Electronics Question on a REL Subwoofer

thedoc46

thedoc46

thedoc46

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Hi,

I have a REL Strata Subwoofer, from quite a while ago. Anyway the thing now pops at low freq and loud scenes.

I called REL up and they said its a resistor on the circuit board that's gone and this is a common problem. However they want a tidy sum to fix it.

I'm no electronics whizz, but I've done small amounts of soldering in the past. I can easily remove the amplifier board out of this sub...However I have no idea how to find the culprit. There's a load of resistors on this board. So to all you budding electronics whizz's. How can I find which resistor is at fault, so that I can un-solder it and re-solder in an exact replacement? Is this something that would need just a simple tool to diagnose? Or does it require inside know how of which resistor does what? Failing REL, do you reckon any electronics TV repair service as such would be able to diagnose and repair? I've rather not send my circuit board halfway around the world.

Please advise.
 
Any resistor I have seen fail is usually a catastrophic failure. Look for burn marks, scorch marks and heat. As for finding it, it may have a part number, but only if it is a large enough surface area. You can get the value by reading the bands on it, but not the wattage or any other characteristics. Best to take it out and have a look. Hopefulyl the point of failure will be readily apparent.
 
BK Electronics made all of these subs for REL. You'll probably find it's got BK's name all over the board.

Give them a phone call:

http://www.bkelec.com/Contact/Contact.htm

Whatever you do, don't email them. They're a small company and emails are very low on their priorities. Phone every time. :)
 
So how many different types of resistors are there? I live in the USA now. What are my chances of being able to source the right component from a local radio shack or whatever?

I called the REL importer/supplier in the USA. and they said they do not sell the resistors to the public, and they replace more than one.. Kinda got the impression he was talking bull, and happy to make $200 here and there on these repairs, that probably only cost him 10cents and 10mins of his time. Even so for $200 its cheaper than a new sub, and the new one wouldn't be the same quality as the REL.

I could however just take it to a local TV repair man.. Would he have the tools and parts? and I ask that question, in mind that I have no idea how commonplace resistor types are ?
 
If you look up resistors online you'll get a visual idea of the things being discussed. Resistors fall in to two common categories of physical size. There's the larger components with bits of wire or tags on the end for soldering on to a board.
Resistor-Color-Coding.jpg
They're easy to deal with.

Then there's the smaller surface mount components which can be as small as a millimeter wide and are a PITA to handle
SMDsizes.jpg


All are replaceable, but the surface mount ones (SMDs) need a special hot air gun rather than a standard soldering iron. A decent repair shop will carry standard values of the large type resistors, and might even have the gear for dealing with SMDs, you'll have to ask. If they don't have the stock then the parts are readily available from electrical wholesalers. They might just have to buy in minimum order quantities though, so don't be surprised if you foot the bill for a few dollars rather than a few cents.

Have a look at your amp board. Does it look like you have just the larger types or some SMDs as well?
 
You can still repair SMD resistors with a normal soldering iron. I soldered an entire surface mount board with one. To make a small SMD desoldering tool, use a paperclip bent to match the device legs.

There are even more variety than those. You can get a variety of power resistors, and without opening it up, its difficult to tell what you have!
 
Thanks fella's

Here's a pic of the board.

aug11081.jpg


I'm no expert, but I can't see anything that's obviously burnt out. There are two small resistors that look dark on the end, but I'm not sure if that's intentional or not? Maybe someone can confirm ?

aug11082.jpg


Here's a higher res picture of those two resistors.

aug11085.jpg
 
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Those are diodes. The stripe denotes which side is which.

Do the caps (Black cyclindrical things with 2 wires underneath) look swollen at all? I am looking at the ones in the sticky up board, they look funny, could just be the picture though!
 
PhillyDee said:
Those are diodes. The stripe denotes which side is which.

Do the caps (Black cyclindrical things with 2 wires underneath) look swollen at all? I am looking at the ones in the sticky up board, they look funny, could just be the picture though!
Click to expand...

No the black cyclindrical things are attached to the loudspeaker banana inputs & outputs, which are used if you want to connect your sub to small satellite speakers, and if you just want to filter the low freq away from the satellites to the sub. I've always used the phono input. Besides those speaker input/outputs have never been used, so i don't think they are part of the problem. Plus they have some clear kind of coating on them that's probably giving the impression that they are swollen.
 
Can we have a close-up of that resistor just below the two large blue capacitors?

It appears to be a 10 ohm but looks like it might have some discoloration in the middle.

Edit: Additional thoughts.. I have a vague memory of repairing a REL where one of those large 470 ohm resistors had failed. I'm talking about the light coloured ones with yellow,violet,brown bands that are shown in your high res picture of the diodes.

Do you have a multimeter? I'd be interested to know what voltage you have across those two diodes and the other pair of diodes that are below the first two (just above the two black capacitors).

From what I can tell from your pictures, these components, together with the large green 3W resistors are forming a positive and negative power supply for the input board.
 
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Sinopa said:
Can we have a close-up of that resistor just below the two large blue capacitors?

It appears to be a 10 ohm but looks like it might have some discoloration in the middle.

Edit: Additional thoughts.. I have a vague memory of repairing a REL where one of those large 470 ohm resistors had failed. I'm talking about the light coloured ones with yellow,violet,brown bands that are shown in your high res picture of the diodes.

Do you have a multimeter? I'd be interested to know what voltage you have across those two diodes and the other pair of diodes that are below the first two (just above the two black capacitors).

From what I can tell from your pictures, these components, together with the large green 3W resistors are forming a positive and negative power supply for the input board.
Click to expand...

Sure, here you go. It doesn't look burned to me. Actually I can't see anything that is burned, or discoloured apart from perhaps those diodes. I also do not have a multimeter. Unfortunately I think I have no choice but to now leave this to the pro's to fix. :(

aug11086.jpg


aug11089.jpg
 
Get a multimeter and test across each resistor to see if you've got an issue - as mentioned though, for a resistor to fail in short timescales is usually due to burning out.

What's on the vertical board that we can only see the underside of?
 
Makhaira said:
Get a multimeter and test across each resistor to see if you've got an issue - as mentioned though, for a resistor to fail in short timescales is usually due to burning out.

What's on the vertical board that we can only see the underside of?
Click to expand...

Vertical board is just where all the switches and knobs and power inputs go.

I don't have a multimeter and even if i did, i wouldn't be able to read the readings, since I clearly do not know enough about this kind of stuff. Was hoping to find something obvious. But since its not obvious I think I'm just going to bite the bullet and either get this repaired or just buy a new sub. Repair is $200 and a new HSU STF-2 sub is $350. Problem is with the repair, i'm still repairing a 15yr old sub. Albeit a good one, but still 15yrs old.
 
Have you asked the question over at the American AVS Forum? www.avsforum.com


It may be possible that a forum member there can recommend a repair shop somewhere local'ish to you. This forum and the UK site AVForums are a wealth of local knowledge, but AVS Forums is predominantly a place for American & Canadian enthusiasts. There's a better chance you could find someone closer to home with the skills to help you.

Good luck
 
lucid said:
Have you asked the question over at the American AVS Forum? www.avsforum.com


It may be possible that a forum member there can recommend a repair shop somewhere local'ish to you. This forum and the UK site AVForums are a wealth of local knowledge, but AVS Forums is predominantly a place for American & Canadian enthusiasts. There's a better chance you could find someone closer to home with the skills to help you.

Good luck
Click to expand...

Yes, I'm a member there too. However IMHO, its not a very good forum. I've rec'd a lot more help and better guidance from this particular thread. I think British forums are 1000x better.
 
There's more than just switches and input sockets on that vertical board.

All the components at the right hand edge of the main board form a power supply for that vertical board. Switches and input sockets don't need a power supply.
 
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