Marantz 2500 Troubleshooting a Hum Problem

[@dzee9481]

Tony excellent repair, today you could not someone as meticulous as yourself, to care and put the effort to finding and fixing such a minor issue such as this hum. Most repair facilities would just say it is normal and works. You are my hero.

[@Rico_G]

For a hobbyist, you have a lot more talent than many so-called pros.

[@bulwinkle]

Thank you for allowing us to hang out in your shop and learning with you.

[@isoguy.]

If I had 1/10 of your skill I would be a genius. Great tutorial, thanks for sharing. 👍👍👍

[@andrewtrezek2405]

Incredible!!! I’m dealing with The same issue on a 2285B I can’t thank you enough for what you shared.

[@rajendrabareto8065]

I also have it on 2285b when the volume knob is @ middle. When I further increase the hum reduces. Did you fix the issue?

[@alexispieltin9379]

I'm sure you have done the optimal and final treatment for this one. Your long search for a minimal hum is really instructive, as many of these complex engines suffer from the same problems. Most 60's and 70's productions inherited bad habits from tube construction history, and did not care of these ground loops as closely as later productions, particularly when digital sources impulsed better architectures for high end audio. It was admitted to use chassis ground as common ground. This proofed problematic in stages with high currents and bad signal separation, and emerging noise from the power supplies. High voltages also economically limited the filtering of supplies, so the AC hum was tolerated. Going further implies much more time and a complex structural overhaul of this Marantz, implying shielding procedures, replacement of the transformer, replacing some resistors for lowest noise ones, chasing for ever better caps, replacing the original PCB for even better ones... Next is to isolate the AC supply in a separate cabinet, replace all internal connectors for military grade ones ... Doing that implies you buy better measuring equipment, reference loudspeakers and sources, a special auditorium with noone singing in the background, no dog barking, no cat asking for food or attention. And even if your clients had no budget limit, it's no proof to produce an absolute 100% noiseless perfect unit. At that point, another simpler solution is to choose another amplifier, with a separate tuner! Well, you know I'm joking, because I think you perfectly get the balance between what has to be made and what is needless, depending of what you initially get and the limited amount of time and money this implies. Going further is needless. All it needs is a nice wood cover, and we will be pleased to see the final results. When it comes to real music, it's not the numbers, the Watts, noise and distortion figures that are the most important. After years of solid state silicon evolution, there is still people preferring vacuum tube electronics, or some combination. After all, it's music you listen, not the relative silence. What makes these old amps and receivers so precious to most audiophiles is not in their small defects, age related scratches and so on. First is the way they sound, second is the way they were made to age well. I'm not certain most nowadays piece of high end electronics will survive 40 to 50 years of service with hard environmental conditions. This survivor was nasty looking when you first looked at it, but the basis was sufficiently good for a restoration. And I'm pretty sure you've probably made it work more reliably and sound better than when it was produced.

[@dl7majstefan753]

Thanks for this video! The small difference in the hums of both channels may be caused by different pcb layouts for left and right channel in the amplifier - i.e. different grounding loops on the pcb.

[@martinda7446]

PS Well done, don't usually see this sort of dedication. The lovely Marantz deserved it.

[@robertfournier7050]

As much as you say high end. I have a hatred for those products due to there complications. I have British amplifiers with very clean sound and the circuits are so simple. Way to go for not blowing the receiver up.

[@glenwhatley4125]

One other observation and question would be: for a dude who is still working and apparently has kids at home, how in the world do you find the countless hours it takes to even just recap these receivers not to mention troubleshoot them? Your wife must be very understanding, too. Hats off to you and thanx so much for documenting your experience and knowledge for us all to glean from...

[@glenwhatley4125]

Also, i find using a very high gain audio signal tracer with isolated ground connected to one part of the chassis then moving to the different 'star type spots' can also find ground loop issues where there is just to much noise for the scope to catch the low level hum or buzz.

[@AxelWerner]

I have a high end super sounding stereo flat screen TV and a high end Synthesizer. When I connected it to the tv for playing it loud I had terrible hum, even each device on its own is dead silent. Then I got myself a stereo audio transformer and put it in between. All hum gone. Sound is perfect now.

[@EngineeringVignettes]

Ground loops can be "fun" to debug for sure, but you found it. Looking forward to the case woodwork. I have used paduk in the past and it has a _interesting_ smell to the wood... and red sawdust gets everywhere, a bit like chalk consistency. Hope you have a good air filtration system. Cheers,

[@InssiAjaton]

The fact that there were the two ground wires suggests to me that somebody had already been battling with the hum. Another thing that comes to my mind is a story how some amplifier was built with the power supply located in another entire box. So the amplifier box received only DC power. Other than that, the little chirp at 120 Hz in my own experience generally was created by diode recovery transients, together with wiring and transformer leakage inductance. Placing the buzz reduction capacitors basically at the bridge rectifier terminals helped. One more comment I have relates to the high gain at the input section of the power amplifiers has been a mantra of amplifier designers ever since they read studies that putting most of the gain to the front reduces or optimizes any (hissing) noise performance.

[@azharzaidi3264]

Hi: I have my vintage Sumo Andromeda power amp giving him to both channels. I tried removing both audio inputs but the hum persisted. Any ideas?

[@InssiAjaton]

Depends on the exacttkind of hum. If it is "clean" base hum, it is most likely due to dried power filtering capacitor (or capacitors). If there is some sort higher pitch added to the low frequency hum, then it could be rectifier recovery spikes I mentioned in my earlier reply. By the way, in the olden days with tube rectifiers, the recovery spikes were unheard of. The selenium rectifiers also were good. The problem started on and off with silicon rectifiers that have been dominant for several decades now.. So, "clean" hum -- check or replace the main electrolytic filter capacitors. With a buzz riding on the hum, you might benefit from some 10 or 20 nanofarad ceramic disk capacitors at the rectifier terminals. On the other hand, there is also a possibility of poor or oxidized ground connection. That would appear as 60 Hz hum (in the US, or 50 Hz in much of the other countries). The aged capacitors produce 120 Hz hum. It may be a challenge to tell which of the 3 hum variants you hear. There are Audio Analyzer programs available for smart phones that could help, if your ears are not trained yet to tell the difference.

[@azharzaidi3264]

@@InssiAjaton Please write which Audio analyzer programs, where I can get it. I am a start up newbee trying out a few things during COVID-19. Thanks.

[@InssiAjaton]

@@azharzaidi3264 I have on my Android phone two analyzers, both obtained from the Google Play Store.. One is FFT Spectrum Analyzer. The other one is Audio Analyzer. I also have one on my iPad Mini, although I'm writing this message on it and don't recall the respective analyzer name. Anyway, should not be too difficult to find on the Apple App Store., if you need one for either iPhone or iPad. Some of the applications tell only the signal amplitude, but the key words should include "spectrum". Like Audio Spectrum Analyzer. I believe all my apps were free, although I don't guarantee it. In any case I have probably never bought any apps costing more than maybe 19 dollars.

[@larryshaver3568]

The blue dial looks very pretty

[@adrongarretson6195]

Sounds like AC line current and I heard it before you even picked up the speaker qrm is a hard thing to get rid of sometimes

[@martinda7446]

QRM is man made noise, QRN is electrical...I think...

[@Joetechlincolns]

@@martinda7446 QRM= manmade interference. QRN= naturally made interference.

[@johncunningham5435]

Well done Tony! "a tough problem".

[@glenwhatley4125]

For a guy who claims this it's just a hobby, you're already 150% better and almost as important more intuitive than most techs I've known in 40+ years. And, the pool I'm taking about are very knowledgeable and well educated technical dudes.

[@PicaDelphon]

Watching this is giving me Flask backs of the late 80's early 90 work at the Pennsauken Mart Trading Post repairing the old Marantz 2500..

[@BobPegram]

So bad that you needed a flask of hooch ever time to do the debuging P. D.? 8-))

[@abiseid]

Padauk wood is so nice to work with. Great choice.

[@boxingday11]

Don't beat yourself up Tony, this made a great fault finding upload, of one of the most difficult problems to find, thanks for sharing with us, all the best, regards carl

[@georgesmith4639]

Somehow this reminded me of the movie "The God's Must be Crazy II" where the woman says "Does the noise in my head bother you"?

[@kylesmithiii6150]

This is good and professional work! Thanks!

[@mitkothemacedonian]

Great video, thank you Tony!!!

[@azharzaidi3264]

Hi: I observed that all grounding wires had steel (ferrite) connectors. Perhaps replacing them with copper ones might help, or direct solder could be better.

[@geirendre]

Excellent video on a topic that really needs to be addressed. Hum and ground noise is hard to fix. Didn't think of the "swaped transformer wires" thing could be an cause for hum. Probably a good idea to use the thick plate under the transformer as a groundplane. Also maybe start-ground power to each channel separately say on each corner of the groundplane, and start-ground the signal wires to each channel on the other to corners? So we keep the ground currents separated from each other, but at the same time at the same potential. Looking forward to the wood case build video. It will be fantastic for sure.

[@robertcalkjr.8325]

Thanks Tony! That amp looks like a lot of work!

[@davesanders4381]

Question; would it be more desirable to connect the two very large Yellow Spade Lugs (power supply) to the same point on the chassis? Connecting them to two different points can cause ground currents between the two points.

[@JohnAudioTech]

Ground loops can create higher distortion as well. Don't I know :)

[@jdmccorful]

Ditto!

[@williegohard1368]

My technique Sa-ex 110 is humming I only notice it when I turn the volume down just like this one

[@martinda7446]

The power grounds and the signal grounds should be separate. Large circulating currents in the power grounds should be kept clear of low level signal grounds. Both ideally star earthed. Some of these amplifiers - like this one have an unmanageable earthing system where only luck will ensure absolute quietness.

[@killmore75]

I liked your video! TY

[@khalidahmedkhan]

Do a restoration video on Onkyo Grand Integra M-508 power amplifier

[@Навигатор-н2д]

Отличный ролик ! Excellent !

[@nomoreslogans]

Same case with my sansui au4900 that I pair with Mission MX-1 that has speaker sensitivity 86dB. I only hear the noise when I put my ear close to the speakers:(

[@martinda7446]

Also when the lid goes on...It may quieten down...

[@dhpbear2]

18:20 - Just looking at the schematic, I can see MANY places where ground-loops could occur - good luck :(

[@CoolMusicToMyEars]

I would short out signalpath to GND until earth noise would go, then look at the earths in the circuits before, very simular noise to a none earthed pickup arm, could even be a broken track on a removed PCB to GND screw point...

[@ThejasonJaw5442]

It's a grounding issues related to the power supply

[@GetMooreProductions]

Please tell me there's somewhere I can buy one of these from you?

[@azharzaidi3264]

Hi: I have my vintage Sumo Andromeda power amp giving him to both channels. I tried removing both audio inputs but the hum persisted. Any ideas? Two months back I had sent it to audio repairs to have the power switch replaced. The tech said he had installed a relay also. Since then I hear the hum.

[@antraciet]

Thanks for this video. I learned a lot again.

[@Justyoutubing479]

Hello tony. Would you consider eorking on my Marantz 2325. Fm isn’t working correctly. It’s not unmuting and it would not play in fm stereo😩😩

[@knottreel]

Is the oscilloscope in the receiver only decorative? It seems like a lot of trouble and cost to add if that was indeed the case. Great detective work. I enjoyed the video. I used to trace down problems like that when I was a technician back in the 80s.

[@xraytonyb]

I think the scope was mostly a gimmick. That said, It does have three functions, two of which are somewhat useful. First is the scope, that shows a pattern for the audio, second is a "tuning Meter" that takes the place of the analog meter and last is a multipath display, to help with FM stereo tuning.

[@GeorgeGeorge-xj2bc]

8:48 in the morning i would never got involved with such a trouble repairing even if i had a gun or a bazooka in the back of my head.This is late at night and after midnight as a meditation repairing.

[@michaelpeterson4348]

Tony , two things ... Number one I want to ask you if you have a balance control slider for the Marantz 2500 . ( Im looking for this part for a friend ) also I have a Marantz 170 DC, left channel out would you be interested in fixing it ? Thank you Michael Peterson

[@expiridionrodriguez8618]

My Marantz SR8000 5.1 Channel 105 Watt Surround Home Theater Receiver is on but don't have sound after I turn on I hear a click where the power supply cable in. Can you tell me what is wrong?

[@azharzaidi3264]

Hi Ray, this video is wonderful. Did you do one for a power amp or a sub woofer?

[@ventureelect]

You are wrong sir, that is not a hammer, I have one on my bench and it is actually called an alignment tool. I am sure of that.

[@williamrainger3600]

I'm a retired broadcast engineer who specialized in audio systems. When I first got into the business an old radio engineer told me, "If you're going to work in audio, get out your beads and rattles because it's a black art." Consider yourself lucky. I spent most of my career chasing problems in thousands of wires spread out over four floors of a television station.

[@chaoyocngowiznet]

Try this simple solution, connect the chassis ground to a true Ground. I owned this unit on the 70's

[@TheDefpom]

Star grounding is always a good way to go, it was basically a requirement when I had a audiophile show car, any hum was not acceptable.

[@encinobalboa]

The 2500 has pre-main interconnects. Noise would have been easily isolated.

[@MrTonmit]

The first big cap's top looks bulged

[@johnnytoobad7785]

You didn't make a mistake..It was an oversight due to a "twisted" factory wiring job and a whole bunch of (discrete) circuitry in small space.

[@jdmccorful]

Ditto!!

[@dhpbear2]

Having not watched the entire video, I'm guessing bad routing of wires.

[@ovalwingnut]

I actually like hummers 🙄 Besides that, this was super interesting. Thank you

[@nalinux]

Are the speakers Tandy LS_One or a clone ? I have a pair of clone, they are not so bad for the price we can find them. Payed mine 10$ :)

[@DAVIDGREGORYKERR]

maybe it is time all amplifiers were based on a SHARC DSP processor instead of analogue with TOSLINK/COAX inputs and Class D output stages hum cannot happen in DSP based amps can we not do audio processing in software (Software Defined Amplifier)

[@bartomiejmiara8975]

I've three amps at my flat - all of them are class D. One in my bedroom for a small set of speakers, one in my daily room for big ones and one on my computer desk. They all sound great, consume less power and are smaller than class A/AB amps I had in the past. This is the future imo.

[@zaraak323i]

That's not a hammer, that's a micro-adjuster!

[@moodyga40]

dirty ground screw tabs to the chassis will cause this hum

[@andymouse]

All running past a CRT!

[@jdekong3945]

yeah, looks nice, but in an amplifier???

[@moodyga40]

sounds like 60hz

[@altops4490]

who can over haul my KRS9600?👀✨

[@larryshaver3568]

my Acurian receiver has worse hum than that,

[@antigen4]

wow what a terrible design - what a rat's nest

[@WApnj]

I'm 14 minutes into this and still waiting to see this noise you are trying desperately to describe displayed on an oscilloscope. Come on just show us the noise and start tracking it down. Too much talking about sort of, kind of, it's a buzz, it's a hum, it's 120cps..etc, etc..... UPDATE .. I watched to the end and still no scope trace. Your comment about not being able to see it on your scope it not believable. If you can hear it a decent scope should be able to show it. Congratulations on gettng it fixed.

[@donmoore7785]

You sure do like to hear yourself talk and criticize something you don't understand.

[@xraytonyb]

Thankfully, I don't like to talk and criticize someone I don't understand....

[@jonathancolling2284]

Don Moore: Thats rather harsh a pretty disrespectful. Sharing this information with us via KZbin is very generous and decent.

[@coldfinger459sub0]

I think I would have given up. If it was mine not a costumer I would have removed the power supply and made it external in its own copper chassis. a hifi upgrade.