Sony TA-N9000ES Power Amplifier - Repair

[@IncognitoChild]

I originally purchased 2 TA-N9000es power amps(run in bridged mode) along with it's pre-amp TA-E9000es over 25 years ago. I moved on from it with Pioneers latest and greatest and then I currently have a Denon 8500. Even now, I still miss it. It doesn't seem to get the love that a lot of amps around that time got, yet I have never found an amplifier that sounded so warm yet accurate as the Sony's. I wish I still had them. I loved the preheat mode - always ready for action!

[@whatcouldgowrong7914]

They were really special, especially for a multi channel!

[@IncognitoChild]

@@whatcouldgowrong7914 I wish Sony would come back to a proper ES product line

[@KuntalGhosh]

only the output drivers are hard to find and rest of the stuff is very common. so you can fix the thing by replacing the dead sony output transistors with modern 2sc5200 & 2sa1943 or 2sc5200n or ttc5200 you can buy legit ones from mouser digikey lcsc. and use two of them to replace each sony transistor as they seem to be like two bjt's in one package by the look of the service manual so it won't be two hard to tie the collectors together and connect the emitter and base of each pair to the pcb. and use 4 regular 0.22ohm 2w resistors as emitter resistor. if you are too concerned about matching output you can replace all the bjt's with 2sc5200n & 2sa1943n . audibility there should not be a difference.

[@whatcouldgowrong7914]

Like I said in the video, since its only ever used as a high power stereo amp, the work and hunting suitable parts doesn't warrant the investment for me... Could have been fun but I don't have the tools for SMD work either

[@morksbeanbag]

It's the Class A cascade sections that cause the failure. I have 3 faulty ones, all failed in exactly the same area. The actual tipping point of where the fault becomes catastrophic is more interesting. Notice the board material for the power supply....epoxy FR4. For the main amp....cheap phenolic junk. To worsen this there are only two screws in the centre of the PCB to hold the board down, the rest of the support is left to the custom made outputs. If you ever lift one of these boards out you will notice it will be badly bowed. Over time the heating (and this amp produces ALOT of heat) and cooling cycles of expansion and contraction cause tiny fractures on the PCB. Extremely difficult to find. I've found other people with this amp who have also found the same areas blown. I'm about 80% done on a clone of the main PCB (it's taking forever....it's a very complex board) that I intend to have made out of 2.4mm thick FR4 with thicker tracks. I may also change the circuit a little to add drivers so that standard outputs can be used. Finding genuine Sony NEN/NEP250 can only really be done now by finding old ES receivers and stripping them out.

[@whatcouldgowrong7914]

Cannot speak to that as I haven’t stripped other areas but this amplifier definitely had its bias set wrong on the 4 ohm setting which caused the thermal run away when the rails were switched to the higher voltage. Its been working fine… so far 🤣

[@whatcouldgowrong7914]

Also forgot to mention you should double check the bias on the correct setting per service manual (its mV not mA) as mine does not run very hot, mostly warm once it's biased correctly...

[@richardbrobeck2384]

It sucks how hard some parts are getting to find !

[@mrwilliamwonder]

I've been using mine since 2001 when I bought it new for $1200. It does not run hot. It takes a lot to get it hot if it ever gets hot. It's been flawless in the 16 or so years I've used it. I use it mostly in bridged mode. Either 2+1 or 2 channel. It has a very nice warm character but not too warm. It powers my Paradigm Founder 100's. Fantastic speaker and amp combo.

[@morksbeanbag]

I am happy to eat my words on this. Once properly biased, the unit runs fairly cool. The mV/mA confusion on the amp (thanks service manual) can easily cause these amps to be set to run very hot indeed. But if you stick the the advice here and set the bias to 11mV the amps will run fairly cool and allow solid operation.

[@sw6188]

I've been repairing and servicing domestic and professional audio for 45+ years and in that time I have never found SONY products to be that desirable. The circuitry is often over-complex using proprietary or difficult to source parts and when the parts are available they're five times the cost of any other comparable part. For the audio gear that I collect and use personally it is mostly vintage Technics and Perreaux. I seek out units with run of the mill discrete components that are easy to find and I keep good stocks of things like output transistors. I don't blame you for not wanting to touch SMD. It was never meant for manipulation by human hands. I will do SMD stuff where necessary but I am not that fussed on it.

[@whatcouldgowrong7914]

Yeah it’s not ideal to work on… it’s certainly a good performer though and one final video this weekend bench testing it

[@markusweissenbock6337]

SMD is easy once you are comfortable with it and yes, Sony is a mess.

[@sw6188]

@@markusweissenbock6337 Yup, I can do it Ok but I wouldn't want to do it all day every day.

[@4067536]

Sony products cannot be repaired.

[@sw6188]

@@4067536 That's not correct. I have successfully repaired many Sony products. I just choose not to work on their equipment these days because of the cost of their spare parts.

[@mikemmikem2758]

Brilliant and clever trick for the 'fix.' I have an original vintage Sony (1987) GX10 ES receiver powering my new Martin Logan 15i 4 ohm speakers and the specs on the Sony are rated 335W into 4 ohms. The receiver is 52 pounds and, as usual for a receiver like this (new or old), runs really hot - that is until I got an ACInifinity cooling unit that solves the problem. The unit sits on top of the Sony and exhausts out the rear but they have cooling solutions for any setup. Have one on my Denon 3800 avr. The nice thing about the Sony (and others of that era) are ac outlets on it so the cooling fan is set to go on/off automatically.

[@hectorchavez1807]

I successfully fixed a dead channel in the same amp, the SMD parts are obtainable and it is possible to do it. A crazy hard work though.

[@whatcouldgowrong7914]

Unfortunately many of the transistors were obsolete or superseded so it would be an unbalanced channel and would require a lot of work to match channels again… The outputs were the biggest problem with no reliable source that isn’t likely to be counterfeit 😞

[@viperwizard491]

@@whatcouldgowrong7914 basic cheap amplifier. dont know what means unbalanced in this case. feedback is meant to correct errors. if 2sc5200 vs 2n3055 then i get it

[@whatcouldgowrong7914]

@@viperwizard491 Unbalanced in regards to transistor gains, sound signature after replacing many components etc. The amplifiers need to be bridged together also. Whenever I have a failure of an amplifier channel, I always rebuild the other channel to me a mirror image with components. Hardly a "cheap" amplifier lol

[@viperwizard491]

@@whatcouldgowrong7914 they dont do matching anymore in factory . if transistors come from same batch. in this circuit output stage gain mismatch could give some loading difference but P/N transistors cant make same. unless buy factory rejects or fakes. bridged gain set resistors are not same and possible reason why magnitude higher THD . wont get from it no where near 0.003%@-3db anyway at least it has looks

[@pauledwards2817]

Great video. Thanks for the insight. I do have one and the transformer does hum quite a bit. What was the final idle power consumption after you got the amp going?

[@whatcouldgowrong7914]

Video coming this weekend with full power consumption and power output. Was very surprising!

[@pauledwards2817]

@@whatcouldgowrong7914 thank you I await with great interest. Quite hot here in the uk so humping power amps around is not my first choice of activity. Right now it’s in store. Sadly I am one of the poor restless people with too much kit and can’t find any combination that is a clear winner.

[@KurtzVintageVibes]

Feel bad giving this video on a thumbs up when it's a bad news story. Great video 👍

[@whatcouldgowrong7914]

Thanks! It certainly was a rollercoaster of sorrow and regret then relief! Thank god for the spare channel!

[@nicholasdagias1673]

@@whatcouldgowrong7914 Hi there, sorry to hijack the topic, but I have a Sharp RP-207 like you have previously repaired. Would you be willing to fix another one ? - Sydney based

[@whatcouldgowrong7914]

@@nicholasdagias1673 I could but shipping it might be problematic?

[@nicholasdagias1673]

@@whatcouldgowrong7914 Happy to cover shipping costs or drop off in person. How can I DM you to further discuss?

[@repsych]

Thanks, that's some fine rejigging work there. I had one of these and it worked really well until some idiot at a party threw a glass of wine into the top plate. As you say the parts are to difficult to obtain and the repair was not economical.

[@whatcouldgowrong7914]

Must have been a very sad day to see one die like that :(

[@PrimeHiFi]

Poor thing. I suppose that’s one of the only plus sides to having a multi channel amp - one channel blows up? Just swap to the next channel and move on :) As for the failure mode? It could be a number of things. I’m thinking either a dirty bias pot sent the channel into thermal runaway, someone screwed with it while it was on the wrong voltage rail making it run away when set to the other rail, or it could have even been the capacitive load imposed by the SRD transformer adapter sending the amplifier into oscillation, killing the output stage. Either way, good “fix”! That’s one of the nicer multi channel amps I’ve seen 😮

[@whatcouldgowrong7914]

She is a beast! My suspicion for it being messed with was that the remaining channels being set to 11mv on the wrong mode which matches the manual and seems unlikely to be there by coincidence… Possible all channels might have gone up if I left it running longer. Pots are definitely a possibility or calibrating it cold / cover off also I guess.

[@Fearwtscomin]

mine went into safety mode this morning =( I'm not nearly skilled enough to do this work myself though, so sadly I have to drive many hours to take it to a repair shop where i'll no doubt be bent over the work bench when its time to pay for the repair. Im super bummed, it wasn't even in use when this happened! I was turned on, and left on all the time even though it wasn't actively playing. I think it just got hot or something and now here I am.

[@whatcouldgowrong7914]

Sad 😞 i hope they can find the parts to fully restore it and read the notes to bias it correctly. Most older repair shops would struggle with smd

[@brunomahle1618]

I salvaged,...I think 5 pairs of the sony 250 outputs when I tore down a 777es.

[@josephlalock8378]

😂 all those "fine gold" capacitors. i'm trying to use mine up on gear that doesn't matter. i've never used those caps outside of the direct signal path either as they really aren't made to be. will they work? yes. are they the ideal cap(to use anywhere) ? no.

[@whatcouldgowrong7914]

Better than the usual Chinese garbage

[@HF-7DXM-6DXW-12]

Great job

[@AndrewTa530]

happy to take it off your hands

[@tomki6asp]

Nice flashlight

[@whatcouldgowrong7914]

Beast of the thing 🙏