Another Fender Frontman 25r mod

Another modification that you can do is a bit trickier and its meant for someone who has a bit more experience in soldering and who has more requirements in terms of sound.

That mod will clean up the sound of this amp and makes it less noisy.
It makes the clean channel really crisp and sparkly.
The drive channel will be much more clear and less muddy.

In theory its simple: Change the 5 pre-amp chips on the circuit board to a low-noise, hi-fidelity OPA2134 chips.

In reality its a bit trickier.

So if you're brave enough lets start.

I assume you've already acquired 5 of the aforementioned chips.

Now its time to separate the chassis from the rest of the amp.
Undo the speaker connection and remove 4 black screws on the top of the amp that are holding the chassis.
Gently take the chassis out from the cabinet.
Now you've got the chassis out and can see all the guts inside.
You need to get underneath the circuit board. But theres some wires from the circuit board to the power socket, switch and transformer.
You've got two options really:
1) Undo all the connections to get the circuit board out.
2) Commence the modification with all the connections intact.

I went with the option nr.2 because first of all the wires can't be easily unplugged and second, you need to put them back as they were and theres quite a lot of them.
When the wires are intact you can still access the necessary parts. It just requires a bit of acrobatic soldering :)

Lets carry on, shall we ?

Pull out all the control knobs on the front panel, remove the nuts and washers holding them in place. Remove that little screw holding the aux input in place.       
Underneath the chassis remove the two screws that are holding the heat sink in in place.
Now you can start working on the circuit board. Undo the 2 wires coming from reverb tank (remember which way they were)
Remove the screws holding the circuit board in place and very gently pull the circuit board so all the pot shafts are coming out from their mounting holes.
You might have to fiddle around with it for a while, but be patient and extremely careful.
Eventually you should be able to lift the circuit board up and see the other side of it.

If you've managed to come this far, then congratulations ! Hardest part is actually over.

Now you can de-solder the old chips and solder in the new ones.
Make sure you solder them in right way around. Theres a little mark on the chips and a little marking on the circuit board. If you pay attention you cant go wrong.

After you've done your soldering, assemble it all back together.

Plug it in and prepare to be amazed !
 
 Thanks to David Moore from www.wholenote.com