SkyTronic 650.682 Power Supply - Page 1
Forum section: electronics / repair

author: c_04
author_rank: Contributor
timestamp: May 05, 2018, 10:31:20 am
content: Hi i have as in tittle 0-30V 0-10A power supply. It was damaged but i rewound transformer and everything is working now... only with some issue.When my fridge is turning on or i switch my transformer solder iron, or switch fan... everytime values which were set are jumping. For example i set 12V... fridge is trning on... my power supply jumps to 17V or more just for second. Is anyone of you who have schemtic for this supply? Its freak that there isnt any uC. Everything works on opamps and comparators i think. In fact even not much of them inside.CheersG

author: JFJ
author_rank: Regular Contributor
timestamp: May 05, 2018, 11:48:02 am
content: Have you checked the mains electricity wiring in your building? A bad protective earth/ground connection could negate the mains suppression circuits of your appliances and reduce the effectiveness of any input filter stage within your power supply unit.

author: Bud
author_rank: Super Contributor
timestamp: May 05, 2018, 12:03:09 pm
content: You said you rewound the transformer. There maybe a problem with excessive interwinding capacitance which allows power glitches on the mains to go through and cause spikes on the secondary. The original transformer may had a better capacitive isolation or had a screen between the windings.

author: c_04
author_rank: Contributor
timestamp: May 05, 2018, 12:12:35 pm
content: I had this supply also in UK and issues were the same. Dont think so both buildings in UK and in Poland could be electricaly bad.I think there must be something wrong inside. I dont know what but i have idea. This power supply switches different parts of wires in transformer. Maybe it is trying to measure voltage at output and if its low then compensate it. Of course its fail. Second thought is that there maybe too low voltages to hold relay coils. Its hard to figure out without schematic. Maybe i unscrew board with relays. Will see how its powered.Yeah something wrong with transformer may be a point too. I rewound it as it was, there wasnt any shields/screens etc. Just insulations. Its Chinese - nothing fancy.CheersGP.S. How to check is that proper capacitance between windings?

author: Bud
author_rank: Super Contributor
timestamp: May 05, 2018, 12:22:50 pm
content: I do not think there is a value for a "proper" capacitance, it is all qualitative. You just want to minimize it. If that power supply had problems from day 1then it is poor design in the first place and you can only try to remediate the issue. I cannot see it from the photos but it does not seem to have any line filter or surge protection? Maybe you could start from that.

author: c_04
author_rank: Contributor
timestamp: May 05, 2018, 01:13:39 pm
content: I dont know it had problems because ive got this power supply yet damaged. Transformer was blown. I rewound it and it is back to life. There is some fuse on back (you can see at second picture - right side down corner, near mains socket). There also filter cap close to power switch which is located on picture left side down corner (that white square - under it is sitting yellow cap). There not another coils etc. Anyway i still think that it must be something stupid. Of course troubles with transformer are also possible. Almost every board in this power supply has its own volatge regulator. That board where is entire control has 7812. I think also relays are powered by this regulator. Whats pointing me to this board is that relays are clicking when fridge is starting. Its not just voltage jumps. Sorry i forgot to mention that - which is important.Thanks for you reply guys.CheersG