Displays '0' & '1' at the same time

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1 year 7 months ago #9177 by SamIam
During installation of the tubes everything was going fine and testing well. After the 4th or 5th tube, during the testing sequence all the tubes would display both '0' & '1' at the same time. The would stay illuminated for the duration of both numbers and sequence through the rest of the digits in a normal fashion. I thought maybe the board needed a reset, so I continued with the build.

Now I have completed the build, I believe I have the clock set correctly, although I'm still trying to figure out some of the setting. However when ever a tube needs to display either the '0' or the '1' it will display both digits.

I have checked my solder connections, the board for any possible shorts, but have not been able to find any yet.

Any advice on what to do next to fix this?

The clock is suppose to be showing 13:54:23 but as you can see both the '0' & '1' are displayed on the first hour digit.
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1 year 7 months ago #9178 by Ty_Eeberfest
It is probably one of the following things, most likely first:

1) Solder bridge shorting pins 15 & 16 of the 74141 IC together.

2) Internal short in any tube between the 0 and 1 will affect all tubes because all like digits are bussed together - see schematic

3) Defective 74141

Look into it later when the dust is clearing off the crater.
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1 year 7 months ago - 1 year 7 months ago #9179 by Ty_Eeberfest
I just re-read your post, This time I noticed what you said about the problem appearing when you installed the fourth or fifth tube. So now I'm going to say the most likely problem is either an internal short in one tube or you somehow managed to bridge the "0" and "1" pins of the tube together. Not sure how such a bridge could happen tho because those two pins are not close to each other.

Look into it later when the dust is clearing off the crater.
Last edit: 1 year 7 months ago by Ty_Eeberfest.
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1 year 7 months ago #9181 by SamIam
Thank you for thee replies. I missed the part about posts getting approved before being published and thought maybe I made a mistake or had a computer issue while trying to post. Feel free to delete this duplicate post. I will try your suggestions tomorrow.

Sounds like one of those issues, where you hope its a bad part because it would be a quick easy explanation to the problem, but at the same time you don't want it to be bad part since that means having to order a new part.
Thank you

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1 year 7 months ago #9183 by Ty_Eeberfest
Yeah, your posts go to moderation for approval until you have a certain amount of posting history. Sometimes we're here and approve posts in minutes, other times it could take a while. It sucks but it's the only sure way to keep Penis Pills and Live! Russian Camgirls spammers out.

If it was my clock I'd be hoping it's a solder bridge around the 74141 socket area. Zero cost to fix that, and I really wouldn't want to have to start removing tubes looking for the shorted one.

Look into it later when the dust is clearing off the crater.

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1 year 7 months ago #9187 by Ian
My money is on a defective tube - it's not that common, but it's not that rare either, especially if the tubes were used ones. This is why the manual recommends strongly to test after installing each single tube.

There is a lower risk way of checking if the visual inspection and the rework on the K155 don't do it: You can snip to 0 and 1 wires of the suspect tubes with a pair of electrical snips, just enough to interrupt the current.

This can be invisibly repaired with a soldering iron on the tubes which don't have a problem.

Again here, do it one at a time, so you know where the problem is. Once you know the tube at fault, there is no option other than to replace it. :(

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