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9090DB, only tape 2 works

Swan1493

Swan1493

New Member
I've got a Sansui 9090DB that all the inputs are quiet except tape 2. Tape 2 sounds great. Is this still a Dolby board issue?

What I've done: de-oxed switches multiple times and connections in back, audio is better every time but only in tape 2. Dolby board pass-throughs reflowed with capacitor leads soldered through roughly as described in the FYI by Pete, this got the receiver out of protection mode. It's a latter model without the common failing green leads to the switch panel so I didn't entirely remove the Dolby board when I reflowed it.

What I know. Phono 1,2, aux input present in both channels but very quiet. Tape 1 has given me intermittent good audio from 1 channel but mostly just quiet like the other inputs.
I'm assuming to keep chasing the Dolby board but any advise as to other roads to try would be appreciated.
 
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Maybe the Tape monitor switch and selector switch. I needed to clean the various waffer sections on 9090 with a tooth brush dipped in deoxit and scrub the black buildup off to get it working properly.
 
1old_wizard said:
+1 on petes' picks..... they sale Deoxit in a bottle & use a black toothbrush.
Click to expand...
Ok I'll focus on both of those switches. I used the spray deoxit 4 times to the wafers and rotated the input switch a few dozen times, that's it. I have some 100% deoxit in a 2mL tube I dabbed into the holes on the tape monitor switch.
I should probably properly remove both switches and dismantle, clean with the 100% deoxit, and reassemble since spray and repeated on/off didn't help.
 
I vote for switches also. We use Corrosion X for clean/lube of switches. Exercise every switch at least 25 times. You can do it with the unit on at low level. That way, you'll know what the problem is.
 
I had tried spritzing with deoxit 3 times and working switches about 50x's and nothing. I removed face plate at the time and it exposed a couple of gaps to get at switches, used pipe cleaners and other assorted items to get to hard to reach places. If you have one of them cheapy hotel tooth brushes the one I had was thin enough to fit between some of the smaller spaces between wafers. Be sure to do both sides of wafers. Mine hasnt had issues sense, although it still only powers on while on its side and not while horizontal but will wait until I decide to tackle known noisy transistors and recap to fix that issue as same time, sounds better than 90% of my receivers as it sits though.
 
Looking more like switches are not the problem. Tape 1 disassembled, cleaned thoroughly. Nothing.
Several hours disassembling the rails and moving the input selector board as to best be available and meticulously cleaning the wafers with contact cleaner, deoxit. Then scrubbed with flat brush, then magic eraser held with tiny hemostats. That really cleaned it up. Rinsed with deoxit and then alcohol swabs to remove any remains of mr clean. Most contact points looked really great on the waffers.

No change in outcome at any point.

Tape 2 still sounds great. Everything else is soft/faint.
 
I'd try switching to one of the dead modes and bending the dolby board a bit ... carefully! Just pull up on a corner and press the board with a pencil eraser in a few spots. Old school trick to track down an intermittent solder connection, which would be typical of the pass throughs on that board. Worked on old TV sets anyway ...

Not to mention old Sansui's ... imagine my surprise when I went digging into a "professionally restored" 9001 and found this.

4channel-wedgie.jpg


Old receiver foot, jammed in between the boards, doing exactly what I mentioned earlier and giving the cold solder a wedgie ... <G>

PS ... if it IS the dolby board, you MIGHT be able to get away with retouching the pass throughs with fresh solder, but ... luck wit dat, eh. Only real way to guarantee results is to pull the board, pin it, and be done with it. Your call there ... do it right, and do it once.
 
sKiZo said:
I'd try switching to one of the dead modes and bending the dolby board a bit ... carefully! Just pull up on a corner and press the board with a pencil eraser in a few spots. Old school trick to track down an intermittent solder connection, which would be typical of the pass throughs on that board. Worked on old TV sets anyway ...

Not to mention old Sansui's ... imagine my surprise when I went digging into a "professionally restored" 9001 and found this.

4channel-wedgie.jpg


Old receiver foot, jammed in between the boards, doing exactly what I mentioned earlier and giving the cold solder a wedgie ... <G>

PS ... if it IS the dolby board, you MIGHT be able to get away with retouching the pass throughs with fresh solder, but ... luck wit dat, eh. Only real way to guarantee results is to pull the board, pin it, and be done with it. Your call there ... do it right, and do it once.
Click to expand...

I couldn't get a bit of change with all manners of gentle and controlled pushing and pulling.
I could get the faint audio from the aux to drop off if I pushed in one spot, but that is the only change I found.
With the Dolby in place I reflowed and dropped extra pins at any questionable point including where I could get the aux audio to drop out and that seemed to have fixed that. But still only tape 2 plays normally.

Only things I can see to do next would be replace the ribbon cable from the push buttons to the Dolby board.
Or learn to trace a signal with a scope and find the common place with the other inputs and tape 1.
 
I'm going to eliminate the input rotoswitch as the main problem. Running a jumper from the Dolby input to the tape 2 input gives me AM,FM,AUX, and 1 channel of phono 1,2 (investigate that later)
So the problem is in the Dolby board between the main input and tape 1 input routes? IMG_6263.JPGIMG_6262.JPGIMG_6263.JPG
 
On the dolby board. Check and make sure that all the wafers in the wafer switch are turning . I had one that the wafer shaft was disengaged and slide from the front wafer. Had to reposition the wafer and shaft . Then push/ snap the shaft back into position.
 
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Hello guys ,
I wanted the help of you with a problem on my 9090db when I turn it on the red light does not light and does not trigger the relay, as if the f-2657 card was not receiving power.
What could it be?
Thank you.
 
Emersonlira said:
Hello guys ,
I wanted the help of you with a problem on my 9090db when I turn it on the red light does not light and does not trigger the relay, as if the f-2657 card was not receiving power.
What could it be?
Thank you.
Click to expand...
Emerson. Start a seperate thread for your 9090DB.:thumbsup: Disconnect and remove your F-2624 driver board and see if the protect relay "clicks".
 
Emerson....
Also check R32 on the F-2656 power supply board. Should be a 1 Ω 1/2 watter. Might just be a bad solder connection on that resistor. Or the resistor may be "open".
 
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Thanks avionic, I tested the f-2656's R32 and it really was open I made the exchange of it and my 9090db came back to work. Thanks you guys are really best.:music:
 
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