Hi all. Taken apart a carlsbro portable mixer amp T150 pa
The power supply has gone down.
tested a few parts & replaced faulty ones. 2x fqp13n50's 1k resistor & 4007 diode
but it still won't power up ? all i get is the red led. not sure if its worth trying..
So going to replace. But the input to the amp says
32v+ grd 32v- the power supply i think is a switch mode ac to dc then through a
few fpq13n50 & isolator...
But can i put a 32v dc transformer onto the amp & is the ground in the middle of the 3 pins
32v+ gnd 32v- is this earth/case sorry but i can get a transformer but it's just + & -
pressume is 32v+ 32v- ...This will let me know if the amp is OK
If not then thinking of changing the amp & power supply
But will need to find out what voltage the mixer section runs on.
it is connected with a ribbon type cable. thin it's 5v as there is a 7805 reg & 7915 reg
there is no schematics for this unit so its a bit of a pain for me.
I'm not the best at working things like this out. any help would be great..
please view pictures if it helps.
chears jimbo

 

If you want to replace the psu with a transformer, you will need to put a Bridge Rectifier on the output of the centre tapped transformer and two smoothing capacitors about 2200uF, from each output to ground, then you can feed that into the amplifier, the transformer should be a 24-0-24, then it will give 32V after smoothing.

The two regulators are +5V and - 15V.

 

If you want to replace the psu with a transformer, you will need to put a Bridge Rectifier on the output of the centre tapped transformer and two smoothing capacitors about 2200uF, from each output to ground, then you can feed that into the amplifier, the transformer should be a 24-0-24, then it will give 32V after smoothing.

The two regulators are +5V and - 15V.

Thanks..when i have the 32v how do i get 32+ gnd 32- from the bridge rect... ac in from tranny then from bridge/rec DC + & - out
where do i take the ground from ? this is where I get lost

 

OK Think i sorted it...the centre tap is our ground with 2 ac wires from tranny
when i put this to the caps link in centre my ground going to amp with + & - 32v comes from here 0v

 

Hi all. Taken apart a carlsbro portable mixer amp T150 pa
The power supply has gone down.
tested a few parts & replaced faulty ones. 2x fqp13n50's 1k resistor & 4007 diode
but it still won't power up ? all i get is the red led. not sure if its worth trying..
So going to replace. But the input to the amp says
32v+ grd 32v- the power supply i think is a switch mode ac to dc then through a
few fpq13n50 & isolator...
But can i put a 32v dc transformer onto the amp & is the ground in the middle of the 3 pins
32v+ gnd 32v- is this earth/case sorry but i can get a transformer but it's just + & -
pressume is 32v+ 32v- ...This will let me know if the amp is OK
If not then thinking of changing the amp & power supply
But will need to find out what voltage the mixer section runs on.
it is connected with a ribbon type cable. thin it's 5v as there is a 7805 reg & 7915 reg
there is no schematics for this unit so its a bit of a pain for me.
I'm not the best at working things like this out. any help would be great..
please view pictures if it helps.
chears jimbo

A pair of 13A 500V MOSFETS sounds like a half-bridge SMPSU. The voltage rating would be at least 600V for a flyback type.

if you have a scope - fire it up with the MOSFETs removed and look at the squarewave that would be applied to the MOSFET gates - supply it with an isolating transformer or loud bang ensues. The PWM drive should be going flat out because there's no feedback telling it to throttle back.

If possible; feed the DC outputs with variable supplies and see if you can influence the PWM duty cycle. Failure to do that indicates a feedback failure - the PWM goes flat out and saturates the core.

Whatever primary side circuitry, needs a source of power for itself. Usually this comes from an extra winding on the chopper transformer - but it needs a mains derived feed to get the ball rolling. start up resistors are common in failure to start (no explosions). Half bridge usually has the resistor across one of the MOSFETs to unbalance it - just enough to stir signs of life in the primary side Vcc winding.

The primary side Vcc requires a reservoir electrolytic, that one causes as much trouble as the others put together.

ripple permitted by failing output filter electrolytics can cause trouble for the PWM control, the voltage sampling divider resistors can drift. There will usually be an isolation opto coupler and associated components which need checking before letting the magic smoke out of all the new parts you fitted.

 

OK Think i sorted it...the centre tap is our ground with 2 ac wires from tranny
when i put this to the caps link in centre my ground going to amp with + & - 32v comes from here 0v

Like this....

 

Like this....

View attachment 136735

Yes that's it just made a schem of it. Sorted. Thanks dodgydave.
I'm a bit slow? just cant get my brain in gear..