BG269 - How to troubleshoot a power supply hum issue. In this case we had an issue with a McIntosh MX110 (non-Z model). But the steps are the same, regardless of the type of gear.
Пікірлер: 70
@Renshen19579 ай бұрын
Interesting video thanks. I wear rubber gloves and performed the same one hand in the pocket, my dad showed this to me when I was watching him repair TV (tube) set. Explained the capacitor cage and that caps hold a charge just like a battery. Credit to Benjamin Franklin for that who upon seeing a bunch of capacitors, to which he remarked it “…It looks similar to a battery of canons…”. How the term became associated with a Voltiac pile is another story. The old adage of checking values of components doesn’t preclude premature failure.
@stephanebureau52994 жыл бұрын
He is a great teacher, I would have like to take electronic classes with him.
@RestoreOldRadios4 жыл бұрын
Mark - a tried and proven troubleshooting technique that was illustrated. Definitely value added. Take care and stay safe during this unsettled times. Best, Don
@djfrank594 жыл бұрын
Its interesting that the new capacitor failed in such a short time. This has actually happened to me 3 times in my career. QC hasn't been that good from the source of manufacture. Had to send back a few already. Either way, you can't overlook new components as being the culprit. Good video. Stay safe Mark.
@ltdees23624 жыл бұрын
An old ham friend of mine taught me this trouble shooting technique many years ago...and you are quite correct, if you don't know what your doing...do not attempt...could make for a very bad day! I'm also surprised you are ordering the same capacitor/manufacture...I would replace all those cans as you will possibly go down this road again...its not worth trying to keep the integrity of a vintage chassis to forsake durability...Once bit, never stick your hand inside the fence again 😎
@pbaemedan4 жыл бұрын
Mark great video, haven't seen this method in a long time, very effective. Thank you for helping to develop basic troubleshooting skills.
@MikeRR1424 жыл бұрын
This was a really good video Mark. Like these! More of them please.
@duanethompson23604 жыл бұрын
Glad you found time to post, good way to do it!
@InssiAjaton4 жыл бұрын
That waveform tells there is low impedance (quick) charging of some bus capacitor, followed by too fast discharge. The discharge rate and the classical exponential shape tells that either there is very little capacitance OR THAT there is leakage/much load current.. On an RC chain, I would measure AC voltages at each capacitor section. It should reduce towards the end of the chain in rather regular fashion. But then I would measure the voltage drop over each of the segment to next resistors and calculate the current in each. If there are no loads attached to the intermediate taps, then the current should be the same throughout the chain. A leaky section would be indicated by a step reduction of the current. If there are loads from various taps, the calculations require measuring those load currents at some resistor likely existing in the side load branch. But the biggest often ignored capability of a modern digital multimeter is the ability to measure AC ripple on top of DC voltage. Some fancier ones even have a dual display, where you can see both AC and DC at the same time.
@davidnguyen5028 Жыл бұрын
I noticed that many Mcintosh MX-110z units after they got updated, the capacitor with values of 50mfd by 4 @350dcv is on the right (when looking at the unit from the front), why is your 50mfd by4 at 350DCV is on the left? Is this the reason for early failure? I thought I had heard from you that it is important match the recommended capacitance of the RC chain, since this could effect the voltage drop down the drain.
@RODALCO20074 жыл бұрын
Great fault finding and explanation. Thanks for sharing your knowledge.
@Wil_Bloodworth3 ай бұрын
Well, that's a fairly significant "ding" on CE Manufacturing capacitors. I know... you only hear and remember the negative anecdotes but this is a very high-end capacitor from a would-be reputable manufacturer. I'm sure it was just a fluke... but it has me wondering. Thanks for the video Mark!
@donh019654 жыл бұрын
Thank you in advance...Reality is getting to be too much...I need to relax for 20 minutes, thank you again.
@johnsenchak14284 жыл бұрын
Real good video Mark
@vintagestereo4 жыл бұрын
amazing video, please upload more of this
@saarike4 жыл бұрын
Excellent repair! I just don't want to test those filter caps with power on. I just use cap-meter and esr-meter. Thanks
@johnbravo75424 жыл бұрын
great tutorial and explanation
@joemartin64393 жыл бұрын
That was a show of how smart you are .I am looking at N elecrichome PA- 300 . Would please do a video on this amp
@jdmccorful4 жыл бұрын
Great repair tip!
@olradguy4 жыл бұрын
Made to Mallory specs on Mallorys original equipment, yeah that figures, always were a problem, I tried to stick with Sprague or Cornell Dubs.
@hespanola7454 жыл бұрын
I would have used the o scope to test each section of the power supply to try and locate the source of the hum,then once i found which section was the source ,then i would use the scope to individually check each cap and resistor to try and locate the origin,tho i might end up having to remove the cap to verify the fault,which you did not have to do with your external cap trick.
@Tysman9094 жыл бұрын
Nice amp. My vintage 1956 Harman Kardon A250 Epic has a Hum also was fine till recently happens only in phono and when my hand is near a certain area it is not as loud as that more like a 60hz Hum and gets louder when hand gets closer. When touch metal anywhere Hum goes away
@richardmelville59734 жыл бұрын
Scope shows classic output from bridge rectifier with inadequate capacitance across it. Can't believe that McIntosh didn't use a filter choke -- especially at the prices they charge(d). My $99 Dynakit Stereo 70 had a large choke and no hum.
@litzdog9114 жыл бұрын
Great video! Why do you think that new capacitor failed so quickly?
@CH_Pechiar4 жыл бұрын
Can you open the bad cap to see how it is built inside?
@bobvecchi79814 жыл бұрын
Wouldn’t it be easier if you suspect a bad capacitor to test the b+ rail for ac voltage with the dmm?
@MartinSBrown-tp9ji3 жыл бұрын
Yes and a lot faster too. It's a test for AC ripple on a DC voltage.
@Enigma7584 жыл бұрын
I wonder if some other issue caused the cap to overstress.
@ralphups77824 жыл бұрын
Very organised, work bench indeed sir.👈😒
@russellesimonetta38354 жыл бұрын
You can che k for bad caps by checking leakage to ground???
@jadney4 жыл бұрын
It seems more likely that the fault was in the connection to the common negative (can.) It could be the wiring to the +85 or I have seen the connection from the can itself to the internal common negative go bad. If you look at the bottom of the can, around the phenolic insulator where the + terminals come out, you should be able to see a small tab that just barely sticks out from under the edge of the metal can. That tab is the conductor to the common negative for the multiple capacitors inside. I've "repaired" failures like this by hitting the can above the tab with a center punch, but it's hard to defend that as a long term solution. I don't understand how they make that connection reliable. Perhaps it's spot welded, but there's never any sign of this in the alum above. It would have been easy to sort this out with a few quick touches of your scope probe.
@Renshen195715 күн бұрын
Rubber gloves never hurt when doing the capacitor tests and the other hand in your pocket
@Tysman9094 жыл бұрын
Great job how can I fix my amp the Hum happens in phono only if touch metal no more hum
@coldfinger459sub04 жыл бұрын
Would like to take the old capacitor can apart to see if cheap no-name Chinese capacitors are used ? or quality Japanese capacitors are used ? Or if they just had a bad solder connection inside the can?
@coldfinger459sub04 жыл бұрын
randomlyselecteduser Thanks I miss that wording .
@The0nionKnight4 жыл бұрын
randomlyselecteduser the build process looks really cool.
@frac4 жыл бұрын
Great video, but that 't' you put on the end of "across" for some reason is like nails on a chalkboard ;-) Keep up the great work, though. It really was an interesting video that I watched from start to end.
@andershammer93074 жыл бұрын
I put one of those caps in a Dynaco ST70 for someone and it came back with the cap completely open. as if the ground inside the cap opened.
@davidnguyen5028 Жыл бұрын
Mi Mark, on the MX-110, what’s the best way to convert line level output sources and using it with the tape head input on the MX-110? I need more line level inputs, I know the aux and tape monitor inputs can be used as line level, but the MX-110 has sweet tube circuitry and I hate to let go to waste. Thanks in advance. BTW, I love watching your videos.
@levai0fjack4 жыл бұрын
I have the same humming sound, on my Copland CTA 501.
@diabolicalartificer4 жыл бұрын
Why did it go bad though? Manufacturing fault or over voltage? It would be interesting to do an autopsy. One other possible cause of 100/120hz ripple is a short....DA.
@williamchow16244 жыл бұрын
Any warranty on the capacitor?
@srtamplification4 жыл бұрын
Awesome!!!!
@davidnguyen5028 Жыл бұрын
Where can I track down a service manual or the schematic diagram for MX-110? Thanks in advance.
@davidnguyen5028 Жыл бұрын
Hi Mark, I noticed that many Mcintosh MX-110z units after they got updated, the capacitor with values of 50mfd by 4 @350dcv is on the right (when looking at the unit from the front), why is your 50mfd by4 at 350DCV is on the left? Is this the reason for early failure? I thought I had heard from you that it is important match the recommended capacitance of the RC chain, since this could effect the voltage drop down the chain.
@prahladramesh65622 жыл бұрын
Mark, I have a similar problem with the Millard 5-20 amp that I just completed , I am getting the same loud hum , tried changing all the caps but the hum stays the same, no change, any suggestions .. Thanks
@MV-Audio7 ай бұрын
Hello! interesting video, as an amateur I immediately thought that it must be a filter capacitor after you stated that the frequency of the noise was 120hz. Rectified 60hz should give 120hz hum without filtering? Or is there something else that could potentially create this particular frequency in the circuit? Electromagnetic interference should have a lower frequency right? Best regards, Victor.
@scratchback20014 жыл бұрын
I own a Leak Point One Stereo 20 valve pre amp and the valve amp that goes with it! Obviously I want the amplifier section to look original which brings me to my question! Instead of buying a 4 in 1 capacitor, why not leave the original in place and disconnect it then buy 4 separate capacitors of the same value and solder them in place using the original as an anchor point only? The effect is the same and if a new capacitor goes bad, it's easier to replace just one capacitor rather than the whole can capacitor on top! I said to my tech here in Australia where I live that I wanted the original capacitors left in place and solder in new capacitors underneath because the 2 capacitors on top are the same colour as the amp itself! I've seen a few problems like this with these new four in one jobs and if you have to drill the rivets out to replace it, it's a real pain! By isolating the problem with this Macintosh amp using a Nichicon cap and an alligator clip, it proves my point! I've seen some woeful restores where techs cut the can in half and stick 4 caps inside it and it looks just awful! Yes, there are situations in old tube gear where you do have to install new tube sockets and safer wiring etc but when it comes down to aesthetics where the amplifier is on display, I don't want two bloody big holes in the amplifier when you can install new ones underneath. When I have friends around, they drool at my restored Leak gear! The power and output transformers in this amp weigh a ton and with removable jumpers to select voltage and speaker impedance, only a fool could make a mistake with this amp! I hope Covid-19 takes a hike! Wearing these masks everyday is becoming tedious as you mentioned! Cheers from down under, Andrew Peter Collins!
@jamesmdeluca3 жыл бұрын
Greetings: I am sorry, but I do not know how you can NOT start by scoping the power supply at the rectifiers immediately. I understand that to create a two level output on the b+. Since you have a power transformer, by isolating the safety ground and all output grounds, you can even tie that floating 85v artificial ground and connect your scope ground to that point and even measure both b+ and b- relative to it. I assume your using that t4st cap to connect the 85v point to ground has a similar affect you still should be doing scoping instead of meter measurements. Hope you checked that new cap b4 installinng it. I was screaming at you to show us all power supply cap signals, aarg!
@anks8884 жыл бұрын
Them caps are rubbish had 3 go bad in a row and just ended up using separate caps and tag strip
@jamesburgess58134 жыл бұрын
I had one section go bad within a day or so with this same brand capacitor. I have been reluctant to use them again since is it so time consuming to change them.
@olradguy4 жыл бұрын
I was reluctant to use them 40 years ago, always had lots of problems when it was Mallory, suddenly open was a common thing.
@markfung64184 жыл бұрын
Thanks for the insight! I would be too afraid to hook up the test cap live..... :-0)) Mark.
@garthhowe2974 жыл бұрын
Why is it specifically a 120 Hz hum? Seemingly a 2x multiplier of the North American AC frequency...
@scottb56624 жыл бұрын
Full wave bridge rectifier output is 120 hz ripple.
@AVadim4 жыл бұрын
Радиола "Ригонда". :)
@littlenellie10283 жыл бұрын
I had a CP manufacture multi can went bad after 5 months. Just because it is "new' manufacture, doesn't mean is it better. :)
@skipperal41044 жыл бұрын
what was that sound when you plugged in the speaker terminal? Sounds like feed back to my uneducated ears. I have a amp that does this. Should it be something to be concerned about?
@schorse10004 жыл бұрын
You mean the loud crackling at 4:20? That happend because an RCA jack makes contact with the hot pin before connecting to ground. It's just heavy noise induction. That's why you should at least turn the volume complete down before connecting thing, even better to turn the unit off. But these days, you can also get RCA plugs with a spring loaded ground sleeve that makes contact first and then moves a bit back to get the hot pin in.
@y_x24 жыл бұрын
It is much safer and simple to use an ESR meter.
@Bishka1004 жыл бұрын
Don't you just hate it when Hum Pixies get inside your capacitors. It's a real problem with these large capacitors because they build their nests in them and then you can never get the pixies out. It's even worse if they get inside a transformer because they can eat through the wire.
@johnsweda29994 жыл бұрын
Don't be critical the amplified just wants to hum along to the tune hahah cheesy ones are the best Anybody had any experience with dirac live with tube amplifiers! it should work really well tighten Up the Bass better synergy You could have used a signal tracer would have giving you the characteristics of the capacitor slope. Maybe there's capacitors are not that reliable long-term use
@exenx29956 ай бұрын
I'm very surprised you got another capacitor from the same place as the bad one when it's pretty much obvious they are stuffing cheap China type parts into these cans when these caps should have lasted another 25 years. You should open the can of the bad one and show your viewers what quality is being used in these replacements to save others the same trouble you went through if indeed they are low quality replacements. Thanks anyway
@moodyga404 жыл бұрын
sounds like 120 hz
@IqbalKhan-hc1hv2 жыл бұрын
A seasoned technician is not supposed to spend hours to detect an obvious problem.
@bobvecchi79814 жыл бұрын
Wouldn’t it be easier if you suspect a bad capacitor to test the b+ rail for ac voltage with the dmm?
@jamesmdeluca3 жыл бұрын
Greetings: I am sorry, but I do not know how you can NOT start by scoping the power supply at the rectifiers immediately. I understand that to create a two level output on the b+. Since you have a power transformer, by isolating the safety ground and all output grounds, you can even tie that floating 85v artificial ground and connect your scope ground to that point and even measure both b+ and b- relative to it. I assume your using that t4st cap to connect the 85v point to ground has a similar affect you still should be doing scoping instead of meter measurements. Hope you checked that new cap b4 installinng it. I was screaming at you to show us all power supply cap signals, aarg!
@bobvecchi79814 жыл бұрын
Wouldn’t it be easier if you suspect a bad capacitor to test the b+ rail for ac voltage with the dmm?