DucatiDave
Member
I have quite a few Sansui receivers, Eight, Seven, 1000a, and on this past Monday I picked up my first integrated amp, an AU-999. I gave it a quick test and it sounded good on the Aux with my iPhone, but it had some scratchy controls. So I took the covers off and proceeded to Deoxit all of the controls. After cleaning the controls, the 999 now has very weak and distorted channels.
The highs and lows are almost nonexistent, while the mids come through reasonably well. Bass and treble controls have minimal effect on sound. At first I thought that the controls were at fault, so I cleaned and exercised them again with zero improvement. I can operate all of the controls and they work as they should, no crackles or anything like that. I am leaning on the 1208 filter board because both channels are exactly the same, and the filter, muting, and tone controls all have some effect on the sound, however minimal. I used a tone generator on my phone and was able to hear a faint tone at 200hz. It got steadily louder till about 1500 or 2000hz at which point it tapered off again.
I recapped my 1000a, so I do have experience with troubleshooting and working on equipment. I know for a fact that the problem lies within the preamp section because I was able to use the preamp on my Eight with the 999 amp and the sound was excellent. Running the 999 preamp through the Eight amp resulted in the same weak and distorted sound.
I have a good clean path from the aux inputs all the way to the 1208 board. All inputs have the same distorted sound, tuner, tape, phono, etc. I also ran jumpers directly from the aux input to the 1208 board, bypassing all of the switches, with the same distortion, which is why I am not leaning on the switches as the problem. I think it is just an incredible coincidence that this happened after using the deoxit. The only thing I find weird is that there are two signal pathways on the 1208 board, meaning that multiple components failed at once. I tested all of the resistors and everything came up good except for r712 and r725. The are supposed to be 1M ohm but they tested at 660k ohms.
Transistors? Caps? Any help would be greatly appreciated. I do plan on doing the preamp mods, but I want to get it running well in stock configuration first. Doing mods on a broken piece of gear is not good, I want to start with a clean slate.
Thanks
Dave
The highs and lows are almost nonexistent, while the mids come through reasonably well. Bass and treble controls have minimal effect on sound. At first I thought that the controls were at fault, so I cleaned and exercised them again with zero improvement. I can operate all of the controls and they work as they should, no crackles or anything like that. I am leaning on the 1208 filter board because both channels are exactly the same, and the filter, muting, and tone controls all have some effect on the sound, however minimal. I used a tone generator on my phone and was able to hear a faint tone at 200hz. It got steadily louder till about 1500 or 2000hz at which point it tapered off again.
I recapped my 1000a, so I do have experience with troubleshooting and working on equipment. I know for a fact that the problem lies within the preamp section because I was able to use the preamp on my Eight with the 999 amp and the sound was excellent. Running the 999 preamp through the Eight amp resulted in the same weak and distorted sound.
I have a good clean path from the aux inputs all the way to the 1208 board. All inputs have the same distorted sound, tuner, tape, phono, etc. I also ran jumpers directly from the aux input to the 1208 board, bypassing all of the switches, with the same distortion, which is why I am not leaning on the switches as the problem. I think it is just an incredible coincidence that this happened after using the deoxit. The only thing I find weird is that there are two signal pathways on the 1208 board, meaning that multiple components failed at once. I tested all of the resistors and everything came up good except for r712 and r725. The are supposed to be 1M ohm but they tested at 660k ohms.
Transistors? Caps? Any help would be greatly appreciated. I do plan on doing the preamp mods, but I want to get it running well in stock configuration first. Doing mods on a broken piece of gear is not good, I want to start with a clean slate.
Thanks
Dave