nixie smps: something went pop...

[trad3mark]

So I had a tube based pedal with a nixie smps. Everything worked great and I decided to try a different tube. The heaters came on no problem, no signal, then there was a pop noise and now the voltage to the anode is less than 9v. Anyone able to give me an idea of what is most likely to have popped and where I should start looking as far as a debug goes?

[thomasha]

Hi,
is it a 555 smps, or what? maybe a new IC or a new IC and mosfet.
I only worked with the Max1771, and burned a lot of them, sometimes a bad contact with the reservoir capacitor is enough to burn it.

Some pictures would help too.

[R.G.]

I had a job designing switching power supplies back in the early 1970s, when switching power was a Big Deal. It's taken a long time for the parts and processes to get good enough that even a small switching power supply is a reasonable target for a hobby.     Back then, every single on/off cycle of every power part was a near-death-event for the part. But life in the power supply lab was exciting!

What popped is likely to be one of the parts that handles power - the power filter caps, the bypass caps on the switching section, the power transistor(s), the power rectifying diodes, even the snubbers that eat up the excess energy left over from each switching edge. Without a schematic and some photos, there's not a lot that can be told about it. It's a lot like posting to a car forum on the internet that your car quit running, and it only kind of goes ugh-gak-ugh when you try to start it. You're going to immediately get a request for more information about the car and its history.

[J0K3RX]

Is this the same as the one you are using?



You posted the link to the above schematic in another thread asking questions about C4 ... Start by looking there, just a hunch

[trad3mark]

Yeah that's the schematic I used. Is it possible that when I changed the tube from a 12ax7 to a 12au7 without adjusting the trimmer the voltage went too high?

I can't see any visible signs of what went pop, but my camera is in the office and I should be able to get photos a bit later. I'm ordering new parts later so I'll include things like new caps, diodes and inductors in that.