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Cleaning Selector Button Switches on a SX-939

I

ignis-fatuus

Member
So I've been wrenching on a SX-939 that I picked up a couple of weeks ago. After recapping it and fixing the issue with circuit protection relay clicking on, I've been listening to it quite a bit. I've noticed that I'm having issues with the input selector switches. I thought I hit them with Deoxit but they are still behaving as if they are quite dirty. For instance, if I press in and hold the phono 1 switch in all the way, I get good sound out of both channels. But when I let go and the switch settles to it's normal sitting position, I find that the sound will be uneven between the left and right channels.

Beyond being difficult to access, I'm really not seeing many means of access by which to get Deoxit into the switches' contacts. Any tricks to get these switches working as they should?
 
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what i do is using a syringe,i inject the push buttons with d100 cycle them a few times but mostly i let them sit until im done with the set if its a rebuild. i then re inject with d100 and cycle them many times.i flush with d5 after switch operation is acceptable. it takes TIME for dexoit to loosen that black crap. it will not however do much for a BURNED switch. i just went round and round on the TONE CONTROL board of a 939. it turned out that cleaning residue was CAUSING static like noise by leaking dc into the signal path. this is the FM pushbutton switch. i WOULD NOT put anything in that switch unless it was giving trouble. you can read all about my tale of eternal torment by googling "sx939 noise in both channels- audio karma". its really hard to get at but from the bottom is the only way once the faceplate has been removed and the module underneath. but the syringe cleaning method will work from the push button end by shooting it in from the front. the contacts are at the bottom of the switch so you would want the thing upright as it normally sits in use.you can also get them from top as there slots in the metal housing.please try and remember about the fm switch
 
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john stumpf said:
what i do is using a syringe,i inject the push buttons with d100 cycle them a few times but mostly i let them sit until im done with the set if its a rebuild. i then re inject with d100 and cycle them many times.i flush with d5 after switch operation is acceptable. it takes TIME for dexoit to loosen that black crap. it will not however do much for a BURNED switch. i just went round and round on the TONE CONTROL board of a 939. it turned out that cleaning residue was CAUSING static like noise by leaking dc into the signal path. this is the FM pushbutton switch. i WOULD NOT put anything in that switch unless it was giving trouble. you can read all about my tale of eternal torment by googling "sx939 noise in both channels- audio karma". its really hard to get at but from the bottom is the only way once the faceplate has been removed and the module underneath. but the syringe cleaning method will work from the push button end by shooting it in from the front. the contacts are at the bottom of the switch so you would want the thing upright as it normally sits in use.you can also get them from top as there slots in the metal housing.please try and remember about the fm switch
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I'll look into picking up some Deoxit D100L. I see that they have one with a needle applicator. Would that suffice you think or is a finer syringe is called for? As for the FM switch, I'm surprised the residue caused problems for you. Reading up on deoxit on their website, I take it that the residue is not supposed to cause shorts or unwanted conductivity.
 
theres a 13vdc circuit in that switch. and i was surprised too as i removed it and disassembled it and almost couldnt believe it but my fluke didnt lie. i use the standard needle that comes on a 10cc syringe. its NO FUN removing that switch either. if the fm switch works as it should i strongly suggest you leave it alone.
 
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i have a typo,its the function board i'm referring to.i encourage you to read the thread i posted.
 
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