Ok thanks sorry for the misunderstanding.
I just tried that but I still have the same distortion linked like that...

With the amp switched on and volume on 0 I read 0.004-0.005 V.

I tested the main power amp input / pre amp out and the distortion is gone so can use the speaker as a second amp.
It also works with the pre amp out to my mixer and just the normal input. Also the headphone output works with main power amp in (doesn't work with main input).

With the device plugged in but not switched on : 0.3 mA
Or do you mean switched on but both volumes on 0?

It doesn't have a Send / Return only has Input, Footswitch, Pre-Amp Out, Power Amp In and Headphones

Just checked the speaker connection with volume on 10 on guitar and amp I got minimum 0.00 V (with guitar on voume 0) and a maximum of 0.88 V (with guitar volume on 10) depending how hard I hit the strings it goes between 0.33 and 0.75 +/-

Thanks for all the response so far!

Quote from: Roly on May 18, 2015, 01:35:33 PM
Measure and post the DC voltage at the speaker connection.  This should be no more than +/-0.25V.  Anything more than this, leave the speaker disconnected.

Wild early guess; it sounds like you might have AC ripple on one of your supplies (notice something is beating with your guitar notes), and a typical cause is a cracked solder joint where the big power supply capacitors fit to the board.

Another stock test if it has Fx Send and Fx Return, or Pre Out/Main In, is to jumper these with a known good lead and see if that makes any difference.

I checked the pre-amp out with the speaker disconnected, put it in my mixer and your right, the distortion's gone on both on clean and gain channel through the pre-amp out.. So does this mean anything in particular?

Also going to check the voltage, my friend is on his way with a multimeter so will post within an hour, you think it is worth to get the circuit board out of the frame to have a look at the joints on it's bottomside?

Thanks

Hi,

i'm totally new to amp repairs and just did some googling lately to try and locate the problem I have with
my Princeton Solid State Amp. (Fender Princeton 112, Tupe: PR226)
The amp still works but has a certain type of distortion on it as soon as you raise
the volume past 1 on the clean channel and as immediately on the drive channel.

The troubleshooting I did so far was to get the head of and have a quick look to see if I could see some obvious errors, I took some pictures while it was open:
http://imgur.com/a/zKp7T#0

After that I disconnected the speaker and reverb to see if that caused any problems.
Went with the headphone in the output only with the head and still had the same distortions but not as quick as on the speaker.

I recorded the distortion with my audio interface:
http://yourlisten.com/blueboo/amp-troubleshooting

Was wondering if there's any things that you think I should test / have a look at.
A friend of mine has a basic multimeter and knows how to work them so could measure some things up..

Also found a schematic for the amp online but the resoulution is quite low:
http://elektrotanya.com/fender_princeton-112-plus_sch.pdf/download.html

Hopefully this is the right place for this issue.

Thanks in advance,

Michiel