I was wondering if somebody could tell me how to fix a problem I'm
having with my Sansui AU-101 solid state amplifier.

Since I got the device, I'm having this problem with my right channel.
The left channel works perfectly, but the right one doesn't produce any
sound. When I turn up the volume to the maximum, I can hear some very
soft noise on the right channel.

I think the problem is located in one of the 4 transistors located at
the rear end of the amplifier. When i was trying to obtain the voltage
going through the transistors, i accidentally hit the base of one of
them, and for a few minutes the amp worked perfectly again. :S

As far as i see, the base of all 4 transistors are not connected to the
printboard. It says 'Hitachi 1060D'. Unfortunately i didn't find any
specifications of the (FET?) transistor on the net, nor do I have a
technical scheme of the amplifier.

I hope somebody will be able to tell me how I can find a nice
equivalent for this transistor.

Thanks in advance!

Robin

In article .com, "Robin" wrote:
I was wondering if somebody could tell me how to fix a problem I'm
having with my Sansui AU-101 solid state amplifier.

Since I got the device, I'm having this problem with my right channel.
The left channel works perfectly, but the right one doesn't produce any
sound. When I turn up the volume to the maximum, I can hear some very
soft noise on the right channel.

I think the problem is located in one of the 4 transistors located at
the rear end of the amplifier. When i was trying to obtain the voltage
going through the transistors, i accidentally hit the base of one of
them, and for a few minutes the amp worked perfectly again. :S

As far as i see, the base of all 4 transistors are not connected to the
printboard. It says 'Hitachi 1060D'. Unfortunately i didn't find any
specifications of the (FET?) transistor on the net, nor do I have a
technical scheme of the amplifier.

I hope somebody will be able to tell me how I can find a nice
equivalent for this transistor.

Thanks in advance!

Robin


Output relay?

greg

"Robin" wrote in message
oups.com...
I was wondering if somebody could tell me how to fix a problem I'm
having with my Sansui AU-101 solid state amplifier.

Since I got the device, I'm having this problem with my right channel.
The left channel works perfectly, but the right one doesn't produce any
sound. When I turn up the volume to the maximum, I can hear some very
soft noise on the right channel.

I think the problem is located in one of the 4 transistors located at
the rear end of the amplifier. When i was trying to obtain the voltage
going through the transistors, i accidentally hit the base of one of
them, and for a few minutes the amp worked perfectly again. :S



Faulty transistors do not exhibit this sort of "working sometimes" behaviour
so there is no point buying any more. If the sound came back after a
mechanical "hit" then there is probably a dry joint somewhere, or as Greg S
suggests, a dirty relay, if there is one. Go back and, with the amp
outputting music to speakers, start tapping the PCB and large components
with a wood or plastic implement and you may be able to zoom in on the bad
connection.




Gareth.




As far as i see, the base of all 4 transistors are not connected to the
printboard. It says 'Hitachi 1060D'. Unfortunately i didn't find any
specifications of the (FET?) transistor on the net, nor do I have a
technical scheme of the amplifier.

I hope somebody will be able to tell me how I can find a nice
equivalent for this transistor.

Thanks in advance!

Robin

In article ,
Gareth Magennis wrote:

Faulty transistors do not exhibit this sort of "working sometimes" behaviour
so there is no point buying any more. If the sound came back after a
mechanical "hit" then there is probably a dry joint somewhere, or as Greg S
suggests, a dirty relay, if there is one. Go back and, with the amp
outputting music to speakers, start tapping the PCB and large components
with a wood or plastic implement and you may be able to zoom in on the bad
connection.

It's not all that unusual, I think, for the transistors' solder joints
to the PC board to go bad after some years on some amplifiers. Seems
to be due to a combination of inadequate wetting of the joint due to
soldering (poor choice of solder/flux in some cases), and thermal
stress on the joint over thousands of heat-up/cool-down cycles.

As Gareth suggested, tapping on the board with a wooden or plastic
probe is a good way to find the locations of such problems. The usual
fix is to remove the existing solder (I prefer to use non-tinned
solder wick, dipped in a bit of liquid rosin flux), lightly scrape the
surfaces of the transistor leads and the PCB pad or eyelet, and then
re-solder with good rosin-core flux and clean the board. If you find
one "cold" or cracked solder joint, it'd probably be a good idea to
re-do all of the joints on all of the power and driver transistors...
the problem might not be limited to one.

Other causes for the "I can just barely hear one channel" problem are
dirty relay contacts (as suggested), dirty switch contacts, worn
potentiometers, and failing inter-stage electrolytic coupling
capacitors. Tracing forwards and backwards in the signal path, using
a signal injector or a detector-probe or oscilloscope, can often pin
down the location of the failing component pretty quickly.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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