The Kawai & Teisco Analog Synths Group

Hi !

Great find. 

As for the switches, I never owned a SX240 so I can't tell for sure, but my assumption is that it probably use standard switches, as on the SX210, DX7, JV90 etc.... There weren't many options those days.

As for the IC, whether it's a LM311 or something else, you can find them really easily. It doesn't have to be the exact make, but any equivalent substitute will do. 

Keep us posted, and hey ! replace the battery there ! ;)




--- In Kawai-Teisco@yahoogroups.com, "synth_o_sphere" <stannloo@...> wrote:
>
> Hi folks!
> 
> Chris here, from Synthosphere!
> 
> Just acquired a defective SX-240 (Kawai).
> Lovely Beast!!
> 
> Now, when I got it, it didn't power up. Nothing, zilch, nada.  :-(
> 
> So, as per my usual routine when I receive used synths, here's what I did:
> 
> 1) Outside inspection and cleanup
> ===============================================================
> This one wasn't too bad on the outside, but still not to my taste (I like'em spot clean!).  See pics in the Photos section.
> All keys responded well, but keyboard seemed loose on the far side (near where it meet the cover).  Also, most keys are dirty, but when trying to clean it up, it doesn't go away.  As if someone tried to clean them with acetone (which dissolves plastic...).  Will have to investigate on that later.  They might need a thorough polish.
> 
> All buttons click properly... Wood ends are very bashed but I had intended to change them anyways for real wood (yup... that's what she indeed said...).  Few scratches under, lots of dust inside the jacks, but the rest seemed fairly ok.  So, good hopes!
> 
> 2) Open it up, overall inspection, vacuum, and further cleaning
> ===============================================================
> Now inside, it was REALLY REALLY dusty, especially under the keyboard! (really, go see the pics in the Photos section for your enjoyment (and horror)).  It makes me sad to see how people can neglect such historical pieces of music hardware... Anyhow...
> 
> But to my great joy, the battery seemed fine: no leaks!  Did not seem like it has been replaced (same USA-colors as OEM). So quite a miracle that it hasn't leaked after 28 years!!
> Hopes got even higher for an easy fix! 
> 
> 3) More specific inspection/troubleshooting
> ===============================================================
> So, first (obvious) thing to do... I checked the fuses.  Surely enough, 2 of them were blown (yay! Good sign!).  The ones on the board AFTER the Power Supply, just where the secondary leads connect.  Both are 1.5A 250V.  
> 
> So I manage to find replacement (they were 1.6A 125V but I figured it'd be fine).  Before installing them, I check the voltages around the Power Supply.  All seems ok, a tidbit high but within tolerance (223 VAC in, then 18.7V and 7.6V at the red and orange secondary leads, respectively).
> 
> So, I put the new fuses in and power up the beast, half expecting them to burst right away.  To my amazement, this didn't happen!  And the SX lit up joyfully and its lovely archaic red LED display shone upon my astonished gaze.
> 
> So I close the cover summarily and play with it for a while, testing all functions and sounds and stuff, assessing the machine.
> First issue, the volume slider doesn't work properly.  Volume is loud wether it's at 0 or 10, though I do hear a small difference between the two, as if the stereo field is better when at 9 or 10. But something rather subtle.  Weird.  Will investigate later.
> 
> Many buttons don't work perfectly, sometimes need to push them 2, 3 or 4 times before they work.  But that's ok.  To be expected on a 28 year old machine like this!  Easy fix (assuming I can find which tactile switch model is the good replacements...). I saw some for sale for the 210, but upon comparison, it seems the SX-210 might use different switches that the 240... 
> 
> CAN ANYONE CONFIRM THIS PLEASE ???
> 
> OK, so, so far, damages aren't bad at all.
> Sound-wise, all seems in good shape, except for the volume issue.
> Great!
> So I put a rag around the battery and let the SX on for a few hours, to charge the thing.  A few hours later, it hasn't exploded and all seems fine.  Turn it off and push my inspection further.
> 
> And this is when I noticed a blown IC !!
> (and this is where I need your help folks...)
> 
> On the ST-17 board, the dark brown one attached to the cover, second from the left side.  See this pic:
> http://groups.yahoo.com/group/Kawai-Teisco/photos/album/1542802729/pic/1859220102/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc
> 
> http://xa.yimg.com/kq/groups/12316546/hr/1859220102/name/IMG_1669.jpg
> 
> And see other images in the same folder, in order to help you properly locate the part.
> 
> *** So, I need help from a fellow SX-240 owner who could open up their cover and take a pic of this IC so I can read what it says on top.  ***
> 
> Otherwise, anyone knowledgeable enough to confirm what I need to buy exactly from Mouse/Digikey or other place that do keep 311's.
> It's just there's a few of them out there now, and I'm not sure if I need a more specific one...
> 
> Thanks guys! (and gals?)
> Will keep you posted on the progress of my repairs and bringing this baby back to life.  With more pics.
> 
> I might sell it once it's completely restored and in 100% top shape. 
> But I might play with it for a bit before, though! haha!  :-)
> 
> Regards, 
> 
> -Chris, from Synthosphere
>