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jammyringo

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    Sydney
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    Australia
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    j

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  1. Hi All, I have an Onkyo TX-DS989 AV Receiver that is not producing any sound. I have tried the headphone plug as well, and no sound there either. I hear 2 relay clicks when I power the unit on and press the "stand-by" button. There are 7 identical capacitors that are either swollen to leakage or very close to it. These are (C5180-C5186) 2pF/500V caps which are on the power amplifier stage. The schematic below is one block on the PCB which is repeated 7x on this board. I will be replacing these caps, but I'm a bit confused whether this is the cause of the problem or not because looking at the block diagram, I can see that the headphone jack taps off the signal before the power-amplifier board (schematic below). Are these blown caps likely to affect the circuit back in that direction? If not, can anyone make a suggestion on debugging this? I have a sig-gen and scope, but have not used them to debug an amplifier before. The last interesting piece of data is that the speaker output does "sometimes" produce a terrible hum, but I can't work out why. Going into the speaker calibration menu selection and playing in there seems to affect it. I had the unit off overnight and now on and running for a good hour, and the hum has not returned, speakers are producing no sound. The fan also is unpredictable about coming on. Any help, even non-specific, general advice on amp debugging would be great! (I have a Sansui AU-717 that has a "no sound" issue as well and I hope to debug and restore). Thanks
  2. Hi all, I mentioned I picked up the above AU-717 a few weeks ago. Trying to get it going (it's in superb condition). Switching it on, the protect LED flashes for several seconds and then the relay triggers and the light goes steady. I hooked up a tuner & tape from known good sources and did not get anything from the speakers (not even an audio "scratch" sound if I jiggle the speaker wires). The "PRE-POWER AMP" switch is set to "Connected". I am a pretty basic level, but have done a bit of debugging electronics over the years. This is a unit that I don't want to muck around too much, but do want to try to solve this. I'm sure the solution is simple one. Basically, no signal at the speakers terminals. What I haven't been able to find yet is a "generic" step by step way to debug this amp, tracing back from the speaker output. I have found a few useful threads (some on this site) for sure, but the terminology is always a bit too far out. I have the user manual and can chip away at this. Interestingly, I have another "sencor" set of amp/tape/tuner where the amp has the same problem! I thought I could use that as a guinea pig to work out the debugging. Cheers, Jim
  3. Hi all, I'm a new addition to the network. Have enjoyed reading through content for some time here, but never signed up until now. I love hi-fi from the 60's, 70's and 80's and have picked up quite a few beautiful pieces over the years. I always work on these things myself, it's a hobby. There is so much to know that I think you have to do it full time I think to really get good at it. My biggest difficulty is when debugging gets me right in to the detailed circuit diagrams and I can't solve a problem, when I know an expert would simply be able to look at the board and understand what's going on. Speaking of that, are there any night-classes or anything devoted to hobbyists in the Sydney region? Lastly, I hate breaking things.
  4. Hi All, Skippy and Pete in particular who seem to be experts on this gear, I've come across a beautiful AU-717 and the matching SC-2110 tape deck. I'm using this thread, which is incredible, to help in my cleaning and tweaking. Just wondering if there is a local supplier of belts that can be recommended? I've found some in the US and EU, but nothing local yet. Here is a photo of the amp and deck. Cheers!
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