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just picked up an sx 1250....some issues..no sound, blowing fuses, etc

markthefixer said:
Right now you have TWO, SEPARATE, FATAL problems in the receiver's power supply. Not leaking crud shorting things out.

Either problem is capable of causing irreversible damage elsewhere in the receiver all on it's own when powered up.

NEITHER problem is a quick fix - or I would have guided you to it.

diodes let current flow one way only - establishing a polarity, shorted diodes let current flow both ways - which kills electrolytic caps because reversing their polarity turns the cap into a short circuit - heating it up instantly.

The 107 board has enough slack on the wires to get at the bottom, the 4 other boards come completely out - most of the work on receivers is done using slack in the wiring to get at the boards for work. Having removable boards is both a luxury and a pita because of the connectors and having to clean them.

The 100v caps WILL HAVE 100 on them instead or 25.

The engine computer caps you speak of could have shorted out and brought everything down, even going as far as popping like a firecracker.

SO can these leaking caps, and the "leakers" were leaking rather than exploding. There is serious damage internally in them, and with ALL THREE on the same circuit showing damage at the same time, it means they are a symptom, not a cause. Shorted diodes d5 and or d6 are the most likely cause, and the capacitor damage will not go away or get better, or even limp along after the diodes are fixed. Chances are they have burned their foil plates together internally - vaporizing the foil connections as the damage creeps along the capacitors toilet paper roll type structure like a cigarette burning as the power is reapplied.
Click to expand...

I've used diodes hundreds of times when I used to install car audio, video, and remote starters and all of that jazz...I didn't realize that if they burnt out they let electricity flow in both directions....that could be a real pain in the arse..haha..

so is there a way I can check diodes d5 and d6 with a meter?

also...where should I be weary of being electricuted..haha..i mean, I have had this unit unplugged for a few days...but I know capacitors store electricity..so i'm sure those 4 big ones could zap me, correct? i'm more familar with DC where you are less likely to be electricuted...what should I stay away from in the receiver?
 
when testing the voltage at the big caps, i'm setting my meter to ac voltage right? or are these dc?

ok...back to the bench now..so here's where I am at...to answer some of your questions:

BOARD 106:

the 25v 1000uf cap on the 106 board is leaking out of the side actually..it's hard to see, but it looks like the side of it busted open...it's the hard to see cuz it's the underside closest to the circuit board...but it has quite a bit of "goo" coming out of it..
there's two big caps in teh middle..it's hard to read them but it looks like 80v 200uf...they are both leaking from the bottom by their terminals onto the circuit board...there's also a 16v 220 uf that is started to leak a tiny bit...

BOARD 107:
both 25v 470's are leaking...both looked like they cracked open from the sides...the goo has gotten on both diodes....in addition, the top 100v 470uf is cracked on the side and leaking a tiny bit...everything else looks as it should....
you had mentioned diods d1-d6...i only see two diodes on this board....I tested both and this is the result: if I put the neg lead on the cathode the pos lead on the anode, i get the results I should...about .5 volts....if I reverse it, I get a beep from the meter but then the numbers slowly go back down to "1." which is what my meter reads when the leads are left idle and not touching eachother...open circuit in other words....NOW if I test the diode with the pos on the cath and neg on the anode WITHOUT doing it reversed first, it will just read 1., open circuit...if I do it neg on cath and pos on anode FIRST and THEN flip them, it will take a few seconds until my meter comes back down to 1....it's like it's draining the .5 volts from first if that's possible....is this normal? also, how the heck to i release the 107 board to free up some slack?
 
The smooth hard brown goop is assembly glue, leaking caps look like puke, not hard brown goop.

The board is supported by plastic posts, the top part of the plastic is hollow and it squeezes in a bit to allow the board to be wiggled up the post - VERY carefully.

You are seeing the charging of the capacitors connected to the diodes, to get accurate readings, one leg of the diode needs to be desoldered

BUT

IF the diodes were short circuited, the numbers would be closer to zero, in both directions. unmistakable and much less influenced by the circuit.

I don't think the diodes are bad, based on the readings you posted, and remembering that most newcomers don't know about the brown assembly glue.
 
markthefixer said:
The smooth hard brown goop is assembly glue, leaking caps look like puke, not hard brown goop.

The board is supported by plastic posts, the top part of the plastic is hollow and it squeezes in a bit to allow the board to be wiggled up the post - VERY carefully.

You are seeing the charging of the capacitors connected to the diodes, to get accurate readings, one leg of the diode needs to be desoldered

BUT

IF the diodes were short circuited, the numbers would be closer to zero, in both directions. unmistakable and much less influenced by the circuit.

I don't think the diodes are bad, based on the readings you posted, and remembering that most newcomers don't know about the brown assembly glue.
Click to expand...

i'm pretty sure what I saw is the fluid leaking from the cap...it looks similar to the stuff that was leaking from my engine computers...it's a brown/yellish clear substance...

ok..so I just wiggle that board off of it's posts? now screws or anything? i'll try to get that removed when I get home from work...

so if the diodes aren't bad, what are you thinking? I'm started to feel brave about re-capping the 106 and 107 board...although we'll see how much slack I get on the 107..haha...I feel ok about recapping..i just don't know about the other stuff...I hate the idea of removing EVERYTHING and reinstalling them..i'm always afraid i'll run the risk of a bad solder joint that could make my work efforts a waste...as of now I have some bad caps on both boards....do you think it could be any issue somewhere else in the receiver? one of the other boards?
 
update:

I just pulled the 2 power amplifier boards (048) and both looks perfect..no leaking caps or burning or anything obvious....i also pulled the protection circuit assembly (091) and it looked fine as well...although there's a section on the edge where it looks like there's 2 paper towel roll looking things..haha...the board looks slightly discolored there..possibly burned? it's a darker shade of brown, but I think it's my imagination getting a head of me...anyways, everything looked fine for the most part....and I was able to pull the 107 board....very easy...

also...i'm now not sure if that goo I saw is leaking caps or assembly glue now....it's really hard..and clearish brown......

anyone have any pics of leaking caps or this assembly glue?

so yeah, where should I go next? any ideas?
 
91rtstealth said:
update:

I just pulled the 2 power amplifier boards (048) and both looks perfect..no leaking caps or burning or anything obvious....i also pulled the protection circuit assembly (091) and it looked fine as well...although there's a section on the edge where it looks like there's 2 paper towel roll looking things..haha...the board looks slightly discolored there..possibly burned? it's a darker shade of brown, but I think it's my imagination getting a head of me...anyways, everything looked fine for the most part....and I was able to pull the 107 board....very easy...

also...i'm now not sure if that goo I saw is leaking caps or assembly glue now....it's really hard..and clearish brown......

anyone have any pics of leaking caps or this assembly glue?

so yeah, where should I go next? any ideas?
Click to expand...

It could be darker, there is some natural heat at this point, and unless it gets way out of hand, all we do is check to be sure the solder joints haven't cracked - although the foil could be fragile there from the heat , so caution and a gentle touch is needed.

It is 95 % likely it is glue, and that the work on the 106 board will get you working again.

BUT, at my direction, there are a few ohmmeter tests to do on the amp cards as long as they are out, to check for shorted caps on the high voltage lines.

also when pulling the amp cards be very very careful for the component that is soldered to the amp board BUT MOUNTED ON THE HEAT SINK, the little leads love to break off flush to the body of the component, so only bend them 1/4 inch or more AWAY from the component's body. If te lead is broken and power applied, the output transistors will be instantly destroyed. So when it all goes back together - we check that very carefully.

REMEMBER, now that the pins have been disconnected from their connectors, they HAVE TO BE SHINED UP so that good electrical contact is restored when they are plugged in. Bad contact can blow things up.... Believe it or not, besides brasso polish, pencil erasers work.
 
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markthefixer said:
It could be darker, there is some natural heat at this point, and unless it gets way out of hand, all we do is check to be sure the solder joints haven't cracked - although the foil could be fragile there from the heat , so caution and a gentle touch is needed.

It is 95 % likely it is glue, and that the work on the 106 board will get you working again.

BUT, at my direction, there are a few ohmmeter tests to do on the amp cards as long as they are out, to check for shorted caps on the high voltage lines.

also when pulling the amp cards be very very careful for the component that is soldered to the amp board BUT MOUNTED ON THE HEAT SINK, the little leads love to break off flush to the body of the component, so only bend them 1/4 inch or more AWAY from the component's body. If te lead is broken and power applied, the output transistors will be instantly destroyed. So when it all goes back together - we check that very carefully.

REMEMBER, now that the pins have been disconnected from their connectors, they HAVE TO BE SHINED UP so that good electrical contact is restored when they are plugged in. Bad contact can blow things up.... Believe it or not, besides brasso polish, pencil erasers work.
Click to expand...

damn..i already put the amp boards and protection board back in..haha...oh well, they aren't impossible to remove again....and I didn't notice anything that was mounted to the heat sinks from the board, unless you are talking about the little "half square" thing that was held in place by a screw?

and yeah, i figured i'd have to clean up those pins when i'm all finished...

ok well I guess i'll end up re-building the 106 board...DAMN! haha...do I have to replace EVERYTHING on the board, or are there a few key things to replace? I just worry about all of those solder connections...i'm sure one or a few will be a pain in the arse to solder or unsolder, therefor I could leave a bad solder joint which could ruin my whole project and piss me off very much..haha...anyone have a spare 106 board I could just throw in to try? hah...

this is what I am thinking happened, but I may call my mechanic to ask for more details..he said his buddy gave it to him and it worked for about 6 months....however, like most shops, or restaurants, I bet he had several speakers run thoughout his shop with very thin and LONG speaker wires...therefor creating lots of resistance...and some of those guys have a tendency to "daisy chain" a few speakers on one lead....so i'm better the amp was working overtime....i've seen that before...miles of thin speaker wire creating a heavy ohm load....if this is the case, what would it damage on the receiver?
 
so where should I start? I'm ready to start messing around with this thing....I was thinking of starting by just ordering the caps and replacing them..what do you think?
 
The demonstrated problem is on the 106 card, so do ALL parts I listed on it. It doesn't help to piecemeal an assembly and NOT get the failed parts, you have damaged transistors, MAYBE caused by a failed capacitor. Other parts - like the zener diodes, could have been blown away during the failure, or stressed to the point of failure, just waiting to fail when the power is turned on with nice shiny new transistors to destroy...

Preventatively, you could replace the protection circuit's parts that are known to eventually die (for a buck or two more).


Then we regroup when the power supply is working, to see if the amps work, or if they have been hurt.
 
wait..i think i'm getting confused...by "damaged transistors" are you referring to the 8 transistors within the heatsinks on the sides? or are their transistors on the 106 board?

I just want to make sure I order the right stuff....am I just ordering the parts for the 106 board, or do I need some other parts?
 
you spoke of "I was thinking of starting by just ordering the caps and replacing them", on the 106 board?

my parts list includes transistors for the 106 board. what I posted emphasized that all the parts for the 106 board be done before re-applying power.
 
91rtstealth said:
ok cool...so if I Just copy that BOM from:
http://www.audiokarma.org/forums/showpost.php?p=4115434&postcount=89

paste it in the ezbuy section, purchase, and get to work?
Click to expand...

yes.

do one part at a time in order to not confuse them with each other, with the capacitors polarity being important, the plus lead is usually longer on the replacement caps, the minus lead is marked with a line of - minuses on the cap's body . on the board there is usually a + near the positive hole and a line through the negative hole that sticks out from under the component.
Pay attention to the polarity when removing each and every capacitor and when in doubt, use the "as found" orientation.

read this thread:
http://www.audiokarma.org/forums/showthread.php?t=43186
to find out about the three transistor leads, their names, and how to identify which lead goes where by the symbol that is printed on the pc board under where each transistor is to be installed.

I'm not tossing you in the deep end here, just giving you initial information so we can have productive discussions how to do things on the board. S o when you start the reaction is not :yikes: but rather ah hah!! - that's what he was yammering on and on about...
 
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91,

Good luck attempting the rebuild. I hadn't done much solid state work before bringing an SX-1080 back to life....all with MTF's and EW's and others' great guidance here on AK. Their advice and directions are like gold. Ask questions and follow their leads precisely. You'll be very happy when your 1250 is singing like new. Best to you on the project!
 
ok..thanks..i figure I will start by doing all of the caps since I have done that before..now as far as everything else goes, do I just match them up by color and/or appearance? the caps have uv and voltage printed on them, so it's easy to just match them up and repalce them old with new...but what about the other stuff..just base it off of color and appearance?

also...I know with boards in the past, I had a heck of a time getting some old cap leads removed...sometimes they break off and them I have to sit there with a solder iron and TINY tweezers tryign to get a lead that's about a nanometer in size out of the board..haha..any tips for unsoldering leads?
 
yikes....three items are backordered..this one isn't available until april of next year!

Aluminum Electrolytic Capacitors - Leaded 100volts 47uF 20% 10X16 5LS
 
you snooze, you lose....

replacements:

512-KSC2690YSTU|1
647-UPW2A470MPD6|2
647-UPJ2A221MHD6|1

that last one I had to use a switching supply cap (made for electromagnetic hell, and then only 5,000 rated working hours instead of 10,000 hours) at twice the price ($0.89 to $1.73 ea) but since there's only one used...
 
markthefixer said:
you snooze, you lose....

replacements:

512-KSC2690YSTU|1
647-UPW2A470MPD6|2
647-UPJ2A221MHD6|1

that last one I had to use a switching supply cap (made for electromagnetic hell, and then only 5,000 rated working hours instead of 10,000 hours) at twice the price ($0.89 to $1.73 ea) but since there's only one used...
Click to expand...

sounds good...placing the order as we speak...as soon as I get it, I'll start with switching the caps since I am familiar with that...any tips anyone for dealing with stubborn cap removal?
 
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