Cheatsheet & Glossary

This final volume is the card you keep on the bench, not the book you read in a chair. Everything below has been argued out at length in Vols 2 through 14; here it is boiled down to tables, formulae, and lists you can scan while a probe is in one hand and a bag of surplus neons is in the other. Nothing here is new — if a number surprises you, the volume that derives it is named in prose so you can go back and check the reasoning. Treat this as an index with the arithmetic pre-chewed: the tube you can trust and the tube you must sort, the five resistor-and-capacitor relations that turn a row of lamps into a counter, the relaxation formula that got you started, the six steps that get you to a working ring, and the handful of safety rules that keep the whole exercise from becoming your last one. Print it, laminate it, and keep the ⚠ line in §15.9 where you can see it.

15.1 Tube quick-select

The single number that decides how hard a build will be is the hysteresis window Vs − Vm (striking minus maintaining voltage). Wide is forgiving; narrow must be binned. This table matches Vol 3; the switching-tube figures and the tritium half-life match Vol 2 as well.

Table 1 — 15.1 Tube quick-select

Tube	Vs (strike)	Vm (maintain)	Vs − Vm window	Priming	Availability
Barium-cathode indicator neon (NE-2 / IN-3)	~65–110 V (nom. ~90 V)	~55–60 V	~12–20 V — marginal	Photo-sensitive; suffers the dark effect	Cheap, plentiful; must be binned
Philips ZA1002 switching tube	~170 V (169.1–171.0 V measured)	~105 V (104.8–105.2 V)	~60 V — luxurious	Tritium primed, <1 ms strike (t½ = 12.3 y)	NOS-only; aged stock strikes erratically 170–220 V
Philips ZA1001 switching tube	(same family; the Philicorda octave-divider tube)	—	large	as ZA1002 family	NOS-only; see sibling ../Philicorda/
Dekatron (integrated 10-stage ring)	—	—	n/a (one envelope)	some types include a priming cathode	NOS; see §15.8 and Vol 5

Notes that never change: ~99.99 % of commercial neons are the NE-2/IN-3 barium-cathode type, so binning is nearly always mandatory. The ZA1002’s tritium priming has decayed through roughly five half-lives on any 1960s tube, leaving only 1/32 to 1/64 of the original — Dekker saw exactly this erratic striking. A dekatron’s anode runs far higher than any of the above: **+400–475 V** (see §15.8).

Luc Small’s three measured IN-3 clusters (the worked example throughout, from Vol 3) after a 48-hour burn-in:

Table 2 — 48-hour burn-in

Cluster	Count	Vs	Vm
Lower	14	73–77 V	38–42 V
Middle	8	82–86 V	42–46 V
Upper	11	88–92 V	48–53 V

15.2 The ring design equations, all in one place

These are the whole of Vol 4’s design mathematics on one card. Define the symbols once: Vs, Vm are a stage’s striking and maintaining voltages (subscript min/max/avg over the binned cluster); I is the lit-stage cathode current and Inom the value you design for (A); Rcat the per-stage cathode resistor (Ω); Ra the common anode resistor (Ω); C0 the inter-stage coupling capacitor (F); Vsupply the rail (V); Vlamp ≈ Vm the lit lamp’s maintaining drop (V); N the number of stages.

Table 3 — 15.2 The ring design equations, all in one place

Quantity	Relation	Purpose
Transfer-bias lower bound	I·Rcat < Vs,min − Vm,max	No stray/false strikes of a resting stage
Transfer-bias upper bound	I·Rcat > Vs,max − Vs,min	Sequencing wins over tube-to-tube spread
Ideal centre	I·Rcat ≈ (Vs − Vm) / 2	Bias parked mid-window for maximum margin
Cathode resistor	Rcat = (Vs,avg − Vm,avg) / (2·Inom)	The value you actually fit
Anode resistor	Ra = (Vsupply − Vlamp) / Inom (Vlamp ≈ Vm)	Sets the stage current on the glow plateau
Coupling cap	C0 sets transfer rise-time	Too small → no transfer; too large → double-stepping
Divide ratio	ratio = N (ring length)	One carry pulse out per N input pulses

Two reference designs to sanity-check any calculation against:

Table 4 — Two reference designs to sanity-check any calculation against

Design	Vsupply	Inom	Rcat	Ra	C0	Tube Vs / Vm
Dekker (10-stage ring)	185–250 V	—	12 kΩ (ideal ~7 kΩ)	82 kΩ	27 nF	drop-shaped neons ~97.5 / ~68.6 V (~29 V window); the 140/100 V pairing is his fictitious teaching example
Luc Small (lower cluster)	150 V	800 µA	18 kΩ (calc 16 875 Ω)	120 kΩ (calc 120 625 Ω)	100 nF / 250 V	73–77 / 38–42 V

The original ring counter (Manley & Buckley, Electronics, Jan 1950) steered the glow with germanium diodes rather than the cathode-transfer-bias trick above; the capacitive-coupling topology tabulated here is Dekker’s.

15.3 The relaxation-oscillator formula

For a single lamp charged through R from supply V, firing at Vs and quenching at Vm (Vol 2), the period is

T ≈ R·C · ln( (V − Vm) / (V − Vs) )        f ≈ 1 / T

with R in Ω, C in F, T in s. It only oscillates if V > Vs — as V approaches Vs from above, (V − Vs) shrinks, the log blows up, and the period lengthens and grows supply- sensitive. Keep R large enough (hundreds of kΩ to MΩ for an NE-2) that the lamp truly extinguishes each cycle. Worked NE-2: Vs = 90 V, Vm = 60 V, V = 120 V, R = 1 MΩ, C = 100 nF → RC = 0.1 s, ratio = 60/30 = 2, T ≈ 0.1 s × ln 2 ≈ 69 ms, f ≈ 14 Hz.

15.4 Design a ring in six steps

The recipe distilled — the long version is Vol 4, with tube data from Vol 3, the supply from Vol 9, and burn-in from Vol 11. Figure 15.1 is this same flow as a card.

1. Bin & burn-in. Burn new/NOS lamps in at rated current (Luc: 48 h) to stabilise Vs/Vm and weed early failures, then measure and cluster them (Vol 11). Design per cluster.
2. Pick Inom. A few hundred µA to ~1 mA; Luc chose 800 µA. Modest current limits self-heating and ageing (Vol 4).
3. Set Rcat = (Vs,avg − Vm,avg) / (2·Inom) — this parks the transfer bias I·Rcat at the mid-window (Vs − Vm)/2. Luc: 18 kΩ.
4. Set Ra = (Vsupply − Vm) / Inom — the overall stage current on the normal-glow plateau. Luc: 120 kΩ.
5. Choose C0 for clean transfer: too small stalls the hand-off, too large double-steps. Dekker: 27 nF; Luc: 100 nF / 250 V (Vols 4, 10).
6. Supply & pulse. A stiff, regulated Vsupply comfortably above Vs (Luc 150 V; Dekker 185–250 V), collapsed by a 555 step/run pulser (Vol 9).

Then re-check the two bounds of §15.2: I·Rcat must sit below Vs,min − Vm,max (no stray strikes) and above Vs,max − Vs,min (beats the spread). If the cluster’s spread is too wide for both to hold at once, re-bin tighter — that, not the arithmetic, is usually the fix.

15.5 The speed ceiling

Deionisation (recovery) time is of order milliseconds, so a previously-lit stage must fully extinguish before the next pulse or the glow smears, double-steps, or stalls. That caps ordinary cold-cathode ring counting at roughly ~1 kHz (Vol 2). Specially-gassed tubes reach perhaps ~10–20 kHz; Dekker only hit ~500 kHz by dropping capacitive coupling entirely and driving the ring with fast TTL pulses through a high-voltage transistor pull-down. Neon counting is a low-speed, human-scale technique — perfect for a watchable dial or a mains-tick divider, wrong above a few kHz.

15.6 Component picks

Matches Vol 10. The passive choices below feed straight back into drift (§15.7), so they are not cosmetic.

Capacitors (coupling / timing — want low leakage, low dielectric absorption, stable value):

• Prefer polypropylene (best), then polystyrene, or C0G/NP0 ceramic for small stable values.
• Rating ≥ 250 V (≥ the rail) as a rule; Luc used 100 nF / 250 V.
• Avoid electrolytics and high-K ceramics (X7R, Y5V) in timing/coupling — leakage and dielectric absorption cause drift and jitter.

Resistors (high-value anode/cathode parts at high voltage — VCR and max working voltage matter):

• Prefer metal-film, 1 % tolerance (low VCR, low noise) for centring the tight bias — not carbon composition (high voltage-coefficient, drift, noise).
• Size wattage by P = I²R (or V²/R) with derating.
• Where a single part’s maximum working voltage is exceeded, use series resistors to share it.

15.7 Drift-hardening checklist

The Vol 7 mitigations, ranked by leverage — work down the list:

1. A stiff, regulated supply (every volt of rail drift eats the margin directly).
2. Bin and match tubes into tight Vs/Vm clusters.
3. Burn in before final measurement — most drift is in the first hours (Vol 11 jig).
4. Centre the bias at (Vs − Vm)/2 and, where you can, pick large-window tubes (ZA1002).
5. Prime the lamps — ambient/keep-alive light, a permanently-lit priming lamp/LED, or radioactive priming — to kill the dark effect and speed striking.
6. Use low-TC, stable passives (metal-film R, film C — §15.6).
7. Keep currents modest to limit self-heating.
8. Add buffer/amplifier lamps for reliable carry between counters (the PA3FWM fix).

The honest caveat, from PA3FWM: even done right, individual lamps misbehave and progressive ageing can make a neon clock unusable after 1–2 years — “fully characterising a neon lamp needs more than just Vs and Vm.”

15.8 Dekatron drive summary

A dekatron packs a whole ring into one envelope: a central disc anode, a ring of 10 main (indicator) cathodes, and guide cathodes (one or two per gap) that walk the glow from one main cathode to the next (Vol 5).

Table 5 — 15.8 Dekatron drive summary

Item	Value / choice
Anode	~+400–475 V through an anode resistor
Cathode current	a few hundred µA to ~1 mA
Counting speed	~1 kHz (specials higher)
Double-pulse / two-guide	needs a 2-phase guide waveform; e.g. many GC10-family counting tubes
Single-pulse	one guide set + internal biasing
Counter dekatron	display/counting current (GC10/GC10B)
Selector dekatron	higher cathode current for switching, not just display (GS10 family)
Carry	tap off a chosen cathode to clock the next decade

Families to know: Ericsson GS10, GC10/GC10B (ETL/Mullard), Soviet OG-4/OA-4, Raytheon CK6910. Famous uses: the Harwell WITCH (dekatrons as memory) and the Bell Punch ANITA calculator.

15.9 High-voltage safety — the quick rules

The full discipline is Vol 14. The short version, and it is not optional:

⚠ Every rail in this series is ~100–450 V DC and a reservoir capacitor stays charged after power-off. That is lethal, and unlike mains it does not trip anything or announce itself.

• Prove it discharged with a meter before touching anything — assume live until measured.
• Fit a bleeder resistor across every reservoir cap.
• Keep a discharge tool (an insulated-handle resistor lead) and use it before probing.
• Single-hand rule — keep one hand in your pocket so no current path crosses your chest.
• Insulate and isolate: insulated probes, no earth-referenced surprises, respect the burn-in jig’s live sockets, and handle NOS tubes (some contain tritium/thorium) sensibly — don’t crush them.

Glossary

• Striking voltage (Vs) — the voltage at which a dark gap breaks down and lights.
• Maintaining (sustaining/extinguishing) voltage (Vm) — the lower voltage at which a lit discharge finally goes out. Always Vm < Vs.
• Hysteresis — the Vs − Vm gap; the memory window that makes a lamp bistable.
• Negative resistance — the region just after breakdown where voltage falls as current rises (dV/dI < 0); the basis of oscillation and regenerative switching.
• Glow discharge — the self-sustaining cold-cathode gas discharge (normal-glow plateau) a neon lamp lives on, sustained by ion bombardment and secondary emission at the cathode.
• Penning mixture — neon with a trace of argon; the argon metastable ionises neon, lowering and stabilising Vs.
• Transfer bias (I·Rcat) — the voltage a lit stage’s cathode current develops across its cathode resistor, which (via C0) pre-biases the next stage to win the race to strike.
• Coupling capacitor (C0) — the small cap linking adjacent stages that carries the transfer; its size sets the transfer rise-time.
• Dekatron — a cold-cathode counting tube with a whole 10-stage ring (anode + main + guide cathodes) in one envelope; shows a spinning dot of light behind a 0–9 dial.
• Guide cathode — the auxiliary cathode(s) between main cathodes in a dekatron that walk the glow one step per guide pulse (one set = single-pulse; two sets = double-pulse/two-guide).
• Selector vs. counter dekatron — a selector (e.g. GS10 family) runs higher cathode current to switch a load; a counter (e.g. GC10) is optimised for display/counting current.
• Trigger tube — a cold-cathode tube with a starter/trigger electrode that fires the main gap on a small pulse; a switching relative of the counting tubes.
• VR tube — a cold-cathode voltage-regulator/reference tube (0A2, 0B2, 0A3, 0B3, 0C3, 0D3, 150B2…) that clamps a rail to a fixed voltage via its flat glow plateau.
• Priming — deliberately supplying seed charges (ambient/keep-alive light, a pilot glow, or radioactive priming) so a lamp strikes promptly and repeatably.
• Dark effect — a neon’s Vs rising and turning erratic in darkness for want of photo-emitted seed electrons; cured by priming.
• Dielectric absorption (DA) — a capacitor’s tendency to “remember” charge, causing timing drift and jitter; a reason to avoid electrolytics/high-K ceramics in coupling/timing roles.
• Voltage coefficient of resistance (VCR) — a resistor’s value changing with applied voltage; high in carbon composition, low in metal-film — matters for the tight bias at high voltage.
• Deionisation (recovery) time — the milliseconds a lamp needs to return to a dark, un-ionised state after extinguishing; sets the ~1 kHz counting ceiling.
• Injection-locked (regenerative) divider — a division scheme that locks a relaxation/regenerative oscillator to a sub-harmonic; unlike a true counting ring it can jump to a wrong sub-harmonic if it unlocks. A neon ring is an exact integer counter; distinguish the two.

15.10 What each volume covers

• Vol 1 — Overview & the cold-cathode counting idea; the five build paths and where each lives.
• Vol 2 — How a neon lamp works: glow discharge, Vs/Vm hysteresis, the V–I curve and negative resistance, the relaxation oscillator, photosensitivity, the speed limit.
• Vol 3 — Which tubes to use: indicator neons vs. switching vs. trigger tubes; sourcing NOS; the marginal-gap problem; the binning procedure and spec table.
• Vol 4 — The ring counter’s theory of operation: common-anode topology, the transfer mechanism step by step, all the design equations, C0 sizing, directionality, Dekker’s worked values.
• Vol 5 — Dekatrons: the integrated ring, guides, single/double-pulse drive, selector vs. counter, families, operating conditions, WITCH & ANITA.
• Vol 6 — Frequency division & accuracy: the ring as an exact integer divider, jitter vs. reliability, counting vs. injection-locked division, the Philicorda case.
• Vol 7 — Drift, ageing & mitigation, with the PA3FWM failure story as the cautionary spine.
• Vol 8 — HV supplies, traditional: valve/selenium rectification, VR-tube shunt regulation, the 150B2.
• Vol 9 — HV supplies, modern: boost/flyback converters, feedback math, current limit, bleeder.
• Vol 10 — Capacitors & resistors: dielectric and DA, metal-film vs. carbon, VCR, wattage, series-R.
• Vol 11 — The burn-in / ageing jig: schematic, socket-bank, BOM, and the measure-and-bin procedure.
• Vol 12 — Worked examples & applications: Luc’s ring, Dekker’s ring, the PA3FWM clock, dekatron scalers, WITCH, ANITA, Philicorda dividers, flashers, NE-2 memory/latches, art uses.
• Vol 13 — Build it yourself: a complete buildable reference ring counter (Dekker + Luc synthesis), schematic, BOM, 555 pulser, bring-up, troubleshooting.
• Vol 14 — Safety: the ~100–450 V discipline, shock physiology, charged caps, discharge tools, the single-hand rule, NOS-tube handling.

References

• R. Dekker, “A Neon Ring Counter” / Ring Counter Variations — https://www.dos4ever.com/ring/ring.html (the design equations, Vs/Vm hysteresis, the ZA1002, binning, deionisation and the ~1 kHz ceiling, tritium priming and its decay).
• L. Small, “Neon Ring Counters” (2016) — https://lucsmall.com/2016/10/08/neon-ring-counters/ (the worked IN-3 build: clusters, 150 V / 800 µA / 18 kΩ / 120 kΩ / 100 nF, the 555 step/run pulser).
• P.-T. de Boer (PA3FWM), “A clock using neon lamps as logic elements” — https://www.pa3fwm.nl/projects/neonclock/ (the ageing/reliability caution and the buffer-lamp fix).
• J. B. Dance, Electronic Counting Circuits (London: Iliffe Books / New York: American Elsevier, 1967) — in the site’s reference library (the canonical text: cold-cathode tubes, dekatrons, VR-tube regulation).
• Manley & Buckley, “Neon Ring Counter,” Electronics, January 1950 (the original diode-steered ring counter).
• Dekatron family & VR-tube data — Ericsson Tube Technical Handbook (1964) and frank.pocnet.net datasheets (GS10/GC10B/CK6910, 0A2/0B2/0A3/0B3/0C3/0D3/150B2).