AU-G33X. Is it fixable, is it worth fixing?

[Gary Francks]

I have an AU-G33X come into my possession that has problems with the input switches.
Stays on phono input unless another input is selected and the switch held in, if you release the switch it goes back to phono.
Power amp section working and comes out of protection with low dc offsets.
All other switches and pots need Deoxit treatment and it looks like all the other stages work.
Now the big question, are the switches mechanically interlocked as I assume? ( never assume because it just makes an ass out of u an me)
Are the parts even available?
Yes, I know 1st I should do a search but I'm guessing someone has come across this before.

One final point, it looks like it was put together without a care and cannot match the construction of my 1000X!

 

[Robisme]

I believe that is how the selector works. May just need the mechanism cleaned. Do the buttons feel "sticky"?

That should be a nice sounding amp, and I would try and repair it. Sometimes you just have to excuse Sansui build quality of the 80's.

Rob

 

[kevzep]

As humans were being phased out and more automation was being used in production, the quality seems to decline, but even so, some of the amplifiers built are some of the best sounding Sansui's...

 

[Gary Francks]

The selector doesn't latch the buttons when they are pressed, from a quick perusal I cannot see any latching mechanism and, yes, the feel isn't right also.
I'm half hoping that when I delve into the internals further that there will be missing parts in the bottom.
If as it turns out there's parts missing then that's a bummer, the Sansui Parts Shop hasn't any switches for it.

 

[Sansuiman]

These are typically an Alps or SMK switch, banked together so only one can be active at a time to the exclusion of all others in the bank. Each switch has a small formed wire catch that sits in a quasi V shaped groove molded into the top of each switch above and slightly behind the switch plunger. Alternate action of the switch causes this wire latch to catch one side of the groove or the other and catch it in either the in (closed) or out (open) position.

In a banked switch array, there is also a spring loaded "rake" that moves to one side and then (by spring tension) returns to resting position. The rake resets all the other switches in the array to out/open position while the switch being pressed latches to the in/closed position until another switch in the bank is pressed, repeating the process.

Check to see if the small spring at one end of the rake is present and that the rake itself is properly lined up. Regrettably, I don't have any good file photos to post to show detail, but if you look closely at the switch bank, it should become apparent what is going on as you press the switches. Most Sansui gear from 74 or 75 through at least 83 used very similar mechanically banked pushbutton selector switch arrays, so turning up parts shouldn't be too difficult.

 

[Gary Francks]

Each switch has a small formed wire catch that sits in a quasi V shaped groove molded into the top of each switch above and slightly behind the switch plunger. Alternate action of the switch causes this wire latch to catch one side of the groove or the other and catch it in either the in (closed) or out (open) position.

In a banked switch array, there is also a spring loaded "rake" that moves to one side and then (by spring tension) returns to resting position. The rake resets all the other switches in the array to out/open position while the switch being pressed latches to the in/closed position until another switch in the bank is pressed, repeating the process.

And they are all the parts that appear to be missing from the switch bank!
All the individual switches are there, fitted to the metal brackets, but unless the latches and interlocks are underneath then it looks a bit of a basket case.

Time for some further investigation this weekend methinks.

 

[Sansuiman]

That's...odd. Post some pictures if you can, I'm curious to see how the switches are setup now. May be some variant I've not seen, or maybe someone did steal parts from it. Thing is, there has to be some mechanism external to the switches themselves to "reset" the banked switches such that only one is on at a time.

It'd be a shame to junk it, that's a nice little amp and well suited to a smaller office or bedroom system. Is it black or silver? Fairly certain they offered that model in both colors, as it matched the RA-990 reverb that was also available in both black and silver.