Diagnosing old Sansui

[fishstics]

First off I'm new to the site, glad to be here . I tried finding somewhere on reddit that could help me out but I figured here would net me better results.


Tldr I was cleaning out aunt's shed and stumbled on this old Sansui 9900z that she ended up giving me and now I'm trying to get it working again.



After some dusting and cleaning the interior I got it plugged up and at first I thought the left channel was dead, but after spraying down with some contact cleaner and making sure the wires were tight I got 3/4 of the speakers working. The right channels on the bottom work fine but it seems the A and B terminals don't work at all on the left channel (C works fine). Right now I have a pair headphones connected to the receiver and the meter showing the left and right channels power levels are jumping like clockwork.


Could it be I need to give the terminals a harder scrub down? The HiFi repair shop nearest to me doesn't open til the 19th so I'm just seeing if I can figure things out before then.

 

[Punker X]

Going to move this over to the Sansui forum. Your posting in the tuner or "radio" forum. You do not seem to be having a problem with the tuner section of your receiver.

 

[DB-7]

Wow. Nice score!

i'm pretty sure the 9900Z is top dog for that model.
@Sansuiman is the most informed on the z series I believe.

What are you cleaning the pots with?
You need deoxit fader lube. Or if real bad deoxit 5 cleaner, then deoxit f5 fader lube after.
Regular contact cleaner wont help much.

 

[fishstics]

Going to move this over to the Sansui forum. Your posting in the tuner or "radio" forum. You do not seem to be having a problem with the tuner section of your receiver.

Thanks! I didn't see that thread when I was browsing through (there's so many lol)

 

[fishstics]

Wow. Nice score!

i'm pretty sure the 9900Z is top dog for that model.
@Sansuiman is the most informed on the z series I believe.

What are you cleaning the pots with?
You need deoxit fader lube. Or if real bad deoxit 5 cleaner, then deoxit f5 fader lube after.
Regular contact cleaner wont help much.

Yeah, I figured deoxit would probably be the solution but there's so many versions and I read some can be harmful on some of the parts if you buy the wrong one that I figured id steer clear until I figured that out. I had some WD-40 Specialist Contact Cleaner laying in the garage that I thought would be fine since it's quick drying. I'll order some deoxit off of Amazon and crack open the Sansui when I get the chance. I did notice some oxidation on parts of the receiver, namely the inside of the headphone jack and the terminal post for the speakers which gave me the idea do get at them with cleaner and a q-tip. The shed it was in was brand new, only a year old. My aunt had a garage that she converted into a living space so it probably sat most of its life there, since my city gets pretty humid that's probably the culprit for the oxidation.

 

[Overundr1]

Welcome to AK.
Nice, one of Sansui's last monster receivers. If you do not mind sharing, what is your level of tech knowledge since many forum members will do their best to give advice based on what you are comfortable doing. Short first suggestion though is with the receiver turned off work the A and B speaker selection buttons on and off numerous times to see if the contacts just need a little care.

 

[fishstics]

Welcome to AK.
Nice, one of Sansui's last monster receivers. If you do not mind sharing, what is your level of tech knowledge since many forum members will do their best to give advice based on what you are comfortable doing. Short first suggestion though is with the receiver turned off work the A and B speaker selection buttons on and off numerous times to see if the contacts just need a little care.

Put me in front of an engine bay and watch me do magic but I'll turn into Shaggy and Scooby Doo on the first sight of a capacitor or circuit board. Not that I'm not willing to learn, my solder game is still pretty novice aside from sticking some wires together.

 

[Sansuiman]

That's a beauty, nice find. The 9900Z uses relays to switch the speaker outputs. There a 3 relays , one each for of sets A, B and C. When you operate the push buttons for a speaker set, the switch is actually controlling whether the relay for that speaker pair is open or closed.

When turning a set on or off (any of the 3) you should hear a faint click from inside the unit near the rear panel each time you push one of the speaker buttons on or off. If you can hear the click the relay is operating, but may have tarnished contacts internally that are not passing the signal, resulting in poor (or no) output on one channel. If you hear no click for a given speaker set, the relay likely has an ad coil and isn't closing. But since you have output on the right channel, it sounds like the relays are making and breaking mechancially, the signal just isn't making it through the contacts in one channel. This is a pretty common issue on a lot of gear of this era (early 80's), the relays used tend to experience this sort of failure. Probably didn't help being in a shed for a while since humidity does a number on certain metals, so I suspect the speaker switching relays are failing internally.

I'm not sure if these particular relays can have their plastic covers popped off so the internal contacts can be cleaned, but if that is the root of the problem, it's likely better to replace them outright anyway in my experience working on other early to mid 80’s receivers and amps.

Just FYI, cycling the speaker switches may or may not render any improvement as they are not switching the audio path directly, but just the relay for the associated speaker set. It's possible cycling the relay repeatedly might cause the contacts to "make" well enough to start passing signal again, but not all that likely. Of course, I'm speculating it's the relays since that is one of the more common, if not the mostly likely problem based on the symptoms presented.

 

[fishstics]

Welcome to AK.
Nice, one of Sansui's last monster receivers. If you do not mind sharing, what is your level of tech knowledge since many forum members will do their best to give advice based on what you are comfortable doing. Short first suggestion though is with the receiver turned off work the A and B speaker selection buttons on and off numerous times to see if the contacts just need a little care.

That's a beauty, nice find. The 9900Z uses relays to switch the speaker outputs. There a 3 relays , one each for of sets A, B and C. When you operate the push buttons for a speaker set, the switch is actually controlling whether the relay for that speaker pair is open or closed.

When turning a set on or off (any of the 3) you should hear a faint click from inside the unit near the rear panel each time you push one of the speaker buttons on or off. If you can hear the click the relay is operating, but may have tarnished contacts internally that are not passing the signal, resulting in poor (or no) output on one channel. If you hear no click for a given speaker set, the relay likely has an ad coil and isn't closing. But since you have output on the right channel, it sounds like the relays are making and breaking mechancially, the signal just isn't making it through the contacts in one channel. This is a pretty common issue on a lot of gear of this era (early 80's), the relays used tend to experience this sort of failure. Probably didn't help being in a shed for a while since humidity does a number on certain metals, so I suspect the speaker switching relays are failing internally.

I'm not sure if these particular relays can have their plastic covers popped off so the internal contacts can be cleaned, but if that is the root of the problem, it's likely better to replace them outright anyway in my experience working on other early to mid 80’s receivers and amps.

Just FYI, cycling the speaker switches may or may not render any improvement as they are not switching the audio path directly, but just the relay for the associated speaker set. It's possible cycling the relay repeatedly might cause the contacts to "make" well enough to start passing signal again, but not all that likely. Of course, I'm speculating it's the relays since that is one of the more common, if not the mostly likely problem based on the symptoms presented.

I was just doing some messing around using the balancing knob to see if can hear any sound coming out of the dead speaker and ended up with a weird goings on. First I jiggled the speaker wire connected to the A terminals on the left channel and got some noise out of the dead speaker. Then I turned the balancing knob all the way to the left to get a clear sound and check for any distortion and as I turned the knob I got some pops and static and couldn't hear the speaker again until I jiggled around the A terminal again. Now I'm getting sound out of everything until I turn off the A switch and the speaker dies again. So I'm guessing the solution should be what DB recommended and wash out some gunk with deoxit to clear out the knobs and the terminals.

 

[Sansuiman]

By all means, make sure the other controls (balance, tone controls, filter, tape monitor switches and the like) are clean first,, as these are all in the signal path, so any one of them can be suspect.

The volume control on these is a real Rube Goldberg arrangement, the volume pot is incorporated into an internal assembly controlled by a small DC motor, attached to a light box and a mylar film that in turn presents a visual moving "bar graph" display of the volume level when the up and down pushbuttons on the front panel are activated. So, cleaning the volume pot is a bit screwy on these, but can be done. Be careful not to damage the plastic light box or the mylar strip inside of it when spraying control cleaning products around them. There is also a dial string that links the volume pot to the motor, so be careful of that as well.

Once you are confident the controls are clean, if you are still having issues with audio loss on one channel, I'd heavily suspect the speaker relays. Replacing them isn't the easiest job, but if they are failing due to poor signal transfer through the contacts, that will be the only way to get the unit reliable again.

 

[fishstics]

By all means, make sure the other controls (balance, tone controls, filter, tape monitor switches and the like) are clean first,, as these are all in the signal path, so any one of them can be suspect.

The volume control on these is a real Rube Goldberg arrangement, the volume pot is incorporated into an internal assembly controlled by a small DC motor, attached to a light box and a mylar film that in turn presents a visual moving "bar graph" display of the volume level when the up and down pushbuttons on the front panel are activated. So, cleaning the volume pot is a bit screwy on these, but can be done. Be careful not to damage the plastic light box or the mylar strip inside of it when spraying control cleaning products around them. There is also a dial string that links the volume pot to the motor, so be careful of that as well.

Once you are confident the controls are clean, if you are still having issues with audio loss on one channel, I'd heavily suspect the speaker relays. Replacing them isn't the easiest job, but if they are failing due to poor signal transfer through the contacts, that will be the only way to get the unit reliable again.

Here's an update. Found an electronics store on the other side of town that had some cans of Deoxit sitting by and ended up snagging one. Got back home and sprayed down the knobs, post terminals and the ground for the phono just in case. Used a Q-tip to really scrub down some of the metal too. I got speakers A and B to respond and all 4 speakers seem to work aside from a weird thing going on with A, where the only time it works is when I put a finger onto the terminals while the speakers are playing. Might be a grounding issue going on at the A speakers but B works flawlessly now and that's where I have connected the other two speakers.

 

[Sansuiman]

Ok. Sounds like you could have a cracked solder joint on the A speaker terminals. Should be an easy enough fix if you decide to pursue it. Enjoy that receiver. Despite its slightly cost reduced build quality and over the top "flashiness", it sounds excellent when in good shape, and still has the heart of genuine Sansui sound inside. It will do a legit 160WPC and then some. The look is a bit unique (and busy) being from the early 80's when everything digital was in vogue, but I've long thought the design was well executed, even if it is kind of dated now.

Note too that if speaker C is selected, having both A and B speaker outputs on will cut off the speaker C output to protect against placing too low of an impedance load on the amp. You can only have two of the three in use at once, and A and B outputs have priority.

 

[Bright_Star]

You mentioned getting it from your aunt, is she the original owner, or her husband perhaps? It would be useful to know if the amp was ever serviced before, or still in its all-original state, perhaps you can post some pics to get a better idea of how it looks inside with the cover off.

The 9900Z is the top model in the series, though I dont know if it suffers from the same issues as the smaller units, 3900 & 4900Z with bad power switches and flickering displays. I was using a 3900Z in a bedroom just for lite background music listening, as a G-9000 would be overkill for that, and them one day, turned it on, totally dead, have not had the time to look into it further. To me, the Z shows signs of 1980's quality cost cutting compared to the Sansui's peak with the G series, especially with all the flimsy pushbuttons on the front panel, but hopefully if you can get it going again, it might perform well for you.

 

[fishstics]

You mentioned getting it from your aunt, is she the original owner, or her husband perhaps? It would be useful to know if the amp was ever serviced before, or still in its all-original state, perhaps you can post some pics to get a better idea of how it looks inside with the cover off.

The 9900Z is the top model in the series, though I dont know if it suffers from the same issues as the smaller units, 3900 & 4900Z with bad power switches and flickering displays. I was using a 3900Z in a bedroom just for lite background music listening, as a G-9000 would be overkill for that, and them one day, turned it on, totally dead, have not had the time to look into it further. To me, the Z shows signs of 1980's quality cost cutting compared to the Sansui's peak with the G series, especially with all the flimsy pushbuttons on the front panel, but hopefully if you can get it going again, it might perform well for you.

Well, I doubt it saw much use. It belonged to my Aunt's late husband. They didn't last very long together and he went back to his home country somewhere around the 90s to early 2000s and she kept it in the garage ever since. When I opened it up it looked essentially brand new, just a layer of dust and some oxidized metal here and there but capacitors seemed in top shape. Spraying the knobs down with Deoxit removed all noise from the equation. Light bulbs inside still work too. My guess is the guy probably bought this thing at a pawn shop or flea market played a couple tunes with it before it got stored. I think it's a step up from the H/K 3390 I had in my setup before. I like this more neutralized sound coming from it.