'76 SFPR Way too much Bass

[bluescb]

Howdy all. I found this '76 SFPR on ebay a few years ago. I can't run the bass pot over 3 at any volume or my Weber C12N starts fartin'. The bass pot is WAY sensitive too. 2.9 - 3.0 - OK... 3.1 and it flaps. The mids and upper tone is REALLY sweet but the bass is...well...wierd. I just put in new 6V6EH - I biased them to run at 14.2W cause it breaks up really nice. I am having trouble finding a Can Filter cap so I haven't replaced it yet. I am playing a tele with Lollars (*great* pups) and an an old '68 SG with Holmes pups(*great* pups too). Of course, the SG farts worse. Is this normal for SFPR? If not, what should I look for?
Thanks

[jjasilli]

Cap cans are available at www.torresengineering.com and Antique Electronics: www.tubesandmore.com

I used the CE 40 20 20 20 can from Antiques.

Cap & resistor values may have drifted a lot. Replacing the filter caps and all the other electrolytic caps in the amp may help.

I haven't heard of issues with the WEber speaker, but did have problems with the Jensen P12N re-issue. My SF Princeton now has an Eminence Red White & Blues. Rated at 125 watts, it does not crap out, sounds great for this application and is generally well regarded.

[hasserl]

IMO your description sound normal for Fender amps. Around 3 is the upper limit for the Bass control in Fender amps IME. I've got a PR, an SR and a Bassman, and I never turn the Bass up past 3 on any of them for the same reason you described above. My PR is also fitted with a Weber 12F150 type speaker, sounds great, but you have to keep the Bass down to 3 or below.

There are some things you can do to reduce the amount of bass response to tame this a bit, if you want to do some mods to it.

[mbratch]

Double check the pot and make sure it still matches the schematic. I had a similar issue with the bass control on my BFDR and upon inspection found it was replaced with a different pot with the wrong taper. I replaced it with a spec pot and it worked much better.

[phsyconoodler]

I just built a couple of Princeton Reverbs and have not noticed the bass fart you are referring to.The speaker is a big factor here.I used a 12" C12N Jensen in both builds.
I did however find there was not enough treble.The addition of a 47pf bright cap cured that.
Because the princeton has a 10" speaker i don't find it big enough to cause bass farts.When you switch to a 12" it should be worse,but it's not in my limited experience.

[1radicalron]

Definitly check the Bass Pot. Sounds like it no longer has a taper to it. Filter caps will definitly help as well. Try a Eminence Rajin Cajun or Legend 105 as a 10" speaker replacement. These speakers handle Bass extremely well. = They also sound Killer as a Fender replacement speaker! + 1 - for the Red, White and Blues - if you have a 12" Baffle.
Bump up the Output Tranny for a bit more Clean headroom.

and SG with T Holmes = Whoa!

[bluescb]

Thanks for all the help!! I will definitely check the POT as it is *old* :)

Yea, I do love my SG / Holmes. You should hear it thru my PR (as long as the bass is way down!). Talk about feel! Man. Jammed with it last night along with a drummer, bass and a 100W Plexi reissue guitarist. Of course the 100Watter had to turn down, but he kept lookin at my little PR while I was soloin'... you know the look...."Damn that little thing sounds good" look! HAHA gotta love it

Thanks again

[jjasilli]

I just built a couple of Princeton Reverbs and . . . did however find there was not enough treble.The addition of a 47pf bright cap cured that.

Psychonoodler: My SF Princeton (non-reverb) is a bit dark too. Where did you put the 47pF cap, across the vol pot? Is it switched?