ESP P3A problems

[cantabile]

I found a PCB layout by r!sc! for ESP P3A in this forum.

http://www.diyaudio.com/forums/showt...227#post735227

Thanks a lot for the posting.

I built some chip amps and they work good.
And this is my first try of solid state amp DIY.

I'm doing with universal PCBs.
I made 1 channel and tested with +12V, -12V rails.

- Output offset DC is about 50mV.
- Both MJ15024 and 15025 are just a little warm.
- I set the bias current around 75mA(by setting the voltage
drop across the two 0.33 ohm resistors is about 50mV).
- +V and -V are about +15V and -15V
- Sounds good.

No problem until now with that channel.
I made one more channel and have some problems.

- Output offset DC is about -3.4V.
- MJ15024 is getting hot in a few minutes. But 15025 is cold.
- I cannot set the voltage drop across the two 0.33 ohm resistors
below 240mV with the VR.
- +V and -V are about +15V and -14V
- Sounds not bad. No hum.

I checked over and over and rechecked.
And I cannot find any problems like short circuits, open circuits.

Could you please give me some ideas or locate the point
for solving this problems?

[cantabile]

I got pictures of the 2 channels.
This is the channel of no problem(1/2).

[cantabile]

This is the channel of no problem(2/2).

[cantabile]

This is the channel with problems I mentioned(1/2).

[cantabile]

This is the channel with problems I mentioned(2/2).

I made this channel with the mirrored layout.
So, you can see the change of direction with BC546s and BD140.

Instead of changing directions, I changed some wiring paths for
MJE15032, MJE15033.

[cantabile]

In the picture, right channel is with no problem.
Left channel is with problems.

[sachserjuris]

Hello

A good design is the Nashville NA 2200 power amp. It´s work with a +20/-20 V to +65/-65 V. In the past, I built the ESP amp but it´s don´t work.

Sandro

[jaycee]

It works just fine when built correctly.

The non-working amplifier is probably oscillating. You need to keep the wires to the output transistors as short as you can. The P3A uses a CFP output stage which will oscillate if not used carefully.

Why did you mirror the layout ? Isn't it possible that you have made an error when doing this ? Why not build your second channel as an exact copy of the working one ?

[gmphadte]

If a pcb is mirrored, then the 3 lead devices called transistors will have to be corrected while assembling
or u will have to buy the mirror copy of the transistor LOL!!!

Gajanan phadte

[cantabile]

After inspecting the voltages of all the points
and changing the parts one by one, I found that
Q1(bc546a) has some problem.

By changing Q1, all the problems had gone.
So, I think that mirroring the layout gives no problem.

Output Offset V = about 10mV
Bias Current = set around 70mA

I'm testing and enjoying the 2 channels now.
Thank you so much.