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- เผยแพร่เมื่อ 2 มี.ค. 2017
- Mackie SRM450v2 SMPS Repair guide Basic.
I made a mistake, the 18 volts for the PFC comes from a secondary coil on the PFC transformer after it has started.
The SMPS then starts.
The SMPS also supplies 18 volts
I used TH-cam video editor to remove a section of video, I see the sound and video are out of sync.
The diode for the pfc ground is the Anode, not cathode.
Have some confidence and you will save yourself a fortune, see this clever guy in Sweden • Repair Mackie SRM-450 V2
I missed a few points, the PFC does supply 18 volts to drive itself, the resistors will get hot if the SMPS does not start.
The SMPS will not start if the PFC has not started.
For a coffee :) (Costa)
paypal.me/JohnBonTH-cam?loca...
I love how Mr. John simplifies everything wish my teachers would of taught us like this ,great job Mr .j!!
Thank you kind sir
I've been hoping to find that kind of walk through for AGES! Thank you!
You’re welcome
Thank you for your feedback
Just had my Mackie SRM450v2 amp back from repair by John, have to say what an outstanding service he provides! If you have any doubt about your faulty amp and what to do with it he truly is the goto expert! Turned around in a week was amazing but he also uncovered a previous bodged repair attempt and resolved that too... Sensible cost means a good few more years form this trusty amp, great that there are still real experts in their field like you able to provide specialist support when needed. Thanks again John
Thank you Malcolm for your kind comments
Do you have a contact for John? Thanks
John B. Thank you so much for this (and other) video, it's great that some poeple like you share they knowlege. Best wishes for you and your family.
You are very welcome
John. Your 1st video helped me repair one of these a couple of years ago. Having seen a couple more, I find a quick way to determine if the two PWM chips are working correctly (after replacing the s/c Q21, D33 & associated damaged components) is to connect 21V DC to VDD (5) R210 & 5V DC to the junction of R248 & D38 (this will fool the Shut Down of U35). Both PWM chips should then sync to 68HKHz. I must say the PCB of these amps is not the best & prone to track damage. Thanks again for your posing your guides
Thank you for your comments and thank you for the tips.
I guess you found they become easier to fix once your familiar with the circuit?
Thank you
Indeed John. Not my normal line of work as I've been out of the repair game for donks. SMD boards are pain to repair
Hi John, thanks for taking the time to do these videos! I was using my SRM450vs in 100+ degree heat and 3 resistors (R243, R245, & R288) overheated. I dabble in electronics repair but I have no formal training so I was just going to start with replacing them. When I search for them on DigiKey, I noticed tolerances can very so I was wondering if I should be concerned with that spec.
Hi Mark,
Those resistors do get hot, especially if the pfc circuit is not reaching the full voltage.
I've not heard of them burning out ever.
The tolerance is not too important, but I doubt they are blown.
Hi John many thanks for the video very informative looking for a wee bit of advice please one of my 450s has lost a bit of its sparkle ive tried all the usual things leads ect sound source but im convinced its the HF Diaphragm as although its got a small amount coming out of it its not crystal any thoughts? thanks
Hi Colin, thanks for your comments.
The HF Diaphragm could be blown, they do fail often at high volume.
Hi john I Have a 450 v2 that is not sending sound to the high speakers the speakers is fine no fuses are blown and the bass works fine what should I look at
I have an srm450v2 that was overheated into the ground, replaced 5 caps, the 2 rectifiers, and the resistor that supplies 18v for the fet to turn on. I'm not blowing fuses, but that resistor is showing 38v where else do I need to look?
Great video. I got a cheap srm450 v2 in the market. unfortunately the pfc is blown together with the resistors. what other parts might be broken ?
Anything could be blown.
The bass fets and smps fets can take out the pfc, or maybe the pfc failed by itself which is common.
Really great video, I have the same board which is dead, no blown fuses but I did find D49 short
I get 15V with the diode removed but nothing when I replaced a new one. Do you thing something is dragging it down on the opamp side??
I guess so if all the other voltages are correct.
At 5:26 - the ground is the D62 *anode* !
I have srm450v2 i had a power indicator but no sound check the mosfet is good change mosfet driver ang 74ch02 and tlc081...when is the trouble of the sicuit
Hey John, great vid. I've had my two SRM450v2 speakers for 10 years now and they've been great! But recently ended a gig in the rain... Now both have a slight distortion in the low end... I replaced the woofers, but no luck... Any ideas?
Thank you!
If water has caused them to fail, it could be anything
Hi John, Have you had experience with Mackie Onyx 1640 Power supplies? I've replaced all the electrolytics capacitors, plus a few other components, but still have the green Power/ mixer LEDS flashing once/ second.
Hi,
Sorry not seen them, sounds like you have a short circuit somewhere or something drawing too much current.
Hi John, v interesting and informative video for the semi professional tinker such as myself. One of my v2s got dropped and won’t switch on. Resistor 245 that you tap on around 7m48s looks like it is burnt out but reads ok, and just gets very very hot now. I am thinking the transformer has taken a knock and is throwing out too much. Is this possible?
Hi Simon,
Thank you for your comments.
Test the big resistor, you should have 380v on one side and nearly 18 on the other.
Dropping the amp may have damaged the pfc coil so make sure it's working by checking the above.
The transformer can't throw out too much.
If the pfc does not start to give 380 volts, the smps will not start and the resistor will get hot.
ps use the zener diode anode / ground D62 for your negative connection on your meter.
Hey, i've been trying to repair my srm ampboard. So far I have had the same problem with the pfc, and replaced all the parts. After doing so there seemed to be a short on the powerlines. After some further research I came upon a 18v zener which went short circuit. (D62) After replacing it, the board still doesn’t work. There is a short on pin 7 and 8 of the pfc chip, I checked with a known good board and there it isn’t present. I’ve been looking but I haven’t found anything. None of the components in direct surroundings of the chip are causing it (service manual), I’m at a loss.. Thank u very much for your help already, and I hope you’ll be able to assist me further 😊
If you put 18.5 volts in the location shown, you might be able to see what is short circuit.
Maybe the comparator is shot.
Hi John, I have a 450V2 that intermittently shuts down during light use. It seems to work just fine for a while, and then the power goes out, and then back on in a few seconds. I have checked the speakers, they appear fine, no loose connections, no fried ics or caps. I'm considering buying a replacement amp for the unit. What things can I check before I take the dive? Again, this is light use and all LED's power off, and then on after a few seconds. Thanks very much and great video!
Hi Mike,
Assuming you do not have the power save enabled, it could be something as simple as one of the 15 volt regulators getting hot and shutting down, or a bad solder joint on the regulator.
It could be something drawing too much power making the regulators get hot and shut down.
John B great I'll start there! That is so much!
John, I just bought you a cup of coffee to thank you for this FANTASTIC video. I have multiple SRM450v2 amps and I have an issue with DISTORTION when turning up the pre-amp volume. Can you please give me some advice as to where to look? I'm thinking that the FETs or a transistor may be bad. Thank you again for this priceless content. *BRIAN*
Thank you very much for your kind donation Brian.
The 2 bass fets usually go short circuit and blow the power supply but I did have the odd fet go open circuit many years ago.
Do you have a multimeter with diode test to confirm they both test the same?
I assume you don’t have access to a scope and signal generator.
Let me know
@@JohnB-2021 Well, I just ordered/received the Silent SDS1202X-E scope and the Silent SPD3303X-E power supply so I'm ready to rock! I have a Fluke as well, so the signal generator is on it's way. Can I remove the bass FETS and test them with the PEAK DCA55? Thanks again!
@@silaratech I guess you can remove them but the heat required to remove them can damage them.
Try diode test and see if they test the same. The atlas tester will blow up if there is more than 5 volts on any pin.
@@silaratech You can put a scope lead on one of the bass wires, don’t connect the earth of your scope lead.
Only the heat sink metalwork is ground.
@@silaratech See if the swing on the music signal looks equal on positive and negative going music.
Hi John. Thanks for the great video. If you have time to answer I'm working on the same v2 model in the vid but mine works just fine until it warms up and when I turn up the volume my power cuts out. All lights and sound gone for a second then come back and repeat. Is this problem common and can you point me in a possible direction. I'm prepared to swap the fets or caps
Sorry that fault could be anything, I have no idea.
Dear John, I have a Mackie SRM450v2. Speaker works, but after about 30 minutes it sounds "crackly". I turn the speaker off then back on and it sounds perfect again. Thoughts?
Assuming the speaker itself is ok, I'd look for at the audio through all the op-amps first, I have seen them become noisy and intermittent.
Hi John, great Video, thanks for taking the time and effort to share it with us. I have a question, I have the same srm450v2, the problem is, sometimes it does turn on, and some other don't, I live in America, so we use 120AC, but i notice that when the voltage is above 120, (125 - 132 AC) the voltage at the 18v rail fluctuates. between 10 and 14 vdc. If it is connected the AC mains to the voltage regulator (118V AC) the voltage gets steady at 14vdc, and if you turn it on and off repeditly it rises to 18 and then it stays on. Also if you turn it off, as the mains capacitors discharges, the voltage at the 18v rail rises to 18, the power led lits and off course then shuts off. I have checked every resistnace, and capacitor, i just cant find any out of value, don't know whats going on. I've replaced the 10 and 4.7 uf caps, they got a bit ESR high resistance. Don´t know if you have had an experience with this kind of problem. I get the same problem in some other chinnese powersupplys, if they are not connected to a voltage regulator they wont work. Could you please point me in the right direction? Ohh, another thing, i have another 450v2 that is (less used) and it works perfectly at 130 AC... Thanks in advance!
Hi, thank you for your comments.
The voltage sense for the mains is based around the comparator next to the PFC circuit. If the mains is too high or too low, the amp won't switch on. I have had some here that don't work as they should. Messing about with the resistor values will fix the issue.
Under-voltage shut down is R290 & 291 & R258.
Over-voltage is R251, R252 and R253
Depending on the version, early boards had one value, later boards had different values.
Early amps had as follows for 'under'voltage'
R291 13k7
R290 182K
R258 6k19 errr yes a really odd value
Later amps 'under-voltage'
R291 = 82k5
R290 = 221k
R258 = 9k31
Early amps 'over-voltage'
R253 = 220K
R251 = 220K
R252 = 4K99
Later amps 'over-voltage'
R253 = 221k
R251 = 221k
R252 = 4k99
Great info and pointers, I have a SRM 450 V2 that I'm trying to repair. main fuse not blown, replace U35, Q10, Q7 , U40 , Q12 and Q11 and a few out of range caps and resistors. However, it keeps physically blowing apart R226, any pointers on what would cause this. At one point I got it to power for a few minutes but the speaker was making a thumping sound. I have a DMM and an ECR meter that I've used to test and replace the damaged caps and resistors. Don't have access to a scope to check signal
You need to power up the circuits and check them with a scope.
If R226 keeps blowing, your SMPS is still faulty or you have a short circuit on the amp.
Thanks John , have a scope on the way i'll have another go at it.
Hi Mate....I was Dj'ing last night and one of my SRM 450's 'Blew'. That is to say, a loud POP and then acrid, burning smell. I was driving it pretty hard I guess. The other Mackie is alright. Any idea what I should be looking for ? Power Supply, driver cone/ magnet ?
See if the amp fuse inside has blown, if it has, don't replace it, get the amp repaired.
Ho John Problems with my amp on 450 v2. when the amp is unscrewed from the chassis and tilted on it's side it works perfectly, when I seat it and power down it won't power back up with the on/off switch. Whem it's on its side the switch turns on/off perfectly? It's almost like a gyroscope when it's seated no power on its side perfect. The speaker did fall over recently. Thank you in advance
sounds like one of the coils may have a dry joint, especially the tall one with yellow tape.
The pcb needs removing from the heatsink and all the joints need checking up near the coils and transformers with yellow tape, that's the power supply end.
Hello John! I have been looking at your video now after having 2 of my v2 speakers go out on me, just found 1 problem om each amp just looking at it, was just going to ask for your opinion on them if thats okey?
On the first one i have CapXon 100v 470uF blown, can not see anything ells thats broken on that one, the amp was smoking alot when this happend, should i be worried that somthing ells is broken in this case?
Second one, i just noticed that C227 just right to the CapXon is blown, nothing ells.
Great videos showing problems on amp to someone like me that just started looking at devices like this! All the best! //Erik
Thank you for your comments.
I have never had a Mackie 450v2 fail because of capacitors.
I expect some components will be blown.
Hi, I have one of these and the pfc driver has blown along with the fet you mentioned. I was wondering if you happened to know the part number for that driver? Any help would be much appreciated.
It’s in the schematic
Hi John, i too have a V2 that decided it was going to take a nap, where are you in the country (i'm Southampton) are you busy and what is the turn around for you to repair? and am i right in saying future damage can be avoided by using a surge protector? many thanks Pete.
Hi Pete,
Yes I think a surge protector would help, together with those 13 amp socket 'checker'
I've seen quite a few blown amps due to the mains socket being wired incorrectly.
I'm in Barnsley South Yorkshire and the turnaround is a few days.
thank you
th-cam.com/video/MS_Iy7u7H5A/w-d-xo.html
I have a SRM 450 V2 which overheats the L3 coil/transformer. Everything works, but it get super hot. It will even smoke, and the glue around it will melt. Any idea what could be the root cause. Or will simply replacing this L3 fix the issue?
The timing must be wrong.
Hello Mr. John. I know this video was made many years ago. But I wanted to ask if you mentioned the PWM controller (originally UTC UC3842AL for me), and if you used a replacement. If so, what would you recommend as a replacement nowadays. I found a few similar ones (UC3842N Texas Instrument, UC3842BN ONSEMI) and Some in China (but I'm not sure about these). But they always differ slightly in terms of parameters. Would you recommend a replacement? Thank you for the answer and the video from the repairs.
Hi Pawel Gawel,
I would not recommend buying anything from China since the PFC circuit draws a specific amount of current, any more it won't start.
The importand part is the 'cut-in' voltage.
There are some that require more than 16 volts (from memory).
I do believe there are similar pwm controllers and have seen the On Semiconductor too, they work ok.
Mouser, RS Components, Farnell, CPC for genuine parts.
@@JohnB-2021 Thank you very much for such a quick answer. Thank you for recommending the stores, I know Farnell and Mouser (in Mouser I bought FDPF 12N60NZ / keying transistor /). In Poland / greetings from Poland / there is also a TME store that is very similar to the above stores. There I bought Ti and ON integrated circuits.
The circuits have very similar parameters. I compared the UTC UC3842AL datasheet / my burned in the power supply / with the TI and ON datasheets. UTC = Von / Voff = 16 / 10V. TI and ON = Von / Voff = 16/10.
The parameters that differ are:
a. Output short circuit - for UTC it is -100, -150, -245 mA (min, type, max)
for TI it is -30, -100, -180 mA (min, type, max)
b. UTC - Line Regulation ΔVREF 12 ≦ VIN25V 6 - 20 mV (type, max)
UTC - Load Regulation ΔVREF 1 ≦ I OUT = 20mA 6 - 35 mV (type, max)
TI - Line regulation 12 ≤ VCC ≤ 25 V 6 - 20 mV
TI - Load regulation 1 ≤ IVREF ≤ 20 mA 6 - 25 mV
c. UTC - Start-up Current Ist - 0.12 0.3 mA (type, max)
TI - IVCC Start-up current Ivcc - 0.5 - 1 mA (typ, max)
d. UTC - Power dissipation - 1250 mW
TI - 1000mW
Is the Start-up current parameter very important for the PWM controller? And the load regulation parameter (although here the datasheet differs a bit depending on the version, even sometimes it is the same).?
I will be grateful for your answer, although I do not want to involve you very much in translating PWM electronics to me, so thank you again for the above.
@@NAANAS I'm a little lost with all the text.
The 3842 will / must cut in at 16 volts and will continue running down to 10 volts.
The supply current is important, it must be similar to the Ti unit but I had an amp the other week with an On Semi.
Are you saying the original is not available?
UC3842AN from memory.
@@JohnB-2021 Sorry, Mr. John. I use a translator, maybe it does not translate properly. Yes, I'm having trouble getting the UC3842AN. It is unavailable everywhere, long waiting period / even a few years /. I found the last three in cpc, even wanted to buy it, but can't find the shipping to Poland option. I wrote to them, whether they are sending them, I got a return e-mail that they will answer me in 5 days, because they have a lot of e-mails now :(.
In Poland, I bought three types of integrated circuits for a trial, they have very similar parameters, only slightly different markings after the numbers: TI - UC3842N, ON - UC3842BNG and STM - UC3842BN. It seems to me that the most important parameter that distinguishes them from the original is Start Up Current, which for the circuit that was in my amplifier is max = 0.3mA. For the ICs I was able to buy, the Start Up Current is max = 1mA. And my little knowledge in this field does not allow me to say if I can use any of the integrated circuits I have bought, because I do not know if this Start Up Current has a large impact on the other electronic components in the amplifier, and if I will spoil something. .. :)
Maybe I can still buy the closest to the original in CPC.
@@NAANAS I guess you could try all the chips in a socket.
If the amplifier starts then the chip is fine.
Once pfc is running, smps will start and produce 18 volts.
I have only a few chips but I ordered some 3844 to see if it would work.
16 volt start, 10 volt running and a low start current is good.
Keep me posted
Hi John, I have the same board here I bought hoping to be able to repair it. I found R233 (3Watt), R230 and R235 all burnt, C167 also looks bad. The track between Q21 and R230 is burnt away. Any thoughts on what might have happened? I have these parts on order. Any suggestions on what else I should check/ replace? Thank you for your time!
Hi,
Yes Q21 will have gone short circuit and blown the chip and many of the surrounding components including the caps.
@@JohnB-2021 Can i contact you via email?
Bad Amp#2 Project: John, I have an amp that powers on but no audio output. The XLR input doesn't light up the green LED light (turning up the volume). I followed your 18.4V and 7.4V procedure and saw good PFC (frequency/amplitude stabilized). However on Q7 (Probing pins 1 & 3) I wasn't seeing a nice sine wave like I was with my GOOD Amp. Can this be the culprit as to why the input circuitry is offline and why I'm not even seeing a sine wave on the Bass/Treble/Speaker outputs (see other thread with my photolinks)?
Hi, I’m out at the moment but will check the email tonight in a few hours.
Sometimes the little resistors on the xlr board can fail if over driven. I’ll check the circuit schematic for the other part later.
Hi Brian, I have sent an e-mail; did you receive it?
Q7 & Q10 are the switch mode power supply fets.
You should see square waves on the pins only if you have 18.4 ish volts on the zener for the PFC circuit and something more than 5 volts, 7 to 9 is good, on the spare pad as shown in the videeo. My latest video may show things more clearly, have you watched it?
Thank you
JB
Hi John. I have a Mackie Thump 12, 120 V. Now i need to use the Module for 220 V Power Supply.
Is it enough, so that i remove the 120 V Jumper connection in SMPS. So that the Module works for 220 V Supply. !!
Please advise.
Thanks,
Stephen
Yes that's correct
@@JohnB-2021 thanks.
With the 450V2...First time seen such a burn out on those secondary side filter caps .... power pri./ sec. device failures , dry solder..Yes..
That pcb had 240 volts put onto the earth.
Hi John. I'm busy working on one. Replaced PFC Fet and IC. Check all timing caps around it. Applying only the 18V I get free running Freq of 106Khz, once synced with the other chip, I get the expected 68Khz. the unit goes on and plays, but blowed the fuse when I switched it on again after lunch. Could it be that the 106Khz is too high?
Hi,
You need to change some of the timing caps too, they do suffer when the chip blows.
The free running frequency should be no more than 90 Khz
Don't forget the filter cap in the current sense line, 680pf from memory
John B will a simple capacitance test show which ones are faulty?
Hi, very nice repair guide. Thank you very much , I have a diagram in hand, I am currently troubleshooting exactly the same speaker amp. It was working the first time after i replaced the PWM driver( SG3525) for the two FETS in the SMPs, but after switching it ON the second time the board was dead again with no green LED lights again, then after diagnosed i found out that there is no 380 Vdc and 18Vdc from the inductor L3 , i checked the input supply for the PFC chip (U36) it is only 12Vdc, and there was no input Vin for the PWM driver (SG3525) as well ,that is why it is not working. I checked the components on the SMPS and PFC but i don't find any fault on them. Do you have any idea why i am getting low voltages?
If the pfc or smps draws too much current, the pfc will not start and you will not have 18 volts.
@@JohnB-2021 in the diagram after L3 . I am not getting 18vdc and 380Vdc respectively. You mean it draws too much current or their is shorted somewhere else?
@@PowerToneAudio Something is not working or drawing too much current.
Look at the schematic, it allows 7.5mA or something like that.
@@JohnB-2021 Thank you John for your attention, I am thinking it might be my PWM controller 3842 is defective which I bought here in Dubai and in my experience some electronics spare parts here as well are not genuine. I had a blown fuse before because mosfet 12n60c was shorted which was driven by PWM controller 3842, that I replaced the chip and the mosfet but with no luck the amp was still dead. Let me double check and test the other parts, and get back to you as soon as possible. Thank you very much.
Hi I have a Mackie SRM450V2 which is dead although there is main on the primary side of the switch mode PSU any ideas to what may be the fault. or weather you would look at it ?
It could be anything, there is a guy advertises on eBay
Hi John, i have an srm450v2 that throws a thermal alarm after being on for 10-15 minutes. With or without input connected and the amp volume up or down. It resets after turning the power off but repeats with a thermal alarm. The amp seems to work fine while operating until the thermal alarm. Any thoughts? Thank you. tony
Is the heat sink very hot to touch when the light is on?
No, it's barely warm.
@@tonyozark
umm It could be anything, it sounds like the thermal control circuit has a problem, never seen that on a V2.
Hi John! i have a pair of bad working 450 v2 , they power on and sound but with hi frequency hiss and overheat (big resistors and caps), even they stop working during long use. I check voltages like you show but there is 14v, not 16.
can that be the problem?
If it's working then 14 is fine, it should be up near 16 volts but won't cause a problem.
If they don't turn on, the pfc circuit is not cutting in and could be caused by anything.
The hiss could be anything too, maybe a noisy op amp.
@@JohnB-2021 tnks!!
SMPS works fine I have the +76 and the -76 I have the DC signal in but no audio out or front LED what can cause no Audio out?
There are 1000 reasons why you have no audio out.
Hello, how are you? My name is Matheus, I'm from Brazil and I'm an electronics technician, I have a srm 450 v2 and I have a problem with the audio, around 10 minutes on it starts to crackle with varied intensity, but it works normally, the entire circuit has already been revised of amplification, given a chemical bath but the defect continues, I thank you.
It could be anything including one of the 30 odd op-amps failing when it gets hot.
If you're an electronics technician, you should understand I have no idea on how to fix your amp that is half way around the planet.
Hello, I have two modules.
1. Resistors R243 and R245 are overheating.
It does not turn on at the first press from the On Off switch, if I turn it off and turn it back on while the lights go out, it works.
2. Sounds distorted at medium volume.
I would be glad if you help.
Sorry, I have no idea. It could be 100 different faults.
@@JohnB-2021 If I don't plug uc3842, there is 18v, when I plug it in, 12v energy drops.
Great video, as a diyer I hate these boards. Much harder to diagnose than valve amps which I normally fix.
Long shot here but looking for any pointers. Speaker would lose power sporadically, stopped turning on altogether a couple of weeks later. Found resistor r245 out of value and replaced it. Found shorted zener diode d62 and replaced it but notice it continues to short every time its turned on. Ever seen this before and likely cause/components needing changed?
Where is D62?
@@JohnB-2021 Thanks for replying, it's the 18v zener diode close to the fuse and has a trace coming from the rectifier. I've replaced high voltage caps, the 12a mosfet and I'm going to change the driver and then give up. Was looking for some insight into an obvious reason for it shorting everytime its turned on but the fuse stays good. The fuse has never popped. The speaker used to turn on then after a while conk out. This continued for a few weeks until it wouldn't turn on at all
@@richardneill2634 You have to look at the circuit before the Zener.
What is causing a high voltage before the Zener is the question.
@@JohnB-2021 thanks John, I'll change the pcf driver if that's the right terminology and see what results I get. I have the part here anyway. Thanks for your help.
Do you do repairs of mackie srm 450v2? I have two that have stopped working. We use them at church and would like to get these repaired.
There is someone on ebay that repair mackie speakers.
Hi, great video, thank for theses advices. I try to fix mine, but I don't have a clue from where my problem is. The low section is good, but the high have a problem. Every thing is good at low level, but when signal reach about 10V, high goes in oscillation, can't localise from where oscillation start due to the feedback... I try to bypass compressor with the strap, change nothing. Limiter seems to be good, I don't think oscillation are made by integrated amplifier. Have you any idea ??? Thanks(excuse my english, I am french)
Your English is certainly more comprehensive than my French.
Probe the input pin to the treble chip pcb, the big pin on the main amp board.
I'd also check your + & - 39 volts, there are 4 big diodes in the top corner of the board.
Use the chassis screws as a ground for your meter.
@@JohnB-2021 Thank you ^^
My supply voltage are good, +/-39V. I have done new check, it appears that the distortion is from filter circuit.
I take a look from R145 at the input of low and high filter circuit and at the high output simultaneously, oscillations appears at exactly the moment when the signal input(R145) start to be in saturation. It need a little bit of saturation, just the top of the sinusoide cut to make the high output goes very wrong !! I don't understand, did that the filtering transform saturation worst, or something else. Never saw that before !!!! Thanks
I will make a FFT to see if filtering is good...
@@drissmorcel6265
Hi,
Sounds interesting.
I would go back to U11 and start finding which amp is getting saturated because they don't.
What input level do you have?
I use 50 to 60 mV
@@JohnB-2021 Hi, I have done a FFT, filtering is good, exactly what they said on schematic, limiter is good too.
I input a 0dB(0.775V eff) signal, a lot more than you do !
Saturation is normal I think, I have 7V eff(10V peak/20dB) at R145 before saturation comes.
.. seems to be logically the maximum of op amps (15V-3V=10V peak).
I think I see a problem where no problem is !!
Saturation simply goes bizarre, and more visible after passed trought the filtering of high, than when saturation occurs for low, I can see a little deformation of signal but not significant.
I can sent you screenshot of my scope to show you what it does.
And may, if you have a SRM450V2 you can try the experiencie, I think you will have the same "problem".
Hi John, I have a Mackie SRM 450v2 Board that seems to cause distortion sound at higher volumes. I've switched the cabinet with a amp module from another working V2 unit and the speakers themselves seem absolutely fine, so I'm certain there's an issue with the board. Would you be interested in repairing this for me? If so how much would you charge? I am in Burton on Trent, Staffordshire and can send the module to you.
Hi, I'm busy but just found a guy on eBay and he lists his number
www.ebay.co.uk/itm/Mackie-SWA1501-SWA1801-SRM450-Thump-series-servicing-and-repair-specialist/153867355114?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160727114228%26meid%3D1b94214fe53f4aa298d69396cff3ff98%26pid%3D100290%26rk%3D1%26rkt%3D4%26sd%3D153867355114%26itm%3D153867355114%26pmt%3D0%26noa%3D1%26pg%3D2060778&_trksid=p2060778.c100290.m3507
Does anyone know what a suitable replacement for the T2 transformer is? Had one that has been dropped and cracked!
They are custom made, you fill not find one on the shelf.
Hello Sir..I would like to ask the values of these resistors on this certain model they are discolored due to heat and I can't get an access on the schematic diagram.These resistors are R-288,R-245,R-243..Thank you so much.
The schematics are available from Mackie, I assume you have not looked.
R288 = 100k, R245 = 47k and R243 = 560k
Do you also repair Mackie HD series amps? I have one which lights up but the amps do not power on.
Hi,
No I haven't ever seen one.
damn. never mind, thanks for replying.
Hello Sir: My SRM450 is totally no power, no LED. I have a high school basic electronics knowledge What could be possibly the problem if I am getting 165v DC out on bridge rectifier SBU8j? Very much appreciated your help. Take care.
There are hundreds of possibilities, even an experienced electronics engineer can spend hours looking for the fault. Check the FET I mention in the video.
Hi I see you video on the SMR450 V1 and the thermal light(LED) staying on and the 18V supply fault, Does this apply to the SMR450 V2 ? I have a version 2 on my bench and on switch on both the Thermal red (LED) and red Peak (LED) are lite. no output but hiss through HF but no audio signal. and a circuit diagram would be very helpful Chris EES Swindon .
Hi, not sure about that fault.
A circuit drawing can be found by looking on the internet including the site at Mackie where they list circuit drawings.
OK John would you take a look at it ....
Hi,
Too busy at the moment, sorry.
i found the burned fuse on my amp and i used another one and i made more damage in it.
I hace another amp that has a slight strange voice when played, and i have no idea where is the problem. I have changed 5 of these amps and after awhile they do the same thing. do you now sir that might have be burned for having a whoosh sound in it. ?
Sorry no idea, it could be anything.
Hi John, whats the best way to get in contact with you? Thanks
here
has this SRM450v2 been modified? at 5:12 you're holding your index-finger near a zener-diode, but just next to that, there are two resistors (R243 & R245). I have a broken Mackie SRM450v2 with just those two resistors broken. I've downloaded the service manual which includes a parts-list, and there it says that these should be 47r5 Ohm and 20k Ohm, respectively. yet, when I look at 5:12, R245 is 47k (I think), and I can't make out what R243 reads, as it's just below the other one. so, after seeing your video, I am really confused and I'm not sure what values to use in the repair of mine.
if possible, could you tell me the values of those two resistors, I will be eternally grateful!
Mackie did change the values of a few components over the 4 or 5 different build dates.
@@JohnB-2021 oh, really? I didn't know that. you wouldn't happen to know what the values and ratings for R245, R243 and R288 are, would you? according to the schematics they should be 47kΩ 3W, 560kΩ 0,5W and 100kΩ 1W respectively, but I noticed that the R288 on your pcb is valued at 200kΩ. I've read stories about them heating up, so I imagine that is why you went with a higher value, but please; tell me if I'm wrong.
@@oed84 Keep the values that you have because other components rely on them.
They get hot when something is wrong.
Hi again. I have a problem with a Mackie srm450v2: it works fine but after 2-3 songs playing the all band suddenly one of the 2 mackie just stop working, power is on but the amp is automaticly off. I must restart the amplifier and it starts again. What do you think could be the problem ? If the temp get to high can it be the reason for witch it stop working ?
If it’s getting hot the temp light will be on.
If the power light has gone off, you have a mains or power supply problem
@@JohnB-2021 hi John..I buy a SRM V2 and when I take home test it the woofer is not working, like no sound but the tweeter is working.. everything is working it's only the woofer is not .I test the speaker and not it's good not toast..what could seems to be the problem in the amp of the woofer .do you think there's jst a resistor that is damage or the amp is blown already..thanks..
@@junealmuete6184 Hi,
I do not think it is just a resistor or simple problem.
There are many chips that control the bass only and a few that are the tweeter only.
Hi John, would like to know why a Quantum Audio QDJ15 Bluetooth speaker cuts off at high volume, if you happen to know.Thanks ahead of time for your time.
Never seen one but it is probably protecting itself.
Hi and thanks John, why do they put a resistor and a capacitor on the woofer positive and negative?
@@felixsantosmolina8872 to filter out the treble
thanks and take care
I have a Mackie SRM v2 that sounds very low, any Idea what maybe wrong?
do you mean quiet?
If it's not the volume control, it could be one of the op amps
@@JohnB-2021 I have 2 actually, one sounds normal as it should but one sounds very quiet at max volume . it had replaced the volume pot and it was working fine and one day started sounding quiet
Well John my good speaker started acting up, it shuts down, if I pass the dented middle in the volume knob it will shut off. I have to turn off the power switch and turn on again to make it work. how can I send both of my speakers amps for repair with you? because I am thinking seriously on buying those replacement amps in ebay so I dont have to deal with this bad engineering Mackie nightmares
Dear John, my friend's SRM450v2 got problem, fuse blown and he replaced it and blown IO UC3842AL and Q1 S8550 due to broken MOSFET 12N60 (0 ohm between pins), so we replaced all those three components (but FET is 13N50 only) and no voltage on part no. D37 (ZD according your video). There should be +18V and is 2V only :( We found schema but very low resolution, not possible to read it. Could you please help us? Thanks in advance.
The schematics are available from Mackie direct
If you watch the video, it says the small smd caps can fail and often do. Use the right parts or you'll never get it working reliably. i.e. Use the 12n60 which is a 600 volt mosfet, not 500. You may have a short zener too, did you check it?
@John B John you are really master! Yes you right, D62 is broken. Schema is here supportloudtech.netx.net/loud-public/#/asset/8901 , thank you!
Just nosing i use rcf believe i found out its pascal who make there amps, what are these v2 boards like?
I believe these v2 Mackies are a very good speaker, they pack a punch and sound more crisp than many other similar power speakers. They are also more powerful than many other speakers of the same size.
V2 series are Full analog circuitry with SMPS. regulation.
Class D for Lf. ( upto 1.5-2 ) kHz and hi pass powered with ST make... TDA 7294..
both lf, & hf are with their specially tuned filters & delay adjusted ( optimised for individual drivers and enclosure ) ..,each having their own mute , standby & clipping/ limiting circuitry..
hello John..how could we convert srm450v2 to 220v AC to fit the voltage here in the Philippines ? theres a jumper on the board which says 120vAC short...220vAC open.is this the key to conversion?many thanks John in advance for your advice.
Hi,
Yes you need to put a wire link in place. On many amps it's covered with white silicon.
John this Mackie is 110v from Canada.I will try to convert it to 220v .is it safe to remove this jumper ? many thanks John !
Hi,
Yes I believe it is marked at sw4 in the circuit drawing.
Cut it out for 220v
THANK YOU VERY MUCH JOHN !
John B how can I make contact with you. I have blown amp that needs repair Mackie 450
Hi John I have a Mackie V2 tha blew the main internal fuse last weekend. I would like to get it repaired how can I contact you to discuss. I can't seem to find anyone locally whose able to work on it at a component level. Cheers
Hi,
Too busy at the moment, sorry.
Hi John, thanks for coming back to me. Cheers
Hi John, I got as far as repairing the circuit and got the PFC to show the correct waveform at around 76K but when I put 7 volts into A7 nothing happens. I've replaced U40 but still no change. Are you able to suggest some troubleshooting steps please? I also noticed that even if I go up to 10 volts on A7, I dont get over 1.5 volts going into pin 2 of U36. VREF from pin 8 of U36 is linked successfully to pin 8 and 5 of U40 and A7 is showing up on pin 9 of U40. Any help much appreciated
How much current is your circuit drawing?
Do you have 18 volts, or 18.5 volts connected to D37 cathode?
I see I made a mistake in the video, the ground goes to the Anode of the other diode D62, I said cathode.
Have you checked Q13?
@@JohnB-2021 At 18.5 V its drawing 40mA. Q13 was replaced. Where should i look next?
I also noticed that even though I have put 18.5 - 19 V in, I only get around 15.5 V into the PFC chip, but it still turns on. I also get 15.5V into the VCC of the comparator chip. However, when the comparator swings to vsat, its only reading around 5.5V at pin 14. Is this normal for this circuit or should vsat be going up to close to VCC (15.5V in this case) ??
@@DM-iv4fb There is a transistor near the edge of the board, TO92 shape, maybe that has blown.
@@DM-iv4fb Do you have 10 volts on U35 yet?
The transistor I mentioned is Q1
hi john b, please a need to replace the mackie srm 450 v2 motherboard (card) I am in usa,can you please let know were I can buy it.
There are companies in the USA that list the v2 amplifier boards, I know this because I have seen them and see they do not ship to the UK.
Have you tried searching on Google?
@@JohnB-2021 thank you, I staring looking on internet. What is the real name for it? I don't want to buy a wrong one
@@TheGordito27
Just a Mackie SRM450 v2 amplifier pcb
I can tell you that the new boards I have seen needed the treble chip board soldering into position and the XLR input board had to be soldered onto the main pcb too.
@@JohnB-2021Thank you so much.!!
Hello I have a problem with the same board. in wont turn on. i took some measuements across the zenner diode D62 and realise is not reaching the proper 16v for the pfc to operate, It cycles from 10 to 13 volts all the time. The same thing happening across the leads of R288 it goes from 350 to 360 volts. I,ve changed the Cap C242 with an 330uf and it turned on with a delay of 1~2 seconds. It helps to reach 16v and starts the pfc but i dont like this solution.
Ive cheked and changed the following parts with new ones and realised that the old ones where also good because the problem isnt gone.
Diodes : d51 , d65 , d7 , d36 ,d39 , d62 , d34
Transistors : Q13 , Q1
Capacitors : c242 , c241 , c184 , c183 , c232
Ic : U35 , U36
The resistors R288 , R245 , R243 are good
I'll be greatful if you could help me , as i see you are an expert with this.
Thanks
Hi,
You need to check the current consumed by the whole circuit.
The 16 volts actually comes from an additional coil wound on the pfc coil, it has 5 or 6 turns and supplies the initial power for the pfc chip.
When powering up the pfc and smps via an external power supply, both circuits should draw no more than 30 t0 40 mA without the smps being enabled.
@@JohnB-2021Ok , so i suplied d37 with an external 18v an it draw 41mA. So the pfc is ok?
@@Kostasp23 Yes that sounds ok.
So power up the smps with enable voltage and see if smps works on scope, the current should be less than 60 mA.
@@JohnB-2021 Hi again. So far the situation is the folowing. Only the PFC with the 18v draws 41mA and at the Gate of Q21 i have 87 KHz. When i enable the SMPS with 7 volts the current draw is 60mA and the frequency in Q21's Gate is 66 KHz. The same frequency (66 KHz) is at the gates of Q7 & Q10. The only diference is that at the Gate of Q21 there is 11Volts & at the gate of Q7 & Q11 is 3.69 Volts. Depending to your video i thing that the mesurements are fine. So the next step?
@@Kostasp23 It's difficult trying to repair an amp without seeing it.
Maybe there is a dry joint, as I have seen, at the secondary coil on the pfc, check you are getting over 16 volts at D34 and ground.
Your 360 volts should be 380 volts.
Hi John, I am from India. I one of the unit the Mackie SRM 450v2 , L11 ( 33UH coil ) is getting heated up. I am suspecting and need to replace. This part is not available in my place as well as online. Kindly guide me. Thanks in advance.
It does get hot, it is normal
@@JohnB-2021 thanks
Sir, one more doubt. The TH1 sensor ( KSD301 075f) is NC or NO type, Kindly clarify. Because this unit has come for repair and attended by some non technical person and few parts missing. Kindly suggest me. Thanks
@@ramaraj05 Its the NO type!
La mía se quemó necesito una cómo puedo conseguirla
Please check the next link www.fullcompass.com/prod/159690-Mackie-0027377-00
Hi John, great video. You really know your stuff. My mackie has blown 2 parts and cant find any to replace. Do you have any links for me please. Or better still depending on your location you could fix for me. Cheers Hugo :)
Hi,
Thanks for your comments.
What are the 2 blown parts?
Where in the world are you?
I'm in South Yorkshire
Hi John,I am in North Wales so a bit of a trek. 12:26 you can see Grey long transister shown underneath the 3 parts covered in burgundy plastic, that went first and then I stupidly replaced fuse before I watched your ace video and then the dark grey rectangle to the right of it blew. What a dope I am :)
Hi Gareth,
Well it's a common failure and takes a few hours to repair and check.
I can repair them for £90 + return postage which is usually £12 UPS
Thats sounds great. My email is hugo@humanandcargo.co.uk. Forward me some details on how we proceed and lets go for it :) Cheers John
Hi! I am Anders from Sweden...I have 2 PCBs of 450V2 which is none working. The fuse is blown on one of them...no burn marks on the PCBs. Have been installed on a club...running 24x7...until they just went off...would you be interested to check these boards?
want to ask PWM ic serial number for 12n60c MOSFET
Get the schematic from Mackie.
I have a 450 has bad cracking sound when turned on
yep, many do.
John B sorry cracking sound all time when you play music you can’t hear it ,no music it crackles like filter cap
@@patrickboudville7951 I've never had a filter cap causse a crackle.
If it's a V1, it could be a noisy transistor.
John B hanks John appreciate i
Hi, Where are you based if ever needed
South Yorkshire
Dear sir,
very good program for power supply
Rashid anwar
Thank you Rashid
Please please stop nervously tapping everything with your biro. Your videos are genrally very interesting but it’s a really annoying habit. Thanks
I agree with you about that tapping, it is very annoying and distracting
Are you kidding me? WTF. The man takes time to make a how to video and tapping something while fencing for a thought bothers you? Grow up.
LMAO
Thank you Jumbicat