Technics stereo. Blowing fuses...........:(
Paul Canning
Hi all,
Hope that someone here can help me.
I have a two year old Technics hi-fi, the ST-CA1080. Its only 2 years old
and not under warranty so when it suddenly stopped working i opened it up
and discovered that a 1.6 amp fuse had blown in the amplifier, it was the
one just inside the power source.
So off i go to local electronic shop and purchase a new set of fuses. But
every time i connect it back up it blows. Obviously this is not the main
problem and something else is wrong.
Anyone got any suggestions?
I really don't want to bring it to a repair shop because that will cost a
fortune.
Any suggestions will be greatly appreciated.
Thanks
Paul Canning
Bedford
UK
Scott Dorsey
On 22 Nov 1997 15:19:45 GMT, "Paul Canning"
<paul.c...@ukonline.co.uk> wrote:
>
>I have a two year old Technics hi-fi, the ST-CA1080. Its only 2 years old
>and not under warranty so when it suddenly stopped working i opened it up
>and discovered that a 1.6 amp fuse had blown in the amplifier, it was the
>one just inside the power source.
>
>So off i go to local electronic shop and purchase a new set of fuses. But
>every time i connect it back up it blows. Obviously this is not the main
>problem and something else is wrong.
First of all, does it blow instantly, or does it take a while to blow?
Does it blow with no speakers attached?
If the answer to both these questions is yes, you've got some device
shorted. If there are no individual channel fuses, it's almost certainly
an output transistor.
If you open up the back and you see lots of big power transistors,
replacing an output transistor is worth the money. If you see a big
black module with a lot of pins and an STK number on the case, throw
the amp away because it's not worth fixing.
Do be aware that these things are designed to have an expected lifetime
of two to four years, so you're getting due for a replacement anyway.
Welcome to the world of shoddy consumer electronics.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Gary Pearcey
On 22 Nov 1997 Paul Canning <paul.c...@ukonline.co.uk> wrote:
>I have a two year old Technics hi-fi, the ST-CA1080.
>and discovered that a 1.6 amp fuse had blown in the amplifier.
>So off i go to local electronic shop and purchase a new set of fuses. But
>every time i connect it back up it blows. Obviously this is not the main
>problem and something else is wrong.
Check the power rectifiers coming off the mains transformer. Perhaps a
power spike shorted one out. They may be separate or in a 4 pin bridge
block.
You will need an ohmeter to test, but I believe in your case you will
read a dead short across a bad rectifier diode. If you find one, make
sure the replacement has the same or greater PIV and ampere rating.
Michael Caplan
Have a look at the FAQ. It has a whole chapter on amplifiers with
ideas on what to look for. Its at:
http://www.paranoia.com/~filipg/REPAIR/
---------------------------------------------
On 22 Nov 1997 15:19:45 GMT, "Paul Canning"
<paul.c...@ukonline.co.uk> wrote:
>Hi all,
>
>Hope that someone here can help me.
>
>I have a two year old Technics hi-fi, the ST-CA1080. Its only 2 years old
>and not under warranty so when it suddenly stopped working i opened it up
>and discovered that a 1.6 amp fuse had blown in the amplifier, it was the
>one just inside the power source.
>
>So off i go to local electronic shop and purchase a new set of fuses. But
>every time i connect it back up it blows. Obviously this is not the main
>problem and something else is wrong.
>
Mark Kinsler
Scott Dorsey <klu...@netcom.com> wrote:
><paul.c...@ukonline.co.uk> wrote:
>>I have a two year old Technics hi-fi, the ST-CA1080. Its only 2 years old
>>and not under warranty so when it suddenly stopped working i opened it up
>>and discovered that a 1.6 amp fuse had blown in the amplifier, it was the
>>one just inside the power source.
>If you open up the back and you see lots of big power transistors,
>replacing an output transistor is worth the money. If you see a big
>black module with a lot of pins and an STK number on the case, throw
>the amp away because it's not worth fixing.
>
>Do be aware that these things are designed to have an expected lifetime
>of two to four years, so you're getting due for a replacement anyway.
>Welcome to the world of shoddy consumer electronics.
Not really. While the mechanical parts of consumer electronics aren't so
great, the electronics lasts just about forever unless external disasters
intervene. There's no way to build an integrated circuit cheaper and thus
have it fail sooner. Doesn't work that way: the problem is that they tend
to discontinue the manufacture of replacement parts after a few years,
which in some ways isn't much better.
Having said that, your particular external disaster was probably that you
momentarily short-circuited the speaker wires and damaged the power
amplifier. Like the man said, this could contain a big Sanyo STK---
module or two of them or separate power transistors. The modules are easy
to replace and generally cheap enough to make the job worthwhile. Some of
the modules have big resistors of about 0.1 or so ohms associated with
them, and it's likely that one of these is open as well. If you've
damaged a power transistor, you also may well have finished off associated
driver transistors and resistors, too.
Before you do anything, though, check the condition of the power supply
diodes. Maybe you got lucky and the only thing wrong is that one of these
shorted.
Panasonic used to be pretty good about protecting their power amps with
fuses. If they didn't in your reciever, install some yourself. Do the
math assuming an 8 ohm load to find the fuse needed for your amp's power
rating. Add 20% or so. Install a fuse (regular-type, not slow-blow) in
series with each amplifier output, usually somewhere between the amplifier
and the speaker selector switch. And have a look at your speaker wires.
Mark Kinsler
Phil Bright
Howdy...
I had a stereo that was blowing fuses left and right as fast as I could
replace them. The reason was that there was a short inside the power
transformer. This probably occurred as the result of 1) a shorted
power transistor, and 2) Low quality design and construction.
Phil
Glenn Watkins
Paul Canning wrote:
> Hi all,
>
> Hope that someone here can help me.
>
> I have a two year old Technics hi-fi, the ST-CA1080. Its only 2 years old
> and not under warranty so when it suddenly stopped working i opened it up
> and discovered that a 1.6 amp fuse had blown in the amplifier, it was the
> one just inside the power source.
>
> So off i go to local electronic shop and purchase a new set of fuses. But
> every time i connect it back up it blows. Obviously this is not the main
> problem and something else is wrong.
>
> Anyone got any suggestions?
>
> I really don't want to bring it to a repair shop because that will cost a
> fortune.
>
> Any suggestions will be greatly appreciated.
>
> Thanks
> Paul Canning
> Bedford
> UK
As I see it, you have only two choices. Take it to a repair shop and let them
fix it or buy a new one. Technics is a good brand and probably worth
repairing, as long as the repair doesn't exceed 50% of the replacement cost.
Most cheaper stereo components use Hybrid devices for the power amps and they
don't hold up to abuse quite as well as discrete components. The comment
about the STK devices being no-good is not right either. If you take care of
your stereo and don't punish it, it could last 10-15 years.
Use thick heavy gauge speaker wires and keep your volume at 50% or less and
you shouldn't have any problems. If you need more volume, then buy an
expensive power amp with a 5 yr guarantee and crank it....................
Glenn Watkins
Blue Ribbon TV Service
Bristol Pa 19007
mailto:blue...@comcat.com
http://www.comcat.com/~blueribb
lee mcdonald
Paul Canning wrote:
>
> Hi all,
>
> Hope that someone here can help me.
>
> I have a two year old Technics hi-fi, the ST-CA1080. Its only 2 years old
> and not under warranty so when it suddenly stopped working i opened it up
> and discovered that a 1.6 amp fuse had blown in the amplifier, it was the
> one just inside the power source.
>
> So off i go to local electronic shop and purchase a new set of fuses. But
> every time i connect it back up it blows. Obviously this is not the main
> problem and something else is wrong.
>
> Anyone got any suggestions?
>
> I really don't want to bring it to a repair shop because that will cost a
> fortune.
>
> Any suggestions will be greatly appreciated.
>
> Thanks
> Paul Canning
> Bedford
> UK
circuit
or via the speaker wires. Check that all is fine, best yet make sure
that speakers
are not connected at all.
I found that I have a fuse blowing in my amplifier (self built from
kits)
and that it was a marginal sizing so i upgraded the size to the next one
up.
If the fuse blows occasionally, then there may be either an intermittent
fault
or there is a gradual failure of the fuse due to carrying near full
rating current
continuously. Be very careful if upgrading the size of a fuse, as this
may have
undesirable consequences.
Was there something that may have led to this problem? Too high a load
(volume)
or spikes via the power supply, etc.
please note that I have only emailed this reply to you. If there is
detail that
you want to use, please post on alt.engineering.electrical
regards
Lee McDonald
ker...@globalcafe.ie
http://www.ozemail.com.au/~kermie
Petercoe
>If you open up the back and you see lots of big power transistors,
>replacing an output transistor is worth the money. If you see a big
>black module with a lot of pins and an STK number on the case, throw
>the amp away because it's not worth fixing.
>
>Do be aware that these things are designed to have an expected lifetime
>of two to four years, so you're getting due for a replacement anyway.
This is a foolish remark.
Pete...@aol.com
35 year tv repair
Petercoe
If someone has to ask about a dead short, someone else should look at the
equipment.
KuoH
lee mcdonald wrote:
> I found that I have a fuse blowing in my amplifier (self built from
> kits)
> and that it was a marginal sizing so i upgraded the size to the next one
> up.
1.6A almost seems too small for a decently high powered amp. Most
amps I've come across use 3-5A fuses at least. Maybe the power supply
in that Technics is very efficient? Heck my little Panasonic VCR uses
1.6A fuses.
KuoH
dont...@nothing.com
Glenn Watkins wrote:
>
> Paul Canning wrote:
>
> > Hi all,
> >
> > Hope that someone here can help me.
> >
> > I have a two year old Technics hi-fi, the ST-CA1080. Its only 2 years old
> > Anyone got any suggestions?
> >
> > I really don't want to bring it to a repair shop because that will cost a
> > fortune.
> >
> > Any suggestions will be greatly appreciated.
> >
> > Thanks
> > Paul Canning
> > Bedford
> > UK
>
one of the power amplifiers that may be blown (one of the two big chips
connected to the heat sinks -- runs about $50). Look at the leads going
into the board and you may see that one of the middle ones from one of
the chips is a little discolored from heat.
I'm not advocating doing this, but temporarily bypassing the fusing
altogether (let's face it, it's broken) you may be able to get one of
the pins to glow so you know which of the two chips it is. Obviously
don't do this unless you know what you are doing, are prepaired for the
worst (as we were), and you don't have another option. This is not
considered good practice.
Petercoe
I doubt that the transformer was shorted.
Andy Cuffe
dont...@nothing.com wrote:
>
> Glenn Watkins wrote:
> >
> > Paul Canning wrote:
> >
> > > Hi all,
> > >
> > > Hope that someone here can help me.
> > >
> > > I have a two year old Technics hi-fi, the ST-CA1080. Its only 2
years old
> > > ....
> > > Anyone got any suggestions?
> > >
> > > I really don't want to bring it to a repair shop because that will cost a
> > > fortune.
> > >
> > > Any suggestions will be greatly appreciated.
> > >
> > > Thanks
> > > Paul Canning
> > > Bedford
> > > UK
If it has IC's for the audio output you can just remove one of them. If
the fuse still blows try removing the other one. If the fuse blows with
both output ICs out you know there are problems in an other part of the
amp, probably the power supply.
If it uses transistors instead of ICs you just need to check them with
an ohm meter. The bad ones almost always measure close to 0 ohms
between at least 2 of the three pins. Once you find the bad pair try
the stereo with them removed. You should get normal sound from the
channel with the good transistors. To determine if there is more damage
to the amplifier you can swap the good transistors into the damaged
channel. Before you remove anything WRITE DOWN where they go because
it's easy to get them mixed up. I strongly recommend that you don't
bypass the fuse unless you don't want to fix it very much. I have seen
a lot of repairable electronics ruined by this type of troubleshooting.
--
Andy Cuffe
balt...@psu.edu
Mark D. Braunstein
KuoH <Ku...@aol.com> wrote:
>lee mcdonald wrote:
>KuoH
This may sound like a tangential comment but the timing is
spectacular...
My 1979 (yes, 18 years ago) Technics stereo receiver finally started
blowing fuses! How's that for reliability! My guess is that the filter
capacitors or output coupling circuitry has finally bit the big one.
In my spare time I'll get a repair manual and dig into to it.
Mark D. Braunstein
markbra...@mindspring.com
Klaus Syttkus
Glenn Watkins (blue...@comcat.com) wrote:
: Paul Canning wrote:
: > Hi all,
: >
: > Hope that someone here can help me.
: >
: > I have a two year old Technics hi-fi, the ST-CA1080. Its only 2 years old
: > and not under warranty so when it suddenly stopped working i opened it up
: > and discovered that a 1.6 amp fuse had blown in the amplifier, it was the
: > one just inside the power source.
: >
: > So off i go to local electronic shop and purchase a new set of fuses. But
: > every time i connect it back up it blows. Obviously this is not the main
: > problem and something else is wrong.
: >
: > Anyone got any suggestions?
: > I really don't want to bring it to a repair shop because that will cost a
My advice: Do NOT bypass the fuse. The amp is having serious problems, and
you will most probably add some problems by mending the fuse.
From my experience there are two possible reasons for blowing fuses:
1. A defect in the power supply (try to check the bridge rectifier and the
electrolytics)
2. a defect in one of the power stages.
Open the cover (can you have a look at the solder side of the PCB?) and look
hard for bad solder junctions and burnt components.
My brother-in-law's amp had quite the same problem. It took me 15 minutes to
find the loose solder pad in one of the power stages and fix the problem.
The fuse had saved all of the components!
Good luck.
Klaus.
Doc.M
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