P101 amp troubleshooting

[EspenE]

I was careless, and accidentally shorted the outputs of one channel in my P101. Althought I have built this amp myself, I am a total newbie when it comes to troubleshooting. Visibly, the PCB and components did seem OK: I couldn't see any burnt components. My P101 is the high-power version. My powersupply voltages are +/- 72V. The faulty channel now measures -50V on the speaker output.

I changed the output mosfets, and tested the board on a +/- 15V supply with 100 ohm safety resistors. The output still measures about -10V: problably indicating that the problem persists. I then replaced all semicinductors: still the same result.

I even took the trouble to build a completely new board, with all new components. Now the new board also measures -10V on the pitput (with the +/- 15V supply).

I am on my wit's end trying to figure this out. I have built two other P101 stereo amplifiers which both works (and sound) very good. There probably is a very simple cause for this, but I can't figure it out.

Any suggestions on how I should proceed with this? All advice welcome.

Thanks, Espen

[jaycee]

What components did you use? Be sure that you did not install eg the VAS transistor backward.

[EspenE]

Originally Posted by jaycee

What components did you use? Be sure that you did not install eg the VAS transistor backward.

Yeah - I've checked this transistor lots of times

I use Exicon EC10N20/EC10P20 output devices. The rest is fairly "standard".

Thanks, Espen

[nigelwright7557]

Originally Posted by EspenE

I was careless,

Any suggestions on how I should proceed with this? All advice welcome.

Thanks, Espen

Could +/-15 isnt enough for the amp to stabilse properly.

What I do is leave off the output transistors and feedback the output back into the LTP and make sure the driver is working right first. This can be done with full volts as it is highly unlikely the driver has anything that will short out the supply.
Once i am sure the drievr is working properly i turn ther bias down to zero and connect one pair of output transistors.
Sounds like a reall faff but it always works for me.