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| TC1 lcr-meter transistor-tester fix |
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| zappenduster:
Hello eevblog forum, here is my TC1 (TC-V2.12k) experience. If your tc1 doesn't switch on anymore check capacitor C11 and C12. I got the meter two weeks ago (18 Euro ebay purchase, shipped from china to germany). I tested about 20 components successfully and then: screen black. I no longer could turn it on. It was not my fault - i surely did not connect a charged capacitor or external voltage to input terminals. Only usb-charging function seemed still be OK: red LED for some time, then turned green. U5 boost-IC of my flawed meter was getting hot; voltage at Cathode of D2 about 15V. With some web-hints i figured out a faulty component: a short circuited C (C11 or C12 - not sure anymore which one; they are connected in parallel). One of them got a 'short' of 120 Ohm. The other's value is 5uF. I replaced both with 100nF and 4,7uF electrolytic 100V-rating. Now the meter works again. Cathode of D2 is now at 37V (47V during usb-charging). This voltage is generated for zener-diode testing. While pcb-inspection i measured some capacitors: C8 = C9 = C14 = C15 = 9 uF. C10 = 118 nF D1 = D2 = D3 = 'SL' marked diodes (schottky-type because U_f ~ 250mV). U1 = 44-pin uC Atmega 324PA ; Y = 16MHz crystal U4 = 8-pin uC STC15L104W for wake-up from sleep / measurement cycle / subsequent automatic power-off U5 = 6-pin boost/step-up IC. Marking AL718 (another forum-post states AL605) U6 = 6-pin charge-IC ZD1 = zener-diode 6V8 ; DZ2 6-pin marked V05. Some pcb miss those two elements - maybe earlier layouts... battery = li-ion 3.7V 450mAh ; some tc1 got a much larger battery (2x base area) At this position there would be a picture of my handmade pcb-to-schematic translation together with the actual pcb - but i can't insert them here... You can find them attached at the end of this post. Current consumption is 300..400 mA (On-state) and 0,2mA in Standby/power-off). That means 150mAh per month (0,2mA * 24h * 31 days). So a fully charged battery would be drained after three months of non-use. While measuring the circuit sometimes this happened: Standby current 0,2mA switched to 10mA for 25 seconds. Then it sank to 15 uA and remained there till next (On-)Button pressing. After some trial and error i ended up adding a 33k resistor to the 5V-regulator output (soldered piggyback onto C15). This seems to do the job of triggering the 10mA_for_25s period immediately after shutdown. By that sleep-mode is reached safely. Operational states (duration/current): 25s -> 25s -> sleep 25 seconds: On-button was pressed, screen is lit, meter tries to identify connected component. I = 300..400 mA 25 seconds: 10 mA current draw after automatic shotdown, screen black xx seconds: 15 uA sleep-mode till next button pressing / measurement cycle If i keep my tc1 busy (pressing button repeatedly) sometimes the sequence is 170s-170s-sleep. I don't know what goes on here... IR remot control detection: The ir-indicator (red dot in upper-right corner of screen) is flickering sometimes although input-area is covered up. I added a 100nF capacitor between Ground and Vcc of ir-receiver. But no change, this intermittend behavior is still there... My guess about U4 port-configuration: Pin_1 is configured as interrupt: pressing button wakes device from sleep. Pin_3 switches on U5 boost-ic. Pin 5+6 used as common input to determine desired automatic power-off time (10s/15s/20s/25s - depending on connections P1/P2 <-> Ground/U4_Vcc). About U4 functionality see also https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/msg1553608/#msg1553608 TC1 manual: www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/?action=dlattach;attach=310740 TC1 high-resolution pictures: https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/2225/ TC1 review + hr-pics: https://lygte-info.dk/review/ComponentTester%20Multifunction%20Tester%20T1%20UK.html uC STC15L104W is described/listed here: http://www.stcmcu.com/datasheet/stc/STC-AD-PDF/STC15-English.pdf Some web search brings up T6 labeled models (monochrome display, ir-receiver is placed on screen's right side). T7 looks the same as tc1. At startup it shows a brand/firmware name for a second. Indicated data of tc1-testet components: As lygte-info.dk review states, scr/triacs are partly recognised as resistor or BJT; h_FE values of darlington-transistors with BE-resistors are much too low. To me also capacitor ESR-values seem low: My Peaktech 2063 LCR-meter shows much higher values (it's presumably identical to Extech 380193 meter; component test-frequency can be switched from 120Hz to 1kHz) What do you think of those misrepresentations/discrepancies? Can i just add a fixed offset to displayed capacitor ESR-values? Thank you to eevblog and previous contributors to that matter... zappenduster |
| hydroksyde:
Thanks, mine just arrived with the same issue. Replacing C12 with a 100nF ceramic fixed the problem.. |
| zmaxpayne:
Hi to all. I damaged mine (tc1). I was so stupid to hook on a charged capacitor :-(. So when i press to measure it stays black. Black screen. The loading led is still working. Do you guys think i can fix it? What component could i damaged? Thx. Stefan from Belgium. |
| indman:
Remove DZ1 = with zener-diode 6V8; DZ2 6-pin marked V05. To give power on a tester without remote elements. If the problem remains, then YOU have damaged the ATMega324 processor. His replacement and a new firmware is necessary. :( |
| cataboier:
Thanks so much ! |
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