Unit displays only 1 zero

Unit displays only 1 zero

Postby adula » Tue Aug 23, 2016 4:10 am

I assembled the unit and after depressing the reset switch the display reads only a zero in the second place. The reset does not cause any other action. The +5 DC voltage is ok on U1 7 and 20 with pin 10 = to 2.46 VDC. I probably have a bad solder joint or two as I did in the O-Scope kit.
Any further trouble shooting help would be appreciated.

Thanks,
Alex
adula
 
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Re: Unit displays only 1 zero

Postby jye1 » Tue Aug 23, 2016 4:30 am

The button is not a RESET. It's for zeroing. Please make sure there is no short between the measurement terminals. And make sure resistors R9 & R11 are installed good. Otherwise, it could cause the device can not get out of zeroing cycle.
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Re: Unit displays only 1 zero

Postby adula » Tue Aug 23, 2016 3:29 pm

Hi,
Thanks for your reply. I will check the soldering and the resistors for a good and correct connection. I am getting old and modern electronics are difficult for me to work with.

Thanks,
Alex
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Re: Unit displays only 1 zero

Postby adula » Wed Aug 24, 2016 6:17 pm

Hi,
Checked various voltages and looked for solder bridges but did not find any, which does not mean there are some.
Checked R9 and R11 they are electrically tied together at one end. I can not see that should be unless the schematic shows it but I can not tell as the schematic is not very clear. R9 reads 0 VDC at both ends. R11 reads 5.05 VDC and 0.48 VDC at he other end. The 4 unit LED display I do not know the unit number but there are 7 segments and 4 displays and is the DP pin the turn on for the display?

Thanks,
Alex
adula
 
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Re: Unit displays only 1 zero

Postby jye1 » Fri Aug 26, 2016 2:00 am

Electrical copy of the schematic is available here http://www.jyetech.com/Products/CapMete ... 00-00b.pdf .

What happen if you don't press the zeroing button?
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Re: Unit displays only 1 zero

Postby adula » Tue Aug 30, 2016 2:58 am

Hi,
Thanks for the reply. When the unit powers up it displays: blank010. I also installed a socket for the display. When I depress the ZERO switch it displays: blank 0 blank blank. Is there a way to set the display so it displays:8888 to see if the display is working?

Thanks, Alex
adula
 
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Re: Unit displays only 1 zero

Postby jye1 » Tue Aug 30, 2016 2:10 pm

It looks the first digit is not working. Normally at power up it should display "3.010". When zeroing button is pressed it displays "C0__". Please check the soldering.
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Re: Unit displays only 1 zero

Postby adula » Tue Aug 30, 2016 3:52 pm

Hi,
Thanks for the help. Do you have the part number for the 4 digit LED display? I probably have a bad solder joint and I will check again. I miss the old tube radios and equipment, You can do more for less but the old eyes are making see the small components.

Thanks,
Alex
adula
 
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Re: Unit displays only 1 zero

Postby adula » Wed Aug 31, 2016 3:20 am

Hi,
I looked up U1 and the LED unit.
U1 pins 23, 24, 25, 26 control the 4 digits to LED pins 6, 8, 9, and 12. All 4 output from U1 read 3.8 or 3.9V. The LED reads 3.8 V on pins 6,8,9, but pin 12 reads 0V. I checked and I do not have continuity between pins 12 and 26, but I do have continuity from the socket to the board underneath on U1 and the LED unit. I may try to put a jumper between pins 26 and 12 to see if there is a physical break in the land on the board. Any suggestions would be appreciated.

Thanks,
Alex
adula
 
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Re: Unit displays only 1 zero

Postby adula » Wed Aug 31, 2016 5:55 pm

Hi,
I soldered a jumper between U1-12 and LED pin 12 and the unit comes up as: 3.010 which you said is correct. Depressing the ZERO sw. and the unit reads: C0 which is correct, but then it stays at C0. Looking at the instructions I started to check the listed resistors when R13 on one end is tied to U1-15 but the schematic shows R13 on one end tied to U1-19 and the other to U1-13. In the TS section the second thing to check is to test poles short (1,2,3 to gnd). What does this mean?
I probably have some bad joints or so but am making progress. Thanks for your help and support.


Alex
adula
 
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