Here's another close up pic of power supply side. Black arrow indicates loose coil. The red side voltage is 1/10th the voltage of the blue side on the 3205's gate pin. I don't have an oscilloscope so all my testing is with a simple multimeter. Not sure if getting right signal from KA7500B controller either. I took the amp to a local repair shop and they confirmed that the power supply was not turning on, but said that without a schematic they couldn't track down the problem without another $200 in labor.
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source voltage measured 14.65
Pin 1: 8.44
Pin 2: 2.52
Pin 3: 4.61
Pin 4: 3.75
Pin 5: 1.5
Pin 6: 3.64
Pin 7: 0.0
Pin 8: 14.65
Pin 9: 0.0
Pin 10: 0.0
Pin 11: 14.65
Pin 12: 14.65
Pin 13: 4.94
Pin 14: 4.94
Pin 15: 4.94
Pin 16: 0.0
found a manufacture date of 2003. ran a soldering iron over the spots I thought might be a loose connection and retested with no difference. hopefully this weekend I can get the two 4700uf caps out and checked. saw no leakage but the tops are domed and soft.
thanks for all the help, I DO really appreciate the help!
Pin 1: 8.44
Pin 2: 2.52
Pin 3: 4.61
Pin 4: 3.75
Pin 5: 1.5
Pin 6: 3.64
Pin 7: 0.0
Pin 8: 14.65
Pin 9: 0.0
Pin 10: 0.0
Pin 11: 14.65
Pin 12: 14.65
Pin 13: 4.94
Pin 14: 4.94
Pin 15: 4.94
Pin 16: 0.0
found a manufacture date of 2003. ran a soldering iron over the spots I thought might be a loose connection and retested with no difference. hopefully this weekend I can get the two 4700uf caps out and checked. saw no leakage but the tops are domed and soft.
thanks for all the help, I DO really appreciate the help!
Took my measurements there. It is a LM393N.
Pin 1: 9.11
Pin 2: 4.30
Pin 3: 14.20
Pin 4: 0.0
Pin 5: 4.37
Pin 6: 4.40
Pin 7: 9.07
Pin 8: 14.72
Source voltage is 14.75v
Also checked voltages at the capacitors in power supply. I had source V coming into all the smaller caps near input. Did not have anything at the 2 large ones by the large coils.
Pin 1: 9.11
Pin 2: 4.30
Pin 3: 14.20
Pin 4: 0.0
Pin 5: 4.37
Pin 6: 4.40
Pin 7: 9.07
Pin 8: 14.72
Source voltage is 14.75v
Also checked voltages at the capacitors in power supply. I had source V coming into all the smaller caps near input. Did not have anything at the 2 large ones by the large coils.
Here are three more shots of the board. I tried to get two different angles of the chip set and then also one half of the FETs. Hopefully they are good enough was having a hard time with lighting.
Attachments
I was hoping to find a schematic diagram close to the circuit in this amp but with the voltages you posted, none that I have appear to be similar. Do you have a digital camera that will take better photos? If no one else can help, I'd need better photos, including at least one good one of the bottom of the board for the around the KA7500 and LM393.
Had an eventfull day. Lighting cooperated so think I got some good pics. Desoldered as many resistors and diodes that I could get to and tested. Everything so far is in tolerances and diodes working properly. Got a few capacitors pulled and getting them tested tomorrow afternoon. This is really turning into an unusual error as haven't been able to find a fault yet.
The pictures are in order of placement on the board. Both top and underside. I labeled the picture overlap.
The pictures are in order of placement on the board. Both top and underside. I labeled the picture overlap.
Attachments
Yeah the company moved to Germany. I tried the last american contact for the company but that site has been idle for years. I got a few more components tested with no new results so put everything back together and put the amp away. Got other projects to work on anyways. Thanks for the help.
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