Mark D. Zacharias
July 31st 03, 03:16 AM
OK, I've been waiting to post this. Here it goes:
First, learn some electronic theory and fundamentals, so that you will not
injure or kill yourself, and so you will know a bad part when you find one.
It is critically important to understand theory of operation and signal-flow
if you are to have any hope of repairing most equipment.
Buy a relatively inexpensive digital multimeter, probably at Radio Shack.
An oscilloscope would also be most useful; a decent used one can usually be
found for 100.00 or less.
Learn the appropriate safety considerations for using the tester and 'scope.
There are special considerations for working on most televisions and other
equipment not using a built-in isolation transformer. Most servicers use an
isolation transformer for any AC-powered unit under test.
Learn how to use the multimeter to measure resistance, voltage, and current.
Learn how to use the oscilloscope to observe and analyze waveforms.
Buy a soldering iron, solder, and desoldering equipment.
Learn how to solder and unsolder without damaging the circuit board.
Find a source for replacement parts. Most suppliers have about a 15.00
minimum order.
Order the replacement parts and install them.
Clean the circuit board where you were soldering. Treat the job as if it
were going to be inspected afterwards and graded for neatness.
Visually inspect the piece for any other problems or safety issues.
NOTE:
You are personally responsible for any safety problems you cause, or those
which you
SHOULD have noticed and failed to correct. So if you work on a TV and it
burns down your friend's house in the middle of the night because
of something you missed or that you caused, they can sue you, even years
later.
At this point you can just replace a blown fuse, if any, plug the unit in,
and hope your new parts don't just fail again because you missed something
or installed a part incorrectly. (Or you could use an AC variac to bring up
the line voltage slowly while measuring voltages etc. MCM sells one for
90.00)
Check for normal operation. Watch for any signs of overheating, hum, smoke,
etc and be prepared to shut down quickly.
Test for longer-term operational stability, check for neatness of lead
dress, re-assemble the rest of the way, making sure not to pinch any wires
etc. Make up your mind to re-assemble the piece exactly as it was. If there'
s screws left over, you did a sloppy job.
Final test the piece, and satisfy yourself that there is no possibility of
leakage current between any exposed metal and the AC line. There are several
ways of doing this. Please refer to the manufacturers' service data or your
textbooks.
Decide how to politely tell friends, family, freeloaders and cheapskates
that you must charge appropriately for your work.
Welcome to the exciting world of electronics repair.
Mark Z.
"Sofie" > wrote in message
...
> George:
> Based on your original posting, a manual and a schematic are NOT going to
be
> much help to you...... it will only be of most use to an experienced and
> knowledgeable tech with the proper test equipment, tools, replacement
parts,
> etc. In fact, most techs will repair this kind of problem without the
> manual and schematic.
> The Sansui 9090 is a very nice old and powerful receiver and is worth
> repairing. Take it to a repair shop BEFORE any failed, botched or
aborted
> home repair attempts and at the very least get a repair cost estimate so
you
> can make an INTELLIGENT repair decision with facts instead of internet
> guesses.
> --
> Best Regards,
> Daniel Sofie
> Electronics Supply & Repair
> -----------------------------------
>
>
> > > Today I turned on the Sansui 9090 and the flashing red protector
light
> next to
> > > the power button continuously flashed and the stereo never did go on.
> The tuner
> > > seemed to be picking up signals, as evidenced by the signal meter,
but
> the
> > > sound output meters registered zero and no sound came from the
speakers.
> Usually
> > > the light flashes red for a few seconds, turns green and then the
tuner
> and
> > > stereo activates. Can someone tell me what the cause might be and if
> there is a
> > > simple fix> > I don't have a manual for the unit, and have no idea
what
> the protector light is
> > > for. Can someone tell me where to obtain a manual?
> > > Thanks.
> > > George
>
>
>
First, learn some electronic theory and fundamentals, so that you will not
injure or kill yourself, and so you will know a bad part when you find one.
It is critically important to understand theory of operation and signal-flow
if you are to have any hope of repairing most equipment.
Buy a relatively inexpensive digital multimeter, probably at Radio Shack.
An oscilloscope would also be most useful; a decent used one can usually be
found for 100.00 or less.
Learn the appropriate safety considerations for using the tester and 'scope.
There are special considerations for working on most televisions and other
equipment not using a built-in isolation transformer. Most servicers use an
isolation transformer for any AC-powered unit under test.
Learn how to use the multimeter to measure resistance, voltage, and current.
Learn how to use the oscilloscope to observe and analyze waveforms.
Buy a soldering iron, solder, and desoldering equipment.
Learn how to solder and unsolder without damaging the circuit board.
Find a source for replacement parts. Most suppliers have about a 15.00
minimum order.
Order the replacement parts and install them.
Clean the circuit board where you were soldering. Treat the job as if it
were going to be inspected afterwards and graded for neatness.
Visually inspect the piece for any other problems or safety issues.
NOTE:
You are personally responsible for any safety problems you cause, or those
which you
SHOULD have noticed and failed to correct. So if you work on a TV and it
burns down your friend's house in the middle of the night because
of something you missed or that you caused, they can sue you, even years
later.
At this point you can just replace a blown fuse, if any, plug the unit in,
and hope your new parts don't just fail again because you missed something
or installed a part incorrectly. (Or you could use an AC variac to bring up
the line voltage slowly while measuring voltages etc. MCM sells one for
90.00)
Check for normal operation. Watch for any signs of overheating, hum, smoke,
etc and be prepared to shut down quickly.
Test for longer-term operational stability, check for neatness of lead
dress, re-assemble the rest of the way, making sure not to pinch any wires
etc. Make up your mind to re-assemble the piece exactly as it was. If there'
s screws left over, you did a sloppy job.
Final test the piece, and satisfy yourself that there is no possibility of
leakage current between any exposed metal and the AC line. There are several
ways of doing this. Please refer to the manufacturers' service data or your
textbooks.
Decide how to politely tell friends, family, freeloaders and cheapskates
that you must charge appropriately for your work.
Welcome to the exciting world of electronics repair.
Mark Z.
"Sofie" > wrote in message
...
> George:
> Based on your original posting, a manual and a schematic are NOT going to
be
> much help to you...... it will only be of most use to an experienced and
> knowledgeable tech with the proper test equipment, tools, replacement
parts,
> etc. In fact, most techs will repair this kind of problem without the
> manual and schematic.
> The Sansui 9090 is a very nice old and powerful receiver and is worth
> repairing. Take it to a repair shop BEFORE any failed, botched or
aborted
> home repair attempts and at the very least get a repair cost estimate so
you
> can make an INTELLIGENT repair decision with facts instead of internet
> guesses.
> --
> Best Regards,
> Daniel Sofie
> Electronics Supply & Repair
> -----------------------------------
>
>
> > > Today I turned on the Sansui 9090 and the flashing red protector
light
> next to
> > > the power button continuously flashed and the stereo never did go on.
> The tuner
> > > seemed to be picking up signals, as evidenced by the signal meter,
but
> the
> > > sound output meters registered zero and no sound came from the
speakers.
> Usually
> > > the light flashes red for a few seconds, turns green and then the
tuner
> and
> > > stereo activates. Can someone tell me what the cause might be and if
> there is a
> > > simple fix> > I don't have a manual for the unit, and have no idea
what
> the protector light is
> > > for. Can someone tell me where to obtain a manual?
> > > Thanks.
> > > George
>
>
>