Amplifier subwoofer Gale 3090

Hello guys ,

I'm new on this forum and I got a problem with this amplifier .

So first time I took this subwoofer with amplifier damaged "no power " , I checked the amplifier board and I found two power resistor missing and some smoked board around , I've changed them and now I got power but some smoke comes out from other resistor I can't find a diagram . The amplifier board is poor exfoliates.
Please if is someone here who can help me .
This using Toshiba 2sa1943 transistor
 

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Mooly

Administrator
Paid Member
2007-09-15 8:14 am
The burnt board is probably normal and is due to chemical changes in the material with heat over a long time.

Those two resistors look like they might be part of a simple Zener stabilised power supply as I can see the diodes and caps next to them. They will run very hot. Check the voltage across the Zeners and see if it is reasonable. Both should be the same and maybe in the 12 to 18 volt range.

I think your problems are elsewhere on the board and you really need a diagram for us to advise better.

I can see 4 power transistors and 4 large white resistors.

Have you checked the transistors to see if any read short circuit from C to E?

Also check those white resistors.
 
The board with resistor it's a random picture on my board that resistors was missing and I tries to find what value to complete without that resistors the amp doesn't turn on .

I bought the same value resistors from ebay and now I got power but there is continuos power on the output and some smoke comes out from 47r resistor four of them around the white resistors .
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
OK :) I think you have to be realistic here... this is not going to be a quick fix.

For us to advise you further we would need at least correct diagrams showing the circuitry.

I can see something called 'V301' that either looks like it is soldered from underneath or perhaps something has been cut out. It is where I would expect the bias preset to be. Just curious on that.
 
That is a 22r resistor there's two of them someone else changed them with another resistors more powerfull but the same value now I've changed them with 22r/1w because after I put the missing resistor smokes come out from 22r resistor .
Before me someone else tried to fix it but not in a good way.
I can't find any diagram from this board I've found the same board on a Sven Ha680w subwoofer there I found the picture with my missing resistors
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Fixing this will need you to power it up with a current limited power supply... perhaps using a DBT (dim bulb tester) as the unit uses a conventional power supply.

It sounds like the amp has a hidden history as well which means anything could have happened in its past.

(I'll move this to solid state as it seems more like a normal amp than a chip amp :))
 
Fixing this will need you to power it up with a current limited power supply... perhaps using a DBT (dim bulb tester) as the unit uses a conventional power supply.

It sounds like the amp has a hidden history as well which means anything could have happened in its past.

(I'll move this to solid state as it seems more like a normal amp than a chip amp :))

Sorry for wrong post .
I haven't got another AC power supply .

These are the pictures with what I've done .
Now that marked resistors 47r 1/4w start to smoke after I turned on the amp.

That v301 is a transistor 2n5551y817 I don't know why is underneath the board .
 

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Mooly

Administrator
Paid Member
2007-09-15 8:14 am
I don't want to sound unenthusiastic but unless you have a proper diagram to make sense of it all then I think it's not looking good tbh.

An experienced tech could probably still recover it from that condition but it would be very labour intensive. The board needs checking against the correct value parts to make sure any replacements are right and then normal faultfinding begins.

There will be more wrong here than just a few resistors. The transistor under the board looks like it is meant to be in contact with the heat sink to sense temperature and keep the bias point stable.
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
I wouldn't say poor quality so much as hacked around. Parts can be desoldered and removed/replaced on these type of boards with no damage at all.

Print gets damaged and lifted because of poor working practices. There are some areas that also look close to shorting.
 

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