Taking Apart a 9090DB and Cleaning

BruceN

New Member
Hello:
I want to start out by saying that I don't know much about servicing vintage equipment but I am learning as I read this great forum.
Way back in the 70's I bought a Sansui 9090DB receiver, a pair of large ESS speakers and an Akai tapedeck. Although I haven't used them in years, I still have the Sansui and the Akai and I thought it would be great if I could get them working again. I recently hooked up the Sansui to an old Technics turntable and some fairly new JBL speakers. If I turn mostly the phono switch back and forth on the front of the Sansui. sometimes it makes a connection and I can get some pretty good sound. Same with the FM tuner switch. From reading this forum it sounds like the switches and pots need cleaning so I bought a Caig Technicians Survival Kit from Parts Express and I was going to follow some instructions I read from this forum on cleaning them. Tonight I was ready to start so I took the wooden cover off the Sansui as well as the front plate behind all the switches. However, I still cannot see the pots because there is another metal plate behind the faceplate which the power meters/guages are built into and I am afraid if I try to take that off, I might not be able to put it all back together or I might screw something up. Anybody with a 9090DB that can offer me some advice and instruction?
Thanks in advance,
Bruce
 
Bruce,

Welcome to AudioKarma.

Have you taken the bottom cover off? It will give you access to some of the pots. If you have the front face plate off, the best way to get to most of the other pots and switches is to remove the tuner assembly. Sounds scary but it’s actually pretty easy. If you look at the chassis, you will see a parting line that defines the lower and upper sections. The upper section of the chassis comes off with just a few screws and the whole tuner assembly comes with it. You can leave everything connected electrically and just move the top section with the whole tuner out of the way. You may have to take some of the wires out of the wire clips to give enough slack.

Be very careful cleaning the Dolby switch. Do not to flex the Dolby board. The Dolby board is a double-sided circuit board with a number of pass through connections that are just solder. These solder pass throughs often loose continuity. When that happens you will get intermittent or no operation of the Dolby features or loose one or both channels.

Good luck with it.

- Pete
 
Welcome to AK I own a Sansui 8080 and LBPete is right about the tuner section just go slow and be carefull and youll do fine.
 
Last night I took the tuner plate off and I could partially see a few pots, however, I tried to see where the wires were going into them and I couldn't. I believe that is where I am supposed to put a drop of cleaner. I then took the bottom plate off the receiver and things were still really not visable to me. So rather than doing something I would be sorry for I took the easy way out and put the receiver back together except for the face plate. I removed some additional thin nut fasteners which secured the rods (to which the knobs were previously attached) to the metal plate behind the face plate. There was some "play" now in most of these knobs. I then stood the receiver on end so that the area I was working on was on top. I then sprayed each rod first with De-Oxit and a few minutes later with ProGold. I let stand on end for a while and turned the rods (minus the knobs) back and forth. I put it all back together. I sprayed the phono connections on back and plugged in the old Technics turntable and played an ancient Beach Boys album. I nervously turned the receiver on. Even though the old record had a few "pops" when playing, it sounded really good now from both speakers. The volume was barely turned up. This "was and is" a great receiver. I plan on hooking up the reel to reel next but since it was working a few years ago, I am optimistic. Thanks, Bruce
 
Welcome to the insanity BruceN.

We're all a bunch of "lunatics":D

BTW, Do you remember what model of ESS's you owned? I've a pair of ESS AMT1's. They're fantastic!

Greg
 
What you have done is a bandaid fix. You managed to get some cleaner down the control shafts. After a while it will probably need cleaning again. If you remove the nuts that secure the controls to the chassis, you should be able to remove the control board with the controls on it. There are lots of connecting wires in this receiver and some are secured to the chassis with nylon clamps. you have to pull the wires out of the clamps in order to have enough play in the wires to remove the control board. Alternatively, if you can see the metal covers on the controls you can look for any small hole in the cover and inject the cleaner there.
 
Bruce,
Dr*Audio is right. You can’t get much cleaning from spraying up the shaft. Here’s a picture of the bottom of an 8080DB. It has the same chassis layout as your 9090DB. I’ve put the spray tube up against an opening of one of the pots on the volume/balance control assembly. There are a total of 4 pots ganged together. Potentiometers have a resistance film and a wiper that rides across it when you turn it. The idea is to get the cleaner on the resistance film and wiper to clean any dirt or oxidation. To do this effectively you need to get the cleaner inside the pot. The rear pots in this stack are about as easy to clean as any you will see. You can actually see the wiper through this slot. The front pots in the stack are more closed up but if you look around it’s circumference, you will find gaps. I’ve circled one and drawn arrows to point out the gaps on a different pot.

From your earlier description, you need to clean the Phono switch. The rotary switches are pretty accessible. Just turn them back and forth and watch which pieces are moving and spray them. Keep moving them back and forth to work the cleaner in.
 
Here’s a picture from the top with the tuner moved out of the way. It gives you good access to the push switches. These are more difficult to clean because it is hard to get the cleaner into them. There are small vent holes on top of these switches. Put the tip of the spray tube flat against these holes to spray directly into the hole. You will need to get a lot of cleaner into the switch so it works down into the contact area. It may take a couple of tries. Push the switch in and out to work the cleaner into the contacts. You can also try spraying into the face of the switch.

If you were able to take it apart and put it back together, doing the actual cleaning is pretty easy. Give cit another try.

- Pete
 
Thanks LBPete. That's just the instruction I needed and it's given me the courage to try again. I really appreciate it.
Bruce
 
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