Sony VCR Repair (SLV-ED10)

[paddyfield77]

I got this VCR from a friend of mine as it stopped working and he wasn't interested in fixing it, makes sense as it isn't worth much nowadays. However, I got a few tapes around the house and I would like to watch them with my kids. I know some basic stuff about repairing electronics.

So it doesn't power up at all. I opened it up and checked the cable and one of the wire was open! I thought I was really lucky and I replaced the cord. I plugged in the power supply (it wasn't attached to the machine) and measured the output voltage and it read way high! +6V line was at +8V, +35V line was around +45V and the +13V and -13V lines were around +18V and -18V.

I am fairly confident that something is wrong with the power supply board and luckily I didn't plug it into the machine. I have also attached the schematic diagram of the power supply board.

So can someone in this forum point me in the right direction to fix this issue? Thanks

[inse]

First question is: what is the VCR doing now?
Basically, only the 6V rail is regulated, the other voltages are defined by the turns ratio of the transformer.
Did you measure the voltage levels around IC201?
You can adjust the voltage with RV201.

[paddyfield77]

Initially it was not powering on. No signs of life at all. I opened the cover and found out that the power cord was broken so I replaced it with a good one I had. So before connecting the power supply board back to the unit's main board, I decided to check if it is working and I found out that the voltages were way above what they should be as I have said in my original post. So I did not plug it into the unit as it looked like there is something wrong with the power supply and it might fry something in the main board.

Yes. I did measure the voltages around IC201. There was 3.7V on the pin which is connected to the optocoupler, 2.5V on the second pin and the third pin is ground.

I did try adjusting RV201 but it did not affect the voltage much. There was only a slight change in the millivolts range when I adjusted it.

[fzabkar]

Check the electrolytic B+ capacitors.

[inse]

Or the regulation is not working properly without a load…

[paddyfield77]

Is it possible to check capacitors without an ESR or capacitance meter?

[paddyfield77]

Replying to @inse - You might right about that but I am worried if I might fry up something on the main board if I plug it in as some voltages are really really higher than what they should be.