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Nixie VU meter

HiFi, LoFi, Tubes, Transistors, ICs, Commercial, DIY

Postby janneman01 » Tue Jan 01, 2013 12:00 am


I have just completed the nixie VU meter from the 11/2012 issue.
It's working on my bench, and I had to change some component values and add a few components. Also would like to share some typos in the BOM. Anybody out there who build this yet?

jan didden
Posts: 24
Joined: Thu Jan 02, 2014 10:37 am

Postby janneman01 » Fri Jan 11, 2013 12:00 am

One change I made is to add 100k resistors from the connection between input capacitors C1 and C4 and the ucontroller to ground. Without those, it took a very long time for those capacitors to discharge and the indication only went down very slowly. Anybody else experienced that?
Also, in the BOM there are two trimmers 'P2' - the last one, 1kohm, should be 'P3'.
Lastly, I had to lower current setting resistors R4 & R7 to 330 ohms to get the indication colums up to about 85 mm and make their sensitivity equal. But I realise that this may be due to different tubes I have.
All in all, a very nice project, thank you Elektor!


PS This was also my very first SMD project and it worked first time
Posts: 24
Joined: Thu Jan 02, 2014 10:37 am

Postby james hill » Sun Feb 17, 2013 12:00 am

Hi Jan

Thanks for the tip, the 100K to ground on the input fixes the response issue. I soldered two SMD resistors to C1 and C4 and linked to ground.

The R4/R7 mod was also necessary, I piggy-backed an additional 1K resistor on top of the original devices.

My IN-9's would still not reach 100% @10mA ,initially needing about double this. I "exercised" the tubes with a HV power supply a ballast resistor and after a couple of "sweeps" they came down to the specified 01-15mA for full scale. Not sure why this should be.

The project was working fine, however I got careless with the inputs, disconnecting them with the unit powered up. This has blown the Psoc, with the Vdd pin now being 2 ohms to ground. I assume this may have been static. I have ordered another chip from Elektor but as a note to others, take care!

I hope Elektor will issue a PCB revision and an amendment to this project so others will not have to botch in additional resistors. I am not sure how the prototype worked without them?

Best Regards,

james hill
Posts: 4
Joined: Thu Jan 02, 2014 10:37 am

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