Repair power supply Sony PVM-9040 - Page 1
Forum section: electronics / repair

author: decoder_82
author_rank: Regular Contributor
timestamp: June 24, 2021, 12:43:50 pm
content: Hello,I am repairing a faulty power supply in a Sony PVM 9040. I have confirmed there is a short in a coil (L652). From the service manual I have found part number 1-424-625-21. But I am not sure where to find something similar to replace it. .Any advice would be appreciated.Thanks in advance

author: Manul
author_rank: Super Contributor
timestamp: June 24, 2021, 01:00:51 pm
content: It depends, but "short in a coil" seems a bit suspicious. Also you provide very little information. Could you post a picture of this coil and also schematic diagram from service manual where coil L652 is show including some of it's suroundings.

author: tunk
author_rank: Super Contributor
timestamp: June 24, 2021, 01:02:27 pm
content: A picture may help.How did you measure the short? AFAIK, many coils have very low resistances.

author: decoder_82
author_rank: Regular Contributor
timestamp: June 24, 2021, 01:19:28 pm
content: The capacitors next to it (C653) leaked. I replaced with a new one and cleaned the PCB with IPA.After this I have tested again and got sparks in L625.Replacing with a coil from another good PSU I had no more issue.Now the question is how to find a replacement part

author: Manul
author_rank: Super Contributor
timestamp: June 24, 2021, 01:44:39 pm
content: It looks to me, that it is just a common mode choke. So it is like two coils on one core and if these two coils are separate from each other, what can be sparking? Probably what is sparking is bad contact where wire is soldered to the pin. What I'm saying is that you likely can fix this coil or rewind it. If it is common mode choke, the exact value is not very critical.

author: decoder_82
author_rank: Regular Contributor
timestamp: June 24, 2021, 03:28:04 pm
content: Thanks I will try to fix the coil that might be easier indeed.

author: Manolo Mos
author_rank: Contributor
timestamp: June 24, 2021, 05:26:24 pm
content: I've seen this kind of coils in short circuit before. I think it happens because the wire vibrates a little to the switching frequency, producing magnetostriction. This magnetostriction makes the wire vibrating, and one wire with other vibrating, makes remove the varnish and then, short circuit.I think this coil is not critical, try to find another similar.I have a PVM-8044 and a PVM-9045, and the C612 47uf 50V is prone to fail too.Best regards

author: decoder_82
author_rank: Regular Contributor
timestamp: June 25, 2021, 08:04:52 am
content: This is exactly what happened, the varnish was gone in some areas of the coil. I managed to fix it.Good stuff about C612. The ESR value was more of less OK but when I desoldered it I saw it was leaking.Thanks for your help

author: ErwinsCat
author_rank: Regular Contributor
timestamp: June 25, 2021, 03:42:53 pm
content: you should be able to rewire the chokes easily by hand. if you made or purchase one of those chokes, try to use some hot glue or silicone glue on the wires to dampen the vibrations and prevent the shorts again.

author: decoder_82
author_rank: Regular Contributor
timestamp: June 27, 2021, 04:45:40 am
content: Indeed I have rewired it by hand with new coil wire. I was not sure about using silicone glue/hot glue. As it might get hot I was afraid it would melt. What kind of glue would be recommended here ?