Because I was not careful, I shorted the right side speaker wires connected to an Akai AA-2350 last year, while it was playing. Consequently, due that channel going dead, I believed the STK-082 muodule was destroyed.
I bought a replacement on E-bay. The plastic bag had the word "Japan" and it came from a US vendor. Once installed, it worked fine and I put the amp away for a couple of months until it was needed.
When that time came, the channel with the new STK sounded weak. Then got very noisy, unaffected by volume control. And it is now silent.
Except a couple of times when the surrounding PC board or heatsink was touched or tapped. Examining all 10 solder connections, all look good and solid.
The few times it came back to life briefly made me imagine internal module connections being re-established from external vibration.
Is it likely that this particular module I got is defective? Like a Chinese copy born to fail? I am tempted to try another but all those I've seen on the auction site look exactly the same as the one I got.
The left channel module in this amp which is still good, has all ten of the pins numbered 1 to 0. A feature that seems absent on new offerings.
I bought a replacement on E-bay. The plastic bag had the word "Japan" and it came from a US vendor. Once installed, it worked fine and I put the amp away for a couple of months until it was needed.
When that time came, the channel with the new STK sounded weak. Then got very noisy, unaffected by volume control. And it is now silent.
Except a couple of times when the surrounding PC board or heatsink was touched or tapped. Examining all 10 solder connections, all look good and solid.
The few times it came back to life briefly made me imagine internal module connections being re-established from external vibration.
Is it likely that this particular module I got is defective? Like a Chinese copy born to fail? I am tempted to try another but all those I've seen on the auction site look exactly the same as the one I got.
The left channel module in this amp which is still good, has all ten of the pins numbered 1 to 0. A feature that seems absent on new offerings.
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> Examining all 10 solder connections, all look good and solid.
Did you take it out in mellow sun-light? Did you use a strong magnifier?
I don't want to be rude/dismissive. But even when experienced techs do repairs, often-enough they pull-hair for a month and *finally* see the hairline fracture, flux-ring or unexpected related damage.
Yes, it could be a factory fault. And I have seen some sneakers. (Work fine for 5 years and then catch fire. In a NYC hi-rise.) But most factory workers do better than most hobby or repair workers. (If their solder work flunks QA too much, they get re-assigned to knob polishing.)
{EDIT for production joke:
I once had a job making plastic Draculas...
There were only two of us on the production line...
So I had to make every second Count... }
Did you take it out in mellow sun-light? Did you use a strong magnifier?
I don't want to be rude/dismissive. But even when experienced techs do repairs, often-enough they pull-hair for a month and *finally* see the hairline fracture, flux-ring or unexpected related damage.
Yes, it could be a factory fault. And I have seen some sneakers. (Work fine for 5 years and then catch fire. In a NYC hi-rise.) But most factory workers do better than most hobby or repair workers. (If their solder work flunks QA too much, they get re-assigned to knob polishing.)
{EDIT for production joke:
I once had a job making plastic Draculas...
There were only two of us on the production line...
So I had to make every second Count... }
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Hi,
First comes first.. the plastic bag tells you "Exact Replacement" So it's more than sure that it's not a Original. Then, instead for STK-082 , it's a replacement for "200737" which usually means the year and week of production. So this IC is supposed to be produced afterwards that number. Now on the BAG you also can see then SK but not STK and also these chips would not come in Plastic Bags and this Chips usually come with Shorted Pins or alt least with connecting foam, even these are not Mosfets. This all is suspicious..
Have you seen, using Google you barely will find a seller which is not Aliexpress.
But, when you shorten the Loudspeaker Cables of this Amplifier, have you checked the 5 Watt Resistor and the 2 pieces of 3 Watts if they have the Value which these resistors are suppose to have? Especially the 5Watt Resistor, could be damaged as well or at least is somewhat defective.
Last but not least as PRR put it: Recheck that soldering again and then clean it up especially between the Chips Legs..usually for old Amps like the one of you have, it could be that the PCB Tracks just besides where you have de-soldered and soldered did become some Hair-cracks underneath the protection SCREEN (Green I suppose) color from the solder joint.. happen to many times.. If you want to know it the legs have been partly disconnected inside the chip then use a Hot Air Gun set temp to about 60degrees C , switch the amp on and steadily heat up the Pins between the PCB and the CHIP. this eventually will make them to connect.. just try it. if the Chip is fried you can not destroy anything, but if it's just a cold Solder spot or haircut then you might find the defective place of it..
That's my five cents.. Hope it helps somewhat..
BTW - Also in China they are producing real high quality chips..times of Copy and making only trash has passed for some times already. But those Chips are not officially produced anymore. and under one hundred white sheep you sure will find a black one..
Unless you get the chip from Akai itself or from Sanyo you always must take chances that it is a fake, low quality or similar. But this point is out of Questions. Because these chips aren't manufactured anymore by Sanyo for over 10 Years by now..
First comes first.. the plastic bag tells you "Exact Replacement" So it's more than sure that it's not a Original. Then, instead for STK-082 , it's a replacement for "200737" which usually means the year and week of production. So this IC is supposed to be produced afterwards that number. Now on the BAG you also can see then SK but not STK and also these chips would not come in Plastic Bags and this Chips usually come with Shorted Pins or alt least with connecting foam, even these are not Mosfets. This all is suspicious..
Have you seen, using Google you barely will find a seller which is not Aliexpress.
But, when you shorten the Loudspeaker Cables of this Amplifier, have you checked the 5 Watt Resistor and the 2 pieces of 3 Watts if they have the Value which these resistors are suppose to have? Especially the 5Watt Resistor, could be damaged as well or at least is somewhat defective.
Last but not least as PRR put it: Recheck that soldering again and then clean it up especially between the Chips Legs..usually for old Amps like the one of you have, it could be that the PCB Tracks just besides where you have de-soldered and soldered did become some Hair-cracks underneath the protection SCREEN (Green I suppose) color from the solder joint.. happen to many times.. If you want to know it the legs have been partly disconnected inside the chip then use a Hot Air Gun set temp to about 60degrees C , switch the amp on and steadily heat up the Pins between the PCB and the CHIP. this eventually will make them to connect.. just try it. if the Chip is fried you can not destroy anything, but if it's just a cold Solder spot or haircut then you might find the defective place of it..
That's my five cents.. Hope it helps somewhat..
BTW - Also in China they are producing real high quality chips..times of Copy and making only trash has passed for some times already. But those Chips are not officially produced anymore. and under one hundred white sheep you sure will find a black one..
Unless you get the chip from Akai itself or from Sanyo you always must take chances that it is a fake, low quality or similar. But this point is out of Questions. Because these chips aren't manufactured anymore by Sanyo for over 10 Years by now..
> these chips would not come in Plastic Bags and this Chips usually come with Shorted Pins or alt least with connecting foam
The ECG/SK replacements did come in plastic bags and did not need anti-stat foam. (I bought quite a few in those days.) I believe this is a vintage "replacement part". Replacement parts (a short-list of better parts at high price which replaced 88% of commercial parts) were hit-or-miss in those days. Especially solo devices, where the "equivalency" was sometimes dart-board. However the metal slab on the Sankens was distinctive and, in those days before WIDE copy-cats, I always assumed were made by Sanken, though maybe not their best.
The ECG/SK replacements did come in plastic bags and did not need anti-stat foam. (I bought quite a few in those days.) I believe this is a vintage "replacement part". Replacement parts (a short-list of better parts at high price which replaced 88% of commercial parts) were hit-or-miss in those days. Especially solo devices, where the "equivalency" was sometimes dart-board. However the metal slab on the Sankens was distinctive and, in those days before WIDE copy-cats, I always assumed were made by Sanken, though maybe not their best.
Solved
Turns out that STK module is OK afterall.
hpro, I followed your instructions but without a definative answer. Except that if I got the channel working, a blast to the board from a heat gun made it stop working.
Repeated tapping on the board narrowed down the area where the "taps" were heard through the amp and speakers. I thought it was a bad cap so removed it, tested it and it was fine. But that drew my attention to a connection right next to it. The centre conductor of a sheilded cable.
The solder connection looked OK but I was able to move the wire up and down within the hole. After resoldering, the amp seems to work well again with no decreasing volume, loud noises or intermittently working.
This amp left the factory that way circa 1979, so a problem not of my doing.
Turns out that STK module is OK afterall.
hpro, I followed your instructions but without a definative answer. Except that if I got the channel working, a blast to the board from a heat gun made it stop working.
Repeated tapping on the board narrowed down the area where the "taps" were heard through the amp and speakers. I thought it was a bad cap so removed it, tested it and it was fine. But that drew my attention to a connection right next to it. The centre conductor of a sheilded cable.
The solder connection looked OK but I was able to move the wire up and down within the hole. After resoldering, the amp seems to work well again with no decreasing volume, loud noises or intermittently working.
This amp left the factory that way circa 1979, so a problem not of my doing.
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Glad you found it andit was the kind of failure I was expecting.
¨Parts do not fail and self repair, so no
That it´s similar sounding to STK is only by sheer chance.
¨Parts do not fail and self repair, so no
Now, external connections? ..... any day of the week.
It´s actual a "Factory/House" number, and must have been so popular that it was prominently quoted.
SK was the very well konown brand of a line of generic replacement semiconductors, very much used by Techs.
That it´s similar sounding to STK is only by sheer chance.
Not suspicious, way back then parts, including semiconductors, were happy inside plastic bags.
THAT ^^^^^^^^^^