Marantz 2285b Part 4 - Final (After troubleshooting a distortion problem) ;)

[@cjay2]

All harmonic distortions are due to non-linear effects in the circuit. Resistors, capacitors and inductors are all linear components. The non-linear components are the semiconductors, and in this particular case, the oxidation on those pre-amp/bypass contacts at the rear of the amplifier. Your troubleshooting method led to those oxidized contacts in the end, but you did notice a small improvement via the substitution of some of those preamp transistors. The difficult part was finding the non-linearity that was producing the distortion, and it was BETWEEN two stages that would have been expected to produce distortion, but were fundamentally working fine. The foil caps are always a better choice if the values are equal, as they are closer to ideal caps. In any case, your good trouble-shooting methods worked out well in the end here. Bravo!

[@jrs0007]

cjay5, nice analysis. Any non-soldered mechanical contact can cause a myriad of issues. Tony, great job of troubleshooting!

[@fernarias]

Two years later...since I was going to work on my 2285b soon, I re-watched this video and can confirm that CE40 on PE01 is factory placed in the wrong direction. On mine and on pictures I found on the net. Thanks for catching this.

[@hughescoston8480]

I happen to have a Marantz 2285B still seems to be working fine! Absolutely love this channel

[@JeffCounsil-rp4qv]

I have a 2252B (I completely rebuilt) and it also has those stupid "automatic" RCA Pre Out/Main-In jacks. I made short external RCA jumpers and no more trouble with them.

[@ahmadalawadhi538]

wish we have some one like you repir vintage receiver. you are great sir . you are so professional 👏

[@MrJohnBos]

Wow, what a fascinating ride down the rabbit-hole of distortion. I learned plenty and loved every minute of sitting on the edge of my chair in anticipation. One of your best KZbin videos ever. Thanks!

[@chriseast6123]

Tony, that was epic, well done. A great demonstration of how to logically find a difficult fault. I can't ever imagine a repair shop even noticing that distortion, as far as that would be concerned it is working OK, so send it back. Tony, your ear for sound/music is far better than you realise, so many people would never notice any anomalies in this amp. I bet your ears are more golden than you realise. This ability comes from years of listening to audio equipment. Nice one Tony, much enjoyed this vid series. Thank you.

[@schoocom]

Hi Tony. Several years ago I worked on a Pioneer SX-5570. I made a complete recap, and it was working awesome except the two filters switches. There was a tiny electrolytic cap coupled to each switch that I replaced by a WIMA cap as usual. Both did the same issue, as I operated them, sound went away, they acted like a mute circuit ... I scratched my head and finally put back electrolytic caps in place, and everything was perfect... I’m happy to see that you have this kind of issues as well 🤪 than you for sharing so much with us !

[@g.fortin3228]

Tony all of the in depth, and even the extra little here and there tidbits of knowledge you share are so valuable !! Thank you!!

[@garynichols1502]

Excellent video. I've got an Adcom GFA-555 MKII that has a high THD and you have given me some new ideas. Thanks!

[@BruceNitroxpro]

I had no idea that the distortion would be any function of the contacts as you finally found. Great job!

[@klm2395rh]

Enjoyed this series on the 2285. That model is a gem IMO. Appreciate how you take the time to explain things as you go along. Im not an ET but have watched several of your projects with great interest

[@steveharrison1144]

Hi, I’m a recent subscriber. I really enjoyed this series. Thank you for going into such detail. The distortion resolution brought everything into life. I look forward to future posts. Steve

[@robharley9838]

Fantastic as usual Tony! I always learn watching you troubleshoot, you have to be one of the best at it. On a side note I wanted to offer a little trick I've been using lately to make working on a turntable easier. I've put an old bath towel folded in half under the turntable and keep a large shop spring clamp nearby. When you don't want the turntable to move, you can flip a corner of the towel up over the edge and clamp it. Quick, easy, cheap, effective. Anyway, for what it's worth. As always, love what you do.- Rob Harley

[@SoddingaboutSi]

Well done. A bit of a challenge. Looks and sounds great.

[@editorjuno]

In my several years managing a busy audio repair shop, I was struck by how many apparently difficult flaws -- like Tony's excessive distortion -- came down to defective simple components like switches, connectors, and pots rather than tubes, semiconductors, or even caps and resistors. So many audio problems that look complex on a scope, distortion meter, or spectrum analyzer wind up needing ridiculously easy fixes.

[@jrs0007]

Bruce, you are so correct. Also, I've found bad solder joints that appeared to be perfect, only to correct a problem with the touch of a soldering iron.

[@srtamplification]

Long series, but well worth it.

[@georgejobin1744]

Hey Tony I ran into the same issue with my capasitors on a project I put a couple coats of liquid tape worked and looked good just be neat and easy with it great video series thanks

[@davidgriffin79]

1:16:14 Looking at this screen the ΔdB is -85-(-20)= -65dB, i.e. a ratio of 0.00056. 1:16:51 now the ΔdB ~ -70-(-20) = -50dB, giving a ratio of 0.003162. As you say, the display is logarithmic (as is our hearing, hence the dB scale) so a ratio of 0.003162 _is_ meaningful since the distortion at that ratio is audible (due to our non-linear hearing) and is clearly visible on the sine wave. Ratios are only really useful if things are linear; once we get into logarithmic perception (our hearing) it's pointless to quote ratios. Still, the concept of dirty contact introducing harmonic distortion is interesting, although I'm not sure of the mechanism that would do this.

[@johnnytoobad7785]

I read (in several articles) that the purpose of the resistors on the Filter-CAP board were safety "bleed" resistors so that the PSU CAPS will (slowly) discharge when the unit is powered off. The only real issue is that you're using a small amount of power (and generating a small amount of heat) across the bleed resistors when the unit is operating. The bleed resistors are "highly recommended" for shop-based external PS circuits. You never have to worry about discharging caps manually and its a heck of a lot safer. I've also seen another design that uses .2 ohm resistors going from cap-to-cap (instead of straight wire). The designer claims it reduces THD and makes the PSU "more linear".

[@JeffCounsil-rp4qv]

I never did like those "automatic" RCA jacks. They've given me lots of trouble. Cleaning them does work, but for how long until the tarnish returns? I make a pair of (approx) 4" RCA cables and never look back. They only stick out maybe 2" tops, barely more than the AM antenna if at all. But this was a long one to find a few issues introducing the distortion. Nice one Tony! Perseverance and patience pays off.

[@PeterMilanovski]

If the RCA jack's are the standard 4 way RCA blocks, there are specific jumper's designed for this purpose! Sometimes it's just a thick piece of wire the size of the centre pin of an RCA jack and sometimes they have a plastic mould on them, the short RCA cables also to! But if you wanted to get rid of the cables, you might find them on eBay? Generally I have those jack's occupied with cables to a graphic equaliser which apart from giving me extra tone controls, it also gives me extra inputs which is always handy.

[@mmaranta785]

Great troubleshooting! It was fun to follow along. I agree a messy bench is a happy bench! Remember Jim Williams from Linear Circuit Technology?

[@jdmccorful]

Supper session! Could eat, sleep, drink this kind of troubleshooting day in day out. Lesson learned, Sharpie in hand when recapping boards along with schematic to verify. Could not ask for a better instructor than Tony! Enjoyed watching, thanks! Concept, Concentration, Common Sense and Control.

[@rolfts5762]

Enjoyed your troubleshooting, the schematicSearch and the result very much, thanks for sharing :)

[@fernandogalloso359]

Nice job Tony!!! i really enjoyed thanks.

[@josephlalock8378]

this was a great series!

[@dl7majstefan753]

Very informative! Many thanks. Proposal: These ugly switched connectors between preamp-out and mainamp-in should be replaced by non switched connectors and a shorting plug.

[@noco-pf3vj]

I saw on the AK forum, there is discussion there about capacitors on the signal path. Polarity caps are there by design, don't change them to non-polar caps blindly. Same with an opamp, don't change bipolar input opamp with FET input opamp.

[@26Jorgeb]

Great analysis Tony.Thanks a lot!

[@BjornV78]

Hi Tony, at 1:07:07 when the capacitor of channel 1 is removed, and you where going to remove the same capacitor on channel 2, you could also used the removed capacitor of channel 1 and put it in parallel with the capacitor on channel 2. That way the distortion should now be double then before if it was the capacitor that caused the distortion. Grtz

[@mdzacharias]

The outer can of the filter caps is not directly connected to the negative lead - or any other. The two leads protrude through the rubber plug at the bottom and no where else. I've measured what I would call ghost voltage on the can but that's all. Meanwhile to insulate the tops of the caps might reduce the ability to vent if necessary.

[@zulumax1]

I was thinking the same thing with these pop top venters as far as being isolated from the outside can. Connect that light bulb across the area in question and check it.

[@mikepxg6406]

Great job. I enjoyed watching. Thank you.

[@ulli-r4z]

Great Job :-) The film-capacitors you used have a much lower dissipation-factor than the original electrolytics. This, in conjunction with stray inductance (all those wires...), may cause some ringing. The higher dissipation-factor of the electrolytics may damp that.

[@sandraledger2612]

Wouldn't Kapton tape be the answer to covering the negative caps?

[@arfer1470]

Fantastic job Tony 👌

[@TrevorsBench]

Another advantage to paralleling capacitors is redundancy. If one cap fails there's another to keep the circuit working

[@sirsuse]

Excellent video Tony!!

[@sonyajones]

Maybe try some conformal coating on the tops of the caps for insulation? Great video! Thank you, Tony

[@gearheadted9210]

another great vid,we are the knights who say NEE!

[@dhpbear2]

Tony, if you DID remove the cap, wouldn't it show up on earlier video footage? (1:31:19)

[@darrylberg1642]

Hi Tony, As you set the external power supply to 20volts the circuit operated in a much better way. What happened when the board was connected back into the Marantz? Did the 19.2V suffice then as the other problems were corrected? Thanks,

[@OllieProphet]

I was wondering this also. I suspect the 19V internal supply was a fine, once the other issues were corrected, but would like to hear it confirmed.

[@Digital-Dan]

So here's the audio chain: Fully restored amp => your high quality speakers => your mic and ADC etc. => my DAC etc. => my cheapo PC powered speakers => My low-pass ears. Good news: sounds great. Bad news: So would anything else.

[@abwdoc]

Hi Tony…what a great, in-depth analysis. That’s why I’m going to take mine to a pro. My right channel is intermittent, and I wouldn’t dream of opening mine up myself. None question though…why are some of the numbers less illuminated than others on your restoration ?

[@R.AudioElectronics]

That was fun! I was getting a little concerned though that maybe those talking caps might of had something to do with that noise🧐

[@HazeAnderson]

A hahahaha! I just now realized that the reason I "felt a tickle" from the Jameco dual rail linear power supply kit that I put together a couple years ago. One of the caps is for the negative rail and I must have brushed the top of that cap with my hand.

[@tommygreist9560]

Awesome video.

[@ronaldgracias2473]

Can you provide a link to that Capacitor PCB board you have used. Nice work, was interesting to watch.

[@psionl0]

There are only ODD harmonics (not even) at the PA stage. The theory is that a push-pull circuit (and apparently a differential amplifier also) cancels out the even harmonics. The complete absence of even harmonics at the PA stage shows that the transistors are well matched.

[@xraytonyb]

You are correct. I misspoke. :)

[@jameswarren1831]

Would adding the film capacitor on the power supply of a class D amplifier have a bigger potential to help due to the higher switching frequencies?

[@mlbabineaux]

Proper grounding is overlooked on lots of electronic equipment.

[@mnoxman]

Paint the surface of the caps with "Liquid Tape"

[@srtamplification]

Hey Tony, have you tried using the Exp( Function? That is what I use on the Tektronics DPO 7254. You can set the exponent to whatever you want.

[@dhpbear2]

16:50 - Those small film caps are added to bypass higher frequency noise to ground. EEVBlog has a great video on capacitor usage vs. frequency: kzbin.info/www/bejne/eJStZ4iaed1krMk

[@NiHaoMike64]

They won't do any good with such a long wire length to the load. Install them right at the load to minimize inductance.

[@williamsquires3070]

Hi Tony. If we number they caps 1-8 from left-to-right, top-to-bottom, then caps 1,3,5, & 7 are the ones you taped because they’re -57v w/respect to circuit ground. But wouldn’t 2,4,6, & 8 be +57v w/respect to ground? I’m assuming this is a split supply (-57 & +57) w/respect to a center-tap on the power transformer.

[@alex1520]

Been enjoying your repair videos for a while now and love them! Seen you repair amps, radios, turntables - do you have any interest in taking on an analog reel to reel tape deck? :)

[@OllieProphet]

Epic troubleshooting adventure! Hat's off to you. Without a spectrum analyzer, I would have called it a day, and pronounced it "fixed", when it clearly needed more attention. In addition to a good scope, what other equipment would you recommend for doing this type of detailed amp health check? Spectrum analyzer I assume, and if so, which model? I'm concerned that these old lab units, like your HP, are getting old now, are very complex, and would be a bear to fix....so reliability is a must. What about for doing frequency sweeps? I know there are software apps that can generate a sweep, but I doubt their output is flat, like your lab quality unit.

[@OllieProphet]

The other question that comes to mind is: How much time did you spend on this receiver? I know you do if for fun, and for our collective learning experience, (thank you!), but I'm thinking if this level of repair would normally be economically practical? Your troubleshooting seemed very efficient, I could imagine a less capable technician taking much longer, and maybe not ever finding the root cause. So....at $75/hr bench time, which is reasonable for someone who relies on this as their source of income, is someone really going to pay for what is probably 10-15 hours of bench work to restore this ole gal? After paying too much to begin with on E-Bay for a "works perfectly" unit? Someone could easily have $3-4K invested. Makes me wish I hadn't sold my original owner Marantz 2385 for $400 in '94. Worked perfectly, too....;-)

[@nage2273]

Hi Tony, What cleaning product have you used to clean PRE OUT/ MAIN INN RCA contacts ?

[@JeffCounsil-rp4qv]

Any cleaner that removes oxidation. Tarnish is oxidized silver plating. Caig DeoxIT D5, MG Chemicals DE-OX-ID, and other brands will work well. Regular "contact cleaner" doesn't help much, if any with oxidation.

[@dxhighendamplifiers]

NI!. (MONTY PYTHON) IF YOU START TO ADJUST FM ... NI!

[@Digital-Dan]

It's hard to read greyed out, but it appears to me that the function just before SQRT on your scope is EXPT, which I take to mean exponent. so (expr) EXPT 2 should square your RMS voltage, right?

[@RectifiedMetals]

Has GW Instek fixed the storage issue on that scope?

[@zx8401ztv]

You should wear a deer stalker hat, you tracked it down and cornered it :-D And now for something completely different :).

[@mmaranta785]

I have an Hp3580a spectrum analyzer. Where can I get it fixed?

[@garybevis8691]

Try Alltest Instruments, located in New Jersey, they do things like that. Good luck M.

[@mmaranta785]

@@garybevis8691 Thanks for the tip. I’ll give it a try.

[@JD-lk7im]

I thought it may be the replacement LED's in the tuning dial generating noise .!!?

[@Learnelectronics738]

Very good video I dol

[@mikerdp1695]

thank you.

[@billsmini10]

Hi, new subscriber here. I wanted to make my first post on your newest video, but my question is too far off that topic. Can you do a full restore on 80's or later McIntosh amplifiers, receivers, or pre-amplifiers? I have seen one or two guys at Audiokarma do complete restores of mid 80's McIntosh equipment, including replacing panel lamps and any electronic component such as capacitors, pots, and ground repairs. The thing is, these are all posted as still shots. I think it would be great to see a 2-3 video series on these repairs/restorations. Thank you, Bill

[@marka1986]

My personal choice.I'm staying with analog scopes.

[@BruceNitroxpro]

Mark A , Not a bad move, but it is nice to have some built in software and a processor to do some simple statistics and other things such as Fourier Transforms. If you have enough to buy a decent modern scope, it would be nice to own them both.

[@marka1986]

@@BruceNitroxpro It probably would just take getting used to. If I acquired one would need to play with it on something that I knew what to expect first.

[@dhpbear2]

Another thing I'd suggest to INSTEK is to allow connecting a PC Keyboard via USB! Does it support that?

[@xraytonyb]

No it doesn't :(

[@dhpbear2]

@@xraytonyb That sounds like something that could be added to firmware (also with no hardware changes) :)

[@lvomotor]

A lower esr will put a larger current draw on the transformer too right? How do you know if it can handle it?

[@JeffCounsil-rp4qv]

No. You *want* low ESR for the power caps. A resistance (higher ESR) would put a higher load on the transformer/Bridge because you are "connecting" the rails to ground through them.

[@PeterMilanovski]

You know what else puts a load on the power supply, Low EPR capacitors! Low or high ESR capacitors won't put a load on the power supply! High ESR capacitors will have difficulty in filtering out ripple but that's about it! A capacitor with low EPR (DC leakage) will act as a short circuit, the lower the residence, the shorter the short! If that makes any sense LoL... So basically, ESR is only important for the power supply, EPR is important for everywhere because it's the failure mode that will cause other components to fail, always!

[@lvomotor]

@@PeterMilanovski this makes a lot of sense, thank you!

[@PeterMilanovski]

@@lvomotor your welcome! I find it frustrating that when it comes to capacitors, everyone talks about ESR! Even though a capacitor with high ESR won't damage anything! So basically you get a piece of equipment and you can feel it running really hot, you then go ahead and check out the capacitors in circuit with an in circuit ESR tester and everything looks fine! You would have done what just about everyone else is doing! There's no easy way around the problem! To really know what the condition of a capacitor is, it has to be removed and tested out of circuit! If it's capacity isn't just under what it's rated for but exactly or over and above! It's bad! That's the first clue but anything more, you are going to either need a dedicated LCR Bridge Meter or one of those cheap eBay component testers, there are lots of those cheap Chinese things but they are not all the same! Look at the pictures and look for one that shows the screen showing results testing a capacitor, apart from capacity it should also have a Vloss reading which is voltage loss or DC leakage current! They aren't the best tool but they do work, I have had one for some time now but I didn't understand what Vloss meant until I got an LCR Bridge Meter and I was able to compare between the two devices and worked out that I already had a way to check for leakage but didn't know because Chinese operation manuals are about as common as hen's teeth! I hope that this was helpful 😃

[@deonschwartz5093]

Hi Tony one question, where do you download all your chamatics from?

[@xraytonyb]

hifiengine.com

[@tubeDude48]

The Loudness button shouldn't have been created! When it's off, you loose some Bass & Mid-range. I like having that PUNCH it gives! --- You cant beat Nichicon. There very reliable.

[@PeterMilanovski]

If you are after an idea to cover the top of the capacitors, there are these sticker sheets that are made of that insulating cardboard that used to be in just about every electronics equipment, they are made to insulate the ends of 18650 lithium ion batteries and are self adhesive! They come in different colours and cutouts, though they are 18mm in diameter... But could possibly prove to be handy for such a situation. Truth be told, I wish someone had done that to the 450V capacitor in the switching power supply circuit before I my knuckle brushed across it... It wasn't horrendous but it definitely was there and you know that I know it was! After all the times that I have been zapped, I would have thought that I would be immune by now but electricity never grows tired of you and is constantly looking forward to your next meeting! So never neglect your technician grade isolated transformer! The medical grade isolation transformer will kill you if it hasn't been modified, it's really ironic that the medical grade isolation transformer will do what it wasn't designed to to LoL.. And those film capacitors on the input! I didn't expect that! So basically, because they last forever, they would be forever contributing! Somehow I felt that a signal tracer might have been very useful in tracking down the distortion problem... I remember seeing Paul Carlson track down a noisy resistor with one and I thought to myself that I would have to know that a resistor was causing noise in the first place to go looking for it, but with just a quick sweep with the RF probe revealed that problem! I personally don't have a signal tracer but it's the one tool that I really want on my bench! A Heathkit would be nice but they are unobtainium here in Australia! Might have to pop over to the Heathkit website and check if they have re released more kits other than the clock and that other thing for which I have no use for!

[@Hello-Earth-369]

Hello Sir, Thanks For Videos, It is Really Amazing Videos. But , I do have Sansui Au-20000. And I have a problem In Amplifier, After I used Altec Speakers Found it the problem, It has a Tone Switch that It Has , Tone -in and Tone defeat , When It is in Defeat, SOund Is Ok , but when Come to Tone -in , Almost two speakers Does have Noise Sound on Woofers, but one of them ( right side ) much more, Is that Possible for you to tell me where is the Problem , I have also Schematic Diagram. If you can give me your E-mail, to send it to you and Check it please. Also I did Recap all Capacitors, with ELNA ( silmic II ) and Some Nichicon, but 95% of caps are ELNA Silmic II. Thanks Best Regards, Farzad.

[@DAVIDGREGORYKERR]

Guys if TECHNICS have their way all HIFI Amplifiers will be fully Digital using High-School mathematics to perform all signal processing that goes on in a normal HIFI amplifier and the TECHNICS SU-R1000 is one such example of using High-School mathematics to do all signal processing, a side effect of using DSP is you can remove the Mains Hum from the signal in situ.

[@tubeDude48]

I *HATE* progressive jazz!!!