I got one subwoofer plate amplifier of a taiwanese company.
It is becoming very hot even at reasonable volume.
I am thinking of reducing the value of R225 connected to Q 211.
or any other better way to keep it cool?
It is becoming very hot even at reasonable volume.
I am thinking of reducing the value of R225 connected to Q 211.
or any other better way to keep it cool?
reducing the value of R225 will increase the Vbe multiplier voltage.
This in turn will increase the quiescent current.
This in turn will increase the quiescent current.
This means i must increase the value to reduce current.
Tried by increasing the heatsink.
It has tip 102/107 pair at the output. This is TO-220 , so very small metal on the device.
this is not
a bad idea but but you have to increase it not reduce it !!!!!!!
it would be wiser to look first how much is the idle as we speak by checking voltage drop in one ( or all ) the emmiter resistors ....
if idle is moving with in reasonable limits then something else is wrong ..... of course a scope will tell you if you low too much then crossover distortion will apear .....
another question is that if the amp gets too warm even with no signal .....also q211 should be attached to the main heatsink ....to be able to compensate temprature and reduce idle ....if loose the amp will get warm
anyway the truth is that before you make any changes the correct thing will be to make sure that amp is working with in specs and then start to look if something is wrong ....
check tha basics first ...then you will see if there is something wrong witha the all thing ...
how much power this amp makes ????? it looks an ok circuit
let us know
a bad idea but but you have to increase it not reduce it !!!!!!!
it would be wiser to look first how much is the idle as we speak by checking voltage drop in one ( or all ) the emmiter resistors ....
if idle is moving with in reasonable limits then something else is wrong ..... of course a scope will tell you if you low too much then crossover distortion will apear .....
another question is that if the amp gets too warm even with no signal .....also q211 should be attached to the main heatsink ....to be able to compensate temprature and reduce idle ....if loose the amp will get warm
anyway the truth is that before you make any changes the correct thing will be to make sure that amp is working with in specs and then start to look if something is wrong ....
check tha basics first ...then you will see if there is something wrong witha the all thing ...
how much power this amp makes ????? it looks an ok circuit
let us know
Hi J,jaya000 said:
that 2ohm and 4ohm spec tells us a lot about how bad this amplifier is.
A good amp will drive the intended reactive load within it's temperature, power and current limits.
This stress driving a reactive load is quite severe.
An easy indicator to see whether the amp is capable of driving moderate, rather than severe, reactive loads is to see how well it drives a resistive load of half the intended impedance.
Your amp is specified as 150W into 4r0 and that equals 24.49Vac into 4r0. However this falls to just 20Vac when delivering 200W into 2ohms.
That voltage drop of -1.76dbV when delivering test current into half impedance tells us that this amp is not designed to even drive a moderate 4ohm reactive load. It might make a decent 6ohm capability amplifier but certainly not capable of driving a severe 4ohm load.
A good amp will deliver better than -1dbV in half load impedance and a very good amp better than -0.6db into half load impedance.
Ohh come on guys, 200W/2r - 150W/4r from 3 pairs of TIP102/107? 
Sry I wouldn't offend anyone but I must state that it's another bowl of rice from Taiwan!
IMHO it's oscillating, try lag compensation in the VAS stage (100pF cap between base and collector of Q204).
Sry I wouldn't offend anyone but I must state that it's another bowl of rice from Taiwan!
IMHO it's oscillating, try lag compensation in the VAS stage (100pF cap between base and collector of Q204).
hi,
b-c caps on the vas will do the job...oscillation can also came from the preamp..use a scope in & out of your amp.
b-c caps on the vas will do the job...oscillation can also came from the preamp..use a scope in & out of your amp.
This a car subwoofer amplifier.
hence i am thinking of reducing the supply voltage because it will be easy to do. Just reduce 1 turn from the inverter transformer output
Or
should i reduce the biasing current & put the lag compensation in the VAS stage (100pF cap between base and collector of Q204)?
hence i am thinking of reducing the supply voltage because it will be easy to do. Just reduce 1 turn from the inverter transformer output
Or
should i reduce the biasing current & put the lag compensation in the VAS stage (100pF cap between base and collector of Q204)?
to locate and ....
face a problem like that .....
IE make amplifier more operable and more safe and stable .....
the things you have to do are :
A) do not jump from one conclusion to the other
B) one step at the time will do better
C) all of the information given above are from real experts and will bring results .
the only thing you have to to do is consider the all very seriouslly and decide what to do .....
for example: i gave you a tip before anything else and before touching anything to see how much is the idle and if amp at no signal allready gets warm ....
thats an indication that either you have ocilation or too much idle
Do you understand any of these terms ???? cause i ve seen no answer to that yet .......
cause in this case this is all academic .....
for example if idle is too much ( for any reason,fault or design error) a capacitor between b-c in the vas stage will do absolutely nothing .....
and visa versa ...
a solution to your problem will not coming by messing up with the power supply also a solution for your problem is not to come up magikway like any of the people of this forum will tell you "add a resistor there and you are done "
usually is a number of things and a certain procedure to bring results
best regards sakis
face a problem like that .....
IE make amplifier more operable and more safe and stable .....
the things you have to do are :
A) do not jump from one conclusion to the other
B) one step at the time will do better
C) all of the information given above are from real experts and will bring results .
the only thing you have to to do is consider the all very seriouslly and decide what to do .....
for example: i gave you a tip before anything else and before touching anything to see how much is the idle and if amp at no signal allready gets warm ....
thats an indication that either you have ocilation or too much idle
Do you understand any of these terms ???? cause i ve seen no answer to that yet .......
cause in this case this is all academic .....
for example if idle is too much ( for any reason,fault or design error) a capacitor between b-c in the vas stage will do absolutely nothing .....
and visa versa ...
a solution to your problem will not coming by messing up with the power supply also a solution for your problem is not to come up magikway like any of the people of this forum will tell you "add a resistor there and you are done "
usually is a number of things and a certain procedure to bring results
best regards sakis
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