Hi
A have just recently built a soundbar from two MarkAudio CHR-70 speakers and two CAT A-803 plate amplifiers.
One of the plate amps are getting so hot that i can not place my hands on the cooling plates.
What could cause this?
The same tings happens when there is no load on the amplifiers.
A have just recently built a soundbar from two MarkAudio CHR-70 speakers and two CAT A-803 plate amplifiers.
One of the plate amps are getting so hot that i can not place my hands on the cooling plates.
What could cause this?
The same tings happens when there is no load on the amplifiers.
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An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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Actually, now that both amplifiers are mounted in the box, the get equally hot.
I do not now anything about the CAT amplifiers, and can not find anything on the internet.
So Any information about them would also be much apreciated.
I do not now anything about the CAT amplifiers, and can not find anything on the internet.
So Any information about them would also be much apreciated.
Can you wind the quiescent current down?
Also it would help if the cooling fins were vertical.
Any chance of a schematic to point you in the right direction?
Also it would help if the cooling fins were vertical.
Any chance of a schematic to point you in the right direction?
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Hi John
I can not find any information about the amplifiers, so i am a bit lost of where to begin.
Usualy there is some potentiometers to regulate the Bias, right?
I am thinking that maybee they are class A, but the get realy hot. The play fine thoug.
Do you have any sugestions to where i maybee can find some scematics?
I can not find any information about the amplifiers, so i am a bit lost of where to begin.
Usualy there is some potentiometers to regulate the Bias, right?
I am thinking that maybee they are class A, but the get realy hot. The play fine thoug.
Do you have any sugestions to where i maybee can find some scematics?
I have had a look around and nothing anywhere. Are there any manufacturers marks on the PCB? Shot in the dark I know.
If you could recognise the bias circuit you could easily change a resistor value to bring the current down to a reasonable level.
Looking at the photo, I would think it is Chinese made and not likely to be class A.
Of course, if there is DC on the speaker, that will cause heat!
If you could recognise the bias circuit you could easily change a resistor value to bring the current down to a reasonable level.
Looking at the photo, I would think it is Chinese made and not likely to be class A.
Of course, if there is DC on the speaker, that will cause heat!
Do you have an advice on how to measure if there is DC on the speakers?
Can i do this without un soldering the speakers, or is it measured without load?
I will have a look at the pcb's, and ser if i can find out anything about the amplifiers that way.
Can i do this without un soldering the speakers, or is it measured without load?
I will have a look at the pcb's, and ser if i can find out anything about the amplifiers that way.
To be honest those amp modules look dreadful. It wouldn't surprise me if they either have a stupidly high bias current set, theyre oscillating, or both.
For this particular application i'd suggest some LM3886 chip amps.
For this particular application i'd suggest some LM3886 chip amps.
Oh and if you had DC on your speakers, you would know it as you would hear a loud POP from them when you switch it on, and the cones would be sticking out. If it was excessively bad, you'd have burned the speakers out.
Getting hot with no load sounds like oscillation to me.
Getting hot with no load sounds like oscillation to me.
I have measured, and there is no DC on the speakers.
But i have noticed that the amps begin to distort when played a litle loud, and this distortion continues when the volume is turned down, and only stops when the amplifiers are turned off, and then on again.
So this is probably oscilation?
I have decided to disgard these amplifiers, and try something else.
I have searched the forum, and i find the lm3886 very interesting. From the amplifiers i have now i have the backplate, heat sink and two transformers, so this could probably be reused. If the transformers are within the voldtage rating, could these be used instead of the dual wound transformers that are sugested for the lm3886 powersuply?
They are arround180va each.
And thank you for the help so far.
But i have noticed that the amps begin to distort when played a litle loud, and this distortion continues when the volume is turned down, and only stops when the amplifiers are turned off, and then on again.
So this is probably oscilation?
I have decided to disgard these amplifiers, and try something else.
I have searched the forum, and i find the lm3886 very interesting. From the amplifiers i have now i have the backplate, heat sink and two transformers, so this could probably be reused. If the transformers are within the voldtage rating, could these be used instead of the dual wound transformers that are sugested for the lm3886 powersuply?
They are arround180va each.
And thank you for the help so far.
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What is the secondary voltage of the transformers you have? I'd be surprised if they aren't at least centre tapped
I have just checked, and you are right, the transformers are center taped. I will measure the secondary voltage one of these days when i get back to the workshop.
I have had a look around, and there are many kits to choose from. Can you recomend any to me?
I find this kit interesting Douk Audio LM3886TF Amplifier Board + Rectifier Filter Power PSU DIY Kit / 1Set | eBay and then run it in dual mono, or the dual mono from chipamp.
I have had a look around, and there are many kits to choose from. Can you recomend any to me?
I find this kit interesting Douk Audio LM3886TF Amplifier Board + Rectifier Filter Power PSU DIY Kit / 1Set | eBay and then run it in dual mono, or the dual mono from chipamp.
No links as such. The first one I made was a simple smallish PCB just intended to test the chips themselves. Later on I designed a "one PCB" stereo amp with speaker protection, that I built into the chassis of an otherwise-dead Cambridge Audio A1Mk3SE amplifier
There are plenty of good kits out there. The one you linked to looks OK to me. You may find better recommendations in the "Chip Amps" section of this forum.
There are plenty of good kits out there. The one you linked to looks OK to me. You may find better recommendations in the "Chip Amps" section of this forum.
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