STK amplifier modules

[Gareth Magennis]

I'm trying to repair an Onkyo surround sound amplifier with a blown STK
422-730.
I wouldn't normally take this on, but it is for a friend who is not very
well, or very wealthy.

Well first off, I can't even find a datasheet for this particular STK, let
alone find an STK 422-730 I could buy.

(STK's from china don't count as they will be fake and I need to get this
working ASAP)
The original is a Sanyo package like this, but this is not a Sanyo part:
http://www.ebay.co.uk/itm/1PC-STK442-730-Package-SIP-ZIP-IC-/263071290874?hash=item3d404555fa:g:OwwAAOSwXXxZW3rW


So I have been looking at substitutes.
There are a whole range of 2 channel STK's with 14 pins, of various
amplifier powers.
Are all these compatible? If I get something close will it just plug in and
play?


There's a whole load of other much cheaper older package STK442-XXX modules
available, eg:
http://www.ebay.co.uk/itm/Hybrid-IC-STK442-130-Power-Audio-Amp-/311345361915?hash=item487da133fb:g:YywAAOSw53NY~ioe

Not being able to find the datasheet means I don't even know the power, but
that is not as important as getting this amp into some semblance of making
sounds again.

Might it be worth taking a punt on one of these cheap older packages not
from China?



Cheers,


Gareth.

[Gareth Magennis]

Dammit, my typo.

It's a STK 442-730.



Gareth.

[N_Cook]

I long ago stopped trying to find exact replacements, settling on 1, or
2 for stereo, easy to find TDA7293. A bit of time working out the pinout
of the original . The only hiccup has been , sometimes the mute line
needs a simple inverter transistor in line with it/them. None bounced
back , is all I cansay on reliability

[Gareth Magennis]

"N_Cook" wrote in message news:olo3iv$jb4$1...@dont-email.me...

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I'm close to liking that idea.



Gareth.

[Jeroni Paul]

Gareth Magennis wrote:
> I long ago stopped trying to find exact replacements, settling on 1, or
> 2 for stereo, easy to find TDA7293. A bit of time working out the pinout
> of the original . The only hiccup has been , sometimes the mute line
> needs a simple inverter transistor in line with it/them. None bounced
> back , is all I cansay on reliability
>
>
>
>
>
> ***********************************************************
>
>
> I'm close to liking that idea.
>
>
>
> Gareth.

I did something similar years ago in a Toshiba VCR that had an STK IC in the power supply. A switched 9V output was low with all other outputs fine and the replacement very expensive, I placed a linear voltage regulator with standby control pin to get the missing 9V, worked perfectly.

[John-Del]

On Monday, July 31, 2017 at 3:45:44 PM UTC-4, Gareth Magennis wrote:

>
> (STK's from china don't count as they will be fake and I need to get this
> working ASAP)

I was screaming about counterfeit semis back in the 1980s when everyone thought I was full of crap.


But.. not all semis out of China are fakes. I'll bet that if you buy that STK on ebay, it will fix the stereo and it will last.

[tom]

"John-Del" <ohg...@gmail.com> wrote in message
news:28fb86db-b929-42cd...@googlegroups.com...

Not only that but you can easily get your money back if it is fake.

[Gareth Magennis]

"John-Del" wrote in message
news:28fb86db-b929-42cd...@googlegroups.com...

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That may be so, ("fake" I have learnt can be a rather inappropriate term to
use), but we don't have the time for the shipping, and expediated shipping
is another $35, making this a VERY expensive punt for my friend.


I did a bit more research today and it looks like all the STK's of similar
type and pin count seem to use the same pinouts, so I have ordered a way
cheaper STK 442-120 from a UK vendor I use when Farnell doesn't have the
product, and who I trust not to sell me total crap, and it will get here
tomorrow or the day after.


I do have the Service Manual of the Onkyo to confirm the pinouts of the
original 442-730, so hopefully this should be a drop in replacement punt
with no drama.
If the volume levels are different, then that can surely be adjusted in the
setup.
It's only for domestic TV viewing so it shouldn't be particularly highly
stressed.



This is not a commercial repair for financial gain, or I would simply refuse
to do it as unviable.



Cheers,


Gareth.

[jurb...@gmail.com]

How much power is this thing ? If it is not too high you can just rewire it to use a pair of LM3886 or something. They are not bad chips. I did that a year or two ago on a unit that used an SVI chip, which is an STK but just considered fancy.

[Gareth Magennis]

wrote in message
news:30addb86-d420-4d3d...@googlegroups.com...

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I now think it would make more sense to use another cheap, easily available
STK module.
They are pin for pin compatible and bolt straight onto the heatsink.
10 minutes to change them.

The 2 x LM or TDA options are going to mean an absolute rat's nest of wiring
to individual IC pins in mid air, not to mention having to sort out a
suitable mute conversion.
How many hours is that going to take?



Gareth.

[Gareth Magennis]

"Gareth Magennis" wrote in message news:_v4hB.468124$YV4.1...@fx18.am4...

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Well, having ordered a STK 442-120 and expecting it to arrive in 2 days max
as usual, it didn't.
Wasn't even dispatched until friday, I assume half the staff are probably
on holiday. Most unusual.

Anyway I decided to have a look at using a pair of LM's/TDA's or whatever,
only to find a new STK 442-130 in my TDA drawer I didn't know I had.
I must have ordered two some time in the distant past and gave myself a
spare.


So, swapping them out really was very quick, and it works.
I believe these 130 version are rated 150W, but I've no idea what they base
this upon, as it is probably bogus.
The Onkyo I have doesn't look hugely powerful power supply wise, so this IC
is probably well overkill over the original, whose specs I could not find
anywhere.

Check out the prices of these, they are not expensive. I even found a US
retailer who were guaranteeing theirs were genuine Sanyo parts.




Another thing. This Onkyo has 2 STK parts, the 442 and a 443 part. The
443 part has 3 amplifiers, the 442 has 2.
Consequently the 443 has more pins.
It turns out that the pinout for the 443 follows exactly the 14 pins of the
442, and simply tacks on an extra 4 pins for the 3rd amp (2 in, 2out).

The motherboard of this Onkyo actually has 18 pins available at the site the
442 was occupying, with circuitry not fitted regarding a possible third
amplifier.
Meaning it was a generic motherboard that could use either 2 x 443 chips, or
1 x 443 and 1 x 442, depending on which model it went into.


So this leads me to believe that these STK chips are indeed simply plug and
play, you select the particular chip with regards to how many amplifiers you
want and at what power.

Which is why people like Onkyo use them?
It would make sense to know you could produce a generic PCB and simply plug
in whatever STK's were appropriate in a single design, and that any future
improved STK's could simply be plugged in instead without any major redesign
work.


Anyway, for not much more that a couple of LM/TDA's, you could perhaps just
find an appropriate STK, you just need to find a reliable source of these.


Good luck, I don't do hi-fi repairs, this is a very good example of why not.




Cheers,


Gareth.

[John-Del]

On Saturday, August 5, 2017 at 2:51:53 PM UTC-4, Gareth Magennis wrote:

> Well, having ordered a STK 442-120 and expecting it to arrive in 2 days max
> as usual, it didn't.
> Wasn't even dispatched until friday, I assume half the staff are probably
> on holiday. Most unusual.
>
> Anyway I decided to have a look at using a pair of LM's/TDA's or whatever,
> only to find a new STK 442-130 in my TDA drawer I didn't know I had.
> I must have ordered two some time in the distant past and gave myself a
> spare.
>

Here's something you probably don't realize: if you didn't order the -120 the -130 would have remained hidden. I don't understand the physics of it but it's best to just admit this stuff happens (plus, you'll feel better)..

[Gareth Magennis]

"John-Del" wrote in message
news:ef2429a7-7279-4f17...@googlegroups.com...

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Yep, I get that. :)

I also no longer get annoyed on the road when I take a wrong turning, or get
lost.
I say to myself, that might well have saved me having that fatal accident.



Gareth.

[tabb...@gmail.com]

a stereo tv? Put the speakers in series on the remaining channel.


NT

[Gareth Magennis]

wrote in message
news:7322c544-feb1-4470...@googlegroups.com...

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No, this is a 5 channel surround sound power amp with Sub signal output.


Gareth.