On Apr 22, 2:09*pm, Joerg
wrote:
JIMMIE wrote:
On Apr 21, 11:40 pm, JIMMIE wrote:
On Apr 21, 6:07 pm, Joerg
wrote:

Bruce W. Ellis wrote:
On Wed, 8 Apr 2009 06:51:53 -0700 (PDT), Tim Shoppa
wrote:
On Apr 3, 10:34 am, JIMMIE wrote:
I have a Systron Donner frequency counter that uses Nixie tubes. The
counter works fine but I am forever replacing the Nixie drivers
74141s. I started to use it this AM an one was out. Is there a
replacement for the 74141, I couldnt find one, or is there a circuit I
could build on a DIP header to replace them. I could probably design
one but I wanted something tried an tested as I dont want to put my
counter board at more risk than I have to.
Domestic 74141's are hard to find these days but on E-bay the Russian
equivalent is very common.
Yes, you could build just about anything with a one-of-ten decoder and
some current-sink drivers to do the same.
If the goal isn't nixie tubes but is a working frequency counter, you
could probably put the counter up on E-bay for somebody who wants
nixie tubes, and use the money to buy several superior frequency
counters.
Tim N3QE
Just remember to cut down on the voltage and current to the nixie
tubes and the 141s will last forever...
One risk with such chips is that a nixie element occasionally reaches
strike voltage while the respective driver output is off. Or doesn't
extinguish right away when turned off. Then the dissipation in the 55V
zeners inside might be too much to stomach for the little chip.
According to the datasheet those things aren't really high voltage switches.
--
73, Joerg- Hide quoted text -
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The current limiting resistor going to the tubes is 39K. Im going to
increase that to 47K and see what happens. After putting in new chips
it may be months to a year before I see another problem with it. I
wish I knew what I was up against if I had a schematic, knew what the
voltages were supposed to be it would help greatly. I bought one a
surplus from where I work and from what I heard of its history it had
ths problem for along time. The second one I got ws at a hamfest and
it too seems to have the same problem. Could it be bad nixie tubes?

Jimmie- Hide quoted text -

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nixies are a burroughs 57505s and some other not readable type.
Ican make out the word "electronics" and the number "7341"
Interestingly these are the ones I dont have a problem with. Maybe I
have found my problem. Now to find a solution. Where can I find these
nxies?

The Burroughs cause problems? And someone replaced a few with other
types? Getting a certain brand and type nixie will be tough. Most nixies
offered these days seem to be from Russian sources. There is also a guy
in NL who specializes in nixie retro clocks, he might know more. If you
really can't find any, there could be a somewhat scientific solution:

Pop one each out of there and hang them onto a voltage source, with
series resistor. Crank it up from zero, see where it lights, then turn
it down and see where it extinguishes. Try at a somewhat elevated
temperature as well. Then you'd have to get the supply voltage inside
the counter to the sweet spot where it's nearly guaranteed that the
74141 will never sit with an output high (meaning 55-60V) and the
segment still lit. This could be done by dropping the ones with lower
striking voltage with a zener plus small bleeder.

--
73, Joerg- Hide quoted text -

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Thanks Joerg

Im not sure if the 210 volts is the design voltage or if something is
wrong with the power supply. I added a zener to get it down to 180. At
180 I think the characters are a little less hazy looking and only
slightly dimmer. I guess I will just have to see how it goes.for now
and keep my eye out for a maintenance manual.

Jimmie