Utracer3 Con Man
Utracer3 Con Man
Utracer3 Con Man
Important !
This kit is the result of many requests from the readers of my uTracer weblog pages to make this project available as a kit for those who do not have the means to build the circuit from scratch. The preparation of the kit has cost me a lot of time and effort, and I make little or no profit on it. The design of the circuit, PCB, the selection of the components as well as the preparation of this document have all been done with the greatest care to prevent disappointment, and indeed a good many of uTracers has now successfully been built! Nevertheless, small errors and or omissions may have occurred and I will be grateful if they are reported to me. A summary of the issues and problems collected so far can be found on the uTracer homepage www.dos4ever.com/uTracer3/uTracer3.html under Bugs and Issues. In case of any problems occurring during the construction of the kit, I will be happy to offer assistance by email as good as possible. It is unfortunately not within my means to offer any kind of guarantee or refund. Finally I would like to stress that the voltages which are generated by the circuit can give you a nasty shock and are potentially lethal. I can never be held responsible for any accident or injury resulting from the use of the uTracer circuit. Purchase of this kit implies that you agree with these conditions.
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Trick to bend the leads of the reservoir capacitors into a nice 90 degree angle
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Use a small box or the like to support the PCB on during component insertion and soldering
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By using a 90 degree connector for the power supply connection, the accidental mix-up of power supply polarity can be prevented
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Since some of the components are located underneath the PIC microcontroller, the separator spacers in the center of the 40 pin socket need to be removed e.g. with a small fret saw.
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The inductors are relatively heavy components. When they are only soldered to the top copper layer, it is not unimaginable that they will (eventually) delaminate the copper layer. What I recommend to do is to first solder two pieces of U shaped wire in the holes in the contact pads, and then to solder the inductors to the wires. Additionally this will create a standof between the inductor (where high voltages can occur) and the tracks underneath the inductors
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When soldering the components to the PCB, allow for some time to let the solder flow through the contact holes to the front side of the PCB. This will create an additional conductive path between front- and back-side contact pad.
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In order for the RFI suppression beads to fit on the PCB they need an additional turn. At the same time this will create some additional impedance.
9. Since earliest boyhood I use this crocodile clamp as a mouth piece to apply solder when I hold a PCB with my left hand (pressing the component to the PCB with the index finger) and hold the solder iron with my right hand. It must look rather stupid, but works great!
10. The PCB is designed for both standard size 5 mm pitch Xtals as well as miniature 2.5 mm pitch Xtals. In this kit the miniature Xtals are used. Be sure to insert the Xtal into the proper pads, and to use the insulating spacer (see picture below)
The circuit is built in this order Each part consists of a construction and a testing / calibration part. Note: normally very little calibration is needed. Each part consists of a list of instructions preceded by a the line can be ticked off when it is executed. so that
Do not skip parts of the manual, because the testing sequence may be different in that case Normally it is recommended to first place the lowest components and than to go to the higher components. In this case the order may be different in some cases because it may be difficult to solder some components when others are already in place, or because of testing reasons. The PGA113s come in an impossible small MSOP-10 package which is almost impossible to handle without special tools. They are therefore already assembled on the PCB
The photographs in this manual were taken during the assembly of the a test PCB. During the assembly one small error (the connections to the LEDs of the opto-couplers were exchanged) as well as several small cosmetic issues were encountered. These have all been corrected for the final PCB. As a result there are some very small differences between the photographs and the final PCB. Where needed they are mentioned the text For most of the resistors 1% types are supplied despite the fact that 5% types are specified. For most resistors values some spares are supplied so dont worry if after construction of the uTracer you have some left Always check the resistance value of each resistor with a multimeter before you assemble it to the board. Some components may have been replaced by alternatives depending on availability from my supplier. below you find a list of replacements used Component in circuit diagram HER108
explanation: The GUI tries to send a 0 this zero is not echoed. After a few seconds the GUI detects that no character is returned resulting in the timeout message.
7. at no circumstance the message Run time error 8020, Error reading comm device should occur. When it does, there is a problem with the USB-to-serial adapter 8. For a full check, connect the RS232 cable (next section) and perform the test described in that section
On the D-SUB connector pins 1,4,6 and pins 7,8 have been connected to fool the handshake signals. Strictly speaking this should not be necessary because the GUI does not check for these signals, but I am never sure what USB to serial adapters do
Tx Rx gnd Tx Rx gnd
4. start the GUI 5. open the Debug/Communications window by pressing Debug in the Miscellaneous section of the GUI 6. press the ping command button 7. the Send string and Echo string should now display:
8. after ca. 10sec the error message: The result string from the uTracer was interrupted should appear . This is the proper response
anode
cathode
Note! C24 was omitted on the test PCB used for the photographs in this manual. On the final PCB it is located next to C4
10. after ca. 10 sec the error message: The result string from the uTracer was interrupted should appear . This is the proper response 11. be sure to remove jumper J4 !!
Vsupl
10. No error message should appear ! 11. The value in the circle is the supply voltage as measured by the controller
5. adjust the Vsupl slide bar 6. press ping on the Debug/Communications form 7. check if the supply voltage measured by the uTracer is now equal to the exact supply voltage 8. if not ,repeat steps 5, 6, 7 9. when equal, press Save to Colibration File on the Calibration form to save the calibration value to the calibration file
Important Note!
It can be that in countries which use a comma, rather than a period as a decimal delimiter (e.g. 3,14 instead of 3.14), such as Holland or Germany , the calibration file is not correctly stored / read. From GUI version 3p7 and higher this problem should be fixed, however, if it persists there are two work-arounds: 1. Manually edit the .cal file and manually replace the comma with a dot. This has to be done after every save to the calibration file. 2. Set the delimiter symbol in Windows to a period (.) to do this: For windows XP go to: start / control panel / Regional and language options select customize and change the decimal delimiter symbol into a . in Windows 7 go to: start / Control Panel / Clock Language and Region / Region and Language / Additional settings / Decimal symbol and then change , into .
Note! The LM337 and some of the components around it have been moved several mm so as to make more space for a small heatsink
-15 V
be careful not to slip with the test pins!
-40 V
Note! There are are 12k1 (12.1 kohm) and 121k (121 kohm) resistors. Do not mix them up!
6. in the main form of the GUI fill in -40 V as start value for the grid bias
8. open the calibration form by pressing Cal. in the Miscellaneous section of the main GUI form
9. switch on the power supply of the uTracer 10. press Heater On! on the main form 11. to skip the slow heating feature press again on Heating 12. start a measurement by pressing Measure Curve 13. read the actual grid voltage on the DVM or multimeter 14. At this point a time out error message will appear because the GUI is expecting a measurement. Remove the error messages by clicking ok 15. Switch off the power of the uTracer to reset the uTracer 16. Adjust the VgridGain slider on the Calibration form if the measured grid voltage is not equal to -40 V 17. Repeat steps 9 to 15 18. When the measured grid voltage is equal to -40 V press the Save to Calibration button on the calibration form to save the calibration value to the calibration file
2. make sure that the GUI is properly installed and tested 3. connect the uTracer to the PC 4. connect the uTracer to the power supply, if possible set current limit to 500 mA 5. start the GUI 6. switch on the power supply of the uTracer
7. Switch off auto-ranging and auto-averaging functions by selecting the 0 2 mA ranges for both the anode as well as the screen currents, and by setting average to none (see picture below)
8. open the Debug / Communications form by pressing the Debug command button in the Miscellaneous section of the main form of the GUI 9. press the ping command button on the Debug / Communications form 10. The returned values for the anode and screen currents on the Debug / Communications form should now display a value of approximately 124 which is the current (1.24) times the gain factor (100x). The exact calibration will be done later on 11. Remove the resistors and clip the ends of R20 and R45
29. R38, 2.7 ohm, 0.5W , 0.5W, use ceramic spacer beads 30. T11, BC558 31. T16, BC558 32. T10, MPSA44 33. T15, MPSA44 34. T13, PN5416 35. T18, PN5416 36. pins for jumper J1 37. pins for jumper J2 38. T9, IRF840 39. T14, IRF840 40. C13, 100uF, 400V, see tips for bending lead in Tips and Tricks 41. C18, 100uF, 400V, see tips for bending lead in Tips and Tricks 42. T12, MJE350, note orientation ! 43. T17, MJE350, note orientation ! 44. insert OC1 45. insert OC2 46. put jumper J1 in place 47. put jumper J2 in place 48. insert fuse Z1 49. insert fuse Z2
The testing and calibration will be done in three steps: A. functionality test of the boost converters B. calibration of the boost converters C. testing and calibration of the high voltage switches and current amplifiers
13. start a measurement by clicking on Heater On followed by clicking on Measure Curve 14. verify on the DVM that the voltages reached are:approximately: 50 + Vsupl and 100 + Vsupl 15. In case this test is passed slowely increase the maximum voltage by testing with the following sequences: start: 50 start: 50 start: 50 start: 50 stop: 150 stop: 200 stop: 250 stop: 300 Nint: 2 Nint: 3 Nint: 4 Nint: 5
16. switch off the power supply 17. connect the measurement clips to the screen reservoir capacitor C13 18. switch on the power supply 19. repeat steps 12, 13, 14
22. calculate X = 200 + Vsupl (Vsupl measured in step 7) 23. open the calibrate form by clicking Cal. in the miscellaneous section of the main GUI form
24. start a measurement by clicking on Heater On followed by clicking on Measure Curve 25. in case the measured voltage during the 200 V phase of the measurement does not equal X, adjust the VsGain slide bar
26. repeat steps 24, 25 until the measured voltage = X 27. save calibration value to calibration file by pressing Save to Calibration file 28. wait until the High Voltage LED is off 29. switch off the power supply 30. connect the DVM to the anode reservoir capacitor C18 again. 31. repeat steps 20-29 again, but now for the anode voltage adjusting the VaGain slide bar 32. wait until the High Voltage LED is off 33. switch off the power supply 34. disconnect the DVM
Part C. testing of the high voltage switches and calibration of the current amplifiers
38. set up the measurement sequence shown below (sweep anode and screen voltages from 2 to 200 V in 20 steps with fixed gains) 39. open the calibrate form by clicking Cal. in the miscellaneous section of the main GUI form 40. start a measurement by clicking Heater On followed by clicking on Measure Curve. Verify that the GUI displays a straight line ( a resistor !) 41. click with the mouse cursor on the last measurement point in the graph (200 V) 42. If the current is not equal to 20 mA, adjust the IaGain slide bar 43. perform steps 40 to 42 until the current measured is 20 mA
44. set the Y1 axis to measure the screen current Is 45. repeat steps 38 to 43 but now for the screen current adjusting the IsGain slide bar 46. when finished wait until the High Voltage LED is off 47. save calibration value to calibration file by pressing Save to Calibration file 48. switch off the power supply 49. remove the two test resistors
Congratulations ! This completes the construction. The uTracer is now ready for use
Additionally it is recommended to include a 1.5 A fuse and two RFI suppression beads in series with the heater connections. The connection of the other electrodes to the tubes will be discussed in the next section. Optionally, the positive terminals of the two reservoir capacitors may be made available for connection to the tube electrodes. The boost converters can supply several milliamps of current so that in this way DC measurements at low current levels are possible. This makes it e.g. possible to test magic eyes.
The top row of plugs is connected to the tube sockets. The bottom row is connected to the uTracer terminals. The bottom row contains a double set of plugs so that it is possible to connect two tube pins to one terminal e.g. to connect a pentode as triode (by connecting both the screen grid as well as the anode to the anode terminal ). A separate set of plugs is connected to a 1.5 V battery for battery operated tubes. Color coding is used to reduce the risk of mistakes: red for screen and anode (high voltage), green for the heater, black for the cathode (ground), and yellow for the control grid. I made overlay cards with the wiring scheme for the most common tubes. For conventional tube testers, such a plug-and-wire solution would be rather dangerous because high voltages can be present on the terminals. In this case the danger is very limited because the high voltages are only present for 1 millisecond, and even then the amount of charge stored in the capacitors is limited, or at least less dangerous than the power an 80 W / 300 V power supply can deliver.
One of the biggest threats to any tube tester are unwanted oscillations which can occur because the tubes are tested under realistic bias conditions while they are connected by long wires which contain many parasitic resonance circuits. With conventional tubetesters, it can very well happen that a tube is destroyed because a destructive oscillation occurs! A big advantage of the uTracer is that the maximum energy stored in the reservoir capacitors is very small, too small to destroy a tube. The oscillations can however disturb the measurement so it is important that they are prevented. One of the most effective ways to achieve this is to include RF suppression coils in the tube connections. At DC the resistance of these coils is almost zero, while the resistive losses quickly increase for increasing frequencies. Furthermore, I strongly recommend using the wiring scheme that AVO uses (and patented) in their tube-testers. The schematic diagram below shows the basic idea for one terminal.
C L
L A E
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The wire connecting say pin one of each tube socket runs in a loop which also connects to the banana plug or rotary switch. At certain intervals an RF suppression bead (e.g. Wuerth no: 74270015) is shifted over the wires. The physical lengths of all the loops has to be approximately the same. The figure on the next page gives an impression of the wiring scheme of my version of the uTracer. Note that in this version the high voltage fuses were not yet integrated on the PCB,