Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting Audio Equipment
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 04-07-2017, 05:45 AM   #1
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Question M-Audio GSR18 speaker, powers on but no sound.

This is a big powered sub, it appears to power on ok (lights come on) but there's no sound from the speaker, not even crackling/pops/hissing. I took the actual speaker out and tested it passively using another amp and it did output music I played (all be it very quietly but as I say I only tested it passively) so that seems to work.

The sub has been used outside a lot and it seems to have been stored in somewhat cold/damn conditions. When I took the circuitry out to have a look I could see straight away there's lots of corrosion on many of the metallic parts and around some solder joints and there's some sort of residue (likely from damp) in places on the PCB.

The caps all look sort of ok I guess, no apparent leaking or bulging, except perhaps for one of the big ones (bottom left in the third picture). It does look ever so slightly bulged but I can't really tell if actually is or if it's just my eyes playing tricks. And there's a small one not far from it that looks a bit suspect (4th picture). Beyond testing voltages I can't do anything else (no oscilloscope) so I post here on the off-chance any of you pros could shed some light on it.

I haven't had any luck locating a schematic for the thing either. M-Audio haven't made these speakers for years apparently.

Thanks in advance!
Attached Images
File Type: jpg IMG_1482.jpg (555.1 KB, 39 views)
File Type: jpg IMG_1483.jpg (574.4 KB, 37 views)
File Type: jpg IMG_1484.jpg (553.6 KB, 38 views)
File Type: jpg IMG_1485.jpg (540.6 KB, 35 views)
File Type: jpg IMG_1487.jpg (428.3 KB, 31 views)
File Type: jpg IMG_1488.jpg (574.4 KB, 40 views)

Last edited by Xandros; 04-07-2017 at 05:49 AM..
Xandros is offline   Reply With Quote
Old 04-07-2017, 05:57 AM   #2
Khron
Badcaps Veteran
 
Join Date: Sep 2006
City & State: Valkeakoski
My Country: Finland
Line Voltage: 230VAC 50Hz
I'm a: Professional Tech
Posts: 1,128
Default Re: M-Audio GSR18 speaker, powers on but no sound.

If you don't have an oscilloscope available, do you have any (other) test equipment?
Khron is offline   Reply With Quote
Old 04-07-2017, 07:04 AM   #3
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Only a multimeter. It has a few useful capabilities but it's nothing special.

To be honest I was hoping for an easy fix, like I'd pull the board out and see something obviously wrong with it such as an exploded/leaking/buldged cap or two or perhaps broken solder joints that I could easily touch up but beyond the corrosion there doesn't seem to be anything visibly wrong with it. I knew right from the start if it was anything more complex wrong with it I was going to be out of my depth. Total hobbyist here you see.

Last edited by Xandros; 04-07-2017 at 07:07 AM..
Xandros is offline   Reply With Quote
Old 04-07-2017, 09:23 AM   #4
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 1,648
Default Re: M-Audio GSR18 speaker, powers on but no sound.

do you hear the relay click ?
you can build a signal tracer with a .01uf capacitor and use your working amp to listen .
petehall347 is offline   Reply With Quote
Old 04-07-2017, 10:48 AM   #5
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

I don't hear anything when I power it on, no clicks or buzzing or... Well anything. Also I can't use the other amp though, it was just a small thing from a stereo we used to test the speaker that wasn't mine and I no longer have access to it (not for a good few weeks anyway).

Last edited by Xandros; 04-07-2017 at 10:52 AM..
Xandros is offline   Reply With Quote
Old 04-07-2017, 01:53 PM   #6
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,733
Default Re: M-Audio GSR18 speaker, powers on but no sound.

http://www.badcaps.net/forum/attachm...0&d=1491561338
It looks like one of the transistor pin (next to c73) is not soldered proeprly, some for the one next to c69 (I know it is double-sided board so it may make contact on the bottom side). So you should look really close at the boards.
I also need good straight shot of the top and bottom side of the board to see how the power relay is driven.
__________________
Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
budm is offline   Reply With Quote
Old 04-07-2017, 03:45 PM   #7
petehall347
Badcaps Veteran
 
Join Date: Jan 2015
City & State: worcester
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 1,648
Default Re: M-Audio GSR18 speaker, powers on but no sound.

pic 2 ..
q1 looks strange and what is that above it ?
d6 looks wonky but might be ok .
also see some solder joints that might be bad .
i also noticed the big transistors arent sitting flat on the heatsink .pic 6
petehall347 is offline   Reply With Quote
Old 04-08-2017, 06:17 AM   #8
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Quote:
Originally Posted by budm View Post
http://www.badcaps.net/forum/attachm...0&d=1491561338
It looks like one of the transistor pin (next to c73) is not soldered proeprly, some for the one next to c69 (I know it is double-sided board so it may make contact on the bottom side). So you should look really close at the boards.
I also need good straight shot of the top and bottom side of the board to see how the power relay is driven.
Good spot, they do seem soldered properly on the underside though;

IMG_1497.jpg

Here's as best shot I can get with my phone camera top and bottom of both boards with a couple of closeups:

front.jpgback.jpgfrontleft.jpgfrontright.jpgbackleft.jpg

Quote:
Originally Posted by petehall347 View Post
pic 2 ..
q1 looks strange and what is that above it ?
Not sure. There are a few splodges similar to it dotted across the board, it seemed to wipe off and didn't appear to be damage to the PCB under it. A not so focused closeup:

IMG_1494.jpg

There's this weird splodge too on the other board;


IMG_1495.jpg

Quote:
d6 looks wonky but might be ok .
also see some solder joints that might be bad .
i also noticed the big transistors arent sitting flat on the heatsink .pic 6
Yea any unsoldered spots I'd seen seem to be soldered on the underside OK. Also with the big transistors I think that's just because I'd already unscrewed the clamps that were holding it down as I'd already looked at the underside of the board so it wasn't sitting flush when I took those pictures.
Xandros is offline   Reply With Quote
Old 04-08-2017, 11:01 PM   #9
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,733
Default Re: M-Audio GSR18 speaker, powers on but no sound.

I will give test points once I look at all the pictures.
Looking at the bottom side of the power supply/power amp board, that black power relay should come on when the unit detects the incoming audio otherwise it will stay in standby mode so the power supply is running at very low level until the relay is turned on.
So for sure you do not hear any clicking sound coming from the relay?
This is going br tough to trace because it is double-sided board.

Last edited by budm; 04-08-2017 at 11:19 PM..
budm is offline   Reply With Quote
Old 04-10-2017, 11:21 AM   #10
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Quote:
Originally Posted by budm View Post
So for sure you do not hear any clicking sound coming from the relay?
Not a thing, even with audio being piped into one of it's two inputs it just sits there quiet as a mouse.
Xandros is offline   Reply With Quote
Old 04-10-2017, 02:20 PM   #11
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,733
Default Re: M-Audio GSR18 speaker, powers on but no sound.

http://www.badcaps.net/forum/attachm...6&d=1491649247
See that U3 (not used) is ? Check the DCV between cold side GND and Pin 4, cold side GND and pin 8 to see what you have.
BTW, you know how to count the pins of the IC, right?

Last edited by budm; 04-10-2017 at 02:28 PM..
budm is offline   Reply With Quote
Old 04-12-2017, 06:18 AM   #12
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Quote:
Originally Posted by budm View Post
http://www.badcaps.net/forum/attachm...6&d=1491649247
See that U3 (not used) is ? Check the DCV between cold side GND and Pin 4, cold side GND and pin 8 to see what you have.
BTW, you know how to count the pins of the IC, right?
I think so but just to be sure; I looked at the IC next to it which has a stripe on one side as do the other chips in the vicinity and based the pin layout on them.

frontleft.jpg

That right?
Xandros is offline   Reply With Quote
Old 04-12-2017, 10:02 AM   #13
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,733
Default Re: M-Audio GSR18 speaker, powers on but no sound.

That is correct pinout for the IC.
budm is offline   Reply With Quote
Old 04-12-2017, 01:06 PM   #14
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

pin 4 seemed to hover around 1.03v, pin 8 hovered around 0.61v
Xandros is offline   Reply With Quote
Old 04-12-2017, 02:02 PM   #15
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,733
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Quote:
Originally Posted by Xandros View Post
pin 4 seemed to hover around 1.03v, pin 8 hovered around 0.61v
You are sure that meter is good? What did you use for GND ref. point?
If it is, then those OPAmp ICs are not getting the +/- DCV run.
budm is offline   Reply With Quote
Old 04-12-2017, 02:29 PM   #16
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Yea I must have done something wrong. I just did it again, now both pins are reading 2.6v or there abouts.

Sorry about that! Not sure if that makes any difference though, but anyway I guess before with the other readings I must have knocked the meter onto a different range or something. This time I made sure it was on dcv autorange and just let it do its thing. As for the ground, I'm using the earth wire as cold ground, presumed that was right since it's attached to one of the screwholes/chassis.
Xandros is offline   Reply With Quote
Old 04-12-2017, 02:59 PM   #17
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,733
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Check the resistance between pin 1 and GND, pin 2 and GND on the input board.
Check the DCV between the two legs of each one of those two caps (marked in the picture) on the power supply/Amplifier board.
Attached Images
File Type: jpg VCCs for opamps.jpg (435.5 KB, 9 views)
File Type: jpg VCC Regulators.jpg (1.97 MB, 14 views)
budm is offline   Reply With Quote
Old 04-12-2017, 02:59 PM   #18
budm
Badcaps Veteran
 
budm's Avatar
 
Join Date: Feb 2010
City & State: S.F. Bay area
My Country: USA
Line Voltage: 120V 60Hz
I'm a: Knowledge Seeker
Posts: 34,733
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Quote:
Originally Posted by Xandros View Post
Yea I must have done something wrong. I just did it again, now both pins are reading 2.6v or there abouts.

Sorry about that! Not sure if that makes any difference though, but anyway I guess before with the other readings I must have knocked the meter onto a different range or something. This time I made sure it was on dcv autorange and just let it do its thing. As for the ground, I'm using the earth wire as cold ground, presumed that was right since it's attached to one of the screwholes/chassis.
I expect about 12~15VDC.
See post 17.
budm is offline   Reply With Quote
Old 05-02-2017, 08:43 AM   #19
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

Hello, sorry for the extremely late reply. I went on holiday around Easter and have been really busy since I got back and sorting this thing out has been an afterthought. But anyway I got around to testing the resistance today and it just keeps reading OL on those pins and gnd. Didn't bother with the caps yet.

Unless OL was an expected result, then I think you may be right and my meter's kaput. Yet another thing goes wrong when I'm trying to fix something else. Story of my life that is.
Xandros is offline   Reply With Quote
Old 05-28-2017, 06:16 AM   #20
Xandros
Member
 
Join Date: Dec 2014
City & State: London
My Country: England
I'm a: Knowledge Seeker
Posts: 51
Default Re: M-Audio GSR18 speaker, powers on but no sound.

OK so, after another lengthy absence I've finally done the tests you suggested.

Resistance between pin 1 and gnd is 3.270kΩ and pin 2 and gnd is 2.950kΩ

I tested the voltage of those caps, one reads aprox 20v the other is approx 19v.

Cheers.
Xandros is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2019
Powered by vBulletin ®
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 08:39 AM.
Did you find this forum helpful?