hello
I have an old onkyo tx sv828thx that has an annoying intermittent problem in the left channel at low volume. I really like the receiver, but its driving me nuts.
It sounds llke a bad connection with breakthrough. (a bit like weak or badly tuned radio signal). Its only noticeable at low volume, and if I crank the volume up for a bit, then back down it is gone, usually lasts about a week then comes back. Its not related to the actual volume position, as when the volume is up, but a song fades out its the same
I think I have narrowed it down to the amp section, as it happens on all inputs, (even if connecting it up with a pre amp arrangement). It also happens on both A and B speaker sets. I have also swapped the speakers and wiring to prove its nothing external.
I have had the lid off and cant see anything obvious, but don't have the experience to know were to focus on.
noticeable at volume levels of 40db or under (as shown on the volume display) and clears when turned up to 0db or above (as shown on volume display)
Anyone have any input for me? Im an electrician, so understand basic fundamentals and can use a soldering iron for things that are not overly fiddly. When it comes to nitty gritty electronics and fine test equipment I am out of my depth.
Any input appreciated, Im happy to google stuff I need to understand more, and can provide more detail on what I have diagnosed so far
I have an old onkyo tx sv828thx that has an annoying intermittent problem in the left channel at low volume. I really like the receiver, but its driving me nuts.
It sounds llke a bad connection with breakthrough. (a bit like weak or badly tuned radio signal). Its only noticeable at low volume, and if I crank the volume up for a bit, then back down it is gone, usually lasts about a week then comes back. Its not related to the actual volume position, as when the volume is up, but a song fades out its the same
I think I have narrowed it down to the amp section, as it happens on all inputs, (even if connecting it up with a pre amp arrangement). It also happens on both A and B speaker sets. I have also swapped the speakers and wiring to prove its nothing external.
I have had the lid off and cant see anything obvious, but don't have the experience to know were to focus on.
noticeable at volume levels of 40db or under (as shown on the volume display) and clears when turned up to 0db or above (as shown on volume display)
Anyone have any input for me? Im an electrician, so understand basic fundamentals and can use a soldering iron for things that are not overly fiddly. When it comes to nitty gritty electronics and fine test equipment I am out of my depth.
Any input appreciated, Im happy to google stuff I need to understand more, and can provide more detail on what I have diagnosed so far
Bit more info, the volume in the left channel is lower than the right when its playing up, there are no pops or crack noises.
I found a service manual on line and have noticed there is a relay on the positive side (both left and right channels switched off the same coil). - R502
Im thinking perhaps the contacts are sus. Does this sound likely?.... Or would it be more likely to be a bad cap or something?..... I don't know what the relay is there for.... Perhaps something to do with overload protection?.... Cant tell what operates it at this stage.
I found a service manual on line and have noticed there is a relay on the positive side (both left and right channels switched off the same coil). - R502
Im thinking perhaps the contacts are sus. Does this sound likely?.... Or would it be more likely to be a bad cap or something?..... I don't know what the relay is there for.... Perhaps something to do with overload protection?.... Cant tell what operates it at this stage.
Unscrew the lid and use it as per normal.
When the amp faults, remove the lid carefully and try pressing on circuit boards (use a small screw driver handle etc) to see if/where the fault clears/restores.
Dan.
When the amp faults, remove the lid carefully and try pressing on circuit boards (use a small screw driver handle etc) to see if/where the fault clears/restores.
Dan.
Thanks KatieandDad and Max, I have the lid unscrewed ready to pounce, and I think Ill Start at the relay (so long as I can locate it ok). I have a plastic screwdriver I use for trimming pots on PCB's at work, so Ill have a prod about with that whilst its running in fault. I don't think the fault is in the volume or tone control pots as they appear to be located in the preamp section. When I ran the amp with a separate preamp, the fault was still behaving the same way.....
Guess if I play about with it for long enough Ill track it down, or fully break it!!! Either way should be a good learning curve. If I manage to fix it Ill e fully satisfied
Guess if I play about with it for long enough Ill track it down, or fully break it!!! Either way should be a good learning curve. If I manage to fix it Ill e fully satisfied
My amp fault came back, after checking all contacts by putting a jumper across them, I couldn't find any fault. I could track it down to somewhere in the left power amp. As Dan recommended I went about pushing the components on the board with a plastic screwdriver. When I touched a transistor (2SC5171) everything sprung back to life! I only just lightly touched it getting the screwdriver in place to give it a proper prod!
I have done a bit of a search for these transistors and it sounds like they may be getting hard to track down. I have read that transistors normally fault to an open or closed state.
From what I described would a bad transistor or bad joint be most likely the fault? If I could get away with re-soldering I would be pretty happy, but the card/board is a total pain to get out to work on so only really want to do it once
I have done a bit of a search for these transistors and it sounds like they may be getting hard to track down. I have read that transistors normally fault to an open or closed state.
From what I described would a bad transistor or bad joint be most likely the fault? If I could get away with re-soldering I would be pretty happy, but the card/board is a total pain to get out to work on so only really want to do it once
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