repairing sansui 9090db vintage receiver

[ctw]

Anyone out that advising me regarding repair a vintage sansui 9090db receiver.
One channel has lower output (wattage) than the other.

Cal

[Don Pearce[_3_]]

On Thu, 27 Oct 2011 17:43:15 +0000, ctw >
wrote:

>
>Anyone out that advising me regarding repair a vintage sansui 9090db
>receiver.
>One channel has lower output (wattage) than the other.
>
>Cal

Could be almost anything. Does it have connectors on the back that
allow you to plug in, say, a CD player? If so try and see if the
problem is still there. If it is, it is certainly the amplifier to
blame. You will need a schematic to get any deeper than that.

d

[chuck]

On Thu, 27 Oct 2011 17:43:15 +0000, ctw >
wrote:

>
>Anyone out that advising me regarding repair a vintage sansui 9090db
>receiver.
>One channel has lower output (wattage) than the other.
>
>Cal


Back in the day when I worked on these beauties, they came in with
intermittent tape monitor switches, low pass filter switches, mode
switches etc., etc.. I would spray Deoxit 5 into these switches and
work them. It might take care of the issue. If not , it is probably
caused by dried out electrolytics in the preamp / tone circuits. Chuck

[Phread[_2_]]

chuck wrote:
> On Thu, 27 Oct 2011 17:43:15 +0000, ctw >
> wrote:
>
>>
>> Anyone out that advising me regarding repair a vintage sansui 9090db
>> receiver.
>> One channel has lower output (wattage) than the other.
>>
>> Cal
>
>
> Back in the day when I worked on these beauties, they came in with
> intermittent tape monitor switches, low pass filter switches, mode
> switches etc., etc.. I would spray Deoxit 5 into these switches and
> work them. It might take care of the issue. If not , it is probably
> caused by dried out electrolytics in the preamp / tone circuits. Chuck

+1

I fixed a 9090db a month or two ago. Both channels coming and going
and half the display out. Oxidized switch contacts and open caps, and a
shorted zener in a power supply feeding part of the display. IIRC there
were bad solder joints at the filament pins on the frequency display tube.
You'll have to improvise on the dial & display lamps if you don't want to
pay a fortune for them. The schematic is on the 'net if you look, and for
free if you look as hard as I did.

Note the 9090db has nothing in common with the 9090 which is an 8080
with a little higher rail voltage for a few more watts.

Equipment this old needs a full electrolytic cap job to be reliable for more
than the next month or two. Seriously. Plus, it will improve the sound. A
lot. Actually, a whole lot if you use good caps like 105 degree low Z caps
intended for switching power supply applications.

Good luck!

Fred

[Mark Zacharias]

"Phread" > wrote in message
...
> chuck wrote:
>> On Thu, 27 Oct 2011 17:43:15 +0000, ctw >
>> wrote:
>>
>>>
>>> Anyone out that advising me regarding repair a vintage sansui 9090db
>>> receiver.
>>> One channel has lower output (wattage) than the other.
>>>
>>> Cal
>>
>>
>> Back in the day when I worked on these beauties, they came in with
>> intermittent tape monitor switches, low pass filter switches, mode
>> switches etc., etc.. I would spray Deoxit 5 into these switches and
>> work them. It might take care of the issue. If not , it is probably
>> caused by dried out electrolytics in the preamp / tone circuits. Chuck
>
> +1
>
> I fixed a 9090db a month or two ago. Both channels coming and going
> and half the display out. Oxidized switch contacts and open caps, and a
> shorted zener in a power supply feeding part of the display. IIRC there
> were bad solder joints at the filament pins on the frequency display tube.
> You'll have to improvise on the dial & display lamps if you don't want to
> pay a fortune for them. The schematic is on the 'net if you look, and for
> free if you look as hard as I did.
>
> Note the 9090db has nothing in common with the 9090 which is an 8080
> with a little higher rail voltage for a few more watts.
>
> Equipment this old needs a full electrolytic cap job to be reliable for
> more
> than the next month or two. Seriously. Plus, it will improve the sound.
> A
> lot. Actually, a whole lot if you use good caps like 105 degree low Z
> caps
> intended for switching power supply applications.
>
> Good luck!
>
> Fred
>

These also had problems with bad (solder) feedthrough connections on the
Dolby switch board.

Mark Z.