High potential testing of an YC-179 high power vacuum tube

I have posted some pictures of the hi pot test setup of my new Eimac YC-179 vacuum tube (MRI pull). This is for a future legal limit (LA amateur regulations) amplifier for digimode and contest CCS amateur radio use. It is better to run a tube cool than to stress a smaller tube for high dutycycle modes. Let’s hope the tube behaves OK. It measured less than 15uA at 16KV DC from A to G so I might have a good pull. (The reason for measuring at such a high voltage is to ensure that the swing that the PI circuit contributes when driven by the tube can be tolerated w/o breakdown).

HV setup to test to 16 KV (below)

Tube in the test rig (below)

Click on the pictures to see the gallery (below)

The HV meter to the left is on the hot side of the rectifier / smoothing cap and has a multiplier shunt that gives 200 x. That means that 80 on the meter on the left indicates 16KV (DC) output. The uA meter on the right is in line and measures leakage current. (uA)  The o/p is current limited on this output. The meter panels are insulated with plexiglass and air gaps to prevent arc overs to the operator. Not that this would help since the HV leads are exposed. However in a future version… (below)   


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  1. YC-156A/179should hipot double rated plate voltage or:13kv with 0 leakage current.Some good tubes have shown false reading on the hipot if ceramic is dirty or contaminated.A tube will show excessive grid current when close to the end of it`s useful life..GL with your project..Jim..K7RDX..

  2. Hi Jim. There is only a few uA (1-2uA) leakage at 13KV. Hardly noticeable. Above that it starts to rise faster but only to 15uA- at 15-16KV. I have used solvent to degrease the ceramics.

  3. Mike Dickerson

    Really wanting to buy that tube. Please contact me if it’s possible. Thanks.

    • Hi Mike. Unfortunetely this tube is not for sale. I am in fact looking for one more of these to have one spare for this future project …

    • Hello Peter. Thank you for your comment. In the limited initial testing with my HiPot unit I have done so far, I do it basically after the same principle as is described in the Eimac engineering bulletin. The main principle of the Eimac engineering bulletin, if I understand it correctly, is to be certain that you control where the breakdown is measured by connecting different electrodes of the tubes together. Eg, if you want to measure from anode to grid, you connect grid and filament together even if the grid is closer to the anode than the filament. The engineering bulletin mentions screen(s), which is/are not applicable for triodes. Also the bulletin is specifically written for larger transmitting tubes. The debarnacling should not be necessary on an YC-179 initially since there is a gettering material in this tube that will likely take care of degassing at least. After degassing debarnacling may of course be done. I have specifically checked that there is a gettering material in the YC-179 with a senior Eimac engineer even if several sources on line says that there is no gettering material present in this tube…

  4. Hi all,

    I just acquired two of these YC-179 tubes. I have pictures if you would like to see them. I have no need for them as I bought them in a large lot of tubes. Let me know if any of you have any interest in them.

    • Hello Joun. You are welcome to send me some pics. Do you info about the source where these came from? I may be interested. However, if the condition is unknown and they have been unused for some time the status of the vacuum and internal elements may be unknown the value is probably not that high.

  5. Kjøpte samme rør brukt i FH i år. Ifølge selger testet og ok. MRI pull. Tenkte å bygge HF trinn og utgangen basert på utgangen i en T368 som jeg har stående, som vist her: http://w4clm.foxtango.org/homepage.htm
    Prøver å finne gode tegninger av trinn med dette røret, men ikke funne så mye enda. Har du noen tips ?
    De Harald/LA6LHA

    • Hei. Dette røret er jo en triode og du kan se på skjema fra HF triode forsterkere for ideer. Det som skiller dette røret fra andre er bla. at det har mye kapasitans mellom anode og katode og dermed ikke er så lett å få til å gå på 15 og 10m. Dermed kan det være lurt å kansellere denne kapasitansen med en serie induktor før tank kretsen. Du må også ha en skikkelig filament trafo. Videre må røret som regel kjøres gjennom en gettering prosess hvis det ikke er brukt på en stund for å hindre overslag. Google “gettering tube Eimac”. En Hi-pot tester kan være lurt å ha tilgang på. 73 LB3HC


    This is a used Device but we took it from a working System in the purpos of regular Service.
    So we sell it as a second Hand Device as a private Person without Garantie.
    The Tube does not have any mechanical Damage outside.
    If you have interest in that Device so feel free to contact us, we have PayPal.

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