Sony TA-4650 V-FET Amplifier (Part 2 - Preamp Control Cleaning)

In this video we tear down the TA-4650 Preamp and controls, clean everything from the ground up using the new ultrasonic cleaner and various other methods. Will this fix the distortion issue?

[@mikemmikem2758]

I did this kind of work many moons ago and what you achieved is truly impressive. Fish and chips on me. Well done.

[@whatcouldgowrong7914]

Thanks! 🙏

[@PeterDyall-bn7ut]

You’re posting really good quality content!

[@whatcouldgowrong7914]

Many thanks, I’m trying to constantly improve 🙂

[@paulschumacher1263]

"Mend It Mark" uses the ultrasonic cleaner a lot on electronics, and it seems to work well.

[@discow00t]

The level of detail is astonishing. Can't wait for the next episode.

[@grateful6595]

Hi. Thank you for the excellent video. I would like to share a few tips on the use of the ultrasonic cleaner: The fluid in the tank is part of the heat sink for the ultrasonic drivers. My instruction manual says to keep the tank at least ¾ full at all times. The drivers get very hot and they are glued to the bottom of the tank. If they get too hot they fall off…Boo! So now you might be thinking, as I was, darn…that’s a lot of solvent…that’s expensive! Well, just fill the tank with water. Get a smaller container and fill it with your solvent of choice, add the parts, put a lid on it, and place the container in the tank. Ultrasonic waves transfer through the walls of the smaller container immaculately. Glass is supposed to work better than plastic, but I haven’t noticed a difference. It is possible to run multiple solvents simultaneously using this method; Soap in one, isopropyl in another, vinegar in another. The smaller containers will heat up, build pressure, and expel some solvent into the water. This does not matter for the smaller containers are isolated from each other. So long as they are not allowed to cool in the tank water they are uncontaminated and there is much less waste solvent to dispose of. Oh, it also works as a sous vide bath. Clean that sucker out really well and cook dinner in it. Great video, best wishes, thanks.

[@whatcouldgowrong7914]

That is a fantastic idea! Thanks for sharing that one as it limits contamination and yes solvent is expensive / you don’t want to change it often or fill the tank… Not to mention the smell of a large bath of dissolved PCB lacquer and other junk floating around…

[@TechStuff365]

Thanks for explaining your motivation to do this monumental work. I was thinking you must have some billionaire client!

[@whatcouldgowrong7914]

I was warned by many older, jaded technicians not to do paid work as it’s a never ending frustration of customers trying to save money and cut corners 🤣

[@Roudaki677]

I have quite a few of the VFET Sony power and integrated amps. The 4650 is the best sounding in the family.

[@andymouse]

Awesome work, that cloud of shite that comes barreling of the components in the ultrasound never gets old !....cheers.

[@sebastian_harnisch]

Great video (as always)! Thank you! One remark: I'm not sure whether you actually used isopropyl alcohol with the ultrasonic cleaner. If not, this should be understood just as a general remark: Having large quantities of a highly flammable liquid exposed like in an ultrasonic cleaner is very, very risky and should be avoided at all cost - even more so in living areas without proper safety measures. IPA is even more dangerous if heated, but with a flash point of about 11 degrees C room temperature might be enough for a very bad day.

[@whatcouldgowrong7914]

I ran the normal ultrasonic cleaner with a roughly diluted 20% IPA mix to dissolve PCB lacquer. I should have been more clear about this thanks that running pure IPA with heating / ultrasonic is not smart… Still probably not ideal with vapour but it had good ventilation

[@mark902]

i love the smell of 70s hi-fi. akai and sony especially. it's like new car smell but better.

[@drdyna]

You should do an experiment, take a couple of inexpensive pots and put them in the ultrasonic and just see how long it takes to lose carbon tracks or create any ill effect.

[@whatcouldgowrong7914]

I did try before I started with a new cheap Chinese tripot with no real effects but I would prefer to try it with something old from a dead 70s/80s amplifier and see what happens. I can definitely say that those silver ALPS plates for the BASS and TREBLE started to shed metal particles after being in there for 10 minutes so must tread carefully. I pulled them out in time luckily...

[@paulb4661]

I'd strongly advise against dipping carbon track pots in there, not only will you destroy the track, but flush-out high viscosity grease, giving that tactile feel to it. Also, although the track itself should be run dry, a tiny amount of sgb or similar on the slider works wonders. In terms of switches, again, sgb contact grease application following thorough job with a jewellery type cleaner is essential. In my experience, there is no substitute to painstakingly taking everything apart, as long as the kit is worth the time it takes.

[@whatcouldgowrong7914]

Definitely agree they need to come apart. I wish pots were more accessible for regreasing and I agree it isn’t ideal. Unfortunately I have had limited success with just spraying pots and they generally get noisy again after a few months so I wanted to try the ultrasonic cleaning route. Loosing the grease is a big downside. Carbon tracks im not sure on yet, im sure it will destroy them eventually but seemed ok for a short wash?

[@paulb4661]

@@whatcouldgowrong7914 I may be wrong (nomen omen), but I cannot imagine a bonded carbon track degrading due to a chemical process. Wear will manifest itself in a thin, loose layer of grounded track material, unless it's terminal, in which case it calls for replacement. Slider, depending on the tip plating material is perhaps the only element to chemically degrade and will of course benefit from an appropriate cleaning agent. If that assumption is correct, then I see no point introducing vibration to the track, potentially loosening it even further, when all it needs is a gentle wipe. Slider will be good as new following a dip in a silver jewellery cleaning bath, IPA flush and a grain of SGB. Furthermore, this will keep the high cp grease around the shaft intact. When it comes to switches, one can safely obtain excellent results with an ultrasonic cleaner, following some dismantling at least. I think it is just as much about cleaning, as flushing out any latent reagents and products afterwards. Then again, many vintage, unobtainium pots are perhaps better left alone, at the mercy of spray cleaners, unless you have a precision mini lathe and a steady hand/workshop and... skills worthy of a Swiss watchmaker!

[@marcvdfv8431]

small advise from an oldtimer... clean the boards only when you're finnished with them, not inbetween steps.

[@whatcouldgowrong7914]

Thanks for the advice, the main reason I cleaned them was to limit how much bad smoke was generated during desoldering. I give the boards one last wash with IPA at the end :)

[@stevesmyth4982]

A 97 V rail is most unusual in a preamp/phono stage, any idea why Sony would do that? That's good work you do, thanks for the videos.

[@whatcouldgowrong7914]

From what I can see in the schematic, it seems responsible exclusively for the phono stage supply which uses those 2 rare VFETs at a high voltage. The service documentation is confusing as it mentions 78V but 100V is clearly written in other places and on the PCB itself… I suspect there may have been a design change as running capacitors basically dead on their max rating with no safety margin is highly unusual?

[@DieselRott]

Putting the shaft of the pot inside the ultrasonic cleaner affects the shaft lube.

[@ismaelnavarro9589]

Saludos, buen video; que lubricante usas para los interuptores?.

[@whatcouldgowrong7914]

Superlube PTFE - grey tube. Can use any light grease really

[@ismaelnavarro9589]

@@whatcouldgowrong7914 Thank you!

[@jacobs7281]

Thanks for this detailed video @ 23.12 , is it a glue ? Used there?and @23.57 what type lube used ?

[@whatcouldgowrong7914]

Superlube PTFE grease - silver tube :)

[@jacobs7281]

@@whatcouldgowrong7914 thank you

[@jacobs7281]

@@whatcouldgowrong7914 just clarifying , so both places @23.12 and 57 it is the super lube. Is that correct?

[@whatcouldgowrong7914]

@@jacobs7281The brush is Deoxit gold which I use for the contacts and so the fingers stay in place, the lubrcation which only goes on the top latching mechanism is superlube. Can use many things though, just what I use :)

[@meraydin1]

would you share non-sped-up version especially disassembling and assembling switches and potentiometers? please :) (I've tried 0.25x playback speed but it was terrible)

[@whatcouldgowrong7914]

I can do that if there is enough interest, I can do dedicated videos for each switch type or longer ones but unfortunately the videos are already very long and there doesn’t seem to be much interest in realtime teardowns as it is many many hours of work consolidated down. I have another amplifier of the same design to be done later.

[@meraydin1]

@@whatcouldgowrong7914 What you've done is very important and tricky. I would just cut those parts and post as seperate videos... "Servicing a Sony switch bank" or something like that... I'm sure it will be very interesting and useful for vintage electronic world :) I'm sure you'll get many questions about what chemicals you use while assembling ;)

[@whatcouldgowrong7914]

@@meraydin1 Next sony amplifier coming ill do some seperate videos on those switches for you. In regards to what I use Deoxit Gold D100 for contacts goingnback together and the switch grease was superlube PTFE in the silver tube 🙂