These notes are subject to change on a regular basis. We suggest you use your browser's refresh button each time you visit this page so you get the latest document version. We suggest you download/save the PDF construction document rather than simply click on it. It's several megabytes so may take a while to download. We're working on perhaps breaking it up into several parts to make it a little easier to open on-line.
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Download the latest 2y-const01r.pdf construction document. |
The basic units does NOT use chips U2 EEPROM, U4 SOURCE TB62710, nor U7 TPIC6C595.
Do NOT install the 8 pin socket in the U2 position. An 8 pin IC socket is used for U6 LM358 - make sure this chip is fitted as this is the WBlin driver.
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Correct Orientation of Lambda ModuleAlthough the pre-built Lambda module comes 100% tested, early models kits did not have the 25 gold pins soldered on (latest units do!). Refer to the images to ensure the pins are correctly soldered on. Click here to see other views. The main board also uses a 25 pin socket made up of a strip of 24 pins and a 25th pin shown here. |
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Thermocouple Inputs/Thermistor Reads incorrectly1. U8 MC33204 has been changed to an LMC6484 chip. It is shown as an MC33204 on the silk-screen. Early kits may have included the MC33204 - this is an issue ONLY if you are trying to use thermocouples with 2Y1. 2. There is an error in the original component list. The feedback capacitor C36 (around the thermocouple amplifier U8C) shown at right, designed to prevent noise pickup, was originally specified with a relatively large value (1 nF). The capacitor stores charge as the thermocouple mux switches between channels. This has the effect that all thermocouple channels (and the logger button) bleed through and the actual thermocouple value read is an average of all the inputs. The solution is to simply remove R36 as the circuit is still stable without this capacitor. The best way to remove C36 is to snip it in half with side cutters and to then individually remove each half with soldering iron and pliers. Here is a combined schematic for the mux & thermocouple amplifier. 3. Some Lambda (λ) modules incorrectly used a 10k resistor (R31 shown on the λ-module here). as a pull up for the internal temperature measuring thermistor. Resistor R31 on the λ-module should have a 47k value. This is only an issue if you use cold junction compensation for reading thermocouples. R31 is the resistor almost between the MC4052 (16 pin) and the BB DAC 7612 (8 pin) chips - it should show 4702 if correct. The incorrect value is 1002. λ-modules shipped from 10 Feb 2010 should be correct. |
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No PC logging, or Display shows "nd"Symptom: There is no RS232 communication to attached displays or to an attached PC. There is an ERROR on the Rev 1.0b PCB and pin 15 of the RS232 chip (HIN202/ST202) is floating rather than grounded. On the underside (solder side) of the PCB you should connect a short wire link between U5 pin-15 and the capacitor-leg/solder-pad shown (a GND point). RS232 driver schematic. Click on the image to enlarge (note that the fix originally shown here was to connect a different pin to GND - the correct pin to ground is Pin-15. Once this fix is made, both Pin-13 and Pin-15 should be at GND potential. You can check that both pins 13 and 15 of the HIN202 read 0V when probed with a voltmeter from the component side - do this with power applied!Do not assume you have a problem with the HIN202 chip if you get "nd", or cannot communicate with your unit. Make sure you have NOT reversed pins 2 and 3 on the DB9 connector. If you use a USB to Serial adapter then make sure you know exactly the COM port that is being used. See here for more RS232 problem diagnosis. |
2Y Status LED Operates Differently!The RED status LED does not operate as per other Tech Edge units and as described in the original 2Y user manual. It flashes to indicate warmup, logging, and PID errors, but goes OFF during normal operation. This will be fixed in a subsequent firmware update. For Rev 0862 firmware, a correctly operating 2Y unit has the Red LED OFF and the Amber LED on strong with a faint flicker. The Green LED should always be on when power is supplied to the unit. The LOG button also functions as the auto-free-air calibrate button when pressed for 6 seconds. |
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