Feb 24: New board received, I have loaded the low voltage power supply, prescaler and seconds counter.

How do you test the logic when the display won't be working until the end of the build?

LEDs to the rescue!  Push an LED into the base-emiter holes of the final decode transistor hole and it  will light up.  See the movie

Jan 29: New layout finished and boards ordered, 10 day turn.

Added seconds hold switch, fixed numerous layout errors, added AM/PM neon bulb.

Jan 22: 

 

After debugging the hours counter, I discovered that the long lines from the flip-flops to the decoders are ringing.  Unfortunately, these lines are capacitively coupled to the very sensitive bases of the Flip-Flop transistors, causing false triggering.  One solution to reflections on traces is to slow down the edges.  I added an RC load to each decoder line to slow the edge and raised the decoder impedance.  The counter is now counting splendidly.  

 

 In building the high voltage supply I came across a number of layout errors that required cuts and jumpers.  After I got it running I decided that this board has too many mistakes to continue, I have learned enough to re-layout the board. 

 

Re-layout is in progress

Jan 6:  Board arrived, being loaded

 

 

 

 

Jan 9: 50/60 Hz jumpers for prescaler tested

 

Jan 12: counters loaded, working on decoders

Jan 8: PS, 60 Hz extract, and divide by 10 loaded and working

 

 

Jan 17: decoders loaded.  I discovered that LEDs can be temporarily used to check operation before the 200V supply is built.

Jan 6: blank board

 

 

 

Dec 14:  Layout done, PCB ordered, due XMAS

Features:  build as either 12 or 24 hour display,

24 jumpers allow control of display on/off to save NIXIE life.

50Hz or 60Hz jumpers for worldwide use

12 VAC input,

no ICs,

Nixie tubes are socketed

 

 

 

 

 

layout

 

 

 

 

 

Schematic (pages are out of order)

 

 

Aug 23:  on third transformer as I gradually increase the wattage

Board on wall continuing

 

 

 

9VAC  800mA

too small

 

 

 

 

 

 

12VAC 1A

still too small

 

 

 

 

 

 

12VAC 1.66 A

gets hot but may work....

 

 

 

 

 

 

Aug 1: The high voltage supply has been tuned and is supplying 160 Volts driving 6 Nixies and 4 neon lamps.

 

The switcher case is running at 172F, the die can't be more than 175F, the max temp is 300F, so the heat sink seems sufficient.

 

This board will be run continuously as a lifetime test.

 

This board will not be a kit, is an abomination to me, it mixes technologies of different eras, but it is a good test of the discrete switching supply.

 

Next, I need to update the transistor clock with an additional flip-flop for day/night to allow for jumpering of hours to switch off the display.  Also I intend to add 50/60 Hz jumpering to the kit to help the non US builders.

 

 

 

 

 

July 17: The test board is loaded and mostly working.  The power supply needs some adjustments to raise the power delivered at 200 Volts.  It droops and barely lights the displays.  The inductor current will be raised to about 2 amps.  I am awaiting parts from digikey.

 

Following that, a final layout using the transistor clock circuits, the HV supply and the Nixies will be attempted.  I hope to keep it to about the same size as the transistor clock and also add jumpering for 50/60 Hz options.

July 12: 2nd test board partially loaded and original power supply connected.  This tests the PIC circuitry and program.

 

The purpose of this board is to test out the high voltage supply for a full load and to test the NIXIE socket footprints.  Note the NE-2 bulbs are too bright, the current will be lowered.

 

Next step -> load the HV supply and run with 6 Nixie displays

 

 

Note: this board is just a test board, it has ICs and even a surface mount component on it.  The final kit will have only 1950's parts on it.  (although it will have a TO-220 transistor.  It shoud be a TO-3 part, but they are too expensive, pity)

 

After I get this board running, I will take the transistor clock layout and put the Nixie displays and HV supply on it for the final kit.

 

June 15: Nixie test board loaded and PIC is cycling thru digits -  see the movie ->

 

June 6: High Voltage supply board running

 

 

Upper trace: 50 Volt/div

Lower trace: 5 Volt/div on a .5 ohm so 1 Amp/div

Timebase: 20uS per div (showing about 8KHz)