Mackie SRM450v1 Simple Repair Guide & Sweep Test with Mikroelektronika's MikroC pro for Pic32
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- čas přidán 6. 03. 2017
- Mackie SRM450v1 simple repair guide and frequency sweep test using a Pic32 programmed with MikroElektronika's MikroC Pro for Pic32 and a Keysight Technologies DSO-X 2012A Oscilloscope.
Thank you John! I've begun watching your past videos and learn something from almost each one.
Thank you Koffi, I'm pleased you like them.
Have we spoken before?
Did I repair a V2 for you?
As usual, another interesting video. Get well soon!
Thank you kind sir
Thanks for sharing this information, very clear!. In my case, my SRM450V1 still sounds amazing but when I turn it on, with no input signal or nothing plugged in, the hi freq driver makes a noise (the same as a circuitry that has a lack of grounding cable). I check the connections, visual inspection and slightly bend the board to find if there was a bad or crackled solder and I coudn't find anything.
It could be absolutely anything.
Thanks sir
Thank you too
Hi John I have just got into mikroE,, I’m getting on 65 bit late but feel the need, do the compilers have a free mode, is in so many lines of code,,
I ask as I brought Pic, Arm, AVR, DSP ,, BUT DIDNT STOP TO THINK ABOUT COMPILERS.. love your channel I found it so help full. Thanks steve
Hi Steve, Thank you for your comments.
Yes all Mikroelektronika compilers are free to use up to 2k of code.
A TFT installed will put the limit over 2k.
Thank you.
I've got =and - 26V and no voltage on my top end transistors. On the bass side I have around + and - 40V on the transistors. Any ideas?
hi john where abouts are u in uk i.m in leeds . my bass keeps going off . when i leave it for a hour it works again but just for few mins. please can you reply
Love that sweep test John! Could i ask what the step time of you generator was and the time base settings on the DSO please
Hi, Thanks for your comments.
I had the scope set to 20 seconds per division, the sine wave generator goes up in 10 Hz every 0.8 of a second.
1 second to 1.5 seconds is still good for capturing the bottom end.
10 seconds per division is good for a normal test, I set it to 20 to show the function of the 3 switches.
Thank you
Hi John, Curious what you are using for a speaker load when you run your tests?
Hi,
A 200 watt 4 ohm for the bass and 50 watt 4 or 8 ohm for the treble
Hi John. I'm trying to assist with my local primary school with their Srm 450 v1 with no hf sound. I changed the hf driver. But still no sound. This video has been a great help. What would you suggest that I test for the hf side of the board. I'm good with a multi meter and soldering iron. Thank you!!
Unfortunately, the loss of treble on the V1 450 is not easy to diagnose.
It could be anything from the input to the output. You would need an oscilloscope to diagnose the exact fault.
@John B Thank you for your quick reply. I'm guessing not cheap fix?
John. Thanks so much for sharing your knowledge with everyone! Our church has 15 of these Mackie SRM 450 V1 powered speakers. Of the 15, 6 have similar issues. The frequency response of some have minimal gain on lows while others have high freq. attenuation. Due to tight quarters and minimal spacing on pins of U9, it's extremely difficult to measure the VCO. I don't like shooting from the hip, but I may need to just replace the component. How certain are you about the VCO issue causing frequency response issues? I found a place in the US that sells the V2164 VCO. My soldering techniques are fairly good, but I still occasionally lift pads. So I need to be certain before R/R of U9. Can you shed more light on this? Thanks so much for your expertise!!!!
Manny Abeles
Hi,
Thank you for your comments.
The VCA will not reduce the power output by much, it just shifts the response unless of course it has failed in some way. The chips don’t fail unless one of the +|- 15 volts rails have fallen to zero, that has a very good chance of blowing the VCA
@@JohnB-2021 Thanks so much for your help on this circuit!
On one of the Mackies, I traced poor frequency response back to the crossover circuit. Both of the power supply voltages to the VCO are nominal. But due to minimal access to some of the SMT parts, I experienced difficulty troubleshooting further. Knowing your expertise, what is the likely component/circuit in the crossover which could cause this type of issue? I have 6 Mackie SMR450 V1 with similar problems. Your proficency in your videos have really been a major benefit for our church. Thanks again!
@@mannyabeles1969
Good morning Manny, other than the voltage controlled amplifier, there is also the volume potentiometer, it can fail / wear out in such a way that you would not have all of the bass amplified. I have seen that a few times.
Lots of treble and not much bass (just a small amount of bass)
@@JohnB-2021 Hi John.
Thanks again for your advice!
Sorry I didn't get back to you sooner. I hadn't had time troubleshooting the last few days.
Another srm450 failed in our church. I put this one and three other circuit boards on the bench in a line to make similar measurements. The volume control (after tracing out each of the pins) measures as expected on all four PCBs. I did discover that my schematic is incorrect. This schematic (Rev A, 1998) shows J15 on the input of the potentiometer. On the PCB, the wiper output connects to J15. Nonetheless, the volume pot is not the cause of poor frequency response, although it sounded like a great suggestion. I suspect the issue for each of these is still in the crossover circuit.
Among these four Mackies, I have two SRM450's with poor low frequency response and two with poor high frequency response. All power supplies (+/-80, +/-45 & +/-15) all appear nominal.
I'm running out of ideas. So anything you might suggest at this point will certainly be helpful. Also, if there's something with which I can help you, please don't hesitate to ask. I'm a retired electrical engineer with 38 years of experience. During those 38 years, the one thing I've learned is to know when to ask for help! Thanks again so much for your time and expertise!
@@JohnB-2021 Hi John,
Thanks again for all your help! I'd like to share with you what I discovered. On one of the 450s, I traced the missing signal for low frequencies, from the speaker output (J16) backwards in the LOW circuit (page 5) and discovered plenty of signal at E26. But on the output side of C149 - no signal present. I thought maybe one of the transistors around Q26 might have been shorted. However, it was actually the capacitor C149 which was faulty. Replaced C149 47uF cap.
I found a second SRM450 with the same issue. After replacing C149 on this unit and the first, both now work like a charm. Maybe someone else can benefit from this discovery.
Thanks again for all of your videos. Keep up the good work!!
I have a pair of these used for practice monitors and yesterday one started humming really bad out of no where. sounds like a ground hum. checked all cables and such and all work fine on one speaker but the other hums really bad when signal is plugged in. any thoughts?
I stopped repairing them because too many corroded or dry joints when they get old.
Hi! and thanx for sharing your skills with us mortals! Ive recently discovered a problem on one of my Srm 450 V2. When powered up, and xlr cable from mixer is plugged in, it comes a loud sounding noise, full tone. Ive switched the external power cable and xlr from the one that is working with same result. Also when linked from the working speaker, the loud sound appear. Both mixer channel is ok.
So i thought this speaker is done. But if you plug a microphone via xlr directly into the speaker it works just fine!
So im planning to open it up and do som checking. Do you have some insighsts to waht it might be?
Best
Kjell Arne
You have the wrong cable for your music.
If the microphone is fine, it shows something else is wrong.
@@JohnB-2021 Thanx for qiuck respond! Yes its confusing. The other speaker works just fine via the mixer, but the humming one doesent with the same set of cables and from the same output from the mixer. But with mic only, its fine..
@@kjellarnekjrgard660 You didn’t tell me you had tested the same setup on another speaker.
If it is ‘buzzing’ it sounds like the diodes on the back of the board may be broken.
@@JohnB-2021 ok thanx, ill open up an see if i can figure it out. Thanx for hellping out!
I have two Mackie SRM450v1's in for repair. They both have very low output. Nothing visually wrong with the circuit boards. The power supply voltages are all to spec (including +-15V regulated). Apparently they both developed the same fault at the same time. Does anyone know where I can find a schematic for this unit?
Mackie share their schematics
I have an SRM450 V1 that has nothing but a LOUD hum when powered on. I've reflowed all of the solder joints with no change; no sign of physical damage to any parts, any idea where I should start? Thank you much, love your videos!
If it has worked with your current setup, it could be anything.
If you have never had it working, start with the input lead, it's probably wrong.
@@JohnB-2021 Thanks John, but I'm getting the hum with nothing hooked too the input; I'm pretty sure a FET or transistor/diode is shorted, just not sure which one? The peak, and other red LED come on, and I've never left it turned on for more than a second or two...bought it that way, really cheap ;)
@@SwampcatsHouse The only thing that comes to mind with a loud hum / buzzing are broken pins on the +/- 75 diodes.
Otherwise it it be anything.
@@JohnB-2021 Thanks for your time John; I really appreciate it! :)
@@SwampcatsHouse Actually I just noticed it's a version one you have, not version2.
It does not have the diodes I mentioned.
Other than one of the diodes in the bridge rectifier being faulty, I have no idea what could cause your 'hum'
I assume it's a loud hum / buzzing?
If not, forget it, they all hiss and hum a little.
Hi John, where in the Uk are you based. I’m in St.Albans, Herts and have 12 Mackie speakers. If any go faulty I will need to bring them to you. Thanks
Hi,
I moved to South Yorkshire
@@JohnB-2021 hi john where abouts in south yorkshire are u/ i.m originaly fron doncaster. my bass keeps going off on my v2 makie. i can drop the amp off to you this weekend if possible
@@grahamsmiffy8737
Hi Graham,
I'm too busy to be looking at speakers, I already have an 1801 that I'm struggling with.
@@JohnB-2021 hi john ty 4 geting back. i.m not in a hurry to get it dun ive a set of RCF speakers to keep me going for now.so if you can do it in next 6 months or so i would be happy with that
Hi John, I have SRM450 Ver 1 230v cabs, I need to use them overseas on 110-120v, Can you tell if possible to rewire these cabs internally for 110-120v? or do I need to change transformer? I cannot find any answer online, Cheers for any help you can give,
I believe the transformers are made for specific voltages so you would need to change it.
@@JohnB-2021 Thanks for your reply. It is a shame as the SWA1501 subs I have from mackie have a 110v or 220v conector on the board
@@steveforster8652 Yes I have seen them.
If you're in the UK, you can get your transformer re-wound to 220v
@@JohnB-2021 They are currently 220v I am from London living in Brazil where most regions are 110v. My city is 220v but if work elsewhere it is a problem. One more question, If i change transformer to 110v use do i need to change any other components or fuses etc?
Steve Forster Hi
Lucky you being in Brazil
No other components need to be changed.
I have a version 2 that has low output sound, can you tell me what to look for ?
Do you have a power led?
Do not change any blown fuses until it has been repaired.
@@JohnB-2021 yes it Powers up, the guy who give it to me told me that the volume pot was replaced, one of the transformer also was replaced. I checked and indeed is written on the transformer that was replaced.
No blown fuses
@@quilla333
I just saw you have low output, not no output.
If you have sound and both the bass and treble are low volume, maybe you are not driving it correctly.
It needs a balanced XLR input
@@JohnB-2021 I do run them in Balanced XLR, the other one sounds louder than the one mentioned before, even changing the cables in the channel output i get low output.