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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