fender princeton amp. ?????????

[T-bone]

howdy do people, this princeton chorus amp sounds reallyt bottom endy, are they naturally that way? if you turn the bass up over 4 it tends to vibrate a lot ( the speakers i mean ) i have resolderd the main caps, tested resistors, made sure all screws are tight, and fixed the chorus channel ( bad op amp ) can any one please tell me what i might try?

[guitician]

Look at the values of the coupling capacitors. They may have put in the wrong value somewhere. The most common values are .01, .02 and .047. Bass amps will use .1, .22 and .47 if you see any like them, I would start there.

[T-bone]

!

cheers mate, all caps are as they should be, the only other thing ive done is ive swaped the effect input jacks with the guitar input jacks as they were pretty scratchy. smoother input but no sound differance, any thing i should look for with the speakers?

[guitician]

Well, if the speakers were replaced with some other type, then they may be "Non-Fender" sounding. All paper cone with a rolled edge are what gets that "Fender" sound and Alnico will have a looser bass than Ceramic.

[T-bone]

they acually look like the same reissue speakers i got in my pro reverb a few years back, it may be they are just worn out! what if i bridge both speakers from the chorus output, dispersing the signal over both speakers, perhaps lowering the bass response and stopping the rumble? any thoughts? cheers t-bone x

[guitician]

I would run some speaker wire from the Pro to the pair in the Princeton to diagnose the speakers.

How do the controls on the amp work? It maybe that the bass one has opened up. I've recently found that on an '87 SS Marshall combo that wasnt working right. I ended up removing all the pots and opening them to clean the oxidation off the resistive element. After putting them back in, the amp was fine. Since yours is of that same vintage, it may be your problem too.

[T-bone]

cheers, will try, any other thoughts on testing power source, im reading 20milliamps @ each speaker output. T_bone x

[guitician]

cheers, will try, any other thoughts on testing power source, im reading 20milliamps @ each speaker output. T_bone x

What are you measuring current for? And how are you loading the output? You want to be careful with SS outputs too, if you accidentally ground a lead while its powered up, it could blow an output transistor.

[T-bone]

was told to mesure dc offset for possible power source problems? make sense? x

[guitician]

was told to mesure dc offset for possible power source problems? make sense? x

Yeah, if you measure DC on the outputs, thats no good. A few millivolts or so is fine.

[T-bone]

too much?>?

so 20 milliamps too much??>?? Bone x

[guitician]

so 20 milliamps too much??>?? Bone x

I think you should stick to the basics of looking for physical problems that arise from aging componants. Too much bass would'nt be caused by DC offset problems, but distorted bass would.

[T-bone]

cool, all solder joints look good, ive already replaced a bad ic from the chorus chanell, works fine now, still getting a rumble as the bass reaches 5-6???? ive cleaned all pots, and replaced all guitar input jacks, any thing else you mat think to try??? id appreciate it, T-bone. x

[guitician]

Is this "Rumble" something the amp is doing by itself? Will it do it without the guitar plugged in? Does it have reverb? Can the reverb be feeding back?

[pantoum]

I have owned a couple of Princeton Chorus amps and I can attest that they all have an unusual amount of bottom end. That's just how they were made. If you are playing the clean channel I wouldn't take the bass past 3. If you are using the dirty channel you can bring the bass up significantly, but I don't think you can dime it without getting unfavorable results.

Even with this quirk, the PC is still a great sounding amp. I don't think I've read about many people modding these amps and I would be interested to see what could be done. Good Luck!