spencer2004
- May 1, 2013
- 17
- Joined
- May 1, 2013
- Messages
- 17
Hello. I am currently trying to repair the power supply of a projector that I just bought (Sahara / Delta AV-3100), it worked great for about half an hour and it suddenly went dead, I am sure that it is the power supply that is at fault as it should be constantly on even when the projector is in standby. I would really like to be able to fix it as I don't think that there are any replacement power supplies for sale for such an old projector.
My knowledge of electronics has huge gaps in it so forgive me for using incorrect terminology, etc. Here is what I know about this power supply:
The power supply uses a flyback transformer which is controlled by a TOP234 IC. The output rails are -5v, 5v, 6.5v, 13v and 17v. Feedback is based on the output of the 5v rail and sent back to the TOP234 via an opto isolator, all other rails are controlled by the turn ratio on the transformer only except for the -5v rail which is regulated with a linear regulator.
Once it went dead there was no output on the power rails at all. I have spent the last week or 2 figuring out how the power supply works and testing all of the components and I came to the conclusion that the IC that controls the switching of the transformer had died to I replaced it and it now outputs something but the voltages are almost exactly half of what they should be (5v is 2.77v, 6.5v is 3.35v, 13v is 7.02v, 17v is 8.72v, -5v is 3.72v). Putting a 5 ohm load on the 5V rail causes it to drop to 2.22v.
Since I don't own an ESR meter I just replaced all of the capacitors and it made no difference. No components show signs of overheating and nothing gets hot when it is powered on. No safety components have been triggered (i.e. fuse and varistor).
The circuit is almost exactly like this except the voltage rails are different, feedback is based only on 1 rail (the 5v one) and the -5v rail comes from a linear regulator.
I am really out of ideas now so if someone could give me any guidance on what I could try next I would be very grateful. I know this amount of time and effort is not worth it but I'm mainly doing it for the learning experience.
My knowledge of electronics has huge gaps in it so forgive me for using incorrect terminology, etc. Here is what I know about this power supply:
The power supply uses a flyback transformer which is controlled by a TOP234 IC. The output rails are -5v, 5v, 6.5v, 13v and 17v. Feedback is based on the output of the 5v rail and sent back to the TOP234 via an opto isolator, all other rails are controlled by the turn ratio on the transformer only except for the -5v rail which is regulated with a linear regulator.
Once it went dead there was no output on the power rails at all. I have spent the last week or 2 figuring out how the power supply works and testing all of the components and I came to the conclusion that the IC that controls the switching of the transformer had died to I replaced it and it now outputs something but the voltages are almost exactly half of what they should be (5v is 2.77v, 6.5v is 3.35v, 13v is 7.02v, 17v is 8.72v, -5v is 3.72v). Putting a 5 ohm load on the 5V rail causes it to drop to 2.22v.
Since I don't own an ESR meter I just replaced all of the capacitors and it made no difference. No components show signs of overheating and nothing gets hot when it is powered on. No safety components have been triggered (i.e. fuse and varistor).
The circuit is almost exactly like this except the voltage rails are different, feedback is based only on 1 rail (the 5v one) and the -5v rail comes from a linear regulator.
I am really out of ideas now so if someone could give me any guidance on what I could try next I would be very grateful. I know this amount of time and effort is not worth it but I'm mainly doing it for the learning experience.