I got a replacement readout for the defective one I have. I had replaced the power supply in that Uniq (Sino) 2-axis display to no avail. The DRO is not counting and I wonder about the wiring. There are DB-9 connectors on these TTL scales and I don't know if they are wired to a standard. The Chinglish manuals are just no help at all they show 4 different pin-out diagrams with no explanation. Will I damage them by miswiring them? Are both scales defective? How do I test them without an oscilloscope? Or, even with one? My BP is cursed lately and it's getting a LOT of hours.
I've got similar problems. My solution, offer a home cooked Angus steak on the grill and apple pie to Don Foreman. Looks like we have to do some gunsmoke too. Don will be out this coming Thursday with his lady, Vicky.
You need to figure out what wires the power goes to. Newall used to have info on their website for using their scales on other readouts, that might help in seeing what the DB-9 connector fits. So you should have a ground,
+5V, A, B, & Z (index). A and B should be quadrature square waves, that means, going in one direction, A goes ON, then B goes ON, then A goes OFF, then B goes OFF, and reverses that sequence in the other direction. The Z Index pulse comes on 1 pulse per revolution on rotary encoders and it's up to the manufacturer on linear scales, I don't know if they have a standard.
I figured out an encoder once without a pinout. Internally there will be a LED or two powered from the 5V, they will have current limiting resistors. So it ohms out like a diode with around 2V drop in series with current limiting resistors. If you use a 5V power supply in series with a 4.7k ohm resistor, it will limit the current to a little over 1 milliamp. So when you hit the negative and positive lead on the right pins it should drop 2-3V across the resistor and you'll have 2-3V across the scale pins. That's because with 1ma, the LED's will start conducting around 2V and the rest of the voltage will drop between your 4.7K Ohm resistor and the internal current limiting resistor. The 1ma limit should prevent burning up anything if you hit the wrong pins. To be safe, you could try a higher ohm resistor, just remember the right connection for the power should start drawing power around 2V. There could be electronics inside that also draws some power like the TTL drivers but most of the power should be to the LED's, probably
40-50 ma for the LED's and maybe 2 ma for the other electronics.
I DO know the scales' wiring. 1-NC, 2-BLK(0 VOLTS), 3-NUL, 4-NUL,
5-NUL, 6-A, 7-+5VOLTS,8-B, 9-Z (Zero), and that matches the old Uniq DRO/Scales book TTL output DB-9. And, it matches one diagram in the new DRO book labeled: Nine core bnc connector jack and sense organ connect table". BUT...there are two more diagrams. One labeled "Optical linear scale signal connector" and "The connector". Each diagram has different placements of the wires. So, I don't really know what the box is wired for and I think I'm pretty good in Chinglish. I also don't know if the scales were damaged when the read-out box died.
So, knowing the wiring on the scales, I do I test them?
For the price, ya got your money's worth. When buying something cheap, it's often worthwhile to buy more than one.
There isn't a single standard for scale connectors, there are some scales manufactured which are intended to be a plug-in direct replacement for a popular connector used among various DRO scale manufacturers.. but many scale makers offer adapter cables and/or modules to rearrange signals or modify signals to match those of a specific DRO readout unit.
Examining some online info regarding the operation of TTL encoders will explain the simplicity of their function. Troubleshooting can be performed with basic instruments, but actual testing will require a known good DRO readout unit.
Aside from the replace-more-assemblies-roulette-game, repair isn't likely. If you're not experienced at repairing electronic gear with surface mount technology, you're essentially limited to checking cable conductor continuity and seeing if any signal activity can be detected on the signal lines.. the rest is basically throw-away low quality crap, no documentation junk, intended to create more landfills on a global scale. But I'm sure the marketing pictures were impressive.
If the internal connections are marked, connecting a known good encoder, even a rotary, will show if the DRO readout unit can count up/down.
Not knowing what you have available it's hard for me to suggest an easy way to test it, the voltmeter is fine. If you can put one lead on A and the other lead on B, it will read close to 0V when both A and B are the same, ~-5V when one is high and the other low and ~+5V the + lead is high and the - lead is low. Other way is if you had a couple of TTL inputs on a PLC card. Radio Shack sells the Arduino microcontrollers for around $35, you can connect to your scales, run a program and read the state of A & B on the PC screen.
Where I used to work, I repaired a few DRO scales, where the reader head slides through the rubber seals, it wore through some wires. They were awfully small wires and soaked with oil but I managed to repair them with by re-soldering. If you get one channel with a reading and not the other, that's probably the one with a broken wire.