I have aquired an amplifier with one working chanel, and one channel that seems to stick to one power supply rail (DC voltage). It uses an STK461 chip amp and the number and structure of the components inside looks relatively simple. Whilst i can aquire a replacement chip i am wondering what other tests i should run or common faults to look for before i go buying a chip that i don't need. Any pointers or links to tutorials etc?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
There's very little externally to go wrong with these chips. The only thing I can think of is to check that the DC isn't coming from a preamp stage (eg a missing rail to one of the opamps). This is unlikely though.
It is likely the chip is damaged possibly due to a short on the channel. Replacing the chip is the most likely fix.
It is likely the chip is damaged possibly due to a short on the channel. Replacing the chip is the most likely fix.
The chip is damaged,I have had simmilar experiences with STK series IC's ~ STK 459 and 4141 ,these chips are very sensitive to shorts in the output.But I doubt if you will be able to obtain a genuine STK 461 as these became obsolete arnd 10 years back...
The chip you're looking for is available at http://pacificsemi.com/search.php for $6.00 each.
Just an advice, when you install those kind of chip, place an alligator clip with a wire at each pin ,hook up to the ground .Just move the clip from pin to pin when you touch the pin with the iron.These are very sentitive to static.
Just an advice, when you install those kind of chip, place an alligator clip with a wire at each pin ,hook up to the ground .Just move the clip from pin to pin when you touch the pin with the iron.These are very sentitive to static.
Mine was seriously abused with static energy but worked perfectly fine.
Watch out for counterfeit STKs by the way folks 😉
James
my supplier says they sell STK461, I will buy a replacement chip, remove the old one and see how i go. The old one has lots of pins, is the best way to remove it to snip the pins at the base then remove, then pull the pins out individually?
Ya, cut those with wire cutter, will be a lot easier,but again, be careful with the iron when you touch the pins from the new IC, ground those pins
What is the best way to ground the pins? Run an alligator clip to somewhere (where), or do i just keep them all connected (so no voltage between the pins)? Sorry for being a tad ignorant.
OK, i finally got around to replacing the chip, now both channels create sound from output, however the right channel has a distict, and relatively loud (and independant from volume controls) hum at 50hz (sounds slightly hasher than a plain hum, hard to explain). This suggests to me that it is something to do with the power supply, what should i be checking for now?
Hi, check for any capacitors that could be bad.If you see one which have the top rounded, it is bad.
what do you mean by "top rounded"?
I have a multimeter that can also measure capacitance, is it possible to measure them in circuit?
I have a multimeter that can also measure capacitance, is it possible to measure them in circuit?
Hi, sometime, capacitor produce gas inside, sometime they explode, sometime the top become rounded like it have had too much pressure inside, sometime, nothing happen but when you see a capacitor with look like to have the top rounded, you can be sure it's probably bad.
But will be easier if you look at some pics on this site, nery good explanation:
http://www.badcaps.net/ident/
But will be easier if you look at some pics on this site, nery good explanation:
http://www.badcaps.net/ident/
I can't see any visibly bad capacitors, is there an easy way to measure them? Which ones should i be checking for problems with first?
.....You can check to see if there is some electrolyte that might have leaked out of the bottom (near the rubber sealed side), or if there is an acrid odor. One channel hums and the other doesn't?? Hmmmm, is there a DC offset on the channel that hums? Is the gain the same between the two channels? If the "hummy" side has higher gain and there is a DC offset, you might want to check the negative feedback loops shunt leg capacitor.
replace all the caps for that particular channel..as the reason why this channel got damaged might have damaged caps also..typically output short circuit..which will definitely damage caps...check for resistors..blackened..ones
Required help stk 4141
Hi all.
i hope somebody help me in the forum.
i am a begginer in electronics.i brought stk 4141 and circuit ,i am able to see line in 2 channels and line out 2 channels and grounding on the circuit but i am not able to see power input,can someone please help me in this please let me know how to where to connect power and volume controls and BT board,thanks in advance.
Thanks
Sagar
Hi all.
i hope somebody help me in the forum.
i am a begginer in electronics.i brought stk 4141 and circuit ,i am able to see line in 2 channels and line out 2 channels and grounding on the circuit but i am not able to see power input,can someone please help me in this please let me know how to where to connect power and volume controls and BT board,thanks in advance.
Thanks
Sagar
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