I was having trouble repairing this unit and while searching for info I came across another Videoton design. It came with the pc case and it was a cheap local sale so I picked it up, out of curiosity.
This one is a full AT size unit that is functional but gave a strange whine/buzzing right from startup. After some poking around it was determined that the noise came from the main transformer. There was also a rattling sound when the unit is rotated or shaked. It turned out that on of the main trafos half core has been cracked and broken. There was no sign of big heat damage anywhere so my guess was that it has sustained some kind of physical shock during shipping or before.
It turned out that other components were also failing so I took the whole unit apart
It looks like a push-pull design. Mirroring the '80s eastern block shortage economy. Whatever parts were available in the market were used for design and production. Max output of this psu is about 150Watts.
It has some EMI filtering.
There are fuses socketed in series both on line and neutral:
It has a decent fan that still spins super smooth:
Inrush current limiter has several holes on it and measures 50-60 ohms. It's blown. It has color coding in the form of three dots:
A foil capacitor was measured open and another 100nf+2x2.5nf X2Y wierdo type was 100-200ohms in one part:
Main capacitors measure not so great and leakage current is high. Some audiophiles might think they look pretty cool though:
The unit has a full bridge rectifier:
Two IRF 740 FETs:
Controlled by SG3526N. Supervisor is SG3543J:
I couldn't take it apart without destroying the original heat transfer/insulator sheets.
These sheets were all brittle and were falling apart:
The main transformer is some high frequency core N27 material. I'm not an expert identyifing transformers so it took me some time until it was revealed
to be EC41 type. My second guess was ETD core:
It's still around and super cheap so I ordered some. The Epcos/TDK part goes by the name B66339G0000X127.
Original main trafo with RC snubber hacked on it:
The main board stripped down a bit:
The secondary current stabilizer is also wound around a EC41 bobbin and N27 core material. It's glued together with some rtv silicone.
Output diodes are schottky types for 5V and 12V rail. -5V is generated by 7905 regulator ic:
There is no real low pass filter with inductors just electrolytic capacitors on the output filtering stage. Old Panasonic, Chemicon and random USSR caps are used. These all test ok.
That's how far a I got now. I'll reassemble the main transformer and also might replace some old parts with matching nos parts. These "vintage" resistors, caps are still shoveled around since so much were made and some are still within specs.
This one is a full AT size unit that is functional but gave a strange whine/buzzing right from startup. After some poking around it was determined that the noise came from the main transformer. There was also a rattling sound when the unit is rotated or shaked. It turned out that on of the main trafos half core has been cracked and broken. There was no sign of big heat damage anywhere so my guess was that it has sustained some kind of physical shock during shipping or before.
It turned out that other components were also failing so I took the whole unit apart
It looks like a push-pull design. Mirroring the '80s eastern block shortage economy. Whatever parts were available in the market were used for design and production. Max output of this psu is about 150Watts.
It has some EMI filtering.
There are fuses socketed in series both on line and neutral:
It has a decent fan that still spins super smooth:
Inrush current limiter has several holes on it and measures 50-60 ohms. It's blown. It has color coding in the form of three dots:
A foil capacitor was measured open and another 100nf+2x2.5nf X2Y wierdo type was 100-200ohms in one part:
Main capacitors measure not so great and leakage current is high. Some audiophiles might think they look pretty cool though:
The unit has a full bridge rectifier:
Two IRF 740 FETs:
Controlled by SG3526N. Supervisor is SG3543J:
I couldn't take it apart without destroying the original heat transfer/insulator sheets.
These sheets were all brittle and were falling apart:
The main transformer is some high frequency core N27 material. I'm not an expert identyifing transformers so it took me some time until it was revealed
to be EC41 type. My second guess was ETD core:
It's still around and super cheap so I ordered some. The Epcos/TDK part goes by the name B66339G0000X127.
Original main trafo with RC snubber hacked on it:
The main board stripped down a bit:
The secondary current stabilizer is also wound around a EC41 bobbin and N27 core material. It's glued together with some rtv silicone.
Output diodes are schottky types for 5V and 12V rail. -5V is generated by 7905 regulator ic:
There is no real low pass filter with inductors just electrolytic capacitors on the output filtering stage. Old Panasonic, Chemicon and random USSR caps are used. These all test ok.
That's how far a I got now. I'll reassemble the main transformer and also might replace some old parts with matching nos parts. These "vintage" resistors, caps are still shoveled around since so much were made and some are still within specs.
Attached Files
nVidia RTX 3080 TI, Corsair RM750I.
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