Newly built ESP P03 (not 3A) - rail to rail oscillation - suggestions?

Status
Not open for further replies.
Hi,

I built Rod Elliott's P03 (not P3A) 60 watt power amplifier.

I have built it on stripboard, which I know is not ideal, but I have checked and re-checked my board layout, and yet I have a weird problem. (I have only built one channel so far, in case of problems like this!)

I used the second schematic here:

High Quality 60 Watt Power Amplifier

At first the amplifier appeared to be playing music, but after a while would latch up to one of the rails with a loud 'hum' and stop working. I decided to change out the two "long-tailed pair" transistors on the input. Note that, although I'm not sure if this makes a big difference or not, I am using BC556s here instead of BC559s - however, until I did this the amp was indeed working, so I don't know if this is the cause of the following problem in itself.

Now, whatever I've done, the amp goes into full rail-to-rail oscillation at about 100khz as soon as it's switched on.

Photo from scope taken at speaker output: (10v/div, 5us/div)

http://i.imgur.com/Uq4sz.jpg

I have made a post over at the ESP forums and one of the guys there has given me some helpful suggestions which I will try tonight, but I just thought I'd put it to you guys too as I know some of you have built this amp and might have some ideas about what could be causing this to happen!

Cheers,

R
 
Status
Not open for further replies.