Glad I searched and found this, Jan. Your videos haven’t popped up in my feed for a few weeks, and I was getting a little worried about you! I thought you might have burned yourself out on repairing things, and that maybe you were taking a break. Glad to see you’re still in action. Keep up the good work! 👍

Nice work, love this era of amplifiers.

One of the best amplifiers in the 80's when it comes to sound at the affordable end and is still good :)

That's a long video (and I'm not complaining). I was falling asleep and kept waking up multiple times and your video was still going on every time :)

@JanBeta

5 жыл бұрын

Haha, nice one. Hope you did sleep well at least. :)

Thanks for the video - it helped me with the repair of my recently purchased 3020 amplifier. Great quality and sound afterwards

Nice repair! I just love NAD! I am still using a 7225 receiver from the 90's, great amp.

You just inspired me to redo my NAD 1700 pre. It needs some love after almost 30 years.

I very much enjoyed this and I’m looking forward to your next video on the NAD. I was watching this lying down drifting in and out of consciousness listening to the soporific effect of your voice. On occasion I woke up startled 😱 following a thud on my chest when the phone fell out of my hand.

I still have my NAD 3140 bought in around 1985 (along with a pair of Wharfedale 506 speakers). And my original C64 and accessories from '83. Your videos always seem to give me Deja Vu or something.

@JanBeta

5 жыл бұрын

That's part of my secret plan to conquer the world with nostalgia. ;)

@davidhinson5467

4 жыл бұрын

Stephen, I also bought a 3140 somewhere around 1979 or 80? Still have it- works great- and bought a later unit a year or so ago from a guy selling his. Love the sound.

Omg you have ultra patience and that was intriguing. I'm a beginner. All I need to do is replace a speaker clip block, but watched all this and now have questions. You're a gem!

The output transistors have the date code year 80- week 23, the replaced one is year 87-week 11. Thanks Jan for this video, I have a more recent 3020i (1990) to repair, and it helped me.

@JanBeta

5 жыл бұрын

Ah, didn't see that. Thanks! Best of luck with your repair. :)

Nice video enjoy watching you doing the repair! I learned something about replacing all the capacitor good idea...good job 👍

The 3020! I got really excited when I saw the notification for this, as I have a 3020i myself. I really like these amps a lot and use mine for my desktop and to connect things like my phone and other devices. Unfortunately mine lacks the little power meter and the weird vertical connectors at the back, as it's a unit from 1991. The front panel is also totally different, having a different style of knobs and buttons. I look forward to the next video on this amp! This one's been really fascinating, and now I want to do some maintenance on mine as well.

@9XThunder

5 жыл бұрын

3020i is bad sounding, you must have the first version or the 3020b !

I had the older version with no tone controls, but it still had soft clipping and the MC phono input (used for a Stanton pickup back in the day). Normally mine ran slightly warm (~40c IIRC??) when idling, but since I bought it new I never had occasion to repair it until the 90's when I recapped many grey ELNA preemptively with Nichicon. I always liked how the designer put the 2955 PNP's closer to the edges of the heat sink, since they live longer when running a few degrees cooler. Thanks for this blast from the past!

@JanBeta

5 жыл бұрын

Nice! I didn't realize the design detail with the 2955s but it makes perfect sense. :)

My 7249OE failed a few months ago and I miss it dearly. So, I'm trying to figure out what I can do to bring it back to life. This video is one of the few that offered insights into what to look at. I have the tools, and I've cleaned up the PCB to order capacitors. Looking forward to the update VDO! : )

I had the 2020 back in the day, along with matching receiver. Good kit.

NAD also did a very nice turntable when this amplifier was around , the 5120 . They were very popular in the mid seventies right up to the late eighties for their quite sublime sound quality and value for money.

Watched it twice. Fantastic stuff!

Excellent video. I have an old nad 3020. Great unit. In storage now but will need a recapping and work when I decide to put it back to use. It has a warmer sound then my mid 1980s NAD Monitor series 1300/2700 combo that I replaced it with, though they have a lot of nice qualities as well. 🙌👍🙌

1 hour long? Let's go, I've got a pint of water and a bag of toffee M&Ms so I'm ready. Thanks Jan.

@JanBeta

5 жыл бұрын

Hope you enjoyed! :)

WHOOHOO! Another video !!! Loved it, great video!

@JanBeta

5 жыл бұрын

Thank you! Glad to be back. :)

I have a couple of those, one in reasonably good shape (though power indicator leds don't light up above volume regulator) and another one completely trashed (lots of hum). Gonna restore both. Have all the parts in the mail and eagerly expecting pt. 2 :)

Great fix Jan, Reminded me of the first time I heard Turrican 2 over my stereo from the Amiga. I hope this is where this one is going ;). Looking forward to the finale on this..

@JanBeta

5 жыл бұрын

Oh, nice idea. I actually considered using this amp for connecting my computers to. :)

@nopochoclos

4 жыл бұрын

I use my nad and others with my AMIGA and C64.. Atari and MSX.. great beast..all of them.

While I always enjoy the retro computer videos on here, it's nice to see some cool stuff like this from time to time ;)

@JanBeta

5 жыл бұрын

Thanks! The audio gear videos will always be a part of this channel, too. :)

You are still lucky. I got the amplifier in such a dirty form that I had to wash it several times in the bathroom under the shower. Moreover, the previous owner began to improve the amplifier and put his capacitors different from the circuit diagram. I returned everything to the factory circuit and the amplifier began to play perfectly. The question is why he did this and I had to redo other people's mistakes. In general, the 3020 amplifier is certainly a masterpiece and ten best rated by audiophiles.

Would you believe we had this exact one when I was growing up! Looking forward to catching up on this vid.

@JanBeta

3 жыл бұрын

I actually just started working on the amp again a couple of days ago. Promised it to a friend but I managed to completely break it (tried repairing it "too much")... A new video is coming soon(ish), too. ;)

@RetroRecipes

3 жыл бұрын

@@JanBeta Oh no! But also, cool!

@user-lh8rb5wx6q

3 жыл бұрын

@@JanBeta This is as close to a manual that I get as I try to get my Two series 20 that WAS working Before I messed around with, both of them, (recap for no reason). Ultimately trying to fix the first one at all. I ran into the same issues on both amps, the voltage regulator is not made for repair without a lot of preparation and good soldering techniques. I wish I could get a new PCB for this card that is held in place by plastic splinters on the back, but I had no such luck searching e bay, So. Ye, please share a new video, you are entertaining and you have a superb cam clarity making the absence of a proper service manual less apparent. They are also totally impressive amps that never stops to surprise me with their detailed and articulated sound, never feeling short of 2*80W. This series 20 version, that is, marked "80W" on the back, the others are fine but dont sound like these original units. Supposedly since of an error in the pre amp making it unusually swingy, thats what I heard anyways. Thanks for your videos and yes, please follow it up! Patrik, Sweden

@CM-dw3gh

2 жыл бұрын

@@user-lh8rb5wx6q did you set the Bias. If so, what tool did you use for the trim pots?

Beutiful job. Ive recapped a few amps and old cassette decks ect. Always a good idea to do it on old amps despite some feel it shouldnt be done. I find recapping therapeutic! Ive recapped my nad c352 amp. The caps I removed were junk, I used panasonic fr and fc mainly. Sounds awesome. Really enjoyed your video, thankyou

@patthewoodboy

2 жыл бұрын

modern caps are far superior to those from 40 years ago , I do the same and also find it theraputic

Great video. Reminds me of the restoration of my bryston 1B preamp.

Great to see you back! :)

@JanBeta

5 жыл бұрын

Thanks Stefan! Hopefully I'm going to be here more frequently again. :)

Nice repair Jan. Well done.

@fghjfghgj

5 жыл бұрын

that's not a repair it's luck if you change everything without reason.repair is find what's wrong than fix

@GeorgeEI7KO

5 жыл бұрын

@@fghjfghgj great comment from channel with zero content. Show us how it's done then...

will there be a part 2? really enjoyed this and keen to hear your verdict

At about 11 minutes.... Jan: 'ok, so let's just plug this in now and see if it works...' Me: glances at timing indication on the KZread player, sees 40+ minutes left to run .... 'yeah, it's not going to work just yet Jan, I bet' :-)

@JanBeta

5 жыл бұрын

Haha, yeah, it wasn’t all that easy. Still some work to do obviously. I plan on completely replacing the output transistors with new ones. Luckily they are still readily available.

@Druman19

5 жыл бұрын

I do this as well, haha. Kinda spoils it for me tho.

@izools

5 жыл бұрын

@His Masters Voice NAD produces some quality amps, too. C320BEE, C355, etc. They also produced some really high grade CD players in the early 90s. I have to believe in NAD to a certain extent as NAD is also my initials 🤣🤣🤣

@spareparts007

4 жыл бұрын

@His Masters Voice Well they were and are the biggest selling integrated amp in history (well over 1 million sold) and 40 years later people are still talking about them, using and restoring them. Prices on ebay are going up and up for these 'junk' amps now. Australians obviously have far better hifi available to them which the rest of the world hasn't heard about.

Great video and thanks for the link to the manuals! Lots of goodies there :) Maybe I can get my NAD CD players back up and running again!

@JanBeta

5 жыл бұрын

Yes, Hifi-Engine is a great resource for audio related info. I use it all the time. Good luck with the CD players! In my experience, they are either easy to fix or really hard. Not much in between most of the times. ;)

@RobertEliason

5 жыл бұрын

@@JanBeta thanks, I'm hoping for a dirty lens :)

@JanBeta

5 жыл бұрын

Chances are good. Fingers crossed! :)

I went ahead and download the schematics and service manual from hifi engine. The R654 and R653 resistors are shown as removed in the service manual and marked as "shorted after idle current adjustment", and are not shown at all the the schematic document. I don't believe they should be present and are just meant to be a test point for the procedure. So in a nutshell, you open them up, install R654 and R653 (which are also listed in the service manual as part number 16-1/4CR 1R0Js, these are 1 ohm 1/4 watt Carbon type, link below should be suitable replacements) and measure the voltage that is present between the emitter and the +30.5 rail to calibrate the output, at idle with no draw of current through the emitter, then short them when you are done. It would be nice if the service manual made it clearer, but that's what I get by reading the schematics. You should check and make sure they are indeed jumped (it looked like they were on in the video) before doing the procedure and remove the jumpers to do the procedure, then close them again when finished (otherwise your amp won't produce any meaningful output signal as this is a push/pull amp). Rx1 and Rx2 are the middle of the a voltage divider that consists of +30.5v to -30.5v all across Q615, RX1 and Q617 on the left channel and an identical on the right consisting of Q616, Rx2, and Q618 on the right channel. Again, this is according to the service manual. I can't confirm that on your particular unit. It's just a well educated guess. www.ttiinc.com/content/ttiinc/en/apps/part-detail.html?mfrShortname=KOA&partsNumber=CF1/4CT52R1R0J&customerPartNumber=&minQty=5000&customerId=

@JanBeta

5 жыл бұрын

That makes perfect sense. Thanks for the description. I'm going to try it just like that and add 1 ohm resistors for measuring. :)

I picked a 3020A up at a car boot for £10 sounds great im happy to have it in my collection

Great stuff! Part 2 please!

Fantastic phono stage on this 3020.

I’m learning to. Going back to college after 30 years taking Electronics AS Degree program to enhance my hobby with electronics and building amps, pre-amp, DACs, speakers. I purchased the ( DER EE LCR METER DE-5000 ) you will not have to guess if capacitors are good or bad. When replacing capacitors some were designed to block DC more then others. There is a reason why some are different. Than some vary low ESR is needed other need 105C + because it may be in power supply next to vary hot resistors or hot MOSFETs. One size fits-all may work but may cause long term reliability or noise or change sound or preference in your phono or preamp

I have had a somewhat newer NAD 304 since the 90s, I used it until I moved out from my parents' house for good. It's still in pretty great condition, been sitting at my parents' for many years now and not seen much use, so the pots have gotten scratchy. I want my parents to be able to listen to music even though they rarely do, so now I replaced it with my wife's NAD C320BEE which is very similar to operate, until I get around to attacking the 304 with some contact cleaner. While I'm at it, I think I'm going to undo a silly and meaningless little mod that I did 20 years ago, linking the preamp to the power amp internally. These NADs are awesome little amplifiers in my experience. They sound good, and I've never had any problems with mine.

@JanBeta

5 жыл бұрын

Nice! Yes, I'm pretty much in love with this little amp, too, now that I've met one in person. Can't wait to fully rebuild it and give it a proper test run. :)

Great video,i have the nad 3020i its running with no problems at all & sounds great,it has been serviced but not recapped. The guy who serviced it said there was no need to recap it,i just took his word for it. Your like share & subscribe sign really works.I nearly forgot to like already subbed.Im a new subscriber loving your channel.

Hi! We missed you.

Lovely little amp. Sounds great driving a pair of Linn index

awesome vid!

The "clippy things" are called stand-offs. For the Bias adjustment you need to install 1/4 watt 1.0 ohm resistors in the locations for R653 and R654. You then measure the bias current by reading the voltage across the 1 ohm resistors. After you have adjusted the bias, you then short out the resistors but leave them installed for the next time the unit is serviced. You can find this information in NOTE 6 of the schematic. ALSO, you got lucky after replacing the caps because you might have damaged one or both of your speakers. See if you can find a non-inductive 8 ohm 10 watt or higher resistor to act as a load until you have verified the repair. If you only have one load resistor you can move it from channel to channel. Then use your scope connected across the load to check for any oscillations or clipping that could be present and might also damage your speakers. An osicllator app from your phone can be used as a sine wave source to observe the output. A procedure I have used to adjust idling current when there is no information is available is to use a current meter in series with the AC power supply to the unit. Adjust the bias down until the current is no longer decreasing. Then slowly raise it until you get the current to go up slightly. Then do the same for the other channel. Measure the voltages (current) across the emitter resistors and try to adjust them equally. Let the amp stabilize for a half hour and check again. Feel the heatsink to see if it is warm but not hot. If you have a distortion analyzer you can also set the bias current by feeding a 10khz signal at about 1 watt and adjusting the bias until the distortion goes to minimum.

@JanBeta

5 жыл бұрын

Thanks for the description, I'll try 1 ohm resistors for measuring. Makes perfect sense. I actually have a 8 ohm load to test amps I built a while ago but didn't use it because I was pretty sure it was going to work alright. But you are right, I really should have been more careful.

@Noneatme

5 жыл бұрын

Aren't the speakers already damaged?

I use a NAD tuner. Love it. Hope the amp serves you well.

@JanBeta

5 жыл бұрын

I'm probably going to give it to a colleague after I finish the restoration. But before I decide what to do, I'm going to test it thoroughly myself (and maybe keep it). ;)

I came here for information on fixing relay problems on a Philips amp and I stayed for the VG8020 MSX box under the table. :)

Hi congratulations for your great skills indeed. What i find surprising is the careless that some designers give to two important regulation issue: offset and bias. They should provide clear points of measurement to make the regulation procedure easier and more efficient. Moreover in old vintage unit like this one (it is almost a 40 years old amp) the trimmers for bias and offset should be replaced with multiturn sealed ones for better control on regulation. And most of the caps replaced as well. A very historical amp indeed. I think they sold them in thousands. Kind regards, gino

Was there ever a follow-up to this one? Would love to see how it turns out. I'm working on one right now, except it's got different (worse) problems. Great video.

Heatshrink to insulate the transistor legs from the heatsink...it's usually what I use and means that there's no chance of losing the insulators or have them fall out :)

Regarding DC offset... the best way to adjust is to disconnect the preamp links, and make a shorting plug that shorts the power amp input to ground. You may find a lot of that DC offset is coming fom the preamp. I'd probably ensure "soft clipping" is turned off as well. As for the output transistors, go for Onsemi or ST branded parts... there's a lot of junk sold as 2955/3055 which are OK if used as pass elements for power supplies for example, but suboptimal for audio.

@jaycee1980

5 жыл бұрын

Also the DC offset has mostly to do with the working conditions of Q601 and Q603.. mostly due to the topology of the circuit. This amp doesn't use the usual "long tailed pair" input stage so it works a little bit different, and its part of what is responsible for this amp's sound characteristic. TBH 100mV or less of offset is not a big problem. The power on "plop" comes from this amp not having power-on muting relays - pretty much any power amp will do this when power is first applied, but the relays keep the speaker disconnected for 2-3 seconds while the circuit stabilises.

I have a nad NAD 3020e I would like to improve its sound which are the components that I must change

excellent video

By replacing all the cap's, the amp is essentially good as new, so even if its working fine, its a good idea to do that with amps this old. And dont cheap out on the cap's, use high quality ones. Some of the later NAD amplifiers, think it was made around middle of 80's, you can actually upgrade the low end/middle end amplifier to high end, by upgrading the filters and replacing caps with high end caps, and transistor replacements. The price difference between the low end amp and the high end amps in this series, is something like 5000 euro, its alot, and defintly worth doing. There is alot work doing that, so its not for beginners, also you have to understand what your doing, and have schematics for the high end amplifier as well as the low/middle end amplifier your working on to understand how to rebuild it to high end.

@JanBeta

5 жыл бұрын

I had very good results with the Panasonic FCs I used before. Good quality stuff. I wish I was pro enough to upgrade the circuitry but that's way above me unfortunately. :)

keep up producing nice video like this as i love watching it...btw, did you by purpose put black-tape on the "PHI" out of "PHILIPS" on your LED TV?

I am experiencing humming/vibrations from the amplifier (not from the speakers) and I’ve located it coming from the golden box. Is there anything I can do to get rid of it?

you could add a resistor in series or in parallel to get the channel output to match.

Hi I have a 7020e amp which has no sound from left channel. It seems intermittent because on and off, sometimes good sometimes not. Can you help please?

Love vintage NAD. Have you ever heard the 902? I love them so much I've bought 3 of them over the last 25 years.

Very good video.

Hello, are you happy with the sound of the amplifier after recap?What is the difference before and after recap?When the sound is better, before or after?

I do enjoy these videos, as well as the retro stuff. I only know the basics of repairing audio equipment. These videos are always a learning experience for me. 👍 I haven't read all the comments and perhaps I am missing something in my understanding, but wasn't the right channel mV measurement reading a negative value (-53mV)? Was that as closest you could adjust it to 0mV or +1mV?

@JanBeta

5 жыл бұрын

Thanks Mark! I'm obviously just a hobbyist with the audio stuff, too, but I worked on quite some amps in the past so there's always at least a tiny bit of experience to share. ;) The mV was negative indeed. And it was the closest I could get, I couldn't get it to positive at all. I think I'll end up replacing the output transistors altogether with matching ones (still readily available). Some commenters pointed me in the right direction for adjusting the idling current, too. :)

@MindFlareRetro

5 жыл бұрын

I wasn't even aware of idling current. #AlwaysBeLearning

i have a 1992 technics SU-X120 40 WATTS / Channel amp, can you advise which parts I should replace to get the biggest improvement in sound quality ?

mach freude dir über die schulter zu sehen.mehr davon lg (: .

@JanBeta

5 жыл бұрын

Vielen Dank! Es kommt definitiv mehr. :)

Did you fit a protection relay circuit? I'm seeing a lot on old amps being ticking time bombs for damaging speakers

Hi, I would like to know what output voltages the transformer has

Those insulators for the output transistors are mica and are much better than the silicone insulators you were wanting to use (much cheaper too). Silicone or trade name Silpads were promoted as easier without need for thermal compound but they have a short life of between 3 to 7 years whereas the mica insulators have an almost infinite life as long as they aren't physically broken. Mica is very brittle so when removing the insulators it is important to slide a flat chisel blade knife underneath them and carefully slide them off the heat sink. Milar would be the worst insulator for a heat producing part as it would melt and break down on the first use of this kind of product.

Jan, do you prefer the Panasonic caps to the Nichicon?

very nice video... thankyou for explaining :-)

Thanks for the video Jan. I just picked up a NAD 7600 at a local thrift store, looking forward to diagnosing the issues when it breaks on me. =)

@BoboButYouCanCallMeTom

5 жыл бұрын

Nad 7600 that is an awesome amplifier, I have its small stripped down brother the NAD 3400 best amplifier I've ever heard.

So what happened in the end? Did you get the bias adjustment to work with new transistors? Did you ever find out about the calibration?

Upgrade the filter caps in the preamp and amp sections, replace caps in critical stages with polypropylene caps and you have one of the smoothest and cleanest amps money can buy.

As for the resistors.... you can use pretty much any low value resistor. I think the schematic actually shows 1 ohm. Thus 30mV would mean adjusting for 30mA idle current.

@JanBeta

5 жыл бұрын

Yes, I think that'll be the thing to do. Makes perfect sense now. :)

Hi. How to check the bias in the NAD 3020A?

i always liked the sound of these amps, sadly they were made cheap and sold expensive, but at least they are repairable. arcam, cambridge audio and nad have all been repaired by me over the years. i dont fix them any more really, i build bespoke metal detectors and custom computers, but i have a vintage sinclair radionics pre amp unit and an amp that goes with it on my bench, i was going to recycle them, but a mate of mine wants to buy them if i restore them, so i'm parts hunting.

Hallo Jan, leuke versterker: klinkt ie een beetje als een Sansui AU-317/AU-505? Warme(maar niet doffe) sound dus? Heb korte tijd een NAD C-370 gehad; krachtige versterker,ziet er mooi uit,afstandsbediening,relais schakelingen. Maar soundwise lang niet zo(vol en warm) als Sansui. Mijn smaak althans.

Nice!

used to run mine through a equaliser as it seemed lacking in treble. also the plastic was very brittle and bits would break off from the bottom edge

Does this amp have genuine power attenuation or is that led thing above the volume knob some gimmick linked to the volume, I know a lot of guitar amps these days do power attenuation.

@aaa000777

5 жыл бұрын

The LED's were power indicator's marked in watts. Quite handy to see how hard you were pushing the amp.

29:17 I noticed a missing resistor just pause and see at the center of you screen, between those polyester caps, behind to the larger one next to a small transistor on the side where original pair of transistors are. maybe that is the reason why you have high bias voltage

Hi, I have a Nad 3020 ser.20 after replacing all the electrolytic capacitors, there is a pops in the right channel of the amplifier. By removing the jumpers, the popping disappears.When I disconnect directly from the power, the popping also disappears.If I want to turn off the selector normally, I have to turn the speaker balance to the far left position. Then there is no popping either. Has anyone had this problem with Nad 3020?

I own a NAD 3120 which needs repair...can you recommend someone in USA who can repair these?

Hi.. I acquired nad 3020 recently.. works fine.. only one problem i see is when I press loudness button the effect is only on left channel..is this something fixable? Thanks

@dennistryon4650

3 жыл бұрын

Yes, it is fixable. Most likely a simple problem of a dirty loudness switch or at the most a bad solder connection.

Music to solder by?

i also have a mains hum when i power up a phillips amp it goes away and returns permanently weird thing is that eq also affects the hum,which caps should i replace? i was waiting to see if you will check for every cap that you changed.. should i go and replace the main filter caps? they are 6800mf each and they are 2

@JanBeta

4 жыл бұрын

If the EQs affect the hum, it originates somewhere before the EQs in the signal chain. I recommend getting a service manual (for example from hifi-engine.com) and look at some signal flow chart (that is most likely provided). If it is an old amplifier, you should replace all capacitors really. Oh, and general mains hum often originates from leaky filter capacitors in the power supply section, maybe that's worth looking at first.

@gorgi991

4 жыл бұрын

@@JanBeta its from 1984 model Philips F4234 problem is the casing its from plastic and theres no easy access to the underneath of the pcb so i need to remove the whole heatsink,then the pcb just to switch the caps,also there are some special german made caps with 4 pins under it so it would be tricky to put a 2pin cap (for the main filter) for start i think i am gonna disconnect the signal board to see if the hum persists which i think it will,then ill change the filter caps

What is the deal with the bottom prong of the left hand fuse holder? It looks like it is bent completely open, you can see it at 42:38

@JanBeta

5 жыл бұрын

Yes, I saw that when I rewatched the video. I'll have to replace that I guess. :)

As the owner of a NAD Series 20 amp, I watched this video. Experiencing a "channel drop". Would this be "fixable", or should I just scrap it?

@FirstWizardZorander

3 жыл бұрын

I know it's a year late, but dropped channels are usually indicative of a failing power amp. If you're feeling up to it, order new power transistors and swap them for that channel.

You can bult in a speaker relais that grounded with a 10 ohms resistor (10 watts or so) to ground if its in off status. EB (com): Speaker Protection Board Component Audio Amplifier DIY Boot Delay DC Protect kit, and 2Pcs Wirewound Ceramic Cement Resistor 0.1 - 10K Ohm 10W Watt 5%

I have no clue about electronics- but that doesn't stop me from watching videos about it :) and I was wondering if you would have been able to use that "superprobe" contraption from Mr Carlson's lab to trace where the hum comes from in such a situation?

@JanBeta

5 жыл бұрын

I think the superprobe would have shown hum nearly everywhere in the circuit as most of it was probably leaking AC from the power supply (the earliest stage in the circuit).

I am desperately looking for someone with the knowledge to fix my mission Cyrus 111 integrated amplifier any help would be fantastic, when I turn it on the stand by light is Amber, not red as it is supposed to be, please help me!!!!

vacuum + brushing = static discharge. which is a good way to toast some components. i do like NAD amps a friend has a huge one, maybe twice the size of yours. maybe i should buy it...you know, just in case i need a 80s NAD amp. lol

@dennistryon4650

3 жыл бұрын

Any static caused by a vacuum and or a brushing should not affect the components while they are mounted in circuit. Static precautions are needed with loose components.

nice video Jan, where did you buy that nice desoldering machine?

@JanBeta

5 жыл бұрын

It's a ZD-915, it's available from various sources. I made a video about it a while back, too.

Two common issues with this NAD circuit (they used it in a few models): The muting JFETs in the preamp stage often die, causing distortion or other problems The output transistors have NO emitter resistors. This becomes a problem when they require replacement - I note one of them in your unit has been replaced. It was not a problem with the older Motorola made "hometaxial" devices, but it is a problem with modern "epitaxial" devices made today. It's a good idea to add 0.22 ohm emitter resistors underneath if you replace the output transistors. This also gives a much better way to measure bias current than the way described in the service manual. I've used Arcol V3 vitreous enamelled resistors for this before. Otherwise, yes, they are nice sounding amplifiers especially for their budget price when released :)

@JanBeta

5 жыл бұрын

That is a good idea. I think I want to replace the output transistors altogether to have a better match (and "fresh" transistors). I'll add emitter resistors when I do it as you suggest. :)

Have you ever worked on a Grundig Locarno 3/U Console? Made in Germany in the 60s. Got one for moving some furniture after an estate sale. It still works!

omg I had this as my 1st hifi amp. The 3020 e and i were later and better

Is there a part II :)

They replaced the transistors but not the capacitors? Also who needs 3 phono inputs?

One question : for sure it was better to change all capacitors, but would it damage the speakers if you changed one, turned on the amp and so on until you find the guilty capacitor?

@JanBeta

5 жыл бұрын

I don't think the noise would harm the speakers in this case. The only thing that kills speakers really quickly is DC voltage, they can take a lot of AC for short bursts usually. It is annoyingly loud though, so it would be a better idea to connect a load and an oscilloscope to check the output.

@dennistryon4650

3 жыл бұрын

I don't really understand why you would want to change one cap at a time. If this was a fairly new amp it would be better to just replace the defective cap but since this amp is 40-50 years old they all need replaced. If you just replaced the defective one you would probably be repairing the amp often since most all of them will fail due to age.

I fixed many of the NAD amps in the 90s. I never understood what the fuss was about. They always sounded completely average to me. Most were very ugly with limited inputs and controls. The Taiwanese parts were very junky and the resistors were always going high. You discovered the conductive glue they gave every owner as an added peeve. I always considered them to be mediocre gear at an inflated price. They made me money so I never complained. Also, the very standard off-the-shelf transistors made parts supply easier so there is that.

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.

@JanBeta

3 жыл бұрын

Lab in is just an input that doesn’t filter the super high and super low frequencies. The regular input has some filters in place. Depending on the audio input and your speaker setup, you can sometimes hear better quality from the lab in because of that. And of course it won’t be a problem to just use the input and power amp and leave the preamp section out of the equation, you are going to be absolutely fine, you just don’t have the controls.

@dankolov1839

3 жыл бұрын

@@JanBeta Thank you very much for the answer.

Those variable resistors are known to fail. Like it so far!!!