Multimeter UNI-T UT55 problem
If you have a UT55 and blow a fuse, be careful how you take it apart! I had the bad luck that when I took the back off, the circuit board stuck to the front - and I stupidly took some screws out of t...
Forum Discussion
Interesting, Gene. Yes, I was looking at the same on on ebay.ca, where the prices range from $47 to $150. That is definitely where I would buy. I bought several of the UT204A clamp meters that way - great Christmas presents.
I am no longer doing guess and test. I found a schematic!!!
http://elektrotanya.com/multimeter_ut55_sch.pdf/download.html
The 200k middle ohms range has the line of contacts straight up on the circuit board (sorry I don't have that quite vertical in the photo).
I can't read the labels (R3, etc) but I can trace the connections to the ten concentric rings on the circuit board. I am pretty certain of the first and second rings as being the contacts connected to the resistors down the left side and the first column of heavy black lines. So there must be a spring contact connecting rings 1 and 2 (I'm calling that contact A) and it has to be on the very outside position on the rotor by direct measurement from the center point of the circuit board and the rotor. That confirms the location where I thought the wayward contact went. I'm pretty well convinced the 2nd and 3rd vertical black line patterns represent rings 5 and 6 just because of the line lengths matching the ring segments, and that they must also have a contact.
Also it strikes me pretty likely the far right line on the schematic and the contact points on its right side represents the two innermost rings - a third contact is already in that position I'm calling contact position K between rings 9 and 10. I have a feeling these make the display show in small print (200, 2, 200, 2, 20, 200) to indicate the ohms range selected, and similar for the other ranges. This feature works.
Two contacts to go, matching the double dark line segments down the middle of the schematic. This is a most interesting puzzle! Anybody have an insight into which rings those double lines represent and what they do?
I am no longer doing guess and test. I found a schematic!!!
http://elektrotanya.com/multimeter_ut55_sch.pdf/download.html
The 200k middle ohms range has the line of contacts straight up on the circuit board (sorry I don't have that quite vertical in the photo).
I can't read the labels (R3, etc) but I can trace the connections to the ten concentric rings on the circuit board. I am pretty certain of the first and second rings as being the contacts connected to the resistors down the left side and the first column of heavy black lines. So there must be a spring contact connecting rings 1 and 2 (I'm calling that contact A) and it has to be on the very outside position on the rotor by direct measurement from the center point of the circuit board and the rotor. That confirms the location where I thought the wayward contact went. I'm pretty well convinced the 2nd and 3rd vertical black line patterns represent rings 5 and 6 just because of the line lengths matching the ring segments, and that they must also have a contact.
Also it strikes me pretty likely the far right line on the schematic and the contact points on its right side represents the two innermost rings - a third contact is already in that position I'm calling contact position K between rings 9 and 10. I have a feeling these make the display show in small print (200, 2, 200, 2, 20, 200) to indicate the ohms range selected, and similar for the other ranges. This feature works.
Two contacts to go, matching the double dark line segments down the middle of the schematic. This is a most interesting puzzle! Anybody have an insight into which rings those double lines represent and what they do?
