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Aikido 12Vac line stage/pre-amp build & review

Did you try plugging in just one channel at a time? If the breaker pops with only one channel that would help narrow it down. Do you have any extra tubes? You could try replacing them one at a time. I guess there is the possibility of a tube having one bad side or both. I had a driver tube that had an intermittent short internally.
 
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I’ll try another power supply this weekend, as well as seeing if I can narrow down which channel. I don’t have any other 6dj8 tubes so I’ll purchase some more to try swapping.
If a tube or power supply was causing the short, wouldn’t it short every time I plugged it in rather than just when an input is connected or am I missing something? I’m still a newbie when it comes to tubes.
 
The one I had problems with seemed fine at idle. But when I passed a signal it would sometimes flash at the bottom and I would get weird noise and hum. A bad tube is just a wild guess. But it doesn't hurt to keep an extra on hand. Was the power supply something you picked up used? It just seems like that is the problem area. Also what source were you using? It isn't balanced is it? Some equipment has separate grounds for right and left channel.
 
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Power supply is currently a variac picked up from barter town. I’m sure I have another appropriate wall wart somewhere. Source is laptop connected to a schiit modi, unbalanced.
I’ll order some more tubes as I’m sure I’ll want to roll them anyhow. This weekend I’ll try to narrow it down to one channel, if I can then I’ll try to see if the problem follows a tube to the other channel.
 
Can’t narrow it down to one channel. Trips the gfi regardless of which channel is connected. Also tried swapping cables and keeping it unplugged at the source end- only trips when source is actually connected.
I don’t have another suitable 12v ac 2+ amp power source so I can’t try a different power source.
I do have a proper 12v toroidal transformer on its way from Arrow, but that won’t arrive until Tuesday.

-found a way under powered 12vac 3va (.25 amps is my math is correct) and it doesn’t trip the gfi- but it’s also not near enough power for it.
 
Given that the heaters are wired in series, I’m guessing that I can’t safely just pull individual tubes to see if it still shorts? In my head that would throw my voltages all off, but maybe I’m wrong.

Edit- or i’d just have an open circuit.
 
With series heaters you will need all the tubes plugged in, it would be an open heater circuit I think. So, it doesn't trip with the under rated power supply? If that's the case it may very well be a problem with the 2 amp supply you were using. It would be nice to have a regulated 12v ac power supply. The transformer should work, but if your house current jumps up so will the 12v in the secondary winding.
 
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Any suggestions on a regulated 12 to 13.5v ac 2+ amp power supply?
A quick search on my end is only turning up ac to dc.
 
As long as you don't get big spikes you should be ok. The regulator would be after the diodes on the DC side anyway. The Aikido I built used a dual regulated supply that cost a bit of $$. Since your building a 12v version you should be ok. I lived in a very rural area and the power was noisy and fluctuated between 120v and 127v. Here it stays between 120v and 123v. Where did you find that chassis? I've been trying to find something I like for the nixie meter kit I have.
 
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Amazon, link below. Width of the wider cutout is 161mm, so after fashioning some sort of mounting thingy, all but the top of the Nixie tubes will show (they measure 160mm).
You’ll hafta do what I did and also order some plexiglass and cut it down to size. I bought a large enough sheet for two plus some scrap in case I crap one while cutting and drilling it.
https://www.amazon.com/gp/aw/d/B07G95V7YC?psc=1&ref=ppx_pop_mob_b_asin_title
 
I still haven’t figured out how I’m going to mount them in there. Currently I’m thinking an aluminum block/strip, cause I should in theory be able to drill holes to slip the tubes through and hold in place with silicon, and drill and tap the bottom to screw it into the base. I’m open for suggestions.

Edit- I haven’t actually measured the tubes yet, that measurement is based off of a photo. I really should measure them.
 
That might work well, depending on how it looks. Definitely worth some non permanent experimentation, thank you!
 
MKG said:
That might work well, depending on how it looks. Definitely worth some non permanent experimentation, thank you!
Click to expand...
I have another type of clamp I may use also. I'll dig them out and take pictures. They are basically like a conduit clamp, only small, plastic and have a screw hole.
 
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I’m thinking one of those options would be a hell of a lot easier than drilling aluminum block. :beerchug:
 
MKG said:
I’m thinking one of those options would be a hell of a lot easier than drilling aluminum block. :beerchug:
Click to expand...
Yup. And I was thinking I could use small washers to space those black clamps out a bit so the tubes aren't right up against the front glass or plexi.
 
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Transformer came today. Wired it up, plugged in an input- doesn’t short! Winning.
Still haven’t heard it, need to wire in a volume pot first. Once I do that and give it a listen (and install some bypass caps) then I can start installing it into the case and doing permanent wiring & routing.
 
MKG said:
Transformer came today. Wired it up, plugged in an input- doesn’t short! Winning.
Still haven’t heard it, need to wire in a volume pot first. Once I do that and give it a listen (and install some bypass caps) then I can start installing it into the case and doing permanent wiring & routing.
Click to expand...
Awesome!
 
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