Power for six (6) GR10G Nixies: 300VDC @ 40mA - small switching PSU?

[Dekatron42]

Hi,

I've tried to find a small switching PSU module that can output 300VDC@40mA to drive six (6) GR10G Nixies - their minimum voltage is 220VDC but most work a lot better with closer to 300VDC (250-300VDC in the datasheets).

I've emailed the usual suspects, Tayloredge and Michael Moorrees, without receiving an answer if their modules can be modified to output 300VDC but I haven't received an answer from any of them.

So, does anyone here have design of a power supply that can power six (6) GR10G at 300VDC@40mA?

I can use more than one module if power requirements are too much for just one module, size is not that important and I might go with a small R-Core 30VA transformer or a dual transformer design if no module exists.

/Martin

[gregebert]

Would you consider running non-isolated from the AC-mains ? I have 5 clocks (3 different designs) that have been running this way for several years, and as long as you design with adequate safety in-mind you should not have any problems. These 5 clocks have a cumulative runtime of 30 years with zero component failures (except for two b6091 tubes).

[Paul Andrews]

The problem with modifying a power supply from 200V to 300V is that quite a few components will probably go out of spec. e.g. the output capacitor and the feedback resistors. Bringing them back in to spec may involve changing the footprint and so is not a simple mod to make to a board.

If you can get a single inductor module, you may be able to use a voltage doubler on the pre-rectified output to get the voltage you want, if not the current.

[SWISSNIXIE - Jonathan F.]

Whats the input voltage?

I would recommend looking at LT3750 l LT3751. They have a refernce design for a 300V 6A capacitor charger (can be modified to nixie supply) and also there is a 500V, 150mA flyback design, which could be modified.I think going flyback is the best version. Of course one also could build an isolated mains supply.

[Dekatron42]

@ gregebert: I'd prefer not using rectified mains, I might use two transformers back to back or one isolation transformer with secondaries like the primary to get some isolation - knowing myself I'd better use some isolation... I sometimes wonder why I am not dead from all the shocks I've got, the worst still show scars.....

@Paul Andrews: I might have to go with the doubler/tripler way and use a low output voltage to get it higher and then use two or perhaps three modules from Michael Moorrees as those seems to be the easiest to use.

@SWISSNIXIE: I'll definitely look into that ic, getting hold of the transformer will probably be the hardest part if there aren't any readily available.

Regarding input voltage I have no direct constraints but what a wall-wart can deliver, in the worst case I can use an isolating transformer with mains input and up to 48VAC output (will probably go for 24VAC as I can then get the voltage for the digital portion from that too).

There are some size constraints as usual but I could probably fit a low profile transformer, or two side by side. The enclosure is some 285 by 75 millimeters and I can vary the height to some extent without it looking wonky. I will use an old Puhlmann Nixie clock (which is dead) as the base for the clock reusing the case and changing it from a wall clock to a desk clock. I won't drill any more holes in the case than there already are (two for switches, one for light detection and one for the power plug) but I can extend the base so that it will be somewhat higher if necessary (very probably).

/Martin

[Charles MacDonald]

On 2019-07-15 4:54 p.m., Dekatron42 wrote:
> @ gregebert: I'd prefer not using rectified mains, I might use two
> transformers back to back or one isolation transformer with secondaries
> like the primary to get some isolation - knowing myself I'd better use
> some isolation... I sometimes wonder why I am not dead from all the
> shocks I've got, the worst still show scars.....

Why not use one of the "Hammond Classics Tube power transformers".you
would need to bring in the Mains to the primary, But that can all be in
an enclosure. for example the 260 series.
http://www.hammondmfg.com/260.htm

400V CT and a couple of 1N4007 and perhaps a filter cap. (if you need
pure DC.) Extra 6.3V at 2A winding to run your digital stuff.


--
Charles MacDonald Stittsville Ontario
cm...@zeusprune.ca Just Beyond the Fringe
No Microsoft Products were used in sending this e-mail.

[GastonP]

Mike's power supplies have a "pulse" output to where you can tie a mutiplier to get higher output voltage than what the board alone offers.

https://threeneurons.wordpress.com/nixie-power-supply/hv-supply-kit/

In one of the examples in that page you have one showing 310V, etc. From back of the envelope calculations one can get not more than 15 mA out of each module at 300V...

[Nick]

My MAX1771 design can probably be pushed to that. Yes, C4 & C6 would have to be higher voltage and R2 changed - the PRC221 range have a working voltage of 200V but are safe to 500V - it would be better to find a 2512 footprint resistor with a 300 or 350 volt working for long term reliability.

D1 would need to be changed from an ES2F to an ES2G (same footprint, 400V Vrrm) but it may be better to find one with the same footprint (SMB) which has a higher RMS working voltage.

A lower ESR FET would also be a good plan - see the web page for details - https://nick.desmith.net/Electronics/NixiePSU.html 

Nick

[Dekatron42]

Thanks Nick, I'll check your design too, but if I am going to make one it'll have to be through hole, too poor eyesight makes it very hard to solder SMD for me.

/Martin

[GastonP]

I had forgot your design. Excellent project page and thanks for reminding me of it!

[newxito]

I did a short test with the components shared in “yet another nixie power supply”, just changed the output caps (450V) and the voltage divider.

It worked ok with 300V/40mA, the efficiency is not great but ok, 87.8% with 12V input voltage, the transformer temperature stabilized around 42 ° C.

Unfortunately the LT3757 is difficult to solder, I always need a lamp with a magnifying glass. I think there is no trough-hole version.

[Paul Andrews]

I think 87.8% efficiency is great.

As far as soldering SMD stuff, get some solder paste and a hot air rework station. It makes short work of those things. Also a magnifying head set for my aging eyes!

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[Kevin A.]

For hot air rework, the Quick 861DW is the best value in my opinion (not affiliated with quick). It competes with stations over twice the price. EEV blog and Louos Rossman have reviews on it.

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