Need help for reparing a ISOTECH IPS-2303 PS / GW INSTEK GPS 2303 - Page 1
Forum section: electronics / repair

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 07, 2023, 10:49:07 pm
content: Dear All,In the ISP-2303 power supply (2 0-30V 3A channels, also known as GW INSTEK GPS 2303), there is a push button for activating the output.If this is not activated, all displays are set to zero ( see picture).When you press the toggle button, the output becomes as normal.But in my unit, it does not work.If I press, nothing happens.I have started to dismount the unit (see pictures).From my preliminary analysis, the button should toggle one of the relay trough the MC14013B flipflop chip, but as I do not have the schematics,my progress are slows.If anybody has the schematics, this would be great.Otherwise, if some one has some experience in this PSU, any help would be welcome.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 09, 2023, 10:09:18 am
content: Really, nobody knows anything about this power supply ?

author: 2N3055
author_rank: Super Contributor
timestamp: January 09, 2023, 11:14:13 am
content: Well,on photo output switch looks bent.. If that is not just a distortion on photo I would start from there...Measure on a switch if there are voltages on it and if there are changes when you activate it..How did it happen? Did you buy it broken? Did it work before? Was there something that happened after which it stopped working?There are several fuses inside..These are analog PSU with digital voltmeters/ampermeters. They can be traced component by component.I don't think schematic is publicly available...

author: simba15
author_rank: Regular Contributor
timestamp: January 09, 2023, 02:39:09 pm
content: So I have made a few repairs to one of these supplies.But my issue has been with the display module, the fuses blow and need replacement ( so I made external holders).I would check all fuses and start looking for voltages measurement points.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 09, 2023, 10:01:53 pm
content: @2N3055I 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 VSSS is to VCC (GND)@Simba15The fuses look OK . I will nevertheless test them next week end ( I have no access during the week).

author: 2N3055
author_rank: Super Contributor
timestamp: January 09, 2023, 10:15:24 pm
content: Quote from: JacquesBBB on January 09, 2023, 10:01:53 pmNow 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

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 10, 2023, 05:39:21 pm
content: Quote from: 2N3055 on January 09, 2023, 10:15:24 pmYes, 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 Ipress 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.

author: ingalopez
author_rank: Contributor
timestamp: January 11, 2023, 12:09:17 am
content: 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?)

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: February 06, 2023, 09:10:14 am
content: 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 otherspower 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.

author: PatrikJr
author_rank: Newbie
timestamp: January 07, 2025, 11:14:34 pm
content: 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.