Starsound 4075 no power need help

[Perry Babin]

That's it. Did you pull it to see if the amp would power up?

 

[Aqeeb127]

Sorry mr babin i see that transistor is connected to 7 and 2

 

[Aqeeb127]

I will let you know

 

[Aqeeb127]

Mr babin you are a genius in these things its turning on now so what is the cause of that

 

[Perry Babin]

Does the amp produce clean audio without excessive DC and without excessive current draw?

Play all channels into a load while watching for distortion at the speaker terminals.

 

[Aqeeb127]

Ok will check it out

 

[Aqeeb127]

I dont got a oscilloscope but i will test and hear what it sounds like on music

 

[Aqeeb127]

Mr babin its seems that the ones i circled is smoking up as soon as i switch the cross over circuit repeatedly and only those gets hot

 

[Aqeeb127]

The dc voltages on the amp without any load and gains closed and no input signal were ch1:200mv ch2:8mv ch3:12mv and ch4:1.2mv

 

[Perry Babin]

Is the current draw more than about 1 amp from the 12v power supply?

For all channels, measure the DC voltage from emitter leg to emitter leg of the output transistors. To avoid overheating, connect the meter, power up just long enough to measure, power down, move to the next channel.

 

[Aqeeb127]

Yes the power is more than one amp

 

[Aqeeb127]

And mr babin what do you mean by emitter to emitter

 

[Perry Babin]

From the emitter leg of one output transistor to the emitter leg of the other output transistor of the same channel.

How much more than 1 amp?

 

[Aqeeb127]

Ok i understand now

 

[Aqeeb127]

The two which heats up emitter to emitter is 130-180mv
And the other two channels are like 2mv max

 

[Perry Babin]

I don't know if this is a problem but it's something that I'd do before you go any farther.

At the point where the emitter resistors are soldered into the board, there are solder connections on the top and bottom of the board. For this type of board (made of CEM, not fiberglass), this can cause various problems.

For ALL components soldered where there is solder on top AND bottom of the board, you need to completely desolder those points, scrape the leads on the components and then re-solder.

Do this any place on the board where you have solder top and bottom on any component lead.

 

[Aqeeb127]

Ok i will do that

 

[Aqeeb127]

Mr babin the audio on the amp has too much distortion

 

[Aqeeb127]

Could it be the biasing transistor because that the one which is heating up