cool cabbage
New Member
I have recently made a series of mistakes that have brought me here for some assistance. I have a limited knowledge of electronics, but am very experienced with computers, and I learned in the same way that I am attempting to learn about electronics. I am prepared to hear all about how much of an idiot I am, and everything I did wrong. Excellent.
With that out of the way, I'd like to explain my situation.
I have an SX-1050 that my father purchased new around 1976. I used it and loved it in my teenage years, moved away from the area for several years, and now we've been reunited. It never seemed to work quite right; it would click off for a few seconds, and then back on. It seemed to get worse as it warmed up. The filter switches needed to be fiddled with a little bit every so often to make everything sound right. My father said that it had always been like that, even when it was new. I used some electronics cleaner on all of the switches and knobs, removed the preamp jumpers (which he said were also always a problem) in order to run it through an equalizer, and blew out as much dust as I could with an air compressor.
Everything worked and sounded great.
I looked for any bad or leaking capacitors inside the unit, and located two on the Power Supply A board. C1 and C9 in the service manual, 220 micro farad 80v capacitors, which had leaked all over the board. I ordered 2 Nichicon UFG1K221MHM capacitors from mouser as replacements. I removed the shield from the back, removed the old capacitors, and installed the new ones.
During the removal, the copper pads to the traces lifted off the PCB. Both pads on one of the connections, and only one of the other. I exposed some of the trace, pre-tinned the trace, pre-tinned the capacitor leads, and made the connections.
The time came to test the unit, and a got fizzles, sparks, and smoke. As it turns out, the coating on the traces was much more delicate that I had expected it to be, and I was much more careless with the soldering iron tip that I had intended to be. I never disconnected all of the wrapped posts on the underside of the unit, so I was kind of working with it dangling from those wires. It was a precarious situation, and a mistake I will be sure not to make again.
I have a younger brother that is a little more experienced in these matters than I am, and he suggested covering the back of the board with liquid electrical tape. We did that, and what I assume to be short circuiting seemed to stop. No more sparks, no more sizzling and fizzling, no more smoke. Great, I thought. Everything should be fine.
I also replaced a blown 1A fuse, numbered "13" on the Power Supply B board at this time.
Now, the transformer hums, and it can be heard very loudly through the speaker. No switches or knobs have an effect on this hum.
I am looking for some advice on this repair, getting rid of the hum, and getting this back to working condition. Replacing the Power Supply A board seems like an affordable and easy solution, but if it would be possible to repair this unit without spending the money, I would prefer to do that.
Thanks for taking the time to read my life story.
With that out of the way, I'd like to explain my situation.
I have an SX-1050 that my father purchased new around 1976. I used it and loved it in my teenage years, moved away from the area for several years, and now we've been reunited. It never seemed to work quite right; it would click off for a few seconds, and then back on. It seemed to get worse as it warmed up. The filter switches needed to be fiddled with a little bit every so often to make everything sound right. My father said that it had always been like that, even when it was new. I used some electronics cleaner on all of the switches and knobs, removed the preamp jumpers (which he said were also always a problem) in order to run it through an equalizer, and blew out as much dust as I could with an air compressor.
Everything worked and sounded great.
I looked for any bad or leaking capacitors inside the unit, and located two on the Power Supply A board. C1 and C9 in the service manual, 220 micro farad 80v capacitors, which had leaked all over the board. I ordered 2 Nichicon UFG1K221MHM capacitors from mouser as replacements. I removed the shield from the back, removed the old capacitors, and installed the new ones.
During the removal, the copper pads to the traces lifted off the PCB. Both pads on one of the connections, and only one of the other. I exposed some of the trace, pre-tinned the trace, pre-tinned the capacitor leads, and made the connections.
The time came to test the unit, and a got fizzles, sparks, and smoke. As it turns out, the coating on the traces was much more delicate that I had expected it to be, and I was much more careless with the soldering iron tip that I had intended to be. I never disconnected all of the wrapped posts on the underside of the unit, so I was kind of working with it dangling from those wires. It was a precarious situation, and a mistake I will be sure not to make again.
I have a younger brother that is a little more experienced in these matters than I am, and he suggested covering the back of the board with liquid electrical tape. We did that, and what I assume to be short circuiting seemed to stop. No more sparks, no more sizzling and fizzling, no more smoke. Great, I thought. Everything should be fine.
I also replaced a blown 1A fuse, numbered "13" on the Power Supply B board at this time.
Now, the transformer hums, and it can be heard very loudly through the speaker. No switches or knobs have an effect on this hum.
I am looking for some advice on this repair, getting rid of the hum, and getting this back to working condition. Replacing the Power Supply A board seems like an affordable and easy solution, but if it would be possible to repair this unit without spending the money, I would prefer to do that.
Thanks for taking the time to read my life story.
so your Receiver can sing again.
