Bought a STR-DB870 second hand, I have cleaned the inside with isopropyl alcohol, checked all connections thoroughly, nothing seems loose or degraded. However, every time I give it even a light tap specifically on the top of the amp it sends a horrible crackling noise through my right speaker, only when I tap it on the top tho, and when I use a bit of force on the sides, and when I bang the table it stands on pretty hard the same happens. And occasionally I get jump scared by it at random in the middle of a movie by the sound, for no real reason.
The noise isn't effected by changing the volume, or input settings, or any other output settings, so I think it's just the amp.
I am using it with a pair of 6 ohm 30 watt book shelf speakers, well bellow what I know this thing can handle but I am going to add a front channel and subwoofer soon enough, and make upgrades when I feel I can.
Is there any trouble shooting you could suggest for sorting this out, other than giving it another clean and tightening the screws, a little lost with how to fix it. Apart from that one issue it's a really nice amp and I would really like to keep it.
Thankyou for any responses, will be happy to post more specific details if needed.
The noise isn't effected by changing the volume, or input settings, or any other output settings, so I think it's just the amp.
I am using it with a pair of 6 ohm 30 watt book shelf speakers, well bellow what I know this thing can handle but I am going to add a front channel and subwoofer soon enough, and make upgrades when I feel I can.
Is there any trouble shooting you could suggest for sorting this out, other than giving it another clean and tightening the screws, a little lost with how to fix it. Apart from that one issue it's a really nice amp and I would really like to keep it.
Thankyou for any responses, will be happy to post more specific details if needed.
Hi . For me your issue sounds like bad soldering joints or broken trace on the right channel amp . To be more detail , search for schematic , it will help to understand signal path and where to look deeper. You said that sound is not volume dependent ,so it must in the power amplifier itself.
These receivers always run "hot" and because of that, they always crap out eventually from the joints problems.
Having has NUMEROUS amounts of those early 2000's model Sony receivers in the shop with intermittent/noise issues, they are plagued with poor quality solder joints through out.
The main issues are usually anything mounted on a heatsink needs resoldering, and some interconnects between boards as well.
Pull the plug, let it sit a while to discharge the power supplies, unless you're proficient enough to know the safe procedure using a 100 ohm resistor, for discharging capacitors...
Upon close inspection, usually with a magnifying glass, the poor connections are visible, being "ring joints" on the board at those bad connections.
The heating/cooling of the heatsink-mounted regulators/transistors causes the joints to break loose, with a ring-like crack around the soldered pins.
A regulator IC even with one pin faulty - all 3 pins should be re-soldered carefully.
Depending on the unit, the main board may have a removable access panel on the bottom, otherwise the service manual (mandatory for smart servicing) contains instructions on access/removal.
Additionally, the "static sensitive" devices in the unit are to be respected, because if they are disturbed by any charge from your body or a slip of a metal probe, you then have a useless paperweight and/or a doorstop.
Having has NUMEROUS amounts of those early 2000's model Sony receivers in the shop with intermittent/noise issues, they are plagued with poor quality solder joints through out.
The main issues are usually anything mounted on a heatsink needs resoldering, and some interconnects between boards as well.
Pull the plug, let it sit a while to discharge the power supplies, unless you're proficient enough to know the safe procedure using a 100 ohm resistor, for discharging capacitors...
Upon close inspection, usually with a magnifying glass, the poor connections are visible, being "ring joints" on the board at those bad connections.
The heating/cooling of the heatsink-mounted regulators/transistors causes the joints to break loose, with a ring-like crack around the soldered pins.
A regulator IC even with one pin faulty - all 3 pins should be re-soldered carefully.
Depending on the unit, the main board may have a removable access panel on the bottom, otherwise the service manual (mandatory for smart servicing) contains instructions on access/removal.
Additionally, the "static sensitive" devices in the unit are to be respected, because if they are disturbed by any charge from your body or a slip of a metal probe, you then have a useless paperweight and/or a doorstop.
I would bet on connectors / Flex cables.
I believe there is a standing DSP board on the right side.
Check if a long screw or a heatsink touches the case or chassis when You slap on it.
Apply some bending force to the flats near the connectors.
Check for dry joints. On mine there are some heavy gauge copper cable bridges.
I believe there is a standing DSP board on the right side.
Check if a long screw or a heatsink touches the case or chassis when You slap on it.
Apply some bending force to the flats near the connectors.
Check for dry joints. On mine there are some heavy gauge copper cable bridges.
Thanks, I'll take it apart and have a look over the right channel, and the relevant path when I get the chance.
I'll be sure to check all the components fixed to the heatsink, this unit does have a removable bottom panel, and I've taken it apart a fair few times so should be easy enough to check, just to be sure the attached image is the kind of thing I should be looking for right?
Yeah I'll check them again along the signal path, the major heatsink is screwed directly into the case, when you say "bending force to the flats" is that a case of just giving all the ribbon cables a bit of a wiggle and making sure their nice and secure?
Just checked along the right channel signal path, and there was a bit of poor soldering which you can see in the attached image, this connected to a large film capacitor, which lead fairly directly to the right channel output, makes sense why there was such a loud crackle when disturbed, and why it wasn't effected by any setting changes. I fixed the joint with a touch of solder, and now there is no trouble at all, really happy I could fix it so fast, good thing about these old amps is you can actually do real DIY to them!
MAAC0, haha yeah, 90% sure that's what you meant, I did give them all a wiggle before putting everything back together, always good to make sure 😀
Sometimes broken solder joints are not visible even with a magnifying glass. In cases like jours I take my soldering iron, rework ALL joints without wasting my time by searching the fault(s). 30~60Min later the job is done😉
Indeed, sometimes the whole soldered joint doesn't attach to the pad, and sometimes the pad itself breaks loose (from shock/dropping).
In those cases, I don't waste my time going over the whole board, I wiggle the components and look for movement of the soldered lead, it's much quicker.
When you work in a busy shop, time is money.