#86 - NAD 3225PE stereo amplifier repaired and tested 

I don't understand why this channel doesn't have more subscribers. You an excellent technician, teacher and filmmaker. Thanks!

That was amazing. I'm a software guy, I know nothing about electronics really, but to take something that is broke in an unknown way, dig in, figure it out and fix it IS amazing. I always wondered where one would even begin such a repair... and now I know. Thanks!

I watch these videos with great interest. I have no understanding of electronics and I'm not learning anything. But here I am.

Look at that gorgeous hand layout. Those traces are art.

Another great repair, always good to mention cascading faults, I have seen to many people change one transistor at a time and wonder why they keep failing.

Awesome video. Thank you. I bought a 3225PE brand new in 1988 and still have it but it needs some TLC. Watching your video has given me the confidence to start the project.

Very systematic and thorough approach. Best 32 min I spent today. Excellent work. Subscribed.

Excellent work..... Proper old school repair... These videos have aided me to do my own repairs, saving classic old kit from the scrap heap. Thank you....

THIS GUY IS GOOD !!!! knows his stuff,thank you.

Thanks for making this video. Informative, clear and concise. Keep up the excellent work.

Always enjoy your videos, Thank You!!

excellent video. I had one of these amps in about 1994 when I worked my first job in a hifi shop. I bought it from a customer who was looking to trade up, used it for a couple of years before moving on to something else. it saw occasional use for the next dozen years or so, then I gave it to my nephew 5 or 6 years ago when he wanted something to use with a record player, and he's still using it daily. in all that time its never needed the lid taken off, not a peep of a fault.

I understood more of repairing from this single video then dozens of others. Thank ou very much. Subscribed ofc.

Well done! Thank you for another interesting video. I usually take a few pictures when disassembling equipment, especially when there will be a delay for parts. That plus some small containers for parts makes sure I can get it back together correctly.

Now I need more videos from you. I enjoyed this walk-through.

very nice repair! always waiting to see notifications from your channel!

I bought one of these in 89 and am still using it today. Nice to see another one rectified. Mine still purrs like a kitten as it did on day one. Dust was never an issue.

Best electronics teacher out there.

Good job! I gave up on an attempt on this one, couldn't find the right drivers. Great to see someone succed! :D

I think that's the exact NAD my brother had in the 90's, great amps.

Very very instructive, bravo from France !

Great repair work, well-explained, no-nonsense, and highly knowledgeable. Subscribed. My other fave channels for electronics repair are Uncle Doug and D-Lab.

Excellent class. Thank you very much.

Great video - thanks for posting

I still have an NAD 4020A AM/FM Stereo Tuner I bought new almost 40 years ago. I bought that with a matching NAD 3020 integrated amplifier, which I no longer have. I got a lot of use out of those in my college days.

Great repair and vid! Thanks

Great, thanks. This unit was similar to the type I scavenge, nearly always multiple failures and fun to fix.

Awesome info, thanks for sharring. :)

NAD. New Acoustic Dimension. I'm full of useless info. One of the reasons NAD amps blow up more than most, is the lack of Emitter follower resistors.

Great video

Good work, thanks.

Good tutorial ...

What a smashing repair, i love the old school amplifiers :-D The black module type amplifiers are not too reliable. The second i saw the T03 transistors i thought 2n3055, i have used them in power supplys and amplifier repairs with it's complimentry pnp :-) That NAD didn't look too high a quality, most of the parts looked quite ordinary. People payed a lot for NAD amplifiers on the understanding that the money was spent on the inside.

great job! I enjoyed that one! My knowledge of amplifiers is sorely lacking!

Great job! I'm subbed.

Great video :)

Well done. Great!

Nice narration and excellent repair, as always

excellent repair job and video as always. by the way, you could use the FFT on scope to measure the THD of the output signal or at least check the quality in terms of harmonics

You got you self a new subscriber 🙂🙂👏👏👍

Great video with a pro at work......

Nice repair as always, well done.

Could you do measurements on THD , use 2 channel oscilloscope, and make different between channel one and two, channel one can be input channel two can be output with resistor divider to scale it down . You can do it over frequency with 4 ohm load

You did a very nice job! I also often repair Amplifiers. In most cases i get Car-HiFi, PA and Home-Cinema Amplifiers. And i can say that 90% of all dead AMP's has blown fuses in cause of grilled driver- and Output Stages. When i bring the repaired AMP back to it's owner i like to look closely how they connect them to their speakers. I often see Speakers with too low impedances for the AMP. And sometimes the owners have connected more than one speaker in parallel to one channel so the impedance is way to low. If you put two 4 Ohm speakers in parallel you get 2 Ohms. When you put them in series you get 8 Ohms. When they didn't understand the Problem, i like to show them the impedance-results with a simple Multimeter that is set to resistance measure Mode. I simply reconnect the Speakers in a way so the AMP don't gets overloaded. The most devices shows informations about the allowed impedances depending on the wiring printed on the backside near the speaker Terminals or somewhere else. Or you have to read the manual to do it right. And i know for Home-Use the most Amplifiers are designed for impedances of 8 to 6 Ohms. 4 Ohm devices exists, but they are not so popular. I only knew some expensive Home Cinema Systems that can easily handle 8 to 4 Ohm and some down to 2 Ohm. My last two Home Cinema Amp's can handle down to 4 Ohms but i first have to activate this in a special setting menu BEFORE connecting the speakers. Car HiFi AMP's are normally designed for minimum 4 Ohms - Current devices can handle down to 2 and 1 Ohms. But you always have to read the Manual to make sure you don't fry your Amp with stupid connections. I have two 4-channel Amp's that can handle down to 2 Ohms in 4-Channel Mode. When i set it to 3 Channel Mode (two channels in bridge mode) the allowed imedance of the bridge is limited to 4 Ohms while the other two channels can still handle down to 2 Ohms. I believe the manufacturer's information and i don't like to test it otherwise. There are many ways to fry an AMP. And Remember - Only 80Watts electrical power is enough for a full fire.

Wow, a PE. Top of the line back then

Does anyone know why those resistors have a loop in one of the pins? Is it a mechanical vibration mitigation, or some sort of additional inductor?

Does anyone know why there is a loop in 2 resistors legs at 14:30. I have never seen that before.

Great video! Thank you for being so clear and making this a step by step tutorial. More of this please Subscribing as for today

hello, I have a Nad 3020A, will there be a problem with the amplifier if I turn on my dac in LAB IN and remove the jumpers from NORMAL IN and PRE OUT? I have never used LAB IN, but when I included my dac in it. The sound has improved significantly. But I don't know if I use this switch, is there a problem with the amplifier? Thanks and send greetings.

I have a model 602 NAD stereo cassette deck which powers up but otherwise does not work. I really like the unit and have not been willing to just throw it away. I would be happy to ship it to you if it's OK.

thanks for the video yo! nice work

Good way to build perfect pre amp-power Amp connectors, just build one set, thanks

Hello, a newbie here, I have a similar AMP. L-Channel is OK but the R-Channel is distorted. What could be the potential causes? btw, before this, the AMP has no power, found 1A F505 fuse is busted i replaced it, Q508 also resoldered, and the power turns ON. But R-Channel is distorted. pls adivse thanks

Nice job. And charming Russian accent. 😊 By the way, shall you use 240V bulb instead fuse at first power up?

Witam serdecznie . Borykam się z nad 3225 pe którym mam problem ze zwarciem w lewym kanale niby wszytko jest ok i gra ale po dodaniu głośności pala się prawie wszystkie tranzystory i dwa rezystory, jaka może być tego przyczyna sprawdziłem juz prawie wszystkie kondo i są one ok wiec co może powodować te przypadłość Włączony przez żarówkę 100 w lekko się ona żarzy z góry dziękuję za wszystkie propozycje Hello and welcome . I'm struggling with the 3225 pe, which I have a problem with a short circuit in the left channel, everything seems to be OK and it plays, but after adding the volume, almost all the transistors and two resistors light up, what could be the reason? I've already checked almost all the condos and they are ok, so what could be the reason? cause this condition. Turned on by a 100 W bulb, it glows slightly. Thank you in advance for all your suggestions

Great video. I have the 3020 with bad channel, uses same transistors but I can't figure it out😩 with I had your skill level

Hi FeedbackLoop. I notice you showed some images of parts used. Regarding the transistors 2SB649AC and 2SD669AC as shown in NAD schematic. When searching there is a lot of confusion on the Hfe classification suffix "C" and of course I want to stay away from Ebay sellers (Bad experience with transistors , probably fake) Some major supplies like LCSC have as AC and others A-C. I see one package shows the 2SB649A-C from LCSC and viewing your footage, seems to work OK, so assume is Hfe C. The other is the 2SD669A "C" which you don't show package. LCSC show a 2SD669A and their spec sheet doesn't really indicate if part is C "Hfe", instead shows all B,C,D variations. I have an email with them , no answer as yet. Did you order - Manufacturer Foshan Blue Rocket Elec, Mfr. Part # 2SD669A, LCSC Part #C328595 ??. Last part was BD139. Digi Key have BD139G ( which I have) and also noticed they have BD130-10 ( higher min Hfe I think and what is in NAD Schematic). What did you use from Digi? as yours seem to work well. Do you think the BD139G would also be suitable- specs seem same apart from lower Min Hfe . Thks

I want you to have a pair of expensive speakers.

Наверное уже не звучит как 3020 A // Series 20

Quite old? Then my stereo stuff is ancient, 1980 or older, the Japanese golden era.

CRAP, EVERYTHING LOOK LIKE RUNNING IN SLOW MOTION.