East Tester 5410+ not drawing current.  - Page 1
Forum section: electronics / repair

author: Luv2Learn
author_rank: Newbie
timestamp: September 16, 2024, 01:07:16 am
content: I bought a ET 5410+ from a bin store. I got it home and doesn’t work. It reads voltage when I hook up a source to it but when I try to put a load on something it doesn’t work. Just says 0 amps and watts and voltage stays same. I looked at the board and using a schematic from a member of this forum Morris6 I found some shorted resistors, 2 mosfets and a blown trace right by where the + side enters the pcb between p1 and p12. If I jump the trace the load kicks on but no way to control it. No matter the setting it draws as many amps as it feels like. Even after the OC protection shows it still pulls current with the trace jumped. Could be more issues but I am not an expert and have only basic knowledge of electronics. there is no noticeable burnt components on the board and it all looks perfect except the trace that is broke.Is it worth trying to fix or are the possible problems deeper than the ocean? I appreciate any help or advice from the brilliant members of this forum.the schematics morris6 made are the zip file. the page I edited is testing I did so far with shorted resistor and mosfets in red.I do have some troubleshooting tools. Multimeter, Soldering station with rework gun, DC power supplies, oscilloscope and a thermal image camera.ET5411Aplus-MAIN-Mosfet.pdf(751.2 kB - downloaded 56 times.)ET5411AplusSchematics.zip(827.77 kB - downloaded 49 times.)

author: MathWizard
author_rank: Super Contributor
timestamp: September 16, 2024, 07:03:44 pm
content: So it's not brand new right ? As long as none of the controller IC's got damaged, it should be pretty repairable.It's always a good idea to check the power supply section voltages. Was it Q10,11 and R112/113 that burned out ?With it un-powered, I'd check as many parts around there as possible, make sure the op-amps for those MOSFETs don't have any pins shorted to GND or anywhere else.Sounds like someone strained The ELoad too much, but something could just fail on it's own too, and then problems start snowballing.Check what some of the opto-couplers are doing, like U2,U3 on the MAINsense page. About 1V is a typical diode drop for the photo-diode.

author: morris6
author_rank: Regular Contributor
timestamp: September 16, 2024, 07:42:49 pm
content: This ET5410+ of yours seems to have been part of a major overload event. The trace between P1 and P12 blown.., Oeps.May I suggest the following procedure?The system has six parallel current regulated channels. I would take out all the power mosfets and then check all the power supply voltages of the ET.When all power voltages are good measure the DRIVE voltage, pin1 on P8 or P3, and see if the voltage makes sense: +12 V for a no current command and -10 V for full current. You can use the V- bus as "zero" point.You observed the ET indicating the voltage of a hooked up power source. Now, if you put the ET in Constant Voltage mode and select a voltage setting just over or just under the voltage of your source, the DRIVE signal should change indicating that regulation is working.Now replace the power mosfets with known good ones, one by one, to find any faulty channels. Of course there will be some deviations, or maybe instability, if one or more channels are not active yet.Have fun, and good luck,MauritsPS. Power mosfets in the ET5410+ are IRFP250N. The schematic is for ET5411+ that has IRFPF50.

author: Luv2Learn
author_rank: Newbie
timestamp: September 17, 2024, 12:09:32 pm
content: Quote from: MathWizard on September 16, 2024, 07:03:44 pmNo it was not brand new. It was packaged like it was but the place I bought it from gets AMZ returns so sometimes things don't work but I paid $8.99 for it.Q4, Q10, R53, R70 were shorted out. Ive removed them so far. I will have to order some new MOSFETs and a resistor. I had 1 100k on a different scrap board that fit. I have not found any other problems yet.Thank you for your reply

author: Luv2Learn
author_rank: Newbie
timestamp: September 17, 2024, 12:16:48 pm
content: Quote from: morris6 on September 16, 2024, 07:42:49 pmYes, I seen that the Mosfets are different. Otherwise everything else seems to be the same. Thank you for your time making the schematic and for your reply. I will buy some mosfets and work through your advice. It will be few days at least till I can start testing. I don't have the parts on hand.Thanks again!

author: Luv2Learn
author_rank: Newbie
timestamp: September 19, 2024, 12:34:03 pm
content: My power supply voltages are a little low. 11.5V. Is that ok or will it cause inaccuracy in the readings? Pin 1 of P8 & 3 changes as I change the voltage and current. The -10V only reads -7.94 and the +12 reads +11.5.Is that a sign of more problems or should I start adding the mosfets one at a time?

author: morris6
author_rank: Regular Contributor
timestamp: September 19, 2024, 02:00:35 pm
content: For further troubleshooting only the main board you can disconnect the thick red and blue wiring from the slave board and also disconnect the flat cable from P3 to P8. See if that makes a difference in supply voltage readings.The low -10 rail can be an indication of damage to one or more of the TL072 opamps. The +12 rail has more power so it drops less. Maybe you can feel one or more of the opamps getting hot.You can check some voltages around the opamps, The plus and minus input pins have to be about equal. Compare the readings between the three / six channels.When lucky you can identify a failing channel without having to cut any PCB traces.Maurits

author: Luv2Learn
author_rank: Newbie
timestamp: September 24, 2024, 02:28:31 am
content: U14 has a big drop. It’s 10.15 in and -7.38 out.

author: morris6
author_rank: Regular Contributor
timestamp: September 24, 2024, 08:09:46 pm
content: U14 output should be around -10 V.Did you disconnect the slave board? If so I would suggest to remove U1 for troubleshooting, this double opamp is driving both blown mosfets. Maybe the output stages of this opamp were damaged by the "event". Then measure the -10 rail again.

author: Luv2Learn
author_rank: Newbie
timestamp: September 25, 2024, 02:25:31 pm
content: I did disconnect the slave board. I will take out U1 and let you know the results. Again. Thank you so much for helping me. I am pretty new to electronics but have a deep passion to learn all I can. I have been reading up on allot of the different components and how they work. It can be very confusing sometimes and is definitely not something you can just watch a YouTube video to learn like most things these days. So to you and all the experts in this world my hat is off to you. One last thing. You had mentioned checking the TL072 + and - pins and that they should be close to the same reading. Just to clarify for example U1 would be pins 2&3 also 5&6 correct?

author: morris6
author_rank: Regular Contributor
timestamp: September 27, 2024, 06:04:42 pm
content: Correct, within normal operating range the opamp inputs have equal voltage. But that's only when the circuit, feedback, is functioning correctly. So with all good components in place.U1 is possibly damaged and loading the -10 V. rail too much. So, when after removal U1 the rail comes back to the normal value this confirms U1 is damaged.

author: Luv2Learn
author_rank: Newbie
timestamp: October 01, 2024, 05:22:53 pm
content: I pulled U1 and it is -8.5 now. I also noticed Q3 getting really hot. Not sure if that could be related to the issues with voltage on U14. Q 1-3 appear to be in bad shape though.

author: morris6
author_rank: Regular Contributor
timestamp: October 01, 2024, 06:36:35 pm
content: Q3 is on the slave board that's supposed to be disconnected for trouble shooting..?Remove the slave board and the three power mosfets Q4, 10 and 11 and the maybe shorted resistors. Then measure the -10 V. rail again. Don't put any load on the thing in this stage. If the -10 rail comes up to around -10 V then install Q11 that you measured to be good. Then see what happens when you put some load on the thing to confirm some operation.