Sony STR-6800 SD Troubleshooting

Runicen

New Member
Ok, sorry to post this in a new thread when I have another active on here, but the nature of the request has changed.

In case it's helpful, my original thread was here: http://audiokarma.org/forums/index.php?threads/next-steps-after-sony-str-6800-sd-re-cap.844366/

Before, I had completed a re-cap on this amplifier and thought things were fine. Well, since I found myself with some time off, I decided to bring the amp home (it's intended as an office setup) to really push it and see how it sounded at higher volume.

At first, all was well, but now, even at low volumes, it fluctuates from playing normally (and beautifully) to either the left or right channel fizzing and cutting out before cutting back in. The relay isn't kicking on, connections seem solid and no amount of playing with them seems to make a difference, the cutouts are seemingly random (i.e. not particular to louder musical passages - and I've noted this on classical recordings, so I'm not slamming it with metal or anything). Likewise, I don't think the problem is dirty contacts in the knobs or anything as fussing with those doesn't address the problem.

I'm half wondering if this had been going on at the office for a while or if this is new occurrence, but the bottom line is that I need to figure out what is causing this and fix it. Can anyone point me in the right direction as to where to troubleshoot this guy? Given my druthers, I'd love to keep it in service, but it's not much use to me while playing the "channel cut-out lotto."

Thoughts?
 
it fluctuates from playing normally (and beautifully) to either the left or right channel fizzing and cutting out before cutting back in. The relay isn't kicking on,
Welcome to AK..
Does briefly, quickly, cranking the volume way up and back down improve the sound quality ? The relay itself may have fouled contacts.
 
Welcome to AK..
Does briefly, quickly, cranking the volume way up and back down improve the sound quality ? The relay itself may have fouled contacts.

Thank you.

To your question: it did not seem to. At best, I could get some difference in the crackle - which at first led me to believe it was a dirty volume pot - but there's zero noise from the volume control when it's not having a "fit." I couldn't get it to fix itself by doing that for the short answer.

For a new fly in the ointment: expecting a total trainwreck, I followed up my classical playback by throwing in Paranoid by Black Sabbath and turning it up... It played through all 40 or so odd minutes at a healthy volume with no cut-out whatsoever.

So, our symptoms are cut-outs... sometimes, which may or may not respond at all to messing with the volume control, along with perfect playback of less dynamic material.

Would bad relay contacts cause the amp to fumble more dynamic material but present no issues on less dynamic material or am I getting into the weeds of a more substantial problem here?
 
Would bad relay contacts cause the amp to fumble more dynamic material but present no issues on less dynamic material or am I getting into the weeds of a more substantial problem here?
At low volume level the next time it cuts out. Tap on the protect relay. While listening. Could also be solder connections most likely in the power supply. More dynamic playback requires more current. A bad solder connection or relay contact or even a dirty switch could definitely be an issue.
 
At low volume level the next time it cuts out. Tap on the protect relay. While listening. Could also be solder connections most likely in the power supply. More dynamic playback requires more current. A bad solder connection or relay contact or even a dirty switch could definitely be an issue.

Thanks for the feedback.

It may be a little tricky to tap the relay during playback as it's mounted upside down inside the chassis, but I'll see if I can jury rig a setup which will allow for this.

What is going to follow is a total betrayal of my ignorance, so please bear with me on this.

With regard to the relay, I know they can be weak points on these STR-6800s, but I've yet to figure out a non-destructive way to get inside of the thing and clean it. Is there a trick to popping off the plastic cover without breaking the clips that hold it in place? Given the inconvenient placement of the thing, should I just plan to open it up and give it a cleaning pre-emptively?

And last in line with the stupid questions: what signs should I be looking for that the relay is fine and not responsible for this recent weirdness?

Again, thanks very much for your help here.
 
but I've yet to figure out a non-destructive way to get inside of the thing and clean it
Easy.... Replace it !
And last in line with the stupid questions: what signs should I be looking for that the relay is fine and not responsible for this recent weirdness?
If tapping on it doesn't change SQ. Or if you discover the root cause thats not involving the relay.
 
Easy.... Replace it !

If tapping on it doesn't change SQ. Or if you discover the root cause thats not involving the relay.

Ok. Back to throwing music through this thing to see if it cuts out again. I'll try tapping the relay when it does.

I'm assuming the advice will be to measure the voltage going into the relay here, but another behavior I'm noticing is that turning the amp on "cold" presents a delay in the relay clicking on. The relay clicks on almost instantly if the amp is turned off and turned on quickly after being powered on and activating. Since the relay board has been re-capped, I'm at a bit of a loss here because my first guess would be a capacitor that was slow to charge.

Does this behavior point in a different direction or could that still be consistent with a dirty relay?

Also, with Sony equipment of this vintage, how hard is it to get a 1:1 replacement for one of these relays if a replacement seems advisable?
 
how hard is it to get a 1:1 replacement for one of these relays if a replacement seems advisable
What part number is printed on the relays plastic case? Post a photo of the relays solder connections (foot print)
 
Footprint is outlined in red here:



There's a fair bit of printing on the relay itself.

TYPE MS4U
24VDC
257-12

I'm assuming 257-12 is the part number. There's also a much smaller "076" in the bottom left corner of the top casing if that's relevant.
 
20181001-111401.jpg
I'm assuming the only complication from snipping off the unused pins
Shouldn't have to snip any pins. There are 4 unused pins They will just drop down in the holes already present. See the tiny red dots in the photo above.

Yes just get it soldered flush to the board.
 
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Shouldn't have to snip any pins. There are 4 unused pins They will just drop down in the holes already present. See the tiny red dots in the photo above.

Yes just get it soldered flush to the board.

Thank you for the info. I'd defaulted to thinking of the relay as unobtainium after the number of threads I'd read on here and elsewhere of folks unable to source relays for their own amps.

Now, of course, having gone over all of this, the amp is behaving so reproducing the behavior and giving the relay a love tap to see if it's the source is going to take a bit...

I should probably ask, while we wait, if the cold start relay delay is a concern or normal behavior for something this old. Granted, the "delay" is waiting five seconds instead of barely one for it to click on, but I have a suspicion that the dodgy behavior came up during a run that began with a delayed relay click. How relevant that is, I'm not sure, but it seemed worth a mention.
 
I should probably ask, while we wait, if the cold start relay delay is a concern or normal behavior for something this old. Granted, the "delay" is waiting five seconds instead of barely one for it to click on, but I have a suspicion that the dodgy behavior came up during a run that began with a delayed relay click. How relevant that is, I'm not sure, but it seemed worth a mention.
Cold start delay 2-5 sec. Hot restart the cap that does the RC timing hasn't fully discharged so won't take as long to recharge and fire the relay. Normal behavior.
 
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Well, it's been 24 hours and I have been unable to reproduce the issue of channel cutout on this amp. Yeah, I'm still trying to figure out how that works.

The amp is resting on its side with the bottom cover off so I have direct access to the relay, but it just isn't playing up. Tried the recording that manifested the problem early yesterday - played fine. Threw a pile of rock and classical at it... ditto.

I'm at a loss for what could cause a problem one day and clear up the next. I even made sure that it was a "cold" start today before I started testing it.

Granted, if my "problem" is that I seem to no longer have a problem, it certainly could be worse, but I'm beyond at a loss here. :dunno:
 
Well, it's been 24 hours and I have been unable to reproduce the issue of channel cutout on this amp. Yeah, I'm still trying to figure out how that works.

The amp is resting on its side with the bottom cover off so I have direct access to the relay, but it just isn't playing up. Tried the recording that manifested the problem early yesterday - played fine. Threw a pile of rock and classical at it... ditto.

I'm at a loss for what could cause a problem one day and clear up the next. I even made sure that it was a "cold" start today before I started testing it.

Granted, if my "problem" is that I seem to no longer have a problem, it certainly could be worse, but I'm beyond at a loss here. :dunno:
Maybe a cold solder connection.Tap around the circuit board with something non-metallic. Chopstick, wooden or plastic stick etc.See if you can duplicate your issue. Could also just be a dirty switch or control.
 
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Maybe a cold solder connection.Tap around the circuit board with something non-metallic. Chopstick, wooden or plastic stick etc.See if you can duplicate your issue. Could also just be a dirty switch or control.

Multiple passes during playback on every board other than the tuner board and even that didn't reproduce the issue. Used the end of a sharpie and went to town tapping around.

I know I said the volume knob didn't make a huge difference during the episode in question, but I may try to get at the volume pot and "muting" attenuator switch and hit them with contact cleaner next as a pre-emptive strike. While both seem to be operating fine, there is an enclosure around the back of both, so it's possible there are parts of those works I haven't properly cleaned yet.
 
Looking at the relay, I'm noticing that the two "outside" connections are slightly off-center. What I mean is that, of the four copper contacts that click together, 1 and 4 do not completely match up with the copper contacts they're joined to. However, since they're both uniformly "off" towards the outside of the relay on their respective sides, I assumed this was intentional.

Is this a sign of a defect in the relay or are they designed in this way? The offset is maybe 1mm and they seem to contact just fine, but that there's an offset at all seems odd to me.
 
Still a few days in and *knock on wood* no full dropouts.

What I have experienced is a very low-grade fizz on a David Arkenstone CD. One track features some pretty mid/bass heavy synth swells and the speakers are giving me some crackle on those. The speakers seem otherwise sound, so I'm inclined to think they're not the source of the issue - particularly with the full drop-outs from a few days ago.

The only thing that springs to mind here is that, in the re-cap I found on here that I used as the template for my own work, the tech replaced the ceramic caps which handle the bass filtering. I skipped this step and stuck to the electrolytics, none of which were upgraded to stacked film. At this point, I'm wondering if having left those components original would give the amp fits at higher volume and explain all of the symptoms thus far.
 
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