The schematic you posted does not show the power amplifier section that has the problem.

The difference in DC voltage at the outputs of the paralleled ICs produces a current in their series output resistors that heats both of them. The amplifier manufacturer probably selected matched ones so the voltage difference and resulting current and heat are tiny.
Here is a schematic from the datasheet with my comments:

 

The schematic you posted does not show the power amplifier section that has the problem.

The difference in DC voltage at the outputs of the paralleled ICs produces a current in their series output resistors that heats both of them. The amplifier manufacturer probably selected matched ones so the voltage difference and resulting current and heat are tiny.
Here is a schematic from the datasheet with my comments:

See page 2 of the TS's download.

 

Hm. Going by @Audioguru again comment in the diagram added, there would be around 20W or so dissipated at 0.075mV difference. So, the small measured offset voltage is not so small after all.

 

The schematic you posted does not show the power amplifier section that has the problem.

The difference in DC voltage at the outputs of the paralleled ICs produces a current in their series output resistors that heats both of them. The amplifier manufacturer probably selected matched ones so the voltage difference and resulting current and heat are tiny.
Here is a schematic from the datasheet with my comments:

Thanks Audioguru again for your input. The schematic I uploaded was the only one I could find for my monitors. Anyway if I understand correctly, the only way to remove or balance the dc offset is by replacing the ic until I find 2 that match. (I really hope not). Is there any other way to sort it out? The ic I removed does still work, I removed the ic that felt like it was getting the hottest, but they do all share the same heatsink, so perhaps I was mistaken. What would be the best way to proceed?

 

It is just possible C10 or C12 could be leaky and upset the bias a little.Try to measure the DC voltage across R19 and R22.
It should be zero. If there is any reading, the cap may be the fault.

 

It is just possible C10 or C12 could be leaky and upset the bias a little.Try to measure the DC voltage across R19 and R22.
It should be zero. If there is any reading, the cap may be the fault.

I'll check that quickly & report back, it would make sense that a faulty component caused the issue as it was working fine to start with. Holding thumbs for a simple solution here.

 

Now I see the paralleled power amps at the bottom left of the huge schematic.
Yes, if C10 or C12 is leaking current then it could cause the DC heating. Replace both with high quality new ones.
R19 and R22 affect the AC gain and if they have different resistances might cause heating when the amplifier is playing high levels.

 

Thanks for all the input. The caps seemed to be fine, but I replaced them anyway. I can't seem to find R22 though.. - sorry found it
.

 

It is a VERY POOR idea to put two modules in parallel, like that. Even worse, it is a DUMB STUNT!!! The simple and valid method is to have them out of phase and use the two outputs bridge-style. That is universay accepted and it works very wel in hundreds of instances, including the manufacturers application notes. How come nobody else saw the major goof in the design, AND CERTAINLY it is a MAJOR GOOF!!! You just do not do it because at east one of the modules will overheat.

 

It is a VERY POOR idea to put two modules in parallel, like that. Even worse, it is a DUMB STUNT!!! The simple and valid method is to have them out of phase and use the two outputs bridge-style. That is universay accepted and it works very wel in hundreds of instances, including the manufacturers application notes. How come nobody else saw the major goof in the design, AND CERTAINLY it is a MAJOR GOOF!!! You just do not do it because at east one of the modules will overheat.

Not really. It's not uncommon to see amps in parallel. The small value .1 ohm resistor in series with the outputs of both amps compensates for imbalances.

 

Not really. It's not uncommon to see amps in parallel. The small value .1 ohm resistor in series with the outputs of both amps compensates for imbalances.

I have not seen it as "common" and besides, it is so very simple to use the modules as a bridge that there is no good reason to do it any other way than as a bridge circuit, and avoid the overheating problem. Just because somebody does it does not make it a smart choice. Dumb things being done in publicwill not make them any less dumb!

 

Well you are certainly entitled to your opinion but others may disagree.

 

Some people use a high power 4 ohm speaker and other people use a high power 8 ohm speaker.
Here are the amplifiers for them:

 

It is a VERY POOR idea to put two modules in parallel, like that. Even worse, it is a DUMB STUNT!!! The simple and valid method is to have them out of phase and use the two outputs bridge-style. That is universay accepted and it works very wel in hundreds of instances, including the manufacturers application notes. How come nobody else saw the major goof in the design, AND CERTAINLY it is a MAJOR GOOF!!! You just do not do it because at east one of the modules will overheat.

Just so you know, this is not my design (I'm nowhere near capable of designing electronics to start with). This is a Behringer studio monitor. They are about 10years old and have worked well up until now and even now only one of them has started acting up. I'm not too sure why you think it's a bad idea / dumb stunt considering they've lasted as long as they have. Also they really sound good too. You are totally entitled to your opinion, however dissing my speakers isn't exactly what I'm after. If you perhaps know of a way to get it back to the functional state it was in for the last 10years, please let me know.

 

Just an update regarding the overheating issue, as a last resort I decided to try higher value ballast resistors. I replaced the 0.1ohm with 0.75ohm 3W. Lo & behold the amp is not overheating anymore. It's still getting warmer than the other speaker, but there is a massive difference. It's no longer going into protect & making the "ticking" noise it was before. Playing it side by side with the other, I cannot tell a difference in volume at all either. So my question now is, am I doing any harm by increasing the value of the resistors?

 

Just so you know, this is not my design (I'm nowhere near capable of designing electronics to start with). This is a Behringer studio monitor. They are about 10years old and have worked well up until now and even now only one of them has started acting up. I'm not too sure why you think it's a bad idea / dumb stunt considering they've lasted as long as they have. Also they really sound good too. You are totally entitled to your opinion, however dissing my speakers isn't exactly what I'm after. If you perhaps know of a way to get it back to the functional state it was in for the last 10years, please let me know.

Just because some company has done things that worked in the past does not mean that they will always get things right. A new manager who is an MBA and NOT an engineer can really cause problems, I have seen that happen.
Not every theory translates to good performance every time, the problems are usually in the details. You may have heard that before. IT IS TRUE!!

 

Just because some company has done things that worked in the past does not mean that they will always get things right. A new manager who is an MBA and NOT an engineer can really cause problems, I have seen that happen.
Not every theory translates to good performance every time, the problems are usually in the details. You may have heard that before. IT IS TRUE!!

I get it, you feel this is a crap design. Judging by how Im struggling to get it working properly, perhaps it is. But right now, I already have these monitors, purchased a long time ago, completely unaware of how they had connected the ic's or anything electronic related. They've served me well up until now and I'd like to fix it. Pretty straight forward.

 

I get it, you feel this is a crap design. Judging by how Im struggling to get it working properly, perhaps it is. But right now, I already have these monitors, purchased a long time ago, completely unaware of how they had connected the ic's or anything electronic related. They've served me well up until now and I'd like to fix it. Pretty straight forward.

Revising the circuit to operate as a bridged amplifier is a possibility, BUT it may be physically difficult because of the layout of the PCB. So if the performance is as good as you require, then I do not suggest making changes. increasing the value of the series resistors is certainly a valid and logical fix that should work well.

 

Revising the circuit to operate as a bridged amplifier is a possibility, BUT it may be physically difficult because of the layout of the PCB. So if the performance is as good as you require, then I do not suggest making changes. increasing the value of the series resistors is certainly a valid and logical fix that should work well.

Thanks MisterBill2 for your help, I'm not planning on modding them coz then I'll have to do both of them. I'd rather just fix the one with the problem. The higher value resistors seem to have worked, although it does still seem to get a bit warmer than the other. My biggest concern was to not potentially do more harm. Thanks again.

 

I went back and looked at the original circuit. There are two resistors, R17 and R20, that must be matched, both shown as 20K ohms. These two set the exact gain, and thus DC offset, of the two modules. In the parallel amplifier circuit posted farther in, the resistors for setting gain on the two devices are shown as 0.1% tolerance, which is not common to find in most audio equipment, and certainly costs a lot more. So, given that you did see quite different voltages, it might be worth the effort to measure those two resistors actual values. That might be the source of the problem.