Sony TA-5650 VFET Amplifier Service and Restoration

Being the first VFET amplifier I’ve worked on, this Sony had a few issues that needed to be fixed. Added to the restoration that was also needed, it ended up being a very comprehensive task. VFET amplifiers are a rare breed, and require specialized care to get working properly. This Sony was no different. There are many modifications and service bulletins that were done to guarantee the stability and working condition of this amplifier for the next few decades. Watch along as I bring you through the process!
Relevant links for the TA-5650:
TheVintageKnob article:
www.thevintageknob.org/sony-TA...
HiFiEngine:
www.hifiengine.com/manual_lib...
Informative forum post on the TA-5650:
www.stereonet.com/forums/topi...

[@roms4277]

Hello, i own Sony-TA-N7B power amp and it's just incredible !!!

[@mistermac56]

Great restoration and attention to detail. Back in the late 70's, we had four of these integrated amps in our audio editing rooms for radio and TV commercials. They sounded great, but were a pain in the rear for me to keep serviced. I spent a lot on the cost of long distance calling communication with Sony tech support. There were four engineers at Sony at the time that knew the amp inside and out. They were great with service tips and shipping out a good supply of VFETs and Sony sold them to us at cost. They gave me the same tip you detailed on using an alternate test point for the bias. Once I performed the service bulletin mods on the amps, we didn't have any issues ever again. We eventually replaced the amps in 1983 and my boss gave the Sony amps away, and I wound up with one and all of the spare VFETs. I used the last complementary pairs of VFETs about five years ago, when I did a complete restoration.

[@PrimeHiFi]

Thanks for the kind comment and great story! Glad to hear you also worked on these amplifiers. They’re a real treat to work on, as long as it isn’t over and over again ;) Cheers!

[@frankgeeraerts6243]

One other superbly build amplifier from the seventies.........nice job , i could trust you ....

[@Rudolphe_]

Wildly fascinating to see the process. Great Video.

[@firaonoyus2112]

Beautiful oldschool amplifier is reborn, amazing work.

[@PrimeHiFi]

Thank you!

[@voenixrising]

This was the first hi-fi component I purchased (new) after graduating high school in 1976. Like all of these units, mine blew up. Not once, not twice, but three times before I abandoned it in 1986. But when it was working...the sound was heavenly!

[@ZVM600]

Надо головой больше думать 😂

[@stephencrozier396]

Same age as me! It's aged better than I have though lol. Great work, love this channel!

[@PrimeHiFi]

Thank you, glad you enjoyed!

[@stephencrozier396]

@@PrimeHiFi I did. Look forward to the next one!

[@Casualfulltime]

Dude your attention to details are insane. You are a real master!

[@PrimeHiFi]

Thank you so much 😀

[@MD1969]

This is it profesional work and restoration....congrats !

[@ladronsiman1471]

Wow.. This is great i have the same and also the 8650 ,This is so huge for me

[@chromasonictv6369]

What a great job on this amp

[@gregwilliams2746]

Wow - you do beautiful work!

[@PrimeHiFi]

Thank you! Cheers!

[@alynicholls3230]

Nice work mate, though my focus is the service and repair/reverse engineering of metal detector technology I can fully appreciate your work and level of detail. The hardest job for us these days is parts, I buy alot of job lots of new old stock transtitors ics diodes, some old parts are just not available today modern replacements bring often more problems, but diligent searching can yield what u need there is nothing better than looking for an out of production chip and turning up so military spec metal can versions or ceramic ones, better spec than the plastic originals. Nice clean proper work top marks mate.

[@adaboy4z]

I have a Yamaha B-2 Power amplifier I would love to get it serviced. You do a thorough job!!

[@user-fe3hs6oc3n]

Beautiful amp beautiful work

[@PrimeHiFi]

Thank you!

[@NOMADCREATIVESOLUTIONS]

Great job Man, what a nice bit of kit

[@PrimeHiFi]

Thank you 😊

[@bwdnz]

Great stuff as always man. Nice work.

[@PrimeHiFi]

Thanks homie

[@Trucam2020]

Excellent video. Thanks.

[@paulschreuder4211]

Restored with love! Very nice and professional job. Thanks for sharing this i love the longer video :-)

[@PrimeHiFi]

Thanks! Glad you enjoyed. More to come

[@sthellems]

@@PrimeHiFi Hello - I have a nice TA-5650 myself and wondered if you would perform a similar restoration? Thank You!

[@paulmichaelfreedman8334]

@@sthellems He's probably not into repetitions for obvious reasons, but I'd sure love to have a crack at it.

[@TrevorsBench]

Well done on this amp. It polished up nice

[@PrimeHiFi]

Thanks Trevor!

[@fredsk1]

Another great vid - nice work mate 👌

[@PrimeHiFi]

Thank you!

[@johnnyshinnichi1785]

Great video, and you obviously know you're stuff. But it would be nice for numpties like me if you showed us how you do some of the work. I'd love to know how you clean the faceplate for instance.

[@shaun6023]

Nice job , well done.

[@bpalpha]

I subbed man. Love your work. Really nice and unique pieces you work on.

[@PrimeHiFi]

Thanks! More to come

[@nazeerabdulrahuman9526]

Excellent work ❤❤❤

[@thomasstanfel7589]

Love this video !!!! Great job

[@user-ip5du5sz8i]

Superb job!!!

[@rods6405]

Nice Work Top Notch! I use to fix these for Sony in the 80's the sound out of them was the best such low distortion. That speaker switch selector the wipers have carved a groove on the board carbon such a shame! Your luck the protection relay has not corroded! Again great work! We (in Australia) also had problems with corrosion on the audio plugs that go onto the boards they use to come in to the workshop green ! Yours looked ok!

[@PrimeHiFi]

Thanks for the kind words! They really do sound great. I was surprised at how good the condition of this amp was. Cool to hear you worked on these amps. They are really nice to work on, but the VFETs get the heart racing a bit when troubleshooting.

[@naadbrahmasound2955]

Very very Nice Work

[@don7680]

First time viewer. Really nice job, nice equipment! All super professionally done. I'd love to know how much time you've got total in this. When doing this extensive a restoration, I wonder what problems can be accidently induced?

[@shahzadkhan-nd1jg]

Jabardst sir ji

[@benlopez4788]

Great video. Thanks for the info of where else to use to check bias. I have one of these amps and did replace the 4 killer diodes on amp board also. Thanks

[@PrimeHiFi]

Thank you! Yes, I enjoy adding little bits of information like that to help others out who may be dealing with the same issues I do during service. Enjoy!

[@benlopez4788]

@@PrimeHiFi I went and opened my amp up this morning. Checked 20v and it was at 25v and 97 volt was at 125v. I adjusted pot Rt401 for 20v and now my 97v is good too. I checked dc offset and it is within specs. I then I checked bias in locations you mention and will adjust to 50mv after a good warmup. Question as long as my bias is good checked in location you mentioned bias should be good then correct? I do appreciate this wealth of info you are providing. Thanks again

[@every_science]

wonderful

[@frozzle]

great stuff

[@PrimeHiFi]

Thanks king

[@mikeparker7709]

You can substitute the Vfets with TO-3 2N3055 and its compliment. I had that same amplifier

[@tee-jaythestereo-bargainph2120]

Great job , thanks for the video loved these ole Vfet amps -would love to ger my Sansui Au 717 done up like this its one owner thats never been opened up except once to clean with F9 dexoit learned my lession with D5 like many others -

[@tee-jaythestereo-bargainph2120]

You live in the U.S. ?

[@PrimeHiFi]

Thanks! Yes, I live in New England.

[@tee-jaythestereo-bargainph2120]

​@@PrimeHiFi I had to watch twice I always learn something thanks Conor

[@szvencel]

Thank you for sharing your work through this video with all of us. The restoration work you have carried out is outstanding, congratulations and compliments! I own the same amplifier, the suicide diodes have been replaced and the amp works very nicely, but I am really wondering if the sound would improve by getting all those old capacitors replaced. Would you share the information about how do you do the polishing of the faceplate? I also cleaned it, but I was afraid to polish it to avoid any damage to the texts. Also I am curious how did you do the polishing of the backplate and RCA sockets. Once again I am speechless on the job you've done with this amp.

[@PrimeHiFi]

Thank you! I use Simichrome on a microfiber cloth, using extremely light force. Have to be careful around all silkscreen lettering. On the RCA jacks, I do the same.

[@2008alde]

I recently pull out of storage my old Sony TA-4650 integrated amp. Plugged it in, connected the comnponents and it worked. the only problem was teh balance was a little scratchy but I fixed that. I hadn't used it muchover the last month so when I went to play some LP's last night, the speakers cut out. I heard teh relay cycle back on but the moment Iput the stylus down .. BANG! the speakers cut out. After some investigating, it seems that when I have anything plugged into the phono inputs but without playing an LP, there is a soft repeated thumping coming out of the speakers, especially one channel. If I increase teh volume .. BANG!, the speakers will cut out and the speaker relay will recycle again. This only happens with anything plugged into the phono inputs. the tuner and AUX inputs are fine. Now, I think I may have blown something because stupid me forgot the amp was on whrn I went to plug in another turntable and it made that typical sound that I don't think I have to explain. Did I possibly cooke the phono preamp?

[@rogercarlsson8679]

I remember this from the 70th. Green PCB's? Looks much newer than something from 1978.

[@chinmeysway]

nice 😊

[@Prozacel]

Always a pleasure to looking and learn new steps for restauration! What you use to polish the front panes?

[@PrimeHiFi]

I use soap and water to clean the faceplate and then follow up with a very light treatment of metal polish in some instances. Thanks!

[@horaciorecalde1689]

Hace 3 dìas que comprè este modelo y la verdad, me gusta mucho como suena. El video es excelente y hoy es la tercera vez que lo miro. Si puedes, comenta con que limpiaste la placa frontal. Ella quedò hermosa y me gustarìa limpiar asì el mìo. Un saludo desde Argentina.

[@ukrainehamradio]

Nice and meticulous work. Congratulations! What thermal pads for power transistors do you recommend? Do they need additional thermal paste?

[@PrimeHiFi]

Thanks! I use silicone thermal pads. You can get them from Mouser, NTE, or eBay. They don’t need any extra thermal paste.

[@ukrainehamradio]

@@PrimeHiFi Thank you! I have ordered silicone thermal pads from Mouser.

[@yourbiglebowski]

Great video! I have one question: the white cable soldered in the centre of the voltage doubler (mod @24:46) is soldered or otherwise connected to the inner front plate?

[@PrimeHiFi]

Thanks! It’s connected to chassis ground. In this case, I soldered it to the back side of the circuit board. Thanks for watching!

[@jerdobi]

Great restoration. I have one of these where 3 VFETS died, but I sourced them from Japan. I rebuilt the power supply and testing it out of circuit wasn't obvious as the test points voltages didn't match what I expected. Any pointers on how you tested the power supply?

[@stillastillsfan]

Bautiful job. Assuming 1k - 1.5k for labor + parts. Can you comment on how difficult it would be to change out higher quality RCA input connectors and what is involved? Thanks, Don

[@mikemmikem2758]

I applaud you for such dedication to restoring old great ones. I have an original Sony GS10 ES receiver and was wondering if you would be interested in restoring it I live in Daytona Beach, Fl. Thanks again for the great videos.

[@PrimeHiFi]

Thank you for your kind words! My schedule is currently full and I’m not taking in any work, but I have references if you’d like 👍🏼

[@mikemmikem2758]

@@PrimeHiFi thank you and I would like some references

[@AudioElectronicsChicago]

Outstanding 👌🏻👌🏻

[@cochinada01]

Outstanding work! I have one suggestion only if I may. I would very much like to see and learn how you do some jobs like drilling the holes for the transistors and polish the plugs. would it be possible to insert some very short time-lapses of these processes in future restorations? Perhaps you have already did it in previous videos but I'm knew to your channel. Subscribed BTW.

[@PrimeHiFi]

Great suggestion! Thanks for watching. More to come soon!

[@mikemmikem2758]

You're like an original Sherlock Holmes.

[@bertjetolberg103]

Did Sherlock also swing the cam only

[@emilebennett1732]

I'm looking at buying one of these, fully restored, in the UK. Would love to know peoples thoughts on the sound, those who've heard one. This restoration is incredible, I wish I could buy this amp itself!

[@PrimeHiFi]

Thank you! If you buy one, you won’t be disappointed! Make sure the work was done well and it will last you a very long time! 🙂

[@jonlaws4493]

I own both the TA-5650 and 4650. They are very sweet sounding amps and well worth buying if you can get one at a decent price. Do make sure that you do the service upgrades and be very careful with the VFets as they are almost irreplaceable. I also replaced the signal path capacitors (100uf/100v with polypropylene caps).

[@juanfrancis1980]

Es cierto que los amplificadores con transistores vfet se queman con facilidad? Podrías darnos algún consejo para su buen uso y evitar que se puedan quemar? Perdón no se escribir en inglés! Gracias

[@PrimeHiFi]

Gracias por tu comentario. Los amplificadores VFET no son inherentemente inestables, pero los problemas comunes con otros amplificadores pueden ser catastróficos con los amplificadores VFET. Requieren un servicio especializado y una cuidadosa atención a los detalles: una vez que los VFET explotan, no tendrá suerte. No hay reemplazos disponibles. ¡Gracias de nuevo!

[@scottroberson2656]

I’ve got a tan 8550 vfet amp in the shop needing some work can’t wait until it gets done if it ever does ,those vfets are scary to work on and time consuming . There’s an old ad out there floating around on the internet with a bunch of techs standing over the amp with their white lab coats on just staring at it scratching their heads like its some NASA device their working on .

[@szvencel]

Could you share the size of the original 10000uF/50V capacitors in millimeters?

[@Hi-Fi_Surgery]

Hello can you send me the name of the clips you use for measurments? BTW you have ballz of Steel, personally im not taking any Vfets on my bench :)

[@PrimeHiFi]

Hi Mariusz, the probes are Tektronix SMG-50 and also Pomona Minigrabber Thanks for watching! Glad you enjoyed. This is my first VFET amplifier on the bench. I liked it a lot, but it did get my heart racing during test ;)

[@cruise2023]

Hi! Great job and as you said probably better than new ! The ta-5650 isn't that expensive to buy used, I fear the full restoration cost more than what the unit worth and then the V fets no longer available. I have been trying to buy ( out of Japan ) the ta-8650 without luck. I settled for the ta 3200f amp and matching pre the ta 2000f both obviously V fets. Bought them at a good price even with shipping to Australia. The plan was to give them a restore. My fear and risk is the V fets will they all be working to spec !!! Can I ask, is it worth while as back up to purchase say the ta 3200f as a spare to pull the V fets off if needed either now or a later stage ? Would they be compatible for either the amp and pre-amp ? Many thanks... hope to get a reply.

[@PrimeHiFi]

Thank you! The 3200F doesn’t use VFETs , so it won’t be suitable to use parts from unfortunately. Hope this answers your question

[@rainman3269]

See you use the Panasonic FC capacitors ... I've used them in my rebuilt boards ... Think they are really nice sounding ... Is that what you have found using them ... Very nice work and fun watching ... Kind Regards in advance

[@PrimeHiFi]

Panasonic FC capacitors are great! I use them for their high reliability and long life. They are also very nice looking too :)

[@lohoch5506]

How do I send in a unit to you for restoration? I have a mint Revox 720 preamp tuner. It would make an interesting showcase for your channel

[@nigelpearson6664]

Warmer sound,, it ran hot. 70 mV might make sense. This Sony was one of the best. Slightly thin at 50 mV. Better than a Krell? To my ears yes.

[@nigelpearson6664]

I remember the 90mV bias . Much warmer. Sony had customers issues.

[@Stelios.Posantzis]

Great video once again. It's both enjoyable and educational - steady hand helps a lot too. 12:41 Why is there this purple wire going across the pcb? I never understood that habit, especially Japanese manufactures, of using every opportunity the get for creating a rat's nest. What's the point of having pcbs if you are going to use jumper wires like these. The other thing that annoys me is the mixed use of wire-wrap connections and molex plugs. Just make up your mind: do you want easy of assembly? de-assembly? or just solid connections? I used to really dislike wire-wrap connections and eventually got a wire wrap tool - of course now I think they are awesome. But the tools is expensive for the random diyer to get, especially if they only plan to fix one device only. These are gripes I have about all Japanese manufacturers, not just Sony. All of them were obviously using the same system of manufacturing. But you have to hand it in to Sony, even before their signature pristine boards came about in the late eighties, this device bears all the marks of quality (even thought it belong to an up-market line of products, on account of the v-fets used). The re-flowed and de-fluxed board reveals this clearly as well as other details such as the use of hinges, pcb holding brackets, bespoke heat sinks etc. 23:29 Disassembling and reassembling this adds 2-3 hours to the bill, if all goes well. 25:00 What mod is this? How can one find it? Does it apply to every voltage doubler? 25:38 Brushed aluminium is a restorer's nightmare: if is has oxidisation patches and signs of abuse it's impossible to get back to original. Anodised aluminium or - even better - painted aluminium are much better at aging well. That came out great. 30:20 It ought to sound like valves, on account of the v-fets for sure. Do you remember how it stacks up compare to the higher end v-fet power amplifier you restored? I can't remember whether it was mono-blocks or just a TA-8650...

[@rods6405]

"Why is there this purple wire going across the pcb? " I down loaded the manual (could not remember I use to work on these ) its the ground from the unregulated rectifier board it has to supply current to both channels for both the plus a minus rails to the output vfets so they use a wire instead of a a PCB track more current. See it all the time as a after thought but this looks like a design feature !

[@johnnytoobad7785]

So where you can buy SONY VFETS at a reasonable price ? I heard Nelson Pass purchased ALL of the NOS VFET's in circulation.

[@fmoyano]

you can not

[@Roudaki677]

Not sure if Nelson bought "all" of the VFETs in circulation. I had a few hundred matched sets that the late James Bongiorno (of SAE, Ampzilla etc..fame) sold me for the cost of postage! back in the 1990's. I also purchased as many as I could from the regional Sony service center in Dallas when no one wanted the VFETs, thinking about future projects that I simply have no time for. I also know a few collectors in India as well as Singapore that had some genuine parts until 2021. I gifted all my parts to Nelson a few years back knowing they'll be in good hands and admitting that my life is pretty much dedicated to my full time job and I have not time for projects. In one of Nelson's videos with the audiphiliac, you seen a bunch of the VFETs in pink ESD foam and Nelson mentions a friend gifted those.

[@andreask2288]

50-80 hours work Projekt...😉

[@MarksofDistinction]

What’s the cost for you to redo one just like this

[@oliverlison]

Increasing the capacity, is it not taking the system out of balance?

[@sony7032]

How much indian price & how to bring shipping.

[@jonathanhendry9759]

Is that just regular carpet or anti-static carpet? I see people doing electronics on carpet and it gives me the willies.

[@PrimeHiFi]

Regular carpet. I like to live on edge 😈

[@1964Cobo]

airplane camera and to much talk, check out brit guy and his positive way to find out and present electronic failure and how to fix it, on his funny style.

[@PrimeHiFi]

Thanks for the very enlightening comment. I’ll be sure to hold the camera still and not say anything in my next video just for you :)

[@roerdomp16e]

Be aware that the speaker relays in the v-fet series are very unreliable. A black piece of plastic has 2 rivets in it to hold the contacts in place. This black plastic tends to crack and the contacts tend to move from their place.

[@PrimeHiFi]

I’ll keep that in mind. Thanks for the info!

[@timothypreseau8741]

Wow. It sounds just like my computer speakers.

[@alexandrezanol]

Top notch work, but I hear silpads are worse than thin mica. What gives?

[@PrimeHiFi]

Thanks for your kind words. I hear varying opinions. My firsthand experience, as well as the observations from technicians I trust, reveal that high quality silicone pads are just as effective as mica and grease. They also don’t dry out overtime, and are a very clean and elegant solution.

[@OrganNLou]

These have become VERY difficult to find!!!!!

[@petercroft3273]

Your videos are interesting but I can't watch them. You wave the camera around so much that I feel giddy. I can't watch. I wish you'd use a tripod, or at the very least try to hold the camera steady.

[@WillemvanLonden]

Sorry to say, but because of the wild camera movements this video is barely watchable. Please give your viewers some rest.