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Twice Bitten Sansui 9090DB

ImWolf

ImWolf

Active Member
Sansui 9090DB Serial No. 826100046. After poking around the data bases here, this might be the oldest one on the AK site? (not necessarily a good thing). I started describing this receiver on a previous (Repairs & Servicing in Washington State) thread, which has now been deleted entirely.

After 3 months with the most highly recommended tech in my area, he gave it back to me with multiple issues and told me never to bring him another one. $240 for some bulbs and some cleaning? He told me along the way that the Dolby function had been by-passed because he saw “about 10 jumpers added”.

1) Channel Dial Illumination. The lighting at either end of the dial
keep turning on/off at will. Tapping on top of the cabinet or pushing
on the face sometimes affects the lighting.

2) Left and Right channel output is inconsistent. Mostly a problem
with the Right channel going out, and resumes when I rotate the
Input Selector Knob.

3) Tape Monitor Functions Crippled. While listening to Radio or Aux
input, pressing one of the Tape Monitor buttons should bypass the current input, but does not.

4) Dolby function is messed up. I usually leave the Dolby knob at the
OFF position, but when I do turn it to other settings the audio will
either stop completely, or change tone/volume a lot.

5) Bass, Trebble, and Midrange filter switches and knobs barely make a difference to the sound of what I'm listening to at the time.

I contacted a 2nd tech in the vicinity describing the above, and he wanted nothing to do with it. Ended up taking it to another tech and just got it back home a few days ago. After inspection he e-mailed me estimates;

Needs new
1 PUSH SWITCH CIRCUIT BOARD
2 Dolby board
3 Filters
4 input switch
5 rewiring

Repair cost could be about $800

Or you can use Radio and aux input only.
Lights we will replace it.
Sound we can fix it and replace capacitors (filters)
Repair cost could be about $285-$345

When I asked him about what needs to be rewired, he said there were wrong connections, and connections missing. Also, the 36 contacts between the Dolby Switch & daughter board had grey ribbon cable that didn’t look right.

I know there aren’t any NEW parts he mentioned to be had, and I didn’t want to go for either of his quotes for his idea of a full, or partial repair.

To start with I’m going to post a bunch of pictures, and hopefully you guys who are very familiar with these might spot something that doesn’t look right. The only things that jumped out at me are that the bracket some units have to support the F-2624 Driver board is missing (not sure it ever had one), and 4 of the screws (closest to the faceplate) that hold the Tuner Tray down are also missing.

Then, I really want to remove the Tuner Tray and take some photos of what’s under there to get an idea of what these two techs are talking about relative to added jumpers or strange wiring.

From what I’ve studied thus far, it looks like I would only need to pull out 3 plugs that are side by side connected to the F-2653 Eq. board, and possibly the one yellow wire connected to the “Front End” with a small spade connector. The faceplate appears to be attached to the Tuner Tray with 2 small screws on top, but it looks like I can just pull off the tuning knob, and then slide the tuner tray back after removing the necessary screws?

If for some reason however it would be safer to remove the faceplate first for reasons I’m ignorant of, please let me know. Also, would it be better to do this with the unit laying flat, or on it’s side like others choose to do?

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This last photo of someone else's unit shows the missing bracket over the Driver Board. Do all the 9090DB's have one originally?

Driver Board Support Plate.jpg
 
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Looking back myself, a lot of the wiring and soldering on the inside of that back panel does look messed up. Is this an example of Sansui's best work?
 
I've seen worse. Plenty worse.
The plastic dash light enclosure is not yellowed or cracked, that tells me heat has been kept to a minimum.
That's an excellent sign.

There is nothing unusual about the wiring except the fact the tech snipped all the wire ties and did not replace them.
Sloppy work. Did he also forget any screws? Particularly grounding screws.

The function switch is a notorious failure point on the 9090/8080, db and non-db alike.
If it can't be cleaned, there is a guy on flea-Bay that makes a drop-in substitute for db and non-db.
It aint' cheap, but it's works.

Any equipment this old is going to have switch issues.
In most cases, a good tech can clean the contacts, but not always.
Some controls simply get worn out, or get too corroded to salvage.

It's one thing to pay a tech top dollar for his services, but if he doesn't fix it, he either owes you money, or has to make it right.
 
The intermittent lamps are likely just bad solder connections on the fuse lamp sockets (I see this all the time). The Dolby PC board can be completely disconnected and bypassed without loosing the tape monitors (see posts about Dolby bypass). The input selector switch usually responds to cleaning well (if not it can usually be repaired). There are flame proof resistors on the driver board and some in the power supply circuit, that need to be replaced. I don't remember ever having to replace the main filter caps on a 9090 or 9090DB (and I have serviced many). There may be some other issues that need attention, but that is a VERY nice receiver, and deserves to be fixed.
 
It's really so sad how some of these great recievers have been butchered up. I had one like this and I ended up parting it b out just to much wrong with it..
 
ImWolf said:
Is this an example of Sansui's best work?
Click to expand...
Tipical sansui wiring yes, early unit, seems in good condition, just dirty, symptoms mentioned are the usual for a 50 year old untouched unit.
Too much drama around the dolby board on my opinion, resolder (some pins), clean it well, change the cable IF needed and move on, not need to hack it is my experience and personal opinion.
But I usually work on basket cases, I've seen units parted out just for laziness and/or over enthusiast people that dives in just replacing stuff, hacking and then having a very pretty BIG paperweight.
You're in a great place to start, good luck..
 
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The lamp problem is bad solder joints on the lamp holders.
The intermittent channel is the selector switch needs cleaning or the speaker relay needs to be replaced.
There are instructions for properly bypassing the Dolby board. This one was done improperly, that's why the tape functions don't work.
The ribbon connectors to the Dolby board need to be replaced if they are the green flat flex cables. Normal ribbon cable works fine. If you can find some ribbon cable with solid wires it's easier to work with.
All the solder joints on the tuner regulated supply board will have to be re-soldered.
Any flameproof resistors in the amp section must be replaced.
This is The Way.
 
ConradH said:
It's dirty, but I'm not seeing all these horrible things that were described. Would be nice to see the underside of the boards.
Click to expand...
Agreed. I already made the mistake of not popping the top off between visits to the two different tech shops. Now I have missing parts and nobody to directly point a finger at. The guy that I just got it back from did however add some new scratches to the already abused cabinet. This receiver was not someone's well preserved treasure!

Later today I will remove that faceplate just to keep it from being damaged while doing more disassembly. I've never worked on anything like this, so I need to go slow and try not to make things worse. I've done a lot of reading on this subject, but that's no replacement for real experience. And there are opposing views on so many aspects of cleaning and repairing.

In the days ahead you can probably expect some silly questions from me, like what's a flame proof resistor, and where are they? LOL
 
ImWolf said:
In the days ahead you can probably expect some silly questions from me, like what's a flame proof resistor, and where are they? LOL
Click to expand...
I think he's talking about 'fusible resistors' those things drift in value with time causing problems mainly on the driver board. Information about them is on the pinned section of Sansui frequently asked and more.
 
Hipocrates said:
I think he's talking about 'fusible resistors' those things drift in value with time causing problems mainly on the driver board. Information about them is on the pinned section of Sansui frequently asked and more.
Click to expand...
I'm pretty sure they are flameproof. But they go open so they end up being fusible.
 
Just take it easy and be structured, this unit require some work, but that's it.
One section at the time, easy and methodically... the main issue on this units are the pots, switches and fusible resistors.
After that, is destroyed traces, these boards are very delicate, so try to practice in something before so you can hone your soldering skills.
To have a functional Dolby; is some tedious work but is not complicated.

I clean my switches, encoders and pots like this.

1. Flush them with IPA and exercise them.
2. Apply Deoxit and leave it for 12 to 24 hours, (tiny amount)
3. Flush them with IPA and exercise them. Let them dry
4. Apply deoxit and excersize.
I use syringes to get to tiny places, put the IPA and the deoxit there.

Put, paper towels around then so you don't flush everything. While this works for me, other people with better skills than me disassemble everything, If you do that be extremely precise about the wafers order.
dr*audio said:
I'm pretty sure they are flameproof. But they go open so they end up being fusible.
Click to expand...
Agreed, however since the information is provided as ''fusible resistors", I clarify to the OP so he can find it and not get confused.
 
Hipocrates said:
I clean my switches, encoders and pots like this.
Click to expand...
In anticipation of some cleaning, I at least (now) have a spray can of CRC 05103 QD Electronic Cleaner (same as 99% IPA?), and a small jug of the DeoxIT D100L with the Needle Applicator. These are just for pots and switches. I've been lightly brushing on the PCB's so far, but the component side of these need much more. Lots of opinions out there too on the best way to really clean these things up.

Just checked evilBay and there are 3 of my missing brackets listed.... $50 - $80 (nuts!). I wonder how many techs out there discover they have left over parts they can sell online? Is there an AK data base for chassis and associated hardware part dimensions?
 
Hipocrates said:
Only swithes, F5 for pots, D100L can hurt the carbon on the pots is what the internet says and since those pots are rare, I'm not taking the chance and use F5 for that.
Click to expand...
Isn't the "carbon on the pots" what I want to hurt, and get rid of?
 
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