[Heath] Looking for nixie tubes for 104 A transceiver

[JF]

On 2/17/2015 4:56 PM, John King via Heath wrote:
> My grandson's Heath 104A transceiver has a couple of nixie tubes in 
> the VFO display out. They are heath part number 411-295 which is a 
> SP-352 display tube. Does anyone know of a source for these display 
> tubes. If so please advise me of the source. He is KG5EOV, Morgan, 
> a high school freshman. I want to help him get the display working. 
> He has it pumping out its' rated output in watts thanks to the 
> gracious assistance of Mike Bryce, WB8VGE of the Heathkit Shop.

Unless you luck out and find some new old stock that are still good, 
new neon frequency display replacements are now very expensive and 
not worth the cost for most SB-104A owners. The problem with those 
digital displays was the way they were manufactured many years ago - 
they used narrow HV gas-discharge channels for the number segments, 
and the cubes were laminated together in layers which eventually 
allowed the neon gas to leak out. So, even if you find unused old 
stock, it's possible that some or all of the gas may have leaked out 
over the years, causing dim or missing number segments. Occasionally 
they turn up on eBay, and some time ago I bought some; however, 
because of age they were dim, a waste of time.

The ideal fix is to replace the display board with new circuitry that 
drives same-size low voltage LED digital readouts - back around 
2002-2004 Mike Bryce used to sell such a kit that was a direct 
drop-in replacement and also eliminated the RF-noisy HV (180V ?) 
converter board that was needed to light the original neon displays, 
but you will have to ask him if he still has any kits. If not, maybe 
you can persuade him to give you a copy of the schematic and parts 
list. If you get one you might consider using higher-value dropping 
resistors, as the displays seemed a bit too bright to me.

Let us know if you find a schematic for the LED display board, I 
imagine quite a few 104 owners would like a copy.

73
John   KE5ZB





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