Altec MX6021

[lincolnkorg]

Re: Altec MX6021

Thank you for your reply Agent24, I will take some pictures of these parts and post them in the evening. Thanks so much once again, much appreciated.

[lincolnkorg]

Re: Altec MX6021

Hope these pictures help.

[momaka]

Re: Altec MX6021

Oh boy, where to begin here....

Here's a "short" list
1) The primary cap looks bulged (and you said it is), so that needs to be replaced.
2) Anywhere you see black sooth or burn marks - clean it up well with IPA (Isopropyl Alcohol). Black sooth like that can be conductive.
3) Right in front of transistor Q2, there is a small blue capacitor with what appears to be brown/black glue - remove all of this glue, because it is bad (it goes conductive with heat)
4) Top left corner of this picture, you have some lifted traces. Probably best to remove the coating on top of it and coat it all with solder. Make sure the trace is continuous throughout.
5) Top center of same picture above, you can see some SMD resistors badly soldered - check those on your multimeter. They should appears as a very very low resistance reading (probably even short-circuit).
6) Replace caps C11 and C14 on the primary side.
7) Post a picture of the secondary side... and also probably a good idea to check the secondary side output rectifier(s). Replaced the caps too, if they look or test iffy.

If you decide to test the power supply (I suggest doing that without connecting it to the rest of the Behringer unit), attach a incandescent light bulb (60-100W) in series with the line cord. This will limit the current if there is something wrong with the power supply, so that you don't end up blowing out Q2, the main fuse, or any other components. Here's a diagram how to connect the bulb as well as what to expect, in case you're not sure:
https://www.badcaps.net/forum/showpo...4&postcount=70
... if the bulb stays lit for more than a few seconds on your power supply, you have a short-circuit or faulty component somewhere (most likely the primary side).

I also noticed that C25 was mounted in an angel, wondering if this was tampered by the previous person who tried to fix it. The polarity of C25 is reversed (smaller reading on diode test on one side and bigger reading when the probes are reversed, not sure if this is the right way to test) when compared to C24. Does that matter? Should I reverse C25 to match C24?

Don't reverse the polarity of any capacitors without knowing first which is the correct way they should be installed.

If you look on the PCB, you will see that each electrolytic cap has a "+" symbol next to one of its sides - this is the positive side of the cap. The negative side of the cap (i.e. the side with the stripe on the cap) should be opposite of that.

[lincolnkorg]

Re: Altec MX6021

Thank you so much Momaka.

I will follow the steps you mentioned. Will take a while for to source all the spares and get them shipped. I will attach pictures shortly.

A couple questions. Do SMD caps have polarity? C25 is the SMD in question. Also im not sure the 4 SMD resistors are of the right values. A picture posted here showed those resistor values as 1R00. The value of the ones on the board read 1002.

Thank you so much once again for taking the time to go through the pictures and giving dicrectuons from where to start. Ill remove the components in question and clean the board while i wait for the parts to arrive.

[lincolnkorg]

Re: Altec MX6021

Here are the pictures of the secondary side.

[momaka]

Re: Altec MX6021

You're welcome!

Do SMD caps have polarity? C25 is the SMD in question.

No, ceramic caps (be it SMD or regular through-hole), as well as film caps (polypropylene, polyester, etc.).... do *not* have polarity.

Only electrolytic and Tantalum caps have polarity.

Also im not sure the 4 SMD resistors are of the right values. A picture posted here showed those resistor values as 1R00. The value of the ones on the board read 1002.

Measure across them and multiply that reading by 4 (since there are 4 in parallel, the resistance will be 1/4 of the printed value on each resistor)... though chances are your multimeter probably won't be able to measure that low (0.25 Ohms, if they are all 1 Ohm resistors, as the value 1R00 would imply).

[Behemot]

Re: Altec MX6021

Film caps, especially axial, do have prefered orientation though (good for audio circuits).

[lincolnkorg]

Re: Altec MX6021

Thabk you Momaka and Behemoth.

So its safe to leave the those SMD caps as they are. Im learning and this is great knowledge to have.

To reduce the cost, im going to the local market this weekend to source as many components as I can and then order the rest from Aliexpress or UTSource.

Thanks so much once again folks for the inputs and help. Much appreciated.

[lincolnkorg]

Re: Altec MX6021

Does anyone know the values of the resistors in the heat shrink tubes. R25, 26, 27, 28 along with the wattage? Would be handy to know the values of the rest of the reaistors as well.

Thanks in advance.

[momaka]

Re: Altec MX6021

So its safe to leave the those SMD caps as they are.

Yes.

To reduce the cost, im going to the local market this weekend to source as many components as I can and then order the rest from Aliexpress or UTSource.

Sounds good.

I just don't know about the electrolytic capacitor brands you'll find there though (hence you may not get good quality capacitors). Doubt it there will be any quality genuine Japanese caps. Then again, AliExpress is also full of counterfeit Jap. brands, so I don't know what better (or worse, really). As for UTSource, I have no idea what they have.

In any case, if you can't find any Japanese brands that look genuine, then at least try to go with some of the known Taiwanese brands that aren't too terrible like Taicon, Teapo, Su'scon, OST, Elite, and Lelon to name a few. Or SamWha and Sam Young (Korean brands typically used in Korean TV sets).

Does anyone know the values of the resistors in the heat shrink tubes. R25, 26, 27, 28 along with the wattage? Would be handy to know the values of the rest of the reaistors as well.

No clue, but you can remove the shrink tube around them and read the values. Wattage will vary, so just try to match the size. Also, I think those resistors are likely either flame-resistant or flame-proof metal-film type - in which case, DO NOT use regular carbon-film resistors.

Film caps, especially axial, do have prefered orientation though (good for audio circuits).

Good call. Forgot about those, mostly because I don't see them very often in modern stuff.

[lincolnkorg]

Re: Altec MX6021

Thank you Momaka. The brad names you mentioned are super helpful. Will look for these brands. Will be careful about those big resistors.

For the bridge rectifier, will any part number close to the one mentioned on the diode do or do they have to be a perfect match?

Thanks a mil for your time and sharing your knowledge.

[kaboom]

Re: Altec MX6021

Just posting quick here...

That driver IC is directly connected to the MOSFET gate, via JMP2. If/when the MOSFET shorts, IC must be replaced.

I see a crater on the 1351 on lincolnkorg's board.

DO NOT use regular carbon-film resistors

Or "regular" metal film ones, those (their coating) burn too.

[momaka]

Re: Altec MX6021

Thank you Momaka. The brad names you mentioned are super helpful. Will look for these brands.

Well, look for Panasonic, Rubycon, Nichicon, and United Chemicon if possible first, as those are the good Japanese brands. Just make sure they are genuine. To do that, have a look at some pictures here on BCN how those should look. If you get any that look iffy, post pictures here before using them.

Between counterfeit Japanese brands and the lower-quality-but-somewhat-acceptable Taiwanese brands I mentioned above, I'd go with the latter.

For the bridge rectifier, will any part number close to the one mentioned on the diode do or do they have to be a perfect match?

For bridge rectifier, you just have to match the current and reverse (DC) blocking voltage - i.e. if you have a 4 Amp 600V bridge rectifier, then the new one should be rated for at least 4 Amps and at least 600V.

That driver IC is directly connected to the MOSFET gate, via JMP2. If/when the MOSFET shorts, IC must be replaced.

I see a crater on the 1351 on lincolnkorg's board.

Good call!
I previously dismissed that as dust in the photos given. But it could well be a crater/bump in the IC, as you say. If it is, then an incandescent light bulb in series with the PSU will be an absolute must... unless lincolnkorg wants to commit to a kaboom.

[kaboom]

Re: Altec MX6021

Good call!
I previously dismissed that as dust in the photos given. But it could well be a crater/bump in the IC, as you say. If it is, then an incandescent light bulb in series with the PSU will be an absolute must...

I saw the dust. It looks like there's a central blister, or at least former hotspot.
I've "peaked and tuned" the image, and uploaded it...

unless lincolnkorg wants to commit to a kaboom.

[lincolnkorg]

Re: Altec MX6021

Hey Momaka and Kaboom. The IC actually looks fine to the naked eye, good catch. I’ll replace it anyway to be sure. Either way I will use the incandescent bulb, getting these components are a long wait this side of the world. So not going to risk it at any cost.

Thank you for the tips on the caps and diodes. Finding the ratings of these components is a challenge without markings on them or schematics. You guys have been very helpful. Cannot thank you guys enough.

At this rate pretty much all the components on the primary side needs to be replaced (not forgetting a few caps on the secondary side as well) I just hope the zener diodes are fine. Finding their values could be difficult.

Thanks a ton guys....

[XeeTehparadox]

Re: Altec MX6021

i have purchased MX6021 (12/5/2012)

I have problem click button power with unable to power on. (15/8/2019)

i using multimeter and checking tested DC 0V....


DC voltage output what is 12V or 15V or 18V ?

DC Amp current rate 2A or ?A ??

Yellow = VCC + or - GND ?
Red = VCC + or - GND ?
White = VCC + or - GND ?

[momaka]

Re: Altec MX6021

DC voltage output what is 12V or 15V or 18V ?

It's a split-voltage power supply (i.e. Vcc and Vee, with ground/center-tap reference.)

DC Amp current rate 2A or ?A ??

Can't say, but judging by the rectifiers from the pictures others have posted, I'd say 6A just to be on the safe side (probably need much less than that.) For testing, you could probably use even two 12V power supplies connected in series, with the mid-point being the common (make sure to use ungrounded power supplies if trying this to avoid any ground issues.)

Yellow = VCC + or - GND ?
Red = VCC + or - GND ?
White = VCC + or - GND ?

Yellow = Vcc
Whilte = Vee (i.e. -Vcc)
Red = common/GND

So if this is a dual 15V power supply for example, then Red to Yellow should read 15V. And Red to White should read -15V.

[lincolnkorg]

Re: Altec MX6021

A very late post, but I had some time and the spares handy and got down to replacing the spares on the primary side. Connected the lamp in series and there's no short anymore. There's no output too. Does anyone know if the power supply needs to be connected to the amplifier board to switch on the power supply or I should be getting voltage without connecting to the amplifier board. I get around 1.7 to 1.9 volts DC at the input of the octacoupler, nothing on the output. Replaced caps at the secondary side, still nothing.

Thanks for any help I can get in advance.

[momaka]

Re: Altec MX6021

Does anyone know if the power supply needs to be connected to the amplifier board to switch on the power supply or I should be getting voltage without connecting to the amplifier board.

I think you should be getting output, even without the amp board, as there is no standby PSU and no external signal wire to tell the PSU to turn On remotely.

Of course if you can, do try it with the amp board connected, just to see if that changes anything (though I doubt it.)

I get around 1.7 to 1.9 volts DC at the input of the octacoupler, nothing on the output. Replaced caps at the secondary side, still nothing.

Sounds like the PSU is trying to start, but not quite there yet.

Were the output rectifier diodes checked for proper diode readings and no short-circuit?

Besides the output caps and IC on the primary side, what else has been replaced? Just asking, since it's been a long time and would make it a bit easier to catch up on that. (I already re-read the thread, but just to get a more clear picture.) Looks like we may be getting closer with this one.

[fobby]

Re: Altec MX6021

total newbie here.
Just want to share some details of my experience here, got lot out of this thread.
Had a power surge from broken neutral recently.
the system can power on, kind of, just getting constant clicking noise.
unplugged everything except the the power supply, still hear the constant clicking noise, like it's from a capacitor, what does that mean usually?

I don't have any visible burnt out smd's, just the same burnt glue on the R25, 26, 27, 28 and also the blue cap same as this

Oh boy, where to begin here....
...
2) Anywhere you see black sooth or burn marks - clean it up well with IPA (Isopropyl Alcohol). Black sooth like that can be conductive.
3) Right in front of transistor Q2, there is a small blue capacitor with what appears to be brown/black glue - remove all of this glue, because it is bad (it goes conductive with heat)
...
6) Replace caps C11 and C14 on the primary side.

Momaka, how did you know that C11 and C14 needs replacing?

I've already ordered and just waiting for the blue cap c3
didnt take any before pics, but this is after cleaning out the glue


btw if anyone else is looking for more information
blue cap c3: 2kv 102k
r25/r26: brown blue brown
r27/r28: brown green red


im getting about half the resistance on R25/26, is this normal?
Should i replace those too?