Technics amp problem

[[email protected]]

I've got an older technics amp (no tuner) that gets crackly on both
channels after it runs about 30 minutes or so. Sounds fine when you
start it up. Switchs and pots have all been cleaned. Any
suggestions? I'm guessing power supply but not sure what it could
be. Do the big caps start leaking after they get hot?

[GregS[_3_]]

In article >, wrote:
>I've got an older technics amp (no tuner) that gets crackly on both
>channels after it runs about 30 minutes or so. Sounds fine when you
>start it up. Switchs and pots have all been cleaned. Any
>suggestions? I'm guessing power supply but not sure what it could
>be. Do the big caps start leaking after they get hot?

Caps are not supposed to get real hot. They can leak and, or, go bad.
Are the crackles the same on both channels. How many caps are there.
Does the amp include a preamp, etc.

greg

[[email protected]]

On Jan 6, 12:43*pm, (GregS) wrote:
> In article >, wrote:
>
> >I've got an older technics amp (no tuner) that gets crackly on both
> >channels after it runs about 30 minutes or so. *Sounds fine when you
> >start it up. *Switchs and pots have all been cleaned. *Any
> >suggestions? *I'm guessing power supply but not sure what it could
> >be. *Do the big caps start leaking after they get hot?
>
> Caps are not supposed to get real hot. They can leak and, or, go bad.
> Are the crackles the same on both channels. How many caps are there.
> Does the amp include a preamp, etc.
>
> greg

Don't know that the caps specifically are getting unusually hot, the
whole unit gets warm after a while of course. Both channels and yes,
it has a pre-amp in it as well with source and tape selection switches
as well as a couple tone controls. No tuner. Have it hooked to a pc
running itunes and nothing else except speakers.

You think I should be looking at the preamp? I was suspecting the
power supply since it hit both channels but don't have a clue as to
what in the power supply would cause this symptom.

[news.kc.sbcglobal.net]

> wrote in message
...
On Jan 6, 12:43 pm, (GregS) wrote:
> In article
> >,
> wrote:
>
> >I've got an older technics amp (no tuner) that gets crackly on both
> >channels after it runs about 30 minutes or so. Sounds fine when you
> >start it up. Switchs and pots have all been cleaned. Any
> >suggestions? I'm guessing power supply but not sure what it could
> >be. Do the big caps start leaking after they get hot?
>
> Caps are not supposed to get real hot. They can leak and, or, go bad.
> Are the crackles the same on both channels. How many caps are there.
> Does the amp include a preamp, etc.
>
> greg

>Don't know that the caps specifically are getting unusually hot, the
>whole unit gets warm after a while of course. Both channels and yes,
>it has a pre-amp in it as well with source and tape selection switches
>as well as a couple tone controls. No tuner. Have it hooked to a pc
>running itunes and nothing else except speakers.

>You think I should be looking at the preamp? I was suspecting the
>power supply since it hit both channels but don't have a clue as to
>what in the power supply would cause this symptom.

Often the speaker relay contacts develop intermittent connections on older
units. Try tapping on the speaker relay when the problem occurs and see if
that affects the problem.

Also try switching, turning and generally manipulating the various controls
and switches. One or more may be causing the trouble.

Mark Z.

[Chris Hornbeck]

On Tue, 6 Jan 2009 20:27:13 -0600, "news.kc.sbcglobal.net"
> wrote:

>Often the speaker relay contacts develop intermittent connections on older
>units. Try tapping on the speaker relay when the problem occurs and see if
>that affects the problem.
>
>Also try switching, turning and generally manipulating the various controls
>and switches. One or more may be causing the trouble.

Excellent stuff. Also resolder the legs of any voltage regulator
IC's, as these tend to develope ring cracks with age (heat/cool
cycles).

In fact, get a really bright light and examine *all* PCB solder
joints. Can't hurt!

All the best fortune,
Chris Hornbeck

[Tim Schwartz]

wrote:
> I've got an older Technics amp (no tuner) that gets crackly on both
> channels after it runs about 30 minutes or so. Sounds fine when you
> start it up. Switches and pots have all been cleaned. Any
> suggestions? I'm guessing power supply but not sure what it could
> be. Do the big caps start leaking after they get hot?

James,

While I don't disagree with the other posters, look to see if your unit
uses an STK IC driver module, something like an STK-3042 or an STK-3076,
among dozens of different numbers and variations. I have certainly seen
this series of IC's, especially if the design does not include a heat
sink go bad in the way you describe. It could also be an output IC,
especially a stereo one, since its effecting both channels. You might
try looking at the soldering on the IC's, or hitting them with some
freeze mist once the crackling starts.

Of course, your amp might not use them at all, which would make my post
sort of useless. If you put out another posting, please include the
model of your amp.

Regards,
Tim Schwartz
Bristol Electronics

[jamesgangnc]

"Tim Schwartz" > wrote in message
...
> wrote:
>> I've got an older Technics amp (no tuner) that gets crackly on both
>> channels after it runs about 30 minutes or so. Sounds fine when you
>> start it up. Switches and pots have all been cleaned. Any
>> suggestions? I'm guessing power supply but not sure what it could
>> be. Do the big caps start leaking after they get hot?
>
> James,
>
> While I don't disagree with the other posters, look to see if your unit
> uses an STK IC driver module, something like an STK-3042 or an STK-3076,
> among dozens of different numbers and variations. I have certainly seen
> this series of IC's, especially if the design does not include a heat sink
> go bad in the way you describe. It could also be an output IC, especially
> a stereo one, since its effecting both channels. You might try looking at
> the soldering on the IC's, or hitting them with some freeze mist once the
> crackling starts.
>
> Of course, your amp might not use them at all, which would make my post
> sort of useless. If you put out another posting, please include the model
> of your amp.
>
> Regards,
> Tim Schwartz
> Bristol Electronics

Thanks. It's a technics su-8044 and it does have the stk amps in it. The
stk0039n to be exact. Looks like they are on a fairly decent heat sink.
Last time I looked at any of those stk amps some were cheap and some where
hard to find. The unit is 40w per channel.

[Trevor Wilson[_2_]]

"jamesgangnc" > wrote in message
m...
> "Tim Schwartz" > wrote in message
> ...
>> wrote:
>>> I've got an older Technics amp (no tuner) that gets crackly on both
>>> channels after it runs about 30 minutes or so. Sounds fine when you
>>> start it up. Switches and pots have all been cleaned. Any
>>> suggestions? I'm guessing power supply but not sure what it could
>>> be. Do the big caps start leaking after they get hot?
>>
>> James,
>>
>> While I don't disagree with the other posters, look to see if your unit
>> uses an STK IC driver module, something like an STK-3042 or an STK-3076,
>> among dozens of different numbers and variations. I have certainly seen
>> this series of IC's, especially if the design does not include a heat
>> sink go bad in the way you describe. It could also be an output IC,
>> especially a stereo one, since its effecting both channels. You might
>> try looking at the soldering on the IC's, or hitting them with some
>> freeze mist once the crackling starts.
>>
>> Of course, your amp might not use them at all, which would make my post
>> sort of useless. If you put out another posting, please include the
>> model of your amp.
>>
>> Regards,
>> Tim Schwartz
>> Bristol Electronics
>
> Thanks. It's a technics su-8044 and it does have the stk amps in it. The
> stk0039n to be exact. Looks like they are on a fairly decent heat sink.
> Last time I looked at any of those stk amps some were cheap and some where
> hard to find. The unit is 40w per channel.

**As previously stated, this is your #1 suspect. Hit it with the freezer
spray (after it warms up) and see what happens. As also stated, check the IC
carefully for dry joints.


--
Trevor Wilson
www.rageaudio.com.au

[[email protected]]

On Jan 9, 11:27*pm, "Trevor Wilson"
> wrote:
> "jamesgangnc" > wrote in message
>
> m...
>
>
>
>
>
> > "Tim Schwartz" > wrote in message
> ...
> >> wrote:
> >>> I've got an older Technics amp (no tuner) that gets crackly on both
> >>> channels after it runs about 30 minutes or so. *Sounds fine when you
> >>> start it up. *Switches and pots have all been cleaned. *Any
> >>> suggestions? *I'm guessing power supply but not sure what it could
> >>> be. *Do the big caps start leaking after they get hot?
>
> >> James,
>
> >> While I don't disagree with the other posters, look to see if your unit
> >> uses an STK IC driver module, something like an STK-3042 or an STK-3076,
> >> among dozens of different numbers and variations. *I have certainly seen
> >> this series of IC's, especially if the design does not include a heat
> >> sink go bad in the way you describe. *It could also be an output IC,
> >> especially a stereo one, since its effecting both channels. *You might
> >> try looking at the soldering on the IC's, or hitting them with some
> >> freeze mist once the crackling starts.
>
> >> Of course, your amp might not use them at all, which would make my post
> >> sort of useless. *If you put out another posting, please include the
> >> model of your amp.
>
> >> Regards,
> >> Tim Schwartz
> >> Bristol Electronics
>
> > Thanks. *It's a technics su-8044 and it does have the stk amps in it. *The
> > stk0039n to be exact. *Looks like they are on a fairly decent heat sink.
> > Last time I looked at any of those stk amps some were cheap and some where
> > hard to find. *The unit is 40w per channel.
>
> **As previously stated, this is your #1 suspect. Hit it with the freezer
> spray (after it warms up) and see what happens. As also stated, check the IC
> carefully for dry joints.
>
> --
> Trevor Wilsonwww.rageaudio.com.au- Hide quoted text -
>
> - Show quoted text -

Thanks, I'll give that a try and report back :-)