Electronics Genius Needed!

[S10xGN]

I'm replacing 3 "oozed" caps on my computer sound system that no longer powers up, an old Altec Lansing subwoofer system that (to me) sounds too awesome to chunk out. Of course, Rat Shack has nothing but phones and batteries now, so I had to order them from Amazon. While waiting, got a question:

I had to cut the power leads to get the electronics tray out. I thought I had cut the 2 power wires in different places so I could tell them apart, but after lining them up the cut lengths are the same (DOH!). Will polarity matter since the power supply is from a transformer? Looking at the board, the lines feed into 4 diodes, two aligned from one lead and the other two aligned from the other...

 

[TurboBob]

the 2 wires from the transformer can be switched around without issue (which is why they are the same color......)

Bob

 

[S10xGN]

the 2 wires from the transformer can be switched around without issue (which is why they are the same color......)

Bob

Thanks my little genius! That's what I was hoping for...

 

[TurboBob]

"little"........? apparently we've never met in person......

 

[Razor]

Yupp.. AC has no polarity. DC is a different situation..

 

[dynoman]

If it doesn't power up you might want to check those 4 diodes also , those change your AC to DC , the caps smooth the DC signal.

 

[SloGN]

"little"........? apparently we've never met in person......

Hahaha lol

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[S10xGN]

Thanks my little genius! That's what I was hoping for...

That was a compliment, Bob!

If it doesn't power up you might want to check those 4 diodes also , those change your AC to DC , the caps smooth the DC signal.

Well, those 3 caps were definitely splooged. You can see the big one up front and the two upright ones towards the back have tan goo at their bases. I'll try them first and go from there. Didn't think diodes ever went tits-up...

 

[dynoman]

That tan goo I believe is a type of adhesive used to hold the caps in place because they are bigger components that could vibrate and break the solder joints. On power supplies after checking for a blown fuse ( if there is one ) the bridge rectifiers ( diodes) are the next thing I always check .

 

[TurboBob]

diodes don't fail that often of their own accord.

usually they are murdered by something else.

they most often fail shorted, which will then blow the fuse (again), before you reconnect the transformer test the diodes with an ohmmeter (on diode check range if it has one)

B

 

[S10xGN]

diodes don't fail that often of their own accord.

usually they are murdered by something else.

they most often fail shorted, which will then blow the fuse (again), before you reconnect the transformer test the diodes with an ohmmeter (on diode check range if it has one)

B

Can do, but the fuse was A-OK and it's a small one...

 

[GSTOY]

Can do, but the fuse was A-OK and it's a small one...

As stated above, the goo on the base of the board is to hold them in place. If a capacitor lets loose, you will usually see it at the base of the cap or at the very top you will see a noticeable bulge. Mouser is a great place to get replacement electronic parts. If the power supply is working, I would suspect the IC that is heat-sinked is probably the audio output amp chip. Really need to find a schematic diagram, because without one, your sort off chasing your tail unless your familiar with electronic circuits.

 

[S10xGN]

As stated above, the goo on the base of the board is to hold them in place. If a capacitor lets loose, you will usually see it at the base of the cap or at the very top you will see a noticeable bulge. Mouser is a great place to get replacement electronic parts. If the power supply is working, I would suspect the IC that is heat-sinked is probably the audio output amp chip. Really need to find a schematic diagram, because without one, your sort off chasing your tail unless your familiar with electronic circuits.

Whaaat? I'm no genius, but I'm not buying this. There are 2 dozen other caps on this particular board w/o the goo, and I've seen thousands of caps on dozens of boards before and this is my first time seeing this. Why would they "glue" 3 caps and no others ? ? ? Anyways if replacing these doesn't get it I'm only out $17, the whole thing goes in the sh!tter, and I buy something new...

 

[dynoman]

I started my electronics career in 1974 at Teledyne Packard Bell right out of high school doing TV repair and believe me I've seen thousands of caps glued to the board. Look at the end of the cap where the leads come out, that is where they leak from . Those 3 caps are the largest on the board the rest are smaller and don't need the extra support. I hope the caps fix it, but I doubt it . Sam

 

[S10xGN]

Well, ya'll were right. The new caps did nothing. This Altec is in the trash and a new Klipsch system is on the way...