IsoTech IPS603 power supplies -faulty - Page 1
Forum section: electronics / repair

author: Lesolee
author_rank: Regular Contributor
timestamp: April 06, 2015, 02:05:09 pm
content: Two Isotech IPS603 power supplies were being thrown out at work because they were faulty. That seemed like a sad end to what are quite nice power supplies. They are still currently being manufactured and since they both had different faults I thought it would be worth a bit of mix & matching to see if one could be salvaged with little effort.One of them was blowing the mains fuse instantly and the other had a flickery non-functional display. I tried swapping boards over and that didn’t work. Evidently the faults are both in the power board at the back.I thought I would tackle the blowing fuse one first as an easier proposition. The first guess has to be that the primary semiconductors were blown so I desoldered and removed the heatsink assembly closest to the mains input. The in-circuit resistance readings were suspect but on removing the heatsink the transistors just measured as non-directional shorts. The NPN bipolar transistors (as identified by the 2SC3320 part numbers) were readily replaced for a few pounds and that power supply burst into life.Now it can be that a passive component fails and takes out the semiconductors. If that were the case the semiconductors would blow again, either immediately or fairly soon. But in any case replacing the passives is beyond my interest level!Having one working power supply and one faulty one is nice when you don’t have a circuit diagram. I used the good one to feed the bad via a connector labelled “power”. The bad one then had a good display and seemed happy.The voltages on the good power connector wereYellow +5VBlack 0V (ref)Orange +5VBrown -15VRed +15VThe faulty one wasYellow 0VBlack 0V (ref)Orange +4VBrown -13VRed +13VIncidentally, I found the 0V colour by spotting a 74HC373, looking up the data sheet power connections and buzzing pin 10 to the black wire on the connector.It looks like the faulty one is parametrically faulty, so perhaps a feedback path is broken, giving an incorrect voltage on all the rails. But I am not a service engineer and without a circuit diagram I am a bit stumped for now.Legal disclaimer: if you get a shock off working on such a power supply don’t blame me. The internal voltages are likely to be high for a while after turning the power off and working on mains equipment with the covers off is always potentially risky.

author: Hydrawerk
author_rank: Super Contributor
timestamp: April 06, 2015, 02:22:26 pm
content: It looks like a rebadged GW Instek PSP series power supply.http://www.gwinstek.com/en-global/products/DC_Power_Supply/Programmable_Single_Channel_DC_Power_Supplies/PSP-Series

author: SeanB
author_rank: Super Contributor
timestamp: April 06, 2015, 02:36:37 pm
content: I will guess that rail is supplied via CN3 on the main board, using the small SMPS transformer to generate it. The fault is likely capacitor related, on the primary side C14 is near an electrolytic which looks like it is unhealthy, you could replace that capacitor, and with it C33, C37 and the other 3 electrolytics in the area, and it will most likely be back working. As well a low 5V rail says either a secondary side diode is open circuit or dry jointed, though a faulty capacitor is a good reason.

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: April 06, 2015, 02:46:32 pm
content: Off course, capacitors! What else?

author: matt6ft9
author_rank: Contributor
timestamp: April 06, 2015, 03:59:08 pm
content: Lesolee, This power supply looks identical to the three PSP-405's I repaired awhile back.See here:https://www.eevblog.com/forum/repair/a-gw-instek-psp-405-lab-bench-power-supply-repaired/msg632952/#msg632952Looks like the other PS's in the series also have the same problem.Matt

author: Lesolee
author_rank: Regular Contributor
timestamp: April 06, 2015, 04:37:00 pm
content: Quote from: matt6ft9 on April 06, 2015, 03:59:08 pmMatt, that's very helpful, thanksIt's not quite identical. I seem to have some extra bits which are depopulated in yours.The relevant caps in mine are all 105°C rated and look in good condition. However, on much muchmuchcloser inspection I spotted R31 in that same area as being a bit (unnaturally) brown.The control board, DPS4005 (which hopefully google will now be able to find) is the same in mine and that chip with the v1.89 label on it has the same version on mine.

author: c_04
author_rank: Contributor
timestamp: April 14, 2018, 06:52:20 am
content: HiI have PSP-603 power supply (yours look the same), mine uses 8951 uC with separate board signed as DPS4005. Is there anyone who could share bin file for this uC. Today ive checked - my is blank. I can share bin file for eprom if needed. My is 27C512 rom is V.1.89.RegardsGreg

author: Peter1
author_rank: Newbie
timestamp: January 22, 2019, 05:06:30 pm
content: Hi, I got a defektive PSP-603 and could use some help.The 2 pcs 2SC2625 in the input high voltage switcher are fully shorted, both of them.Does anyone know what the voltage after the rectifier should be when it operates normally?I removed the 2 transistors and injected 26V DC on the capacitors after the rectifier diodes AND connecting 60V AC to the Mains input (Voltage switch set to 115VAC but my PSU is max 60VAC) the power supply then blinks the display and the relay is clicking once a second or so.I will try to inject +5V, +15V and -15V also, just to check if it works ok, before buying new caps and transistors, or I will build in another switch mode PSU to deliver the "rail voltage", just need to know how high the voltage must be but assuming the output regulator is a series regulator, the voltage must be in the range 62-70V (ASSUMPTION!).SO, if anyone know what the voltage must be, that would be a great help, also it would be nice to know if the voltage is fixed or if it changes according to what output voltage is required?

author: FrenchieRaf
author_rank: Newbie
timestamp: January 28, 2019, 09:21:36 am
content: Hi from France,Maybe I could help,what voltage are you looking for?Just after mains bridge rectifier?

author: FrenchieRaf
author_rank: Newbie
timestamp: January 28, 2019, 03:18:30 pm
content: And, there are other interesting threads on this forum about repairing this psu or ips603 .https://www.eevblog.com/forum/repair/a-gw-instek-psp-405-lab-bench-power-supply-repaired/https://www.eevblog.com/forum/repair/gwinstek-psp-603-repair/I think there was some kind of schematics, of this one or a similar one.As far as I remember this is no linear (series) regulation, it is a smps with a variable output.MAybe even more thhreads if you look for:https://www.google.com/search?client=firefox-b-ab&ei=jcZOXPWgF4e2aYX9j-AN&q=ips603+eevblog&oq=ips603+eevblog&gs_l=psy-ab.3...4283.6144..6216...0.0..0.79.518.8......0....1..gws-wiz.......0i13i30j33i160.3DYUPf8uYnshttps://www.google.com/search?client=firefox-b-ab&ei=YRxPXLrCEO-clwS2nIeADw&q=psp603+eevblog&oq=psp603+eevblog&gs_l=psy-ab.3...4736.5077..5340...0.0..0.68.179.3......0....1..gws-wiz.2mhmwOIcWYM