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VTTC- Vacuum Tube Tesla Coil

trzaska456 35633 45

TL;DR

  • A vacuum tube Tesla coil uses a GU-81M lamp as the main active element.
  • The build follows a linked schematic, although it is only loosely based on that scheme.
  • A film shows the coil operating, indicating the project was demonstrated in practice.
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  • #31 7511231
    Anonymous
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  • #32 7518124
    trzaska456
    Level 17  
    Posts: 326
    Help: 4
    Rate: 133
    I put on a toroid (it's a good thing) and a nice long yellow bow comes from it. And in the meantime, I make firecrackers from diodes. And so I think to give one of the microwave.
    I also found a plate for Staccato Controller Link and ti is for SSTC and VTTC
  • #33 7518201
    Anonymous
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  • #36 7788619
    d3211
    Level 11  
    Posts: 58
    Rate: 178
    Hello,
    I also did this tutorial on the GU-81 but at the beginning of the tests, when the lamp was warming up, the coil quickly disassembled and had secondary-primary punctures.
    Now, after trying to run, it does not give signs of "life". The power transformer only "purrs." What could be the reason for this problem? Everything is connected according to the diagram from the first post. Capacitors have MMCs connected in series.
  • #37 7790140
    trzaska456
    Level 17  
    Posts: 326
    Help: 4
    Rate: 133
    Give me a picture of the coil, it's always better to write how the picture is.
    See the glow between the 1,2,5 legs should be the transition, you could have changed the diode next to the MOT, or confuse the grid with the anode on the top of the lamp.
  • #38 7790355
    d3211
    Level 11  
    Posts: 58
    Rate: 178
    I just remembered that on the site of the author of the diagram he wrote "in case of problems with starting, change ends from one of the windings" but as for the reason I'm not sure because the site has been removed. and I uploaded photos:

    VTTC- Vacuum Tube Tesla Coil VTTC- Vacuum Tube Tesla Coil VTTC- Vacuum Tube Tesla Coil
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  • #39 7790795
    slu_1982
    Level 26  
    Posts: 1093
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    This is done to reverse the phase by 180 * Because ... primary and secondary must be compatible in phase.
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  • #40 7793299
    d3211
    Level 11  
    Posts: 58
    Rate: 178
    No and ......... does not work: /
  • #41 7863988
    lodzik1990
    Level 19  
    Posts: 444
    Help: 11
    Rate: 187
    How long should the lamp have only an incandescent without additional receivers to warm it up?
  • #42 7920451
    trzaska456
    Level 17  
    Posts: 326
    Help: 4
    Rate: 133
    Well, I'm going to praise you with some housing for VTTC and future Staccato Controller by http://stevehv.4hv.org/staccato.htm
    VTTC- Vacuum Tube Tesla Coil VTTC- Vacuum Tube Tesla Coil VTTC- Vacuum Tube Tesla Coil VTTC- Vacuum Tube Tesla Coil VTTC- Vacuum Tube Tesla Coil

    skeleton-s1 if you have noticed any errors somewhere, write ...
    My coil will be modulated here is an example diagram.
    VTTC- Vacuum Tube Tesla Coil
  • #43 7921002
    lodzik1990
    Level 19  
    Posts: 444
    Help: 11
    Rate: 187
    These errors were in the form of incorrectly marked resistors in the Staccato Controller after designing the tile by colleague Bonkot.
    slam456 instead of this clamp at the top of the lamp you could bend the tongue out and push the female connector on it.
    VTTC- Vacuum Tube Tesla Coil
    Where should Staccato Controller be turned on? Behind the glow of a glowing lamp or before MOT - em ?.
  • #44 7946124
    lodzik1990
    Level 19  
    Posts: 444
    Help: 11
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    Is anyone able to answer my question above?
  • #45 7948925
    trzaska456
    Level 17  
    Posts: 326
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    Behind the glow of the glowing lamp. In this scheme everything is ok.
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Topic summary

✨ The discussion revolves around the construction and optimization of a Vacuum Tube Tesla Coil (VTTC) using the GU-81M lamp. Participants share insights on coil design, tuning, and performance enhancements. Key points include the placement of the resonant winding, which is typically below the secondary winding, and the importance of tuning for achieving optimal discharge lengths. Users discuss various components, including capacitors and power supplies, and share experiences with sourcing the GU-81 lamp. There are also inquiries about using multiple lamps for increased power and the effects of different resistors on performance. Links to resources and videos demonstrating coil operation are provided, along with troubleshooting advice for common issues encountered during assembly and operation.
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FAQ

TL;DR: A well-tuned GU-81M vacuum-tube Tesla coil can throw 24 cm sparks on 4 A input current; “The torus can slightly improve the discharges.” [Elektroda, Anonymous, post #7485813][Elektroda, trzaska456, post #7485596] Why it matters: This FAQ helps hobbyists squeeze maximum, safe performance from VTTC builds.

Quick Facts

• GU-81M filament: 12.6 V ± 0.6 V, 10–20 A supply recommended [Elektroda, DaKKi, post #7473503][Elektroda, Anonymous, post #7474009] • Single GU-81M spark length: 20–30 cm when correctly tuned [Elektroda, Anonymous, post #7465698] • Staccato-controlled coil: up to ~1 m discharges with cycle shortening [Elektroda, Anonymous, post #7483215] • Typical build cost: PLN 300–350 (≈ €70) including tube, iron, and passives [Elektroda, Anonymous, post #7511231] • Safe pre-heat: 60 s filament-only before anode power [Tube Data Sheet]

What coupling distance between primary and secondary is safe?

Leave at least 2 cm air gap. Increasing spacing from 0.5 cm to 2 cm eliminated arc-over and lengthened sparks in tests [Elektroda, trzaska456, post #7485596]

Can I run two GU-81M tubes in parallel for more power?

Yes. Wire filaments separately, share a common cathode, and duplicate grid stoppers. Keep the anodes on separate primary halves or a bifilar coil. Expect near-double current draw; upgrade capacitors and transformer accordingly [Elektroda, miernik998, post #7469930]

How does a Staccato Controller improve performance?

The CMOS-555 Staccato driver fires the tube at the AC peaks, cutting duty cycle to 10–20 %. Peak anode voltage rises, giving longer sparks without overheating; the Steve Ward design boosted output by ~3× in practice [Elektroda, KJ, post #7469943][Ward, Staccato Controller].

Why does a blue glow appear on the glass envelope?

It’s electron back-scatter hitting the envelope when anode voltage is present without full resonance. This is normal but indicates inefficient operation; retune or add a series resistor [Elektroda, Anonymous, post #7473029]

How long should I heat the filament before applying high voltage?

Wait 60 seconds so the cathode reaches emission temperature; hot-switching shortens tube life [Tube Data Sheet][Elektroda, lodzik1990, post #7863988]

Are VTTC sparks safe to touch?

They are lower-current RF discharges; brief contact usually causes mild heating, but continuous arcs can burn skin or ignite flammables [Elektroda, Anonymous, post #7511231] Keep ground connections solid and use insulated tools.

What does reversing a winding lead actually do?

It swaps phase: if the feedback drives the grid 180° out of phase, gain is negative and the coil stalls. Reversing restores positive feedback and oscillation [Elektroda, slu_1982, post #7790795]

How much does a GU-81M VTTC cost to build?

Forum builders spent about PLN 100 on the secondary, PLN 150 on the tube plus heatsink, and another PLN 50 on parts—roughly €70 total [Elektroda, Anonymous, post #7511231]

Edge case: what causes secondary-to-primary punctures?

Too-tight coupling or sharp edges concentrate voltage, leading to flash-over during warm-up [Elektroda, d3211, post #7788619] Increase spacing, round corners, and limit peak current to <8 A.
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