Oh dear! NumiQueen is sick!

PowerSupplyOpenThe beloved NumiQueen started to have problems the other day. One minute it was fine, and then the next minute the display faded and then only one digit came on, and dimly. I feared the worst, especially as I have become attached to the large bright display of the IV-13s.

I have other clocks in the same room (which Nixie fan doesn't have an excess of clocks?) but that wasn't the point. It's not about knowing the time: any fool can know the time, it's about knowing the time in style...

I turned the NumiQueen off and on. Many years of using Windows taught me that turning off and on solves most problems, but it didn't solve this one. I turned it off and left it off for an hour, to let any hot components cool off. That also didn't help much. The display would run correctly for a few seconds and then dim out again. 

Clearly this was a sick clock. Jürgen from Nixiekits is in the middle of moving at the moment, and he's not online much to ask questions of, so this is a problem that will have to be solved by yours truly.

TheSweatGotOutAfter doing some investigation, the problem appears to be with the power supply. Looking at the output with a scope, the smoothing is not at all smooth. Sniffing the case of the external power supply confirms the suspicion.

I opened the power supply case and this is what is in there:

 The electrolytic capacitors for the output smoothing have indeed vented. One of them has a vaulted dome on top of it, and the other seems to have just splurged gunk over the board.

The inside of the upper part of the case is also telling. The nasty electrolyte is all over it, and it is very obvious that the capacitors are dead:

The final proof

Extracting the capacitors makes the case totally clear. The power supply is only a couple of months old, but both of the capacitors have failed in the same way. One has bulged the top and the other has vented from the base. Normally this should only happen from older, or over-stressed components.

Or... Ones that are crap.


I have never heard of the manufacturer "CTC", but it seems significant that both of these capacitors failed in the same way at the same time and after only a few weeks of service. Possibly a bad batch of components. Possibly a bad manufaturer.

But the point remains: If you have a NumiQueen and you have problems with the power supply, it could well be this the cause.

Fixing it

Fixing it was easy: Solder in two new electrolytic capacitors of the same value, but with a lower coefficient of crapness, and we are on the road again, Now it just remains to be seen if there is a further problem in the design of the supply, or if it really was just some sub-standard components.



#1 stephen matthews 2017-04-01 15:19
HI i had the same problem with my power supply and had it replaced by MR NIXIE have you noticed that the power supply runs hot all the time i don't think its up to the job
whats your thoughts ?
#2 Jeff 2017-04-02 17:36
I also wonder about this after a failure on my jenny reloaded. I wonder if a specific component is failing (like the Cap from Ians clock).

I was thinking of putting on a new HV power supply on my clock to see if that would fix the issue, but I'm not sure if it would work correctly, as the pic chip controls the power
#3 Bob L. 2017-04-02 19:07
I just added one of these 7V 3A medical rated supplies to a Mouser order I'm putting together. $20.75 plus shipping...

I believe a 2.1 A supply ships with the clock? My clock will hopefully ship when the dust from Jürgen's move settles!

#4 Bob L. 2017-04-02 19:09
Oops... left off the link above:

Mouser part number: 108-MDS-030AAC07AB

#5 Ian 2017-04-03 09:23
Also my supply runs hot all the time.

I checked that the supply is not being overloaded. Even at full brightness, we're pulling only 1.6A, so there's plenty of overhead there. I think it's specified just fine, just the components appear to be sub-standard.

I'll update if anything changes, but we're running fine now. When I get home I'll also check if we are running cooler with the replacement caps.
#6 Ian 2017-04-03 09:37
Hi Jeff, what happened on that Jenny Reloaded? Did the tubes dim out or something? I'm pretty sure we could get it going if you want...
#7 stephen matthews 2017-04-17 21:28
just thought i would add more to this post my replacement power supply
failed again same problem two blown caps so had some
spares and repaired it now running again i had not being using the clock as i was not happy with the power supply
but now it dose run cooler and i think it is safe to leave on
so hopefully now it will be OK
#8 Bob L. 2017-04-17 22:32
Hi Stephen,

What is the make and model number of the failing power supply? My NumiQueen is in transit and I already have a replacement power supply in hand (Mouser part number: 108-MDS-030AAC0 7AB). Would like to know what model supply Juergen is shipping to see if I receive the same supply with my kit.

Also want to mention that Juergen is back on-line following his move and has been providing some truly superb customer service with a small customization request. I really like many of his designs... and keep coming back...

Many thanks!


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