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Yamaha wafer switch disassembly limits - C4 preamp

H

Hifibythekg

Super Member
When disassembling these to thoroughly clean them.. can one remove the circular contact that sits on the black plastic centre piece with twelve studs?
Is it ok to bend up the copper contacts to remove everything for cleaning and then bend them back afterwards for retensioning?
Or should a more conservative approach be adopted and just clean as best one can while leaving the elements in place? Less risk of breaking or being unable to realign everything but... maybe not as thorough a cleaning as needed in order to get the best possible contact and signal?
The offending phenolic wafer switch is already removed - advice and comments gratefully accepted.
 
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Thanks Dave, phew, just in time..
So with offending wafer in hand, maybe immerse it in warm water detergent, carefully use small brush to lift old oil and grime, use the finest possible abrasive paper and a dental pick or brush, retension (bend) copper arms to make better contact and apply contact cleaner (in the UK and using Kontact 40.)
Then.. solder the copper rivets too?
Sound like a sensible approach?
 
Thanks Dave, phew, just in time..
So with offending wafer in hand, maybe immerse in warm water detergent, carefully use small brush to lift old oil and grime, use the finest possible abrasive paper and a dental pick or brush, retension (bend) copper arms to make better contact and apply contact cleaner (in the UK and using Kontact 60)
 
Ok..
Hum remains.
Am now revisiting the Headphone and Tone control board and can see blue corrosion on a few 100Uf 16V caps.
What are the best replacements here?
Nichicon FG? Or Panasonic FC? Any alternatives .. would be good to know in case stocks are limited. Low leakage, or low ESR the priority?
 
And I can see some KSC458 which I believe have the noisy reputation?
Best replacement is...?
Anything else to swap on here, the tone controls were behaving a bit strangely..
 
Hifibythekg said:
And I can see some KSC458 which I believe have the noisy reputation?
Click to expand...
These are the current mirrors for the L & R headphone amplifiers. Replacement not required. They are not the 2SC458LG's....Outhouses..
 
Thank you.
And if I struggle with getting these from my supplier (Farnell UK) is there an alternative you could possibly suggest?
 
Was also getting quite a bit off bleed through from Aux to Tuner... could those corroded caps on the Tone board explain this? Or are there any other suspects on this or the power supply board etc to check / change while I’m in this area?
 
Have done all the above and changed some more caps. However.. hum persists.
Question:
If the hum is only coming through the left channel, does this provide a clue as to which board it must emanate from?
For example, could a fault on the psu board produce a hum only audible on the left channel?
 
Also for recapping the 'Function C Board' the best caps to use are Nichicon Muse, yes?
For the 'Flat Amp C Board' one should try to replace with caps that are especially low leakage, low ripple, low ESR? Brand and type recommendations appreciated.
 
Hi @avionic and others..
Maybe have a breakthrough on this hum detection after connecting a turntable..
Cartridge Load switch has a massive drop in volume and clarity when 100ohm is selected!
All other settings for the two Cartridge Load switches have very little or no effect on the audio.
Am I correct to assume that disassembly of these switches is the task to do next?
Is there any other related/close by component that should / could be looked at and tested before embarking on this onerous task...?
 
Hifibythekg said:
Hi @avionic and others..
Maybe have a breakthrough on this hum detection after connecting a turntable..
Cartridge Load switch has a massive drop in volume and clarity when 100ohm is selected!
Click to expand...
100 Ohm setting is for high output MC carts only. With MM carts it will sound like you described and this is normal.
I repeat myself, but why people do not use an ultrasonic cleaner for the switches instead of disassembling them (and probably damaging the contacts)?
 
Thanks Dr. Ear. Good to be informed of this.
Unfortunately, I’ve already unsoldered the switch and don’t possess an ultrasonic cleaner.
Will try to take care. If I don’t service it I may have a lingering regret if the hum persists after further efforts on this C4.
The pF switch was also not making much alteration to the audio from the turntable.
 
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