Laboratory / Maker Kit – Not a consumer product” (Tindie, ReUseCircuit).
• Other hobby testers sell at $34–70: the Vetus Pars programmable chip tester at $34 and $45 (Tindie, Retrotroniks), and the RAM tester’s tops4u variants at $55–70 (Tindie, tops4u).
• The Retro Chip Tester is the community favourite, yet it is mostly sold as bare boards or hand-built at cost, and its EU-only ready-built listing has been retired (8bit-museum.de; Tindie, endresz_eu).
• Above $200 the next step is $600–1,100 professional units (Rapid Electronics, ChipMaster).

That pattern points to a market of hundreds of units, not thousands. Buyers are price-sensitive below $100 and willing to build kits. A tester with real electrical checks and the odd-voltage memories would sit alone between $100 and $200. Two things weigh against making it a business:

• The work never ends. Every new chip type is a library entry someone has to write and verify against a data sheet.
• The support load is real. Small makers on Tindie run these as hobbies.

The honest conclusion: worth building as an open-source project and as a dive, because it solves real problems on my bench, with the market as a possible bonus rather than the reason.

1.5 What happens next

Vol 2 sketches the design: a stopgap on an XGecu T48 that tests the 2112s now, and then a from-scratch board, starting with 16 pins and the parts on my bench and growing to 40.