Altec MX6021

[ramirog96]

Re: Altec MX6021

In that case, the 4 SMD resistors could be replaced with a normal 4 ohm resistor.

Thank you

[zerbino]

Re: Altec MX6021

Hello, could someone give me the value for R15 please ?

SMD R473

[Philippe_Quercy]

Re: Altec MX6021

Hello, could someone give me the value for R15 please ?

[momaka]

Re: Altec MX6021

Hello,
I have a similar problem with the 6021 power supply. I want to replace it with a classic one. Is it possible to do that?

I don't see why not. So long as you can provide the correct voltages with sufficient currents, everything should work as expected.

I think this is a dual-output power supply with a center tap, as I outlined in this post here:
https://www.badcaps.net/forum/showpo...6&postcount=57
^ That said, not sure of the voltage and current spec on the old PSU, but I imagine around or at least +/-15V for the two rails and maybe 3 Amps current max needed. See what chips and ICs the amplifier board has on it first, though. If there are any op-amps directly connected to the PSU outputs, then check the voltage rating of those op-amps to see what is the max they can take - i.e. if they are something like TL084 (which is rated for +/-18V absolute max), then you need to keep the supply voltage at least a volt or 2 lower than the absolute maximum if you don't want to blow the IC up.

Seeing that the original PSU has 25V caps on its output, I imagine the dual power supply rails are indeed at least +/-15V.

[sloba962]

Re: Altec MX6021

Hello,
I have a similar problem with the 6021 power supply. I want to replace it with a classic one. Is it possible to do that?

[Lagodd]

Re: Altec MX6021

Hello

I am having the similar challenge of power supply failure. I don't see anything burnt. Does anyone have a diagram of the MX6021 PSU A13061 board? the measured voltage on different pin locaitons?

[RJARRRPCGP]

Re: Altec MX6021

Had a power surge from broken neutral recently.

That's what I feared, when I was at 285 Clinton St. in Springfield, Vermont during April, 2016 and May, 2016. I saw the signs while looking at my UPS!

Luckily, I was safe at the time, but there were things that weren't working!

The smoke alarm wasn't working in my bedroom and there were only two of them, thus only the one in the extended part of the living room, where I had my plants, was working. (Kidde) Also, with one of the light fixtures, I thought I saw nothing for light when I put in a known working light bulb!

On the busy leg, the voltage dropped to 111V, IIRC. While the other leg was 132V! The scariest was the smoke alarm in the bedroom not working! (Looked like it was a First Alert/BRK)

Possibly all the property needed, was a new or otherwise fresh service drop from Green Mountain Power.

https://www.badcaps.net/forum/showthread.php?t=53717

[momaka]

Re: Altec MX6021

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

Both of these caps filter the primary side auxiliary rail for the PWM IC. One of them is the "start-up" cap (most likely C11). If one or both of these go bad, the PSU may not be able to start up and make chirping or clicking sounds as it tries to start, fails, and then restarts again and again.

The problem is not unique to this power supply. Almost all PSUs that have PWM ICs on the primary side and an electrolytic startup cap can fail like this (particularly if the cap is from a known cheap/unreliable brand.)

And the symptoms of your PSU seem to agree as well:

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?

... though the clicking could also come from the output capacitors, if any have failed. Just because they are not bulging doesn't mean they can't be bad. If they are indeed CapXon and Samxon like the original poster showed in page one, it might not be a bad idea to swap those as well eventually.

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

Yes, that is likely normal.
If you follow the traces on the bottom of the PCB, you will see that R25 and R26 are in parallel. If they have the same resistance printed on them, then the total resistance will be half of that.

Also, resistors tend to go higher in resistance when they fail or completely open circuit. Resistors do NOT go lower in resistance over time / with faults.

Thus, you shouldn't need to replace them.

[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?

[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.

[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

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.

[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 ?

[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....

[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.

[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

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.

[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.

[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

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.