Microlab Solo 9C active Speakers audio cutting out when volume high

[keeney123]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Oh okay, had a vague idea what it was but now I know, thanks for explaining!

Hmm, my soldering skills are probably not up to par as with you guys and people with the more expensive temperature control type soldering irons but I have a few different basic electrical soldering irons and also a butane type soldering iron. I also have solder sucker and do have some separate flux. Would I have to completely remove the solder or could I just paste some flux over the original soldered point and reflow it?

What you would do is put a little flux on the joint if your solder does not already have flux in it. Tin your iron and clean the tip. Then tin it again . Put the iron down on the joint it will melt. as you are touching both pad and lead add solder until flow evenly around the pin and fills the hole and looks kind of cone shape. I like to use 60/40 solder with flux in it to touch up and repair a problem. I do not think a little lead for repairs are going to destroy our planet. Also, remember to clean the joint with alcohol and let dry before turning on the unit.

[keeney123]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Hmm, where do I take the resistance reading from? I have a multimeter but have no idea where I should place the terminals, mind you the Volume/bass/treble controls are all digital. I don't have an oscilloscope, nor do I have access to one but wish I did have one. I did have access to one many many years ago when I learned basic circuit theories at TAFE but didn't follow through into that career.

So the resistance reading would be on the volume control. I do not have the schematic of the unit. The volume Control usually is wired as a rheostat. It will either decrease in resistance as the volume gets louder or increase in resistance as the volume gets louder. Would be dependent as to how the circuit was designed. In either case once you get to the troubled spot and turned off the unit and unplug it from the wall. you would take a reading on the wires going to the volume control. You get a reading and write it down. You then slowly turn the volume control towards where you had good sound. The reading will all of a sudden jump in the opposite direction either from continuity to open or from open to continuity. If you have little clips on you ohm meter You would clip them on and look at the reading as you do this. A picture of the back of the volume control would help.

[afourtrackmind]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Quote:
Originally Posted by budm View Post
That is the signal processor board.
This speaker system has Linear power supply and power amp all in one board.
It is Class D amp setup.


Is that a little crazy to do?

(apologies, I'm having my own technical difficulties. I'm new to the site... ..kinda)

No, just uncommon. Class D takes advantage of single ended PSU and those are now commonly switch mode. Makes everything cheaper to produce.

Is that a TDA7492 amp IC?

[funkster]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

It's not plastic it's made of mica. A mineral.

Ah okay, that makes more sense now lol, I learn something new everyday xD

[funkster]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

So a cold solder joint is where a soldering iron was not held on the joint long enough to evenly distribute the solder in the joint or where the iron was held on the pad or the leg and not on both. This will heat one part up without heating the other so the solder will be cold at the part the iron is not held on. In either case the solder will not be bonded to both parts adequately and oxygen gets into the joint creating more resistance. This is also the reason flux is used in the solder, to boil out oxygen and evenly distribute the heat. Cold solder joints may take some time to show up or then can be intermittent with flexing of the board or temperature changes.
With all that said it seems in your new picture this is not the case. However there are other places on the board that have not completely filled the holes in the solder joint. They most likely are all right. If you were good at soldering I would say touch them up, but I do not believe are experienced at solder so I say leave them alone.

Oh okay, had a vague idea what it was but now I know, thanks for explaining!

Hmm, my soldering skills are probably not up to par as with you guys and people with the more expensive temperature control type soldering irons but I have a few different basic electrical soldering irons and also a butane type soldering iron. I also have solder sucker and do have some separate flux. Would I have to completely remove the solder or could I just paste some flux over the original soldered point and reflow it?

[funkster]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

So by doing one channel at a time you have pretty much eliminated after the channel have split as being the problem. Still one needs to allow for small chance it could be after the split. So I would first look at the power supply voltages when the problem occurs. You would be looking for a change in level or ripple on them. You might also check the resistance reading of the volume control. You would do this by turning the unit on and then turning the volume control to where it causes the problem. Then turn unit off and unplug it from the wall. Then take a resistance reading. What you are looking for is a dead stop on the volume control. Then I would look at the signal processing board. If you had an oscilloscope that would make life easier. Other than that perhaps BudM has some other way to troubleshoot this problem.

Hmm, where do I take the resistance reading from? I have a multimeter but have no idea where I should place the terminals, mind you the Volume/bass/treble controls are all digital. I don't have an oscilloscope, nor do I have access to one but wish I did have one. I did have access to one many many years ago when I learned basic circuit theories at TAFE but didn't follow through into that career.

[keeney123]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Sorry, I thought that was self evident. Plastic is a poor conductor of heat, more like an insulator. I just didn't want anyone to get confused and try to cut up a sheet of plastic and burn up their to-220's. You can get them at Mouser. I think I bought 25 the last time I ordered some.

Not for me, for funkster as he did not know what they were. To me it doesn't matter what material they use to transfer heat. Only time it would matter to me is if I was replacing the part.

[rhomanski]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Sorry, I thought that was self evident. Plastic is a poor conductor of heat, more like an insulator. I just didn't want anyone to get confused and try to cut up a sheet of plastic and burn up their to-220's. You can get them at Mouser. I think I bought 25 the last time I ordered some.

[budm]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Now you should explain why it is made of mica and not plastic.

Thermal conductivity, Break down Voltage, etc.
https://www.aavid.com/product-group/...nsulators/mica

[keeney123]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

It's not plastic it's made of mica. A mineral.

Now you should explain why it is made of mica and not plastic.

[rhomanski]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

I found something weird, and I don't know if it's a normal thing to do but there is a piece of clear plastic in between the heatsink and IC, and both sides have thermal paste on it.

It's not plastic it's made of mica. A mineral.

[keeney123]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Same things happens regardless, I tried one channel at a time connected to the RCA inputs, turning up the bass makes it happen more often at the same volume level, happens a little less when turning down the bass. What does this point to?

So by doing one channel at a time you have pretty much eliminated after the channel have split as being the problem. Still one needs to allow for small chance it could be after the split. So I would first look at the power supply voltages when the problem occurs. You would be looking for a change in level or ripple on them. You might also check the resistance reading of the volume control. You would do this by turning the unit on and then turning the volume control to where it causes the problem. Then turn unit off and unplug it from the wall. Then take a resistance reading. What you are looking for is a dead stop on the volume control. Then I would look at the signal processing board. If you had an oscilloscope that would make life easier. Other than that perhaps BudM has some other way to troubleshoot this problem.

[madan1]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

I found something weird, and I don't know if it's a normal thing to do but there is a piece of clear plastic in between the heatsink and IC, and both sides have thermal paste on it.

that's not weird, but normal. It separates the transistors back ( in your case the chip's back ) from the usually grounded radiator. When putting back the parts be sure to apply new thermal paste and new pad.

[keeney123]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

I found something weird, and I don't know if it's a normal thing to do but there is a piece of clear plastic in between the heatsink and IC, and both sides have thermal paste on it.

This is normal. The plastic part isolates the metal of the heat sink from the metal of the IC electrically, while allowing heat to be transferred between them.

[keeney123]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

What does cold soldered mean? Also I tried to take a close up shot of that area on the board.

So a cold solder joint is where a soldering iron was not held on the joint long enough to evenly distribute the solder in the joint or where the iron was held on the pad or the leg and not on both. This will heat one part up without heating the other so the solder will be cold at the part the iron is not held on. In either case the solder will not be bonded to both parts adequately and oxygen gets into the joint creating more resistance. This is also the reason flux is used in the solder, to boil out oxygen and evenly distribute the heat. Cold solder joints may take some time to show up or then can be intermittent with flexing of the board or temperature changes.
With all that said it seems in your new picture this is not the case. However there are other places on the board that have not completely filled the holes in the solder joint. They most likely are all right. If you were good at soldering I would say touch them up, but I do not believe are experienced at solder so I say leave them alone.

[funkster]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

So I see from here it has no balance. http://gadget-help.com/quick-review-...rolab-solo-9c/


It does have right and left input this way you can plug one in at a time and turn the volume all the way up. You will need to connect both speakers. So try one line then the other. You can also very the treble and bass to there extremes as you are doing this

Same things happens regardless, I tried one channel at a time connected to the RCA inputs, turning up the bass makes it happen more often at the same volume level, happens a little less when turning down the bass. What does this point to?

[funkster]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Speakers look good from the out side, I believe they sell them for > $400.
Every things are inside so the heat is just trapped inside the cabinet, most powered speakers will have heatsinks exposed out in the back plate.

I found something weird, and I don't know if it's a normal thing to do but there is a piece of clear plastic in between the heatsink and IC, and both sides have thermal paste on it.

[funkster]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

So is this where you right and left speaker are connected that I have circled in pink.?

Yep, one connects to the banana plugs to go outside to the left channel, and other internally to the right channel to the crossover.

[funkster]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

So what I see is two places I circled in red. One looks like leg is cold soldered. The other part looks damaged. In the Yellow circle it looks as if a wire on solder bridge shorting out the capacitor.

What does cold soldered mean? Also I tried to take a close up shot of that area on the board.

[keeney123]

Re: Microlab Solo 9C active Speakers audio cutting out when volume high

Speakers look good from the out side, I believe they sell them for > $400.
Every things are inside so the heat is just trapped inside the cabinet, most powered speakers will have heatsinks exposed out in the back plate.

I just wonder about the power supply interfering with the power amp. The power supply would have AC voltage on it. I know on class D amps they are worried about EMF. They even try to keep the speakers as close to the Amp as they can because of this interference.