fender princeton 65

[crowkillr1]

 New to the forum,been lurking finding info for fixes. Been helping a friend at his shop on the electronic side with the guitars and amps. Went to school over 20yrs ago for electronics training.
Now to the problem the amp has no variance on the clean side for the treble and the bass is weak,can turn the pots and the treble just stays loud and the bass is weak from 1 to 10. On the other channel there is very little variance in the treble and bass. The pots aren't even within 10% of their rated value, they arte supposed to be 50k and are only showing 34 to 36k.
Through some research it seems the Princeton line was a little weak for control over the treble and bass. Any thoughts?

[joecool85]

Did you pull the pots out to test them?  They won't test properly in circuit.  If they still test poorly (wrong value as compared to schematic), replace them.  I would also be looking through the capacitors in the tone section and make sure they all look good, if one is disconnected it could exhibit this type of symptom.

[crowkillr1]

 Thank you for the reply. Yes did remove pots from board then checked, have only did a eyeball test to see if any caps were domed or back of board had a burn spot anywhere, before my friend put me onto a more pressing project that needed to be done in 2 days( I hate rush jobs,never turn out well).
Will check the tone section out more throughly. Appreciate the help.

[J M Fahey]

In Fender amps only *real* control is treble.
Bass does not do too much and mid is noticeable only if other two are set very low.
Put all 3 in 0 and open them up to 10 one by one.
That's the *most* you'll get out of them.

[crowkillr1]

 There is no difference in treble if its set at 1 or cranked to 10 it is the same very loud. You should be able to hear a difference but there is none, and yes the bass is weak. The client is a church who also dropped off a Genz Benz bass amp that they say is weak in sound. Which I have to agree after hearing a Peavey we have in the shop.

[phatt]

Check ALL 3 pins on those pots the centre to either end is important as the centre is the moving part and IF it's internally open circuit then nothing will happen.
It is not uncommon for pots to not measure what is stated.
Depends on tolerance specs also.

Re Genzbendy stuff;
Had one a few weeks back, guitar rig.
Claiming 50 Watts. What a laugh you would be lucky to get 10Watts from it.
His main problem was the fancy efx section intermittently dropping out.
I put it down to a very hot day when the problem happened.
Seems those digi things don't like the heat.
switch mode supply with class D power stage or something like that,, but they are very very light.
Saves on freight cost mainly ,, give me a real Amp any day.
Phil.

[crowkillr1]

 Well finally got to get back to the Fender after my friend threw a couple of projects I went through and resoldered the pots and the caps and we have treble control and bass back.

[joecool85]

Well finally got to get back to the Fender after my friend threw a couple of projects I went through and resoldered the pots and the caps and we have treble control and bass back.

Ah, so it was a poor solder joint.  Quite common in cheap Fenders, but I'm surprised it was an issue in a Princeton...unless it's a very well used amp.