View Full Version : First Recap, SX-950


AmericasHigh
10-07-2012, 03:27 PM
So my 950 has been having issues since I got it from my dad and a few months ago it finally completely stopped working. I am about 99% sure I know the problem and thus am looking to do a recap.

I think I am just going to start with the AWR 101-C board (Power supply) and have a few questions.

Here are some pictures I took and my list of caps:
http://imgur.com/a/GApHQ

First of all as you can see C15 and C20 burst and leaked all over the board which I am assuming to be the problem with the unit.

As far as I can tell C12, C18, and C19 have already been replaced (by, I assume my dad) so I am unsure if I should bother replacing them.

Lastly I wonder what I should replace the rest with/where to get them.

I am not an EE and have only a rudimentary knowledge of circuits from freshman physics so if you have any general tips let me know. I do know how to solder but never worked with anything this complex before.

Thanks!

EDIT: Since I completely failed in my first analysis of the problem I will attempt to describe what is happening in more detail. Basically the protection relay engages after intermittent listening to the point now that it will not work at all.

ConradH
10-07-2012, 04:41 PM
That just looks like glue, not burst caps. IMO, you're going down the wrong path without getting it on the bench and doing some tests. It's always a huge mistake to dive into a bulk replacement of parts without fixing the fundamental problems first!

http://conradhoffman.com/capchecktut.htm

markthefixer
10-07-2012, 04:56 PM
That's glue. Do you have a prospective parts list, if so post it so it can be vetted for old, compromise and unavailable parts.

Otherwise, if there isn't a canned 950 list waiting, then if you do a specific starter parts list entry project that I will detail, then I will take that parts list and come up with modern part numbers from a quality supplier.

It ISN'T cut and dried....

Marty, Socal
10-08-2012, 01:37 PM
I started a thread a couple months ago that lists the most current recap lists I could find:
http://www.audiokarma.org/forums/showthread.php?t=457663&highlight=recap+list

Here's the direct link to the SX-950 recap list post with a BOM list by MattSD:
http://www.audiokarma.org/forums/showthread.php?t=364598&highlight=sx1250+recap+list

You can cut and past the caps list BOM into the Mouser website to verify the availability of the parts before you order them!

Hope this helps!

AmericasHigh
10-09-2012, 07:41 AM
Sorry it has been a couple days since I posted but I did a little more digging and found some posts related to my problem.

@Conrad, thank you for the guide! I'll read through it and go do some more digging in the receiver today!

@Marty, thank you for that list it will really help me moving forward.

@Mark
I measured my voltages on the AWR-101C and AWM-062 boards according to this thread

http://www.audiokarma.org/forums/archive/index.php/t-353192.html

Below is a google document with my findings (go to sheet 2). I only have an analog MM so my readings are a little off but everything looks good according to the values I know of.

https://docs.google.com/spreadsheet/ccc?key=0AqtjJbCroBa_dGlyWWpybVlGX3J6N0dIbDU0eGxLU 0E

EDIT: I should also point out that the fuses on the AWR-101C board check out fine.

qprhooligan
10-09-2012, 08:16 AM
Sorry it has been a couple days since I posted but I did a little more digging and found some posts related to my problem.

@Conrad, thank you for the guide! I'll read through it and go do some more digging in the receiver today!

@Marty, thank you for that list it will really help me moving forward.

@Mark
I measured my voltages on the AWR-101C and AWM-062 boards according to this thread

http://www.audiokarma.org/forums/archive/index.php/t-353192.html

Below is a google document with my findings (go to sheet 2). I only have an analog MM so my readings are a little off but everything looks good according to the values I know of.

https://docs.google.com/spreadsheet/ccc?key=0AqtjJbCroBa_dGNFYUJoUHk0dVJibGNNQngtRlRFR Wc

EDIT: I should also point out that the fuses on the AWR-101C board check out fine.

You used an analog meter to measure the voltages? If so I think you will have to reverse the leads when taking the negative voltage readings.

AmericasHigh
10-09-2012, 08:37 AM
You used an analog meter to measure the voltages? If so I think you will have to reverse the leads when taking the negative voltage readings.

Ah yes, I am an idiot. The post has been edited to reflect those changes

AmericasHigh
10-12-2012, 10:31 PM
I have noticed that if I engage the mono switch the relay will click into place. Could this narrow down my problem a bit?

markthefixer
10-13-2012, 12:27 AM
First disconnect the preamp out from the power amp in. Pull the jumpers in the back and see if the protection clicks in.

The voltages you posted look fine, for the power supply, what I can see of the amplifier and the protection board. That leaves an amp o/c sense fault, or an intermittent somewhere else on the board. You DID take the voltages when the protection was NOT pulled in and the amp DIS-connected from the speakers?

ALL pins of the protection board should be reported. That would have revealed more about the board.

intermittent protect = probably relay drive transistor on the protection board AWM-062
Protection Circuit Assembly (AWM-062), total rebuild list

AWM-062: C1: .22uF 10v CSSA: 667-ECQ-V1H224JL2 .22uF 50v o/c sense must be stacked film, not little sky blue sanyo can electrolytic
AWM-062: C2: .22uF 10v CSSA: 667-ECQ-V1H224JL2 .22uF 50v o/c sense must be stacked film, not little sky blue sanyo can electrolytic
AWM-062: C3: 330uF 6.8v CEA: 647-UPW1A331MPD 330uF 10v 1/2 of make polarity free capacitor
AWM-062: C4: 330uF 6.8v CEA: 647-UPW1A331MPD 330uF 10v other half of make polarity free capacitor
AWM-062: C5: 4.7uF 25v CEA: 647-UPW1V4R7MDD 4.7uF 35v ac power sense
AWM-062: C6: 100uF 16v CEA: 647-UPW1V101MPD 100uF 35v timing capacitor
AWM-062: Q1-Q2 2SC869-C 512-KSC1845EBU (ln)to-92 ecb 120v .05a .5w 100mhz 150-800hfe $0.05 ea o/c sense
AWM-062: Q6 SSC945-Q 512-KSD1616ALBU to-92 ecb x60v 1a 0.75w 160mhz 135-400hfe $0.09 timing capacitor charge dump to turn off
AWM-062: Q7 2SC1384-R 512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40 relay drive transistor

don't forget to add the 512-1n4004 flyback diode to pins 9 (anode) and 10(cathode).

AmericasHigh
10-13-2012, 02:56 PM
Thank you Mark!

Yeah I took all the readings when the relay was not pulled in and speakers disconnected.

I'm about to measure the other voltages and will put them up shortly

EDIT:

I updated my spreadsheet on google docs with the new readings. Now that the relay circuit is engaged I can't get it to click off so pulling the pre-out/power-in jumpers had no effect.

markthefixer
10-14-2012, 03:01 AM
rebuild the protection, preemptively. maybe later the power supply if we find evidence of overheating (to be described later).

it's easier than finding an intermittent, we usually do preemptive rebuilds of certain circuits when trouble presents itself.

and when it stops, we know it's GONE... of course we try some easy stuff first, depending....

AmericasHigh
10-14-2012, 03:13 PM
rebuild the protection, preemptively. maybe later the power supply if we find evidence of overheating (to be described later).

it's easier than finding an intermittent, we usually do preemptive rebuilds of certain circuits when trouble presents itself.

and when it stops, we know it's GONE... of course we try some easy stuff first, depending....


Thank you again Mark! Celebrated my birthday yesterday and got a new soldering iron so I was kind of hoping it would come to this.

I've also noticed that on the power supply board there is a slight bow as shown here:
http://i.imgur.com/gmPt3.jpg

I checked the board and as stated before didn't see any obvious signs of bad solders but I thought I should mention this.

markthefixer
10-14-2012, 05:43 PM
latest indication is that it's not solder joints, but rather tired caps and transistors