Initial tube hook up killed High Voltage at test points

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1 year 3 months ago #9797 by Ty_Eeberfest
It certainly sounds like D2 is bad. Now the question becomes "why did D2 fail?" I believe you said HV worked at one point, so what happened?

Look into it later when the dust is clearing off the crater.

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1 year 3 months ago #9798 by Dan1066
Yes, I did have HV at one point. Things went South after I hooked up the two test tubes for the first time. Tubes did not light up and HV went away. No Sparks, no smoke, no noise or excessive heat.

I guess it's time to replace D2 and try again

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1 year 3 months ago #9799 by Ty_Eeberfest
Yes, D2 replacement seems like it's necessary.

I think it would be a good idea to inspect your tube wiring connections really thoroughly before powering up with the new diode. Also, if it was me, I think I'd pull out the opto-couplers that correspond to the anodes of the connected tubes. See if the HV works that way, then put back one coupler, and so on.

Also, I never asked if the tubes are known to be good. It's uncommon but not unheard of for a tube to have an internal short between 2 cathodes or, more dangerous, between the anode screen and a cathode. If you're feeling real ambitious and the tubes are not known good you could check resistance from the anode pin to every cathode pin on both tubes. You should read open circuit or something really close to open circuit, i.e. tens or hundreds of megohms.

Look into it later when the dust is clearing off the crater.

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1 year 3 months ago #9800 by Ian
Can you send a photo of D2?

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1 year 3 months ago #9810 by Dan1066
Photo of diodes attached.

I checked my tubes and all cathode to anode readings showed open circuit.

Before I pulled the opto coupler, I checked the high voltage from Q1 and there was less than 10v. As a backup plan, I have ordered another kit to start from scratch.
Attachments:

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1 year 3 months ago - 1 year 3 months ago #9811 by Ty_Eeberfest

Dan1066 wrote: Photo of diodes attached.

I checked my tubes and all cathode to anode readings showed open circuit.

Before I pulled the opto coupler, I checked the high voltage from Q1 and there was less than 10v. As a backup plan, I have ordered another kit to start from scratch.


Okay, but I was wondering if pulling the optos would make the HV start working again.

Also (and I should have said this before!) do you have a diode test range on your meter? If so, use it to test D2. It should be okay to est it in-circuit. Forward voltage should be about 0.6 volts and reverse should be open circuit.

EDIT: Also - are you positive you have the UF4007 in the D2 position and the 1N400x in the D1 position, and not swapped?

Look into it later when the dust is clearing off the crater.
Last edit: 1 year 3 months ago by Ty_Eeberfest.

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