Sony STR-DB940 pulled back from the brink

[Sudum Gumudu]

A month ago, my Sony STR-DB940 began acting up. The center channel would cut out, and there were constant clicking from the protection relays. Alas, it's given me eight years of faithful service, but I wasn't prepared to do the quite extensive homework in preparation for a new AV receiver purchase just yet. Blu-Ray is still a little bit too expensive, and a new AVR isn't necessary until then.
Last Saturday, I thought, what the f**k, having it repaired isn't cost effective, and its screwed like this anyway, so I decided to have a go at fixing it myself.
I had researched the problem on the Net beforehand. This relay thing is a somewhat common problem with these receivers it seems. The speaker protection relays solder joints becomes bad with age. I opened it, pulled every board out to get to the bottom one. There was four blue components that upon googling the designation indeed showed themselves to be the speaker protection relays.
Not having the service manual thus knowing which relay went to which speakers, I redid all 24 solder joints, and managed to get it put together again,and it didn't say KABOOM when powered on
I have played six movies on it, and I still have sound in all five channels.

[Logistics]

Congrats! It's always nice to hear a story with a happy ending. My monitor was having some problems such as dimming intermittently and uhh... it had some other problem... can't remember what it was, now. Anyway, I took it apart and fixed as many solder joints as I could, including a set that looked really old and cold, and it went back to working great. I still see the dim thing once in a while, but I think people said it was old caps. I noticed the refresh also caused the monitor to switch modes very quickly. When I would enter a program, such as a game, that wanted to change the resolution and such around, it would take a moment to switch over, but not it's much closer to instantaneous. Interesting things happen after rewetting solder joints. :p

[Ethan McF]

Hey dude, im new here, been searching the internet for a while regarding my sony STR-DB940, same problem, the relay is chattering constantly, i will get sound for anything between 2 seconds, to 10 hours, but it will constantly chatter, now ive opened the unit, and am lost al ready, to me the amp is dead, so any help would be great, is it possible for you to give me a little more info on what you done to fix the problem, because i love this amp

Cheers,

Ethan

[PlainBill]

Originally Posted by Ethan McF

Hey dude, im new here, been searching the internet for a while regarding my sony STR-DB940, same problem, the relay is chattering constantly, i will get sound for anything between 2 seconds, to 10 hours, but it will constantly chatter, now ive opened the unit, and am lost al ready, to me the amp is dead, so any help would be great, is it possible for you to give me a little more info on what you done to fix the problem, because i love this amp

Cheers,

Ethan

Free advice (worth every penny I'm charging for it).

1. When we are not meeting face to face, clear communication is essential. This 'stream of thought' stuff gets old fast. Use short, simple sentences.

2. Most of the people here are willing to help you, but you have to help us. If you don't hear from the OP, take a few pictures and attach them to your next post. That will let us see what you are looking at.

3. In the nicest way possible, what are your skills? Have you ever used a soldering iron? Are you able to take this receiver apart and put it back together? From the sounds of this, it is almost a novice project, but I'd hate to have you try to do it, then wind up with some burns from the soldering iron, bleeding from stabbing yourself with a screwdriver, and your hair singed when the STR-DB940 blew up!

PlainBill

[Ethan McF]

Originally Posted by PlainBill

Free advice (worth every penny I'm charging for it).

1. When we are not meeting face to face, clear communication is essential. This 'stream of thought' stuff gets old fast. Use short, simple sentences.

2. Most of the people here are willing to help you, but you have to help us. If you don't hear from the OP, take a few pictures and attach them to your next post. That will let us see what you are looking at.

3. In the nicest way possible, what are your skills? Have you ever used a soldering iron? Are you able to take this receiver apart and put it back together? From the sounds of this, it is almost a novice project, but I'd hate to have you try to do it, then wind up with some burns from the soldering iron, bleeding from stabbing yourself with a screwdriver, and your hair singed when the STR-DB940 blew up!

PlainBill

Hey, sorry, new here, well im not exactly amazing with stuff like this, ive taken the Amp apart, and completly rebuilt it, yea i can solder etc, but i really have no idea on where im going with it, because when i took the amp apart, and from looking at the Service manual, i can't seem to find the relay, so i just need a little help, if anything is avaliable.

Should i attatch images of all the boreds i can take out of the amp?

Thanks, and thanks for the reply,

Ethan

[PlainBill]

Originally Posted by Ethan McF

Hey, sorry, new here, well im not exactly amazing with stuff like this, ive taken the Amp apart, and completly rebuilt it, yea i can solder etc, but i really have no idea on where im going with it, because when i took the amp apart, and from looking at the Service manual, i can't seem to find the relay, so i just need a little help, if anything is avaliable.

Should i attatch images of all the boreds i can take out of the amp?

Thanks, and thanks for the reply,

Ethan

That would probably be best. The OP indicated it was the bottom board, so try to get especially good pictures of that. I'll do a little searching and see if I can find something helpful.

PlainBill

[Ethan McF]

Here are some of the images ive taken, ive found the 4 blue things on the main bored!

Ethan

[PlainBill]

Originally Posted by Ethan McF

Here are some of the images ive taken, ive found the 4 blue things on the main bored!

Ethan

Ahem!! That's board!!! Now all you have to do is get to the other side of the board and solder all the pins on the relays. You've already done the hard part - getting the receiver apart. Don't make the mistake of skipping pins 'because they look ok'.

PlainBill

[Ethan McF]

Originally Posted by PlainBill

Ahem!! That's board!!! Now all you have to do is get to the other side of the board and solder all the pins on the relays. You've already done the hard part - getting the receiver apart. Don't make the mistake of skipping pins 'because they look ok'.

PlainBill

Sorry, from a bad school :|

So the blue things, just solder all the 16 legs again, because there are only 4 legs per relay.


Thanks for your help

Ethan

[Ethan McF]

Originally Posted by Ethan McF

Sorry, from a bad school :|

So the blue things, just solder all the 16 legs again, because there are only 4 legs per relay.


Thanks for your help

Ethan

Sorry just realised after checking throught the service manual, there are 6 legs per relay, so 24 in total.

[PlainBill]

Originally Posted by Ethan McF

Sorry, from a bad school :|

Thanks for your help

Ethan

Mrs. Stewart, my grade school teacher would have said "There are no bad schools. There are bad teachers and bad students."

Glad to help.

PlainBill

[Ethan McF]

Originally Posted by PlainBill

Mrs. Stewart, my grade school teacher would have said "There are no bad schools. There are bad teachers and bad students."

Glad to help.

PlainBill

That would be correct!

I'll let you know how i get on in fixing the amp!


Thanks

Ethan

[SimonM]

I've had the same problem with mine, B speakers didn't work and it kept clicking and sometimes coming up with "protector"

I resolder the relays today as described above. So far so good, it's been over an hour. Hopefully this solves it for me as I'm not ready to give up yet, I need the phono inputs, my new amp doesn't have this!

[SimonM]

Well it's been a few days now and still working perfectly, fixed!

[Furball]

Another 940 with clicking relays and centre speaker cutting out here.

Have already pulled it apart once and randomly touched up the solder joints on the output stages, which made naff all difference, never thought of doing the relays

Was thinking it was new amp time but I just love the sound this one makes, anyhow thanks for the info here I'll break out the Soldering Iron again and wave it over the relay connections

Will report back and if I have anything further to add to the thread I will.

Furball

[Furball]

Result

4mins work with the soldering iron and job done, all points can be got at via the removeable panel underneath.
It took longer to disconnect and remove the amp from the AV rack than it did to solder up the relays

So far its been running for about 20mins and hasnt clicked or dropped a channel once so recon its cured, also the centre speaker output quality has improved by 50% at least, I just hadnt realised how bad it had got

Many thanks to Ethan and the others who have contributed and for anyone else with the same problem heres a pic of the underside of the amp with the relay points that need touching up in RED, the YELLOW dots are a set of connectors that I also touched up as they looked a bit rough.



I've also added it as an attachment just incase the host of the above drops out

Right time for a film I recon

Furball

[Agent24]

And if the host above does drop out your post will end up with a lovely 404 error or something in it I expect.

That's why we say to upload photos here and not bother with anything else.

Good to know you fixed your Amplifier though!

[bklanecky]

Hey guys.

I found this thread through a Google search, and it sounds like I've got exactly the problem being described here.

I pulled off the bottom access panel of the receiver, and found the points noted in the picture. Thing is, they looked just fine.

I'm no expert on electronics, and I've never soldered anything before. I would consider myself very mechanically adept, so I'm sure I can do it, but I just wanted to be clear on what exactly it was that signifies that a spot needs to be re-soldered. Is it kinda flopped-over? Brown? Black? I couldn't find anything that would set any of those points apart from any of the others in terms of how they look.

Any advice would be greatly appreciated.

[Agent24]

Solder joints should be smooth and shiny.

Bad joints can be dull, cracked, or otherwise don't look good.

If you search Google images for 'Dry solder joint' or 'Cold solder joint' you can see many photo examples.

[notorious]

I have a Sony STR-DB940 which seems to have a problem with the center speaker.
it seems weak and is not as loud as the other channels. i done a reset and even tried increasing that channels db but it still is not right. I am using a optical cable to xbox 360 ps3 and pc and the result is the same. i have tried another cable and even another speaker and no improvement. i noticed furball got a 50% better result when he soldered the relays. do you think I should attempt this?