Sencore FE160 help with calibration - Page 1
Forum section: electronics / repair

author: Bargainhunter
author_rank: Regular Contributor
timestamp: November 17, 2024, 04:04:22 am
content: I am having trouble with the calibration of my Sencore FE160. The manual for the FE160 didn't make sense with setting the DC balance and the zero adjust so I looked at the manual for the FE20. My problem is when I set the front panel zero adjust to full clockwise (not mentioned in the FE160 manual but is in the FE20manual) and adjust the dc balance to .7 then the next step is to set the front panel zero adjust to halfway and adjust the zero range adjust so the meter reads zero, it throws the dc balance off. I can go back and forth between the dc balance adjust and the zero range adjust and never get it to stay at zero and .7 on the scale when I adjust the front panel zero adjust to halfway and then to fully clockwise. The service manual reads to adjust the zero range adjust so the meter reads zero at the left hand of the meter scales. The service manual for the FE20 reads to adjust the zero range adjust until the meter reads zero. Does this mean the zero "center"? If I adjust the zero center, I can get the meter closer to calibration but there is no way I can get the meter to read zero on the left hand of the scales with the front panel zero adjust at halfway.Does anyone know what could be wrong? Has anyone on this forum ever calibrated a FE160 and could help me?Thank you.

author: Whitefoot
author_rank: Contributor
timestamp: November 17, 2024, 07:08:32 pm
content: I pulled my FE160 off the shelf. I haven't yet bothered blowing off the dust. This is only about the 3rd time I've played with it in decades. I have no recollection of the calibration procedure, but I do recall the last time I tried it, the switches needed contact cleaner for the meter to be usable. When checking zero with no input, switch thru all the ranges. Any erratic readings may indicate switch cleaning is needed.I checked mine with 1VDC and 10VDC from my calibrator and it seems to be working accurately in the low ranges. The meter zeroes with the ZERO ADJ knob at about 1/8-inch past halfway. It can also be adjusted to center-zero on all ranges. On the 1VDC range, with ZERO ADJ fully CW, it reads about 0.65V. My best guess is this is a compromise setting I made the last time I calibrated it. It's been ages since I did this, so I can't say what I did. Since this is an offset adjustment, I don't think it is affecting accuracy, as long as zero can be achieved.In the manual, it's clear the DC Balance procedure should state that the ZERO ADJ knob be fully CW when setting 0.7V on the 1VDC range. I consider the low reading on mine to be tolerable on an old analog instrument.I would suggest making an adjustment that allows the zero and center-zero settings to be achieved without also achieving the 0.7V. It may be necessary to have the ZERO ADJ knob not be halfway. If zero can be reached, it's not that important where the knob is.

author: Bargainhunter
author_rank: Regular Contributor
timestamp: November 19, 2024, 05:21:07 pm
content: Thank you for your help.I had to keep cleaning the pushbutton switches and finally I was able to calibrate the meter.