headphone socket, volume sliders, HT-700

[cz101]

Hi, fired up my old HT-700 recently and while it all seems to be still functional (phew) the headphone socket and accomp (accompaniment) volume slider seem to have issues.

On the headphone socket, left channel seems to be missing but if put slight pressure on the headphone jack with my finger I can hear both channels fine.

Likewise, the volume of 'casio chord' feature is very low (like 10%) but when slightly move the accomp volume slider it outputs normal volume. I can hear scratching, crackly type sound through speakers when move the slider. Main speakers, left, right line out all fine. Rhythm and main volume sliders work fine.

 

There was a lot of dust on the fascia when I opened the box so am thinking, hopefully, might just need a good clean.

Had the back cover off for a quick check and looks reasonable  inside.. no visible rust or whatever.

So, not too bad overall but any tips on restoring the headphone socket and servicing the volume slider controls ? 

 

 

[pianokeyjoe]

The jack is a issue with the jack lead for the left side solder is cracked. Just open up the unit plug the headphones in and carefully put that pressure and you should see the solder joint on that side lift up and settle back down. IF you do see that you are in luck! Just get a solder iron for fine electronics, and some electronics solder(not lead free!!), and solder down that joint. The volume is dust issue. Since the Casio sliders have grease inside them a simple dusting or vacuum will NOT help. Ironically the slider issue is more of a pain to fix. You need to get electronics contact cleaner(NOT ELECTRIC), and spray in there and carefully move the slider to the LOW volume setting, then go fetch a small q-tip and some alcohol and carefully clean out the inside of the slider doing twisting motions and carefully pulling the q tip out to reveal dust, and old grease grime. Keep doing this then move the slider to MAX volume and do the other end the same way. Now you can spray contact cleaner again and move the slider back and forth slowly. Then you need some ELECTRO-CONDUCTIVE contact grease to spray into the slider and move the slider back and forth slowly. Should fix your issue. IF all else fails, you can always try and find a new replacement slider but then that would be a nightmare take apart job.. I am instructing based on recent experience with what NOT to do with bad or scratchy sliders on keyboards!

[cz101]

thanks for that pianokeyjoe, solid advice. Will get the cleaning bits and report back. The last thing I want to do is approach it the wrong way and make it worse.

[cz101]

just to follow up on this.

Fixed the fader with DeoxIT CAIG MCL F5 Fader Cleaner.

The headphone jack was defective and I replaced it with similar part from a Casio PT-1. Simple enough swap and easy access.

The part is a Jalco 7 pin switch headphone socket. 

 

edit, this is the actual socket if searching for one yourself:

https://www.dropbox.com/s/6xywgxctrdgkc39/jalco.jpg 

Edited July 29, 2022 by cz101
pic inserted

[CYBERYOGI =CO=Windler]

Be very careful with contact cleaner spray. The stuff tends to dissolve the carbon track inside potentiometers. Particularly 1980th slide pots (like in old Bontempis) seem very sensitive to solvents.

 

The first thing I try is to remove dust by holding a vacuum cleaner over the slot of the slide pot. Then play some decathlon on it (quickly move it 20 times back and forward) to remove dirt.

 

Inside headphone jacks is a small leaf switch contact to mute the speaker. When it oxidizes, sound from speaker (possibly also other AUX) will fail. You need to clean that contact with a small screwdriver or cabletie to make it work again.