Sony TA F240 blowing fuses

joshvegas

Member
2007-12-30 9:59 pm
I have an old Sony TA F240 Amplifier which stopped working.

The Amp fails to switch on so i whipped the cover off and had a poke around the power supply and i noticed the slow blow or time delay fuse was blown so i put in a replacement (T2.5A 250V)I also noticed that the little pcb it was mounted on had come loose from transformer itself and soldered that back up aswell. Feeling fairly pleased with myself i screwed it all back together switched it on and was rewarded with a flash of light and a newly blown fuse. At this point the internet and guess work fails me so...

My question is this what could be causing this and how do i fix it?

Other than fixing and modifying guitars this is my first time. be gentle.

Cheers guys.
 
Did you sort this? I have exactly the same amp and I love it but it blew on sunday the 13th =[ it smoked so i took the plug out. but it wont turn back on just like yours. you say there is some kind of internal fuse and something else? could i have a dummies guide to this please?
[IMGDEAD]https://i93.photobucket.com/albums/l68/yewkaybloodflow/Picturenumber-277.jpg[/IMGDEAD]

btw this is mine and was wondering if you could point out aswell to just where what your describing is?
please add me on msn at [email protected]
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Nothings cheap to fix these days. As Jaycee says you need someone who knows what they are doing. Using unsuitable substitute semiconductors is a recipe for disaster, it might be O.K. for short while only, plus there could be underlying reason for failure in first place. But having said that if you can come up with circuit ;) anything is possible :) even fixing it.
Regards Karl
 

joshvegas

Member
2007-12-30 9:59 pm
Hey Guys totally forgot about this post!

Picturenumber-277.jpg


the red circle is the board and the green is where the anti surge fuse is, it will switch on with a new fuse but then blows again and some of the contacts on the board are knackered could this be the problem?.

I'm not that bothered i have another amp but it would be nice to have one for my kitcehn for rock and roll cooking!
 
Sinistersoulz, you will definitely have blown the output transistors in the amp, and possibly more parts. Shorting the output is probably the worst thing you can do to a power amplifier, so the damage is likely to be extensive and not cost effective to fix.

joshvegas, if the fuse blows its because theres a fault somewhere else in the circuit. "Some of the contacts are knackered", which ones? Why did the amp pop its fuse in the first place?
 

joshvegas

Member
2007-12-30 9:59 pm
I have no idea why it blew it just did!

on the indicated board some of the soldering joints look decidedly shaky! particularly the ones connecting the board to the transformer.

Sorry I can't be more specific The amp is at my parents at the moment!


Thanks for taking the time to reply to a total dunce!
 
It's not the outcome I would like, but I have my eye on another sony solid state amp. The TA-F110.

I replaced the fuse and as josh said im greeted by a nice flash :rolleyes: Yes I have done things like turning source direct off and stupid little things like that each with a new fuse each time.
Either a flash and smoke (blown fuse) with no power shown(no green light or anything else that would indicate it)
Or...
Just smoke which smells like the cream you get to put on cuts, umm savlon thats the stuff.
Sorry bit off topic there (Note that the fuse wont blow with just the smoke) :xeye: :confused: :(
 
Well if you can solder and desolder a transistor you can likely fix it in my opinion...

Remove transistors ones at a time... gooogle how to do a transistor diode test...perform said test, replace transistor if OK.
Mark transistor on board as checked, move to next transistor...

After you worked through all of them, and hopefully found some dead ones... it is a good idea to get a service manual to obtain optimal bias point, for reliable use afterwards.

You must also ensure the PSU is OK before running the amp... the PSU boards should be disconnected from the amp boards and their voltages measured, and of course see if the fuse still blows...
 
Talk about bringing a topic back from the dead eh! I finaly got around to checking the transistors which is actually very easy. There is a huge brown mark on the heatsink by the blown one. Its just a matter of locating a replacement transistor. If JoshVegas reads this thread then to get to the problem transistor, flip the amp over and unscrew the 2 black philips screws. you can then lift part of the metal plate off. This will expose the output transistors. If there is a obvious burn mark the swap out the transistor with a new one, ensuring that the legs are in the correct order and it is the same specification of course! It's quite fun if you enjoy fixing things. Especially when it powers up and plays tunes. :)