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Help me, i need one STK 3042

Jose Nieves

Jose Nieves

New Member
I bought one amplifier AKAI AM-U04 in eBay for $ 55 USD i have restored it completely but, in my country (Venezuela) today is not for sale the STK 3042 (voltage amplifier ic) Please, if someone knows about some business of sales electronic parts by internet and that he accept payments in line with credit card, and they send me this STK 3042. Please notify me for this middle (AK)
I include several photos of the beautiful AKAI AM-U04 and his STK 3042.
Thank you, dear members of AK
 

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Hola Jose.

Try getting in touch with AK member Paul C. ( I suggest via PM ). I believe he is the man for those Sanyo STK Power Packs. I understand he´ll ship worldwide too.

Congratulations on your work on the amp. Looks great.
 
The Sanyo STK3042 (NTE1338) is similar to the STK3062 (NTE1339) or STK3082 (NTE1339).

The STK3042 is a dual driver usually used with STK1050 or STK1060 output chips. The STK3062 or STK3082 were used with STK1060 or STK1070 output chips.

The STK3062 or STK3082 are the same as the 3042, but have higher voltage ratings. The pin out's for the 3062 and 3082 are the same as for the 3042.

http://audiolabga.com/pdf/STK3042.pdf

You can order from Sound & Light Electronics, they ship internationally.

http://www.slelectronics.net/STK0_STK5/semicon.htm?PHPSESSID=422b81436fe911073073d2269fc8ebd2

You can order the STK3082 from

http://www.electronicsic.com/sem-stk.htm From ElectronicsIC the STK3082 has a higher rating and costs less than the other two.

And here from Mouser Electronics

http://www.mouser.com/search/refine.aspx?Ntt=STK3042

http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016&Ntt=*STK3082*&Msb=0&Mkw=STK3082&N=1323038

Mouser shows the NTE1339 (equivilent to the STK3082) is in stock now.


The STK3042 (or other) dual driver gets quite hot. It looks like you have room to do what I did. I cut a piece of aluminum sheet the same width and twice as high as the STK driver. I applied heat sink grease to the back of the STK driver, and attached the aluminum with a nylon Ty-Wrap. This more than doubled the amount of radiating area and the chip is cooler.
 
There are a number of suppliers you can order from. If you can't buy these yourself, you may contact me directly.
 
Many thanks dear friend!

Thank you cartvv. I will publish more photos when powers on the Akai AM U04 Already i purchase the STK in electronic sale web site. Thank you so much!
 
Thank you very much to Paul C

I thank a lot by your valuable contribution. Already i made the purchase of the STK 3042 in Sound & Light Electronics. Will delay two weeks in arriving. When i install him it the AKAI AM-U04, i will publish other photos and i will do the explanation that thanks to you and AudioKarma, i managed to restore this amplifier.
Thousand thank and to your order for what can help you!
 
Paul C said:
The Sanyo STK3042 (NTE1338) is similar to the STK3062 (NTE1339) or STK3082 (NTE1339).

The STK3042 is a dual driver usually used with STK1050 or STK1060 output chips. The STK3062 or STK3082 were used with STK1060 or STK1070 output chips.

The STK3062 or STK3082 are the same as the 3042, but have higher voltage ratings. The pin out's for the 3062 and 3082 are the same as for the 3042.

http://audiolabga.com/pdf/STK3042.pdf

You can order from Sound & Light Electronics, they ship internationally.

http://www.slelectronics.net/STK0_STK5/semicon.htm?PHPSESSID=422b81436fe911073073d2269fc8ebd2

You can order the STK3082 from

http://www.electronicsic.com/sem-stk.htm From ElectronicsIC the STK3082 has a higher rating and costs less than the other two.

And here from Mouser Electronics

http://www.mouser.com/search/refine.aspx?Ntt=STK3042

http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016&Ntt=*STK3082*&Msb=0&Mkw=STK3082&N=1323038

Mouser shows the NTE1339 (equivilent to the STK3082) is in stock now.


The STK3042 (or other) dual driver gets quite hot. It looks like you have room to do what I did. I cut a piece of aluminum sheet the same width and twice as high as the STK driver. I applied heat sink grease to the back of the STK driver, and attached the aluminum with a nylon Ty-Wrap. This more than doubled the amount of radiating area and the chip is cooler.
Click to expand...

sorry to revive a thread this old but I was wondering if when replacing this driver on a yammy 840, if this heatshield workaround would be a good idea?

Paul, any chance you have pics of this? You're not talking aluminum foil here right? This would help the driver in cases where the amp was being pushed hard right?
 
Absolutely. We, like everyone else who designed these parts in, got burned on the "not need heat sink" nonsense we got from Sanyo. Anything you can do to heat sink this part is a bonus.

EPI-Center said:
sorry to revive a thread this old but I was wondering if when replacing this driver on a yammy 840, if this heatshield workaround would be a good idea?
Click to expand...
 
This is what I did on a Akai amp. The heat sink comes from an old CRT computer monitor and the STK is sanwitched between the heat sink and a small L shaped aluminium bar.
 

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Reviving this old thread as I think my question is similar in nature.

I've been given a nice Yamaha R-500 receiver, but the relay won't click on. I've narrowed the problem down to either the STK3042II voltage amplifier or the STK2040 pack. To help me determine this, I took DMM readings on the pins of the 2040, it showed the same readings on either side, whatever pin combination I chose. The 3042 has an open reading on one side and not the other, on the same pin combo. Take either/both pack out, and the relay will click on. So given the open reading, I replaced 3042. At the time, I could only get the STK3042III. I think I was told it would work - an improvement on version II? I looked at the schematics and there are some minor differences, but on this advice I went ahead, soldered it in and turned it on - and it promptly blew the power supply fuse.

I'd be interested if there are differences in the II and III that would cause the blown fuse - or does this indicate the STK2040 should be replaced? Or might it be something else entirely? I have the schematic (from AK), but it's so fuzzy it's really not of much use. Any help would be appreciated!
 
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The STK3042II has internal compensation capacitor between pins 6 and 4. The STK3042III doesn't have this capacitor and may oscillate if you don't add an external capacitor. It's enough to blow a fuse. Try to add a 15pF cap between pins 6 and 4 (12 and 10 on the other channel).
 
ecluser said:
The STK3042II has internal compensation capacitor between pins 6 and 4. The STK3042III doesn't have this capacitor and may oscillate if you don't add an external capacitor. It's enough to blow a fuse. Try to add a 15pF cap between pins 6 and 4 (12 and 10 on the other channel).
Click to expand...

Thanks for the info. I have to assume you're talking about one of those small (usually) tan-colored disk-shaped (ceramic?) caps. In my old PCB graveyard, I found a pair of these marked "15J". The codes are kind of cryptic, but based on my reading, if these are already rated in pf, that would be a 15 pf with a -+5% tolerance. Does that sound right?

Does polarity matter on these as it does on electrolytic caps? If so, which goes to which pin as you've specified?
 
ecluser said:
This is a non polar cap, 15pF with ±5% tolerance. Try it.
Click to expand...

Done. And it WORKS! Ran it all evening - so far, so good. Thank you for this tip. I'd have never known to do that, and would have had to order another STK3042II!

I noticed that the new voltage amp ran quite warm, and taking note of earlier postings, I also added a heat sink. Hopefully this will help forestall future failures. Now if can find a pair of the Yamaha "blade-style" knobs, this unit will be 100%.

Thanks again, ecluser.
 

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Glad this thread was revived. I have an Onkyo TX-3000 with driver sanyo IC's - One went and was replaced a while ago, but the heat sinks sound like an excellent improvement.
 
Hello everybody. I see there is an interesting conversation about STK's here so I join and ask for a piece of advice... I have an AKAI AM-U04 amplifier. It has an STK3042 which drives two STK0050II.
Initially I noticed one of the two STK0050II was shorted so replaced...It had sounded good for some minutes :music: then blown again :thumbsdn:.
Checking better with DMM noticed that the STK3042 has wrong output voltages in one of its two channels so I need to replace it too.
Do you think an STK3042III fits? In the datasheets I have found it seems that are missing a capacitor and a resistor between input pins (3-4 and 12-13).
Also do you think the STK3042 damaged "by itself"? Adding a heatsink as you suggested in this thread would be surely a good idea.
 
I think that you should remove the bad STK0050II for testing the STK3042. But you must provide a load for the STK3042. I've explained in the past how to do this in a Yamaha receiver (CR-640 ??). I will find the thread tomorrow and I will post it here.

As I can see from the very bad schematic I've found for the AKAI AM-U04, there is an R-C network on the board, between pins 3-4 and 12-13. I wouldn't worry about the missing R-C network inside the STK3042III but it would be important to add a capacitor between pins 4-6 and 10-12.

BTW, welcome to AK!

Edit: see post #4 on this thread

http://www.audiokarma.org/forums/showthread.php?t=335831

The voltage amp in the Yamaha receivers are similar to the STK3042
 
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If one side of the STK0050II is shorted, it can pull the output from the STK3042 toward one rail voltage. For testing the STK3042 you must remove the STK0050II and connect one jumper between holes 7-8 and another jumper between holes 4-3 on the "edge connector" for the STK0050II. These jumpers will connect the output of the voltage amplifier IC to the output of the power amplifier IC and this will close the signal path loop.
 
Thank you ecluser for your quick answer! Yes, the STK0050II pulls the output to one rail voltage. Originally to -45V. Then after replacing, few minutes working and blowing again shorted to +45V. (It would be interesting to make one full-working from these 2 half-fault :) ).
I've removed the 0050 it and tested the 3042 without providing a load, so I will test as you suggested in the next days. But I'm sure the 3042 is fault because there cannot be any other cause for the 0050II to blow (assumed that the output to speakers is not shorted), do you think so?
However thanks, i will inform you about the next developments!
 
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