Fender deluxe 112 plus repair

[sambo45]

Hi, my first post here..
I'm trying to repair a fender 112 deluxe. The power transistors Q1,2,10,11 keep blowing as well as the fuse. The amp will power up for approximately a minute before this happens.
I've taken the powers transistors out of the board and it lasts over 10mins without the fuse blowing.

Link to schematic: http://www.electronicstudio.net/au-schem-fender.html
Thanks in advance for any ideas of what to have a look at next.
Sam

[DrGonz78]

I'm trying to repair a fender 112 deluxe. The power transistors Q1,2,10,11 keep blowing as well as the fuse. The amp will power up for approximately a minute before this happens.
I've taken the powers transistors out of the board and it lasts over 10mins without the fuse blowing.

First off research light bulb limiter and build one. http://www.ssguitar.com/index.php?topic=2093.0

We don't want to keep blowing parts and fuses. The light bulb limiter will allow you to start checking voltages and troubleshoot the amp without continually blowing fuses. Possibly we have a bad Q8 or Q9 or a power supply problem, although it can be many other issues. So, build light bulb limiter and then we can get started testing for problems. Just remember every time you let the amp run, without a light bulb limiter, and it blows components it is putting stress on the circuits. This can cause other new problems in the amp and make the repair even harder.

[Roly]

Welcome sambo45.


First up, an essential service tool for s.s. amps;

http://www.ssguitar.com/index.php?topic=2093.0

Disconnect the speaker and leave it disconnected until the repair is complete.

"112 deluxe" cct; Q1 and Q2 I can see, but not Q10 and Q11 - please link to the exact circuit for your amp.

[DrGonz78]

The "plus" makes a big difference for referencing the correct schematic.