Need help to identify damaged parts

haimke

Member
2012-08-09 12:32 am
Hello
Drop of water leaked into my amp, burned some parts.
Can you help me identify the parts in the photos and recommend where to buy them ?

[IMGDEAD]http://schindlercode.com/amp/amp_broken_01.jpg[/IMGDEAD]

[IMGDEAD]http://schindlercode.com/amp/amp_broken_02.jpg[/IMGDEAD]

[IMGDEAD]http://schindlercode.com/amp/amp_broken_03.jpg[/IMGDEAD]

[IMGDEAD]http://schindlercode.com/amp/amp_resistors.jpg[/IMGDEAD]

(I tried to take photos from different angles)
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
As you don't know how to identify these components (some even have the part no. printed on them), I assume you also don't know whether the parts that are not burned, are OK or not.

Briefly, the green resistors are wire-wound types. The brand, style and resistance values are printed on them. The black diodes have the type numbers printed on them. The blue film resistors are printed with colour coded bands which you can determine with a colour band chart or on-line calculator e.g: Resistor color code calculator - 3, 4 and 5 band resistors

However, the problem will be that having replaced everything you have pictured, the amplifier will still not work because the cause is not obvious. It is likely to be the output transistors that caused this collateral damage when they failed and that usually cannot be seen.

I strongly suggest you have this repaired professionally unless you have at least basic test instruments and more experience with electronic design, testing and handling of electronic components than your post indicates. Otherwise, you could buy a lot of unnecessary replacement parts, fit them and still have a dead amplifier that needs to be diagnosed properly and repaired.
 

Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
Nice pic but unfortunately, You will need the schematic to identify the resistor. It is most likely the same emitter resistor as fitted to each power output transistor (there are eight here).

Please post the brand and model number of the amplifier so that others can view the schematic, understand your problem and read off parts values. Guessing at pictures may be interesting but not helpful. I read the resistor value as 0.33 ohms, probably 2Watt but as said, that is only collateral damage. The real problem is probably the output transistors and more.
 
The blue resistors around the orange cap? They look OK from here. is there some evidence they are bad that does not show in the photo?

The resistors that are obviously burnt will not be the problem. They do need to be replaced, but resistors don't burn up on their own, they burn up because something ELSE drew excess current through them, usually a shorted transistor.
 

mt490

Member
2010-06-09 2:32 pm
That looks like some sort of custom job.

Out of interest did you disconnect the wires to the right hand amplifier? I ask because the photos strangely have no evidence of any wiring ever connecting to it except the output, since I would expect at least some wires under the board just like the connected and burned amplifier channel even if you disconnected it.
 
The undamaged channel gives values and names for the damaged components in the other channel.

The green severely overheated resistors look like they are 0r33. They look like metal film, or metal oxide, to me.
They would probably be emitter resistors if the outputs are BJT, or source resistors if FET.
There is something between the 2pair outputs. Are they the tops of To220 devices?
They could be drivers.

Is it possible to use the undamaged channel to check that all the ancilliaries & PSU are still working OK?

Are those "gold" tolerance bands? That would indicate 5% tolerance and tell us the amp is very old.
 
Last edited:

haimke

Member
2012-08-09 12:32 am
more photos:
[IMGDEAD]http://schindlercode.com/amp/amp_transistors_01.JPG[/IMGDEAD]
[IMGDEAD]http://schindlercode.com/amp/amp_transistors.jpg[/IMGDEAD]
[IMGDEAD]http://schindlercode.com/amp/amp_complete.jpg[/IMGDEAD]

can someone help me to debug the issue on skype?
I have fluke 287, soldering iron, tools, and I can get oscilloscope if needed.
(I can bring it to technician but I am curious for the hands-on)