Kiran,
Measure the input voltage to your clock. If voltage from your DC wall
adapter have risen 7805 regulator will go hot. Also high voltage to
Nixie tubes might also rise if input voltage to clock is too high.
Sture
Kiran Otter skrev den 2015-03-28 12:55:
Hi folks, glad to find this group!
I've had a Tubehobby clock for several years, the NCV2.1 with the
IN-18 tubes. In the past Jonas has helped, and I even shipped him the
main board for him to repair, but he hasn't responded to my last
request for help, so I thought I would ask here.
Recently, I started to notice that other digits in the tubes were
partially lighting up, and eventually the fuse blew. My assumption
was that the K155ID1 drivers had started to go, so I ordered six of
them off eBay, and tried replacing them.. which isn't hard, everything
is socketed. Well it didn't help, so I contacted Jonas. Jonas
suggested replacing C6, which I did and it appeared to fix the problem.
Maybe a month later, I started to notice the left most digit was
faintly showing numbers, and seemed to be influenced by the next to
right digit. So I thought perhaps the drivers I got from eBay weren't
good, so I swapped them around, trying to see if it made any
difference. Unfortunately, I trashed the two original driver chips
that came with the kit. So far swapping the drivers around among the
six I have, hasn't changed anything.. or if it has, the digits
lighting that shouldn't be have moved from tube to tube.
Well I let the clock run like this for a week or so, and one day I
just happened to feel around the voltage regulator U1 (L7805CV).. and
it's blazing hot. I put a temp probe on it and it's running at 140F in
open air, and when I built the clock, I epoxied a heatsink to it. It
never ever used to get this hot. In fact the clock has run for years
in a closed enclosure with very little ventilation. It just never
produced much heat at all. I swapped both driver chips for two
others, and it still gets just as hot.
When the clock shuts off the display at night, the temp drops to just
above room temperature.
So my guess is has to be one of two things I replaced; C6, or the
driver chips. I think it's the drivers, and I'd like to get a pair
from somewhere reputable so I can at least rule them out as the
problem. I've seen some that appear to be ceramic, instead of plastic
cased.. claimed to be 'milspec' but I donno if that's BS or what.
Any help is appreciated!
Kiran
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