| Electronics > Repair |
| Need help for reparing a ISOTECH IPS-2303 PS / GW INSTEK GPS 2303 |
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| 2N3055:
--- Quote from: JacquesBBB on January 09, 2023, 10:01:53 pm ---@2N3055 I got the unit in this state. I suppose it worked before otherwise it would have been returned . I have the shematic for the GPD units, but this is not of great use as GPD are controlled by a PIC MCU. I have a tuning manual for the GPS, but it does not contain schematics. The output switch is functioning well. The problem does not come from the switch itself. This switch (push button) connects the pin 4 (R) of the 4013 flipflop to GND ( VCC of the 4013) . VSS of the 4013 is -15 V. C and D of 4013 are to VSS S is to VCC (GND) @Simba15 The fuse look OK . I will nevertheless test them next week end ( I have no access during the week). --- End quote --- Now trace from Q1/_Q1 (PIn 1 and 2) to something that drives output relay. Do FF outputs change when activating switch? If there is no output relay, then it will go somewhere to disable output |
| JacquesBBB:
--- Quote from: 2N3055 on January 09, 2023, 10:15:24 pm ---Now trace from Q1/_Q1 (PIn 1 and 2) to something that drives output relay. Do FF outputs change when activating switch? If there is no output relay, then it will go somewhere to disable output --- End quote --- Yes, this is what I started to do. I cannot verify, as I am out of my workshop place during the week, but it seems to me that there was no changes when I press the button. I thus thought that the 4013 chip was bad and I changed it ( I put a socket for the future). Unfortunately, nothing changed. I left the device as is, but will resume the analysis next week-end and will provide more quantitative information. What I thought is that there may be a short circuit after the 4013 that prevent the Q or Q_ pins to change state. But I did not have time to verify this hypothesis. |
| ingalopez:
Besides the output relay (have you located it?), is there voltage on the power supplies you can regulate with the knobs? (prior to the relay). If it is, then check the relay and its driver. As you replaced the 4013, there should be a bad transistor (or ULN 200x section) that drives the relay, provided the power for it does exist (same as the steps relays?) |
| JacquesBBB:
Hello to All, I still do not have the schematics, but try to progress on the repair of this unit. It is slow because I am not retired and do that only part time. I have several others power supplies and try to fix this one just for the fun of it. I have made some progress. - As I have another unit, I could switch the boards and definitely rule out any problem on the power board. - Moreover, I know definitively that the problem comes from the MC14013B, or more specifically from its surroundings. I have isolated the problem. The push button puts R2(4) in contact with S2(6) which is normally at VCC. At present, it does not do anything because R2 is already almost at VCC. As soon as the power supply is barely hot, the resistance between 4 and 6 is around 600 Ohms. But if I redo the measurement after power down and waiting a bit, I find rather 25 k. I've already looked around a bit, but haven't found yet. I know that everything works otherwise, because if I put pins 2 and 3 in contact, I trigger the outputs and everything is OK. By chance (I had forgotten to put the 4013 back on its socket), I also saw that the power supply works very well without the 4013. In this case, you cannot switch the output, which therefore always remains active. I admit that it's not really a problem, and I'm almost tempted to reassemble everything as it is, but since I'm not particularly in a hurry, I leave the beast disassembled for the moment, while waiting to find the culprit. If anyone has a good idea on what likes to go from 25k to 500 ohms between cold and barely hot, I'm interested. I suspect a transistor but with an intermittent failure of this kind, tracking is not easy and can only be done under voltage. I already removed capa C505, but it's not her. To make matters worse, the components are 603s. |
| PatrikJr:
Hello, I found this power supply in a second-hand store, an ISO-TECH 2303. I’ve tested its functions (without load), and the master channel is working, but the slave channel does not regulate the voltage, and the voltage and current displays for both channels are not functioning. I’ve noticed that the regulators (7805) powering this section (4x ES5107 + 12 seven-segment displays) are overheating excessively. I hope someone can help me with a schematic to guide me, as I haven’t been able to find one online. Apologies if I am violating any rules. Best regards. |
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