Mackie HR824 Amplified Speaker Repair
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- Опубликовано: 11 сен 2024
- Evidently this Mackie HR824 Studio Monitor speaker has been bad for months but instead of telling me about it the folks in the studio just turned it off and listened out of just one speaker. Say What!? Anyway, I got it in the shop the other day and set about fixing it. What it was doing was humming at 60 hertz, very loudly. Here is how I fixed it. This is my first HD upload. Hope it looks better. Let me know if HD is worth the upload time.
Long, short, I like all these videos. Just hearing you talk about the symptoms had my brain going to try and figure out the problem before you told us. I think it's beneficial to go over these things to help sharpen our troubleshooting skills. Thanks for sharing!
I am glad I can be of some help. I plan on getting more videos up soon. My problem is, usually I am in a rush to get whatever it is back in service and I forget to get a camera going. Thanks for your support.
Nice HD quality - definitely worth the upload time. Thanks!
Ok. All my videos will be in HD from now on. I sprang for better upload speeds on my internet access. Better than waiting 4 hours I guess.
I bought a pair of these around 2001 and still have them and hardy used them they're still in the original boxes. They sounded great when I had them running the few times I used them.
Ours are used every day all day long and never turned off. I have no complaints with them. All electronics will give up at some point. They do sound good. They aren't what I would call true studio spec speakers but they are good enough.
So I was able to replace all the Electrolytic caps. All were good it turned out. Originally, I had no sound from the sub but did have HF through the tweeter. Now, NOTHING. My +15V is dead. Other voltages are fine at their testpoints. It seems to show up once in a while then disappear again. It's weird! I have tried tracing the voltage. I've learned a lot but still can't track it down. I might just have to send it off for repair.
Check you put the caps on the right way. Don't be ashamed if you did, we have ALL done it.
Similar problem here. One of my 22 yr old Mackies (Rev B board) started buzzing loudly for about 15 seconds before auto power off. Pulled all the electrolytic caps that don't require heat sink removal and all were good except C67 (17% below rated value - below the specified 10% in the design) and C79 which I couldn't get a proper measurement from at all. It's notable that failure is in the auto power off circuit since part of that will be energized all the time. So this seems likely to be cap wear out and not a case of sub-standard caps failing prematurely (cough China cough). The paccom (OEM brand caps) datasheet says 2000hrs - so very standard rated life.
Specifics for those interested: I replaced them with nichicon caps for everything except the 10,000 uF which were Cornell-Dubilier because Allied Electronics didn't have nichicon in stock at that size. Parts cost was $27 for 2 monitors, the large caps were the bulk of that cost. A hot air rework blower was very helpful for cap removal, especially the large caps that were also glued - hot air melted the glue from heating the PCB on the opposite side. Solder sucker needed of course. Also you need a security hex bit for the earth cable removal (bit has a hole in the middle). Buzz problem disappeared after the recapping. Modest soldering skills required, nothing tricky.
Very nice. Thanks for sharing.
The circuit that had the issue is designed to mute the output when it is initially powered up. Here's how it works: When the monitor has been powered off for a while C67 (the capacitor that failed) is discharged to 0v by R99 (10K). When you plug it in then AC2 which is right off off the transformer secondary will go from 0VAC to 36VAC (it's 29VAC in the HR624). D25 and C67 form a half wave rectifier which charges C67 to about -47V (36*1.4 - a diode drop - awful close to the rating on the cap which is likely why it failed). R180 and R181 form a voltage divider so when C67 is zero, the voltage divider that is equivalent to a 8.8v (47k/(47K+33K)*15) voltage source in series with a resistance of 47K||33K = 19.4K this turns on Q43 hard pulling the collector down to almost ground (0.3 saturated or so) which effectively mutes the output. Now if C67 fails to be a capacitor, then Q43 will amplify the 60hz AC2 and you'll see the square wave on the collector. One thing I do find odd is that there should be a current limiting resistor in series with D25 to limit the inrush current into C67. This would control the rise time and also protect D25 from exceeding although it's rated at 30A surge for 8.3ms.
Thanks for the comment and lesson. That is a very good description of the circuit. I am along with you and don't understand why they didn't limit that inrush. They are nice speakers and for the most part pretty solid. The ones I have in the studios are on all the time except for power outages which might come and go very quickly when they happen. I wonder if that is what took the cap out, the bouncing of the line voltage.
@@AERVBlog My pleasure. It's fun to figure out circuits like this. I think the cap is a bit underrated, it should be at least a 63v rating not 50v. The inrush will of course vary because of the sinusoidal AC voltage - you might turn it on at zero crossing or at peak of the sine wave. I imagine the failure is due to a combination of voltage rating, inrush, age of caps and original quality. Put a decent quality cap in an you're good for another 20 years probably.
Would you happen to know where I can order suitable replacement tweeters for a set of MR8’s? Every site I’ve checked so far says discontinued.
Sorry no but I will look into it when I get back home next week.
Great video. When choosing replacement electrolytic caps for these speakers, do I need to worry much about ripple current ratings and ESR ratings? Or just values/voltage/dimensions? Thank you!
Thanks. IMO just go with good quality caps. Low ESR can be important in some circuits but not here. All those other values won't mean much to you. If there is a code for the type on the cap you can see if that code is available but codes change from manufacturer to manufacturer. Basically go for name brand, typical life hours and voltage and don't cheap out on form factor. Get the one that fits, lead spacing and size.
@@AERVBlogthank you!
Hello , I'm writing from Mexico,and I admire your work.
I have the HR824 MK2 with a stuff in the tweeter but I couldn't find the schematic, and I would like to ask if could you help me with that ?
I appreciate your attention, greetings.
I will look when I get back tomorrow.
@@AERVBlog I appreciate your help, thanks so much.
@@MrBekendtx contact me at
aervblog@gmail.com
please. I found the schematics.
Best monitors ive ever owned.. and still do.
A poor mans 1030a
They are pretty good. Still in service here even after the new studios were built.
@@AERVBlog My Bad.. 8".. 1031a. and with the enclosed cabinet (no porting.. which I love) and the passive radiator, the setup really works..
Yep, your reply just came up , so I responded...
Honestly, I do all different genres, and also some film scoring...Like any monitor speaker, you need to know them, but its not often speakers are that across many styles..
My 10.31cents, discount price, 8.24 cents
@@Rhythmattica I had to read that a couple of times before I could figure out the 10.31c. Got it. Thanks for the discount.
The volume pots in my set of these are starting to get scratchy and even cut-out intermittently. Do you think a good De-oxit bath would fix that? If I need to replace them, where would you recommend I get the parts? I don't have the schematics so I don't know the specs. Thanks in advance.
Deoxit would probably do it but you will have to do some twisting. If I remember correctly the pors are pretty well enclosed. I will have to look up the numbers if I have them.
@@AERVBlog Wow, you are quick like a bunny! What do you mean by twisting?
@@tasdau lots of back and forth on the knob. It will take a while for the deoxit to work in. I don't think you will be able to do it at all without taking it apart and getting to the back of the pots.
@@AERVBlog I can take them apart if I have to. I'll look for the specs and part # online. Thanks for the advice.
@@tasdau contact me at aervblog@gmail.com
Help please! Both of my HS824 speakers have been serviced before because when they are turned on they had a shortage and fluctuated in volume. I had to quickly switch the low frequency settings back and forth to get each the sounds to jump to the correct volumes set. The speaker volumes constantly cut as if the speakers have some type of shortage.
If they work a all it is a sign that something mechanical is wrong. In your case I would guess that the 4 switches on the back need cleaned. Not a hard job just get a good cleaner like Deoxit 5. Use just a little, don't make them swim in it. Spray and exercise them. You will have to take the amp out of the box but it is easy.
I have a pair of these monitors, and there is always a very slight hum (worse in one of them...) when they are simply plugged into a power source - NOT switched on, and NO signal running into them...even with no input cables attached...any ideas? Thanks!
Not really but I would check the filter caps and soldering. Sorry I can't be of more help.
I remember seeing a video about the KRK Rokit where the glue over time became conductive. I don't know if Mackie used the same type of glue for their PCB. But just wanted to offer some information. Thank you for taking the time to help us fix our devices.
I see people asking so im gonna ask to see if i get an answer. I have the same speakers but im having problem with one of them. Sometimes the woofer doesn’t sound and i have to move the low cut switch on the back really soft back and forth to make it work but there are times that ill cannot make it works. Any suggestions?
Yup. Clean the switches with a contact cleaner. They used cheap open frame switches that go bad just sitting there for years. You do have to take it apart to do that but it isn't hard to do.
Interesting video. I have a pair of these which had the low buzzing and problems and the woofer on one unit. I cleaned the the auto power switches with contact cleaner and both speakers sounded great for a year or so, however one unit has since lost its tweeter functionality. I don’t drive these speakers hard so I wonder if the same capacitor has blown causing the amplifier that drives it remain inactive. Do you have a copy of the schematic still?
I do. Please contact me at aervblog@gmail.com
One of mine doesn’t make noise periodically. Wondering if that’s an issue with the output
Normally transistor equipment will either work or not. I would check the connectors on the board first before any repairs. It could be a bad or loose solder joint on the speaker plug.
I came across the video because I have the same speakers and one of them appears to be broken. One speaker suddenly lost power. I have tried different power cords and a new fuse but the problem is still there. I couldn't see any damage to the platinum but I don't know too much about it either. For the reason I wanted to ask if you could give me a tip what I can do now. As I said, I don't really know much about it.
Greetings Jonathan :)
Sorry but there isn't much I can offer. All you can do really is check the transformer, the on off circuit and such. Wish I could be of more help.
I have the HR624 model that looks identical but the two big caps are like full of white glue. Is it normal?
Have you cleaned yours?
Both of my speaker have that white thing around the big caps. One is working and the other speakr stoped working.
Probably that white glue around the caps and some other big stuff is there to keep them from moving during shipping. That stuff is normal. Sometimes the guy putting it on gets a little crazy about it and uses way too much. It shouldn't affect the operation. Thanks for watching.
Hi, i looked to your footage, interesting ! Yesterday i had almost the same thing happend with one of my HR824 , the woofer suddenly stopped working, i could just hear the tweeter and after a minute the tweeter stopped working too. Would you know in which direction i can look to replace a faulty thing? I didn't yet open it , but will definitely do this weekend. thanks in advance, Steve
That one I am not sure about. All I can say is a good visual inspection first. Especially on something that vibrates for a living.
@@AERVBlog thanks i will open my speaker one day, lucky i have 4x HR824's
Tengo 1 pareja de "hr824" y lo único que pasa es que uno saca 5 dB más que el otro pero del pequeño, he hecho la medición con una señal rosa.
Alguien me puede ayudar?
Please help. I have these exact monitors and one of them keeps blowing fuses (immediately on power up). I did notice the auto power switch at the back went a few years ago (but they still worked fine). Not sure if this was related?
There are just so many things it could be from a shorted diode to a bad cap or switch. Does it blow fuses when the auto power switch is set to off (if you can even do that)? There are 6 primary voltages coming from the main transformer and all of them have diodes associated with them. The unit is actually on all the time just not drawing much current since the on off switch does not actually break the AC line. I think the first thing I would check is TH1. It is a thermistor from +15 volts to ground and is connected when the Auto Power is either ON or in Auto. Since the only hint I have is the broken Auto Power switch that is my best guess. Then again the switch could be shorting which might cause the symptom too. Wish I could be more help but there are just so many places that could go bad. Thanks for watching.
Great Video. I have a pair of HR 624 MKII I have one working and one not working .. any idea.?
Sorry, not really but as I always say check voltages first. You would be surprised at how many things that alone will fix.
Good video! I have a pair of these, from about the same time frame. They had been stored, sealed in their original boxes for about ten years. I replaced one of the OEM woofers which had failed sometime after the warranty expired before I put them away (dead voice coil) and it worked flawlessly until then. I just pulled them out and discovered that one of them will pulse when on even if there is no signal present. the kicker is that after using it for awhile, it seemed to stop for the rest of the day. I can't hear any difference between the one with the issue and the one without, but looking at while it is doing its thing is like a flashback to some youthful experiments with psychotropic substances... any ideas where to look for the problem? I don't know if the unit with the issue is the one with the replacement speaker without opening it up, but it seems unlikely that it has anything to do with the speaker itself. Do you suppose I can ignore the issue as long as the sound seems unaffected? I used a bit of Deox on the switches and exercised them, but it no effect on the phenomenon. Thanks for any suggestions you might have.
It sounds to me like one or more of the filter caps inside reformed, meaning it came back to life. In a perfect world you would replace the electrolytic capacitors but in the real world you would watch it carefully for a while to see if anything else happens. There is a very good chance it will be fine. It is up to you.
I just experienced one of my Mackie HD824 OEM woofers failing yesterday. Probably the same dead voice coil issue you had with yours. Wondering how you went about removing the woofer and where you purchased the new one from? I have opened up the box and removed the screws from the front face but still can't mange to remove the speaker. My next attempt was going to be to try and pry off the front panel as it seems that it could be removable but thought I would ask before giving it a go. any other advice towards this repair would be greatly appreciated. Thanks.
It has been so long, I don't remember any details but I am certain I didn't pry off the front panel to remove the driver, I believe that I just removed the screws and with some gentle prying with something like a putty knife. If I was to try and remove it now, that is what I would start with. But since it has been so long, it is possible that I might have removed the amplifier from the back of the speaker cabinet but I doubt it. As far as a replacement woofer goes, I think I just read the info on the back of the woofer after I took it out and did a search on the part @@33AndAThirdRPM
Can you fix martin logan purity amplifier
Sorry to say probably not. Schematics are not available anywhere I can find . What are they doing?
@@AERVBlog I have a ML purity with built-in amplifier. Wish I know how it sound and you can do it on RUclips
@@jisoo_love_stars I am sorry, no. I can not find any schematic for it. I wouldn't want to take the chance on that unit.
just replace the fuse
If only that worked. Fuses usually blow for a reason. Of course at times it seems like they put all those transistors and ICs in there to protect that valuable fuse.
@@AERVBlog I changed my fuses and still working