Zvex Nano - Contribution

[nickb]

Not a request but a contribution.

Here is the schematic for a Zvex nano. The oscillator for the power supply does rely on a hand selected device for proper operation. The power supply is very inclined not to start up every time and ends up saturating the inductor and tripping the polyfuse. If you turn the power supply on first and then plug it into the Nano it seemed to come up almost every time.

Enjoy!
nano.pdf

[Helmholtz]

I'm stumped. Do they (mis)use Q1 as a kind of Diac in a relaxation oscillator?

[nickb]

I think it's based on a tunneling effect. You'll find it if you do a search.

[Helmholtz]

Well, it requires some negative resistance.

I can imagine that the breakover voltage (and thus oscillator frequency) is not well defined.

[nickb]

A bit more info.

To get the board out you have to remove the tubes and the tall radial electrolytics. To install new tubes requires that you align and trim the pins. To do this it's pretty much essential to have an alignment jig. I made one per attached drawing using 4mm thick acrylic sheet. Also, install the tubes before the electrolytics as it gives you more visibility as to where the leads are going. Patience is also essential!






Pin Alignment tool.pdf

[J M Fahey]

Thanks, doubly so for the custom tool.
I consider this kind of products a gimmick but itīs always good to know how/what they do.

And one might land in my bench anyway

And yes, the supply oscillator is a needless gimmick, plus requiring hand selecting parts which will work there.

He might very well have used a regular SMPS oscillator and integrated IC such as the popular VIP series or many others.

[Mick Bailey]

A long time ago I built a tiny 1W amp using a 12AX7 preamp with a 12AU7 P-P output. It runs at 270v using a simple SMPS fed off 12v and uses a 555 as the oscillator and an IRF740 as the switch. The DIY inductor is wound on a section of transistor radio antenna ferrite. A paintball mask extractor fan keeps the PSU cool, but a MOSFET with a lower Rds wold be much better. I built it as a novelty, but it really does sound good through a decent cabinet and is still plenty loud enough for home use or recording.

Edit; The Nano uses an Esaki oscillator.

[Jazz P Bass]

Good tutorial on the Esaki Oscillator: Single Transistor Esaki Oscillator Circuit - Bing video