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Clock circuit check

Posted: 06 Apr 2019, 11:07
by viv_bg
I just finished soldering in the components of the clock circuit, but when I do the voltage check I get results between 0.6-0.7V. So far i tried using different cables and power supplies - no change. As suggested by the instructions I also checked the soldering of the components and can't see any obvious problems. Do you have any suggestions where I should try to find the problem? Thanks in advance!

Re: Clock circuit check

Posted: 06 Apr 2019, 21:40
by Martin_H
As a sanity check, measure the voltage at the power input jack. If that's good, then look at the polarity of the Zener diode D1. The zener is installed across the power rails in the opposite direction of a normal diode. If installed the wrong way it would become a short and would definitely drop the voltage that low. It could also trip the multi fuse which should save your power supply.

Check the electrolytic cap C4 as well, but that would likely pop if installed the wrong direction rather than fail short.

Also, if you installed the 74hct04 IC which is part of the clock oscillator, make sure it matches the polarity as well. IC installed the wrong way around can also do strange things too.

Re: Clock circuit check

Posted: 06 Apr 2019, 21:50
by marcelk
We've seen this several times before, where it turned out the multimeter itself is somewhat flaky. See the Troubleshooting page. I would just continue, there clearly is an active signal present.

Screenshot 2019-04-06 at 23.46.51.png
Screenshot 2019-04-06 at 23.46.51.png (300.32 KiB) Viewed 1279 times

Re: Clock circuit check

Posted: 07 Apr 2019, 07:57
by viv_bg
Thank you both for the replies! As suggested I double-checked the orientation of the components and everything is OK. Voltage at the power input is also OK, so it would seem to be the multimeter issue described in the Troubleshooting page. I will try to get my hands on a different meter as soon as possible and check again.