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Thread: Help with Fender Princeton?

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    Help with Fender Princeton?

    Hello all,

    Great looking forum. I'm hoping to get some help with a Fender Princeton amp I stumbled upon.

    I haven't owned an amp of this vintage before so I'm not really up to speed on its value or how to proceed with it. I would like to keep it and play it for years. Despite the cosmetic issues it works fine and sounds amazing. I've attached some photos for reference. The chassis number is A01111.

    Safety-wise, I'm aware it is recommended to replace the two-prong plug. I've heard of the death cap but do not know what or where that is? I haven't opened the amp up but assume it will need to be recapped. How dangerous is it to play this amp as is?

    In terms of cosmetics, should I leave it as is? The grill cloth could use a cleaning. The tolex is hanging on the bottom. Should I try to re-glue it? I respect old things and don't want to mess up something that is collectible.

    Any help or comments would be greatly appreciated. Thanks in advance.



    Last edited by Moxsam; 03-26-2022 at 08:35 PM.

  2. #2
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Your specimen is a pre-CBS model made in November of 1964. Likely it's due for some servicing and maintenance. A grounded 3-conductor power cable and death-cap removal are musts. You'll find the death cap mounted at the rear wall of the chassis, with one lead connected to the power switch. It's a Blue Molded type, similar to the tone caps found on the main circuit board. The filter-cap can should also be replaced -- it's the silver cylinder mounted vertically on the chassis, adjacent to the power transformer. The bias cap should also be replaced, along with the power-rail resistors on the main board. Cosmetically, I would remove the speaker then detach the baffle board from the cabinet and spray the grill cloth with some Windex. Gently wipe it off with a soft rag and repeat as necessary to restore its luster. The bottom piece of Tolex is toast and would best be replaced. If you wish to keep the amp all original, DO NOT affix a Fender logo to the baffle board. It never had one.
    "When injustice becomes law then rebellion becomes duty."

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    Forum Member DanTheBluesMan's Avatar
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    Re: Help with Fender Princeton?

    As for value, today I saw silver face Princeton Reverbs, '68-'69 and nearly all of them were over 3 grand. Black faces are even more desirable.

    I bet that amp could sell in a New York minute at 2 grand, even in its present condition. Clean ones are 4 to 5 grand now.
    "Live and learn and flip the burns"

  4. #4
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by DanTheBluesMan View Post
    As for value, today I saw silver face Princeton Reverbs, '68-'69 and nearly all of them were over 3 grand. Black faces are even more desirable.

    I bet that amp could sell in a New York minute at 2 grand, even in its present condition. Clean ones are 4 to 5 grand now.
    It's not a Princeton Reverb.
    "When injustice becomes law then rebellion becomes duty."

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    Re: Help with Fender Princeton?

    1964 Princeton, great!

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    Forum Member Michael Smith's Avatar
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    Re: Help with Fender Princeton?

    When I was cleaning the grill cloth on my Super Reverb last year, I used a product called "Oxygen Power". I applied it in small sections at a time with a soft toothbrush and then used a rolled up damp cloth to roll over the surface of the grill cloth, rinsing out the cloth frequently until it rinsed clear. I then pointed a room fan at the section I just worked on to dry it out. In retrospect I should have removed the speakers and the baffle board. The job would have gone quicker, but I wasn't in a hurry.

    As for re-fastening loose tolex, I use wood glue, and then masking tape to hold it down until it dries.

    Here is a photo of the grill cloth cleaning half way thru. It had a LOT of nicotine stains, the rolled up cloth I used to remove the cleaning product rinsed out a dark yellow on the first couple of passes. I also used the same product and a soft toothbrush to clean the tolex.

    "When You're Riding Down the Highway at Night, And You're Feeling that Wild Turkey's Bite" ZZ Top

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    Forum Member DanTheBluesMan's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by phantomman View Post
    It's not a Princeton Reverb.
    D'oh. Usually I'm the one who catches that.
    "Live and learn and flip the burns"

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    Forum Member DanTheBluesMan's Avatar
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    Re: Help with Fender Princeton?

    looking again, the non-reverb Princeton are about 1000 less than the reverb models, but still pretty dang pricey.

    Still, that amp is a good project. Good luck and take pics.

    My '69 NR is worth almost 3 times what I bought it for 10 years ago, how long that market will last who knows.
    "Live and learn and flip the burns"

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    Re: Help with Fender Princeton?

    I'll have to try the "Oxygen Power", I've had good luck using Windex, I soak the cloth while vacuuming just below the spray.
    Grill cloth isn't really cloth, so the stain is not absorbed into the fibre, just coats it.

  10. #10
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by Bill Moore View Post
    Grill cloth isn't really cloth, so the stain is not absorbed into the fibre, just coats it.
    An exception is the silverface cloth introduced with the amps of model-year 1968. That weave (silver/black/light blue) is unique in that the light-blue filament is actually a 50/50 blend of rayon and cotton. As such, it is susceptible to absorbing liquids and will exhibit traditional stains as occurs with other woven textiles. Likewise the orange-stripe grill cloth of the mid-70's can also discolor in similar fashion. A new weave was phased in beginning in early 1969, consisting of silver/white/metallic turquoise filaments. The metallic turquoise is composed of an acetate-based material and is (like the balance of that cloth) resistant to liquids and the permeating stains they often cause.
    "When injustice becomes law then rebellion becomes duty."

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    Forum Member DanTheBluesMan's Avatar
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    Re: Help with Fender Princeton?

    maybe it was serendipity but I covered the silver face cloth of my '72/73 Princeton Reverb many, many years ago with black muslim cloth. When I took it off in 2005, it was in very good condition

    my last picture of it in November 2003



    It is my fond hope that somebody is happy making music with it.
    "Live and learn and flip the burns"

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    Forum Member NTBluesGuitar's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by phantomman View Post
    ...A grounded 3-conductor power cable and death-cap removal are musts. You'll find the death cap mounted at the rear wall of the chassis, with one lead connected to the power switch. It's a Blue Molded type, similar to the tone caps found on the main circuit board.
    While working on replacing the power cord with a grounded 3-prong cord, I'd suggest disconnecting the rear 2-prong AC receptacle too. You might shop to replace it with a 3-pronger, but one nice trick you could try is wire that up as a bias test point. I did it on my Princeton Reverb reproduction:







    If that seems like a bit more than you'd feel comfortable with, I'd suggest just wiring the new power cord right to the on/off switch and fuse ignoring the rear AC outlet but leaving it on the chassis.

    You can convert the ground switch to a standby switch easily as well. All of this shouldn't take any value away from the amp and is easily reversible.

    I think your priority are the items Phantomman listed already, though.
    "...pray do not imagine that those who make the noise are the only inhabitants of the field;
    that, of course, they are many in number; or that, after all, they are other than the little,
    shriveled, meagre, hopping, though loud and troublesome, insects of the hour."

    -Edmund Burke

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    Re: Help with Fender Princeton?

    If you decide to keep the A/C outlet, the grounded one is #160-2-N.

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    Re: Help with Fender Princeton?

    Hello again,

    Thank you all for the replies and suggestions so far.

    I had some time tonight to pull the amp apart and do an initial cleaning and brief inspection. I do aircraft maintenance for a living with most of my experience on aircraft from the 50s, 60s and 70s. I have a fair amount of experience working with electrical systems but I'm certainly no expert. I'm aware of the dangers of working around capacitors and if I decide to do any of this work myself I will definitely get myself familiarized with safety procedures. I'm confident I can do a decent job soldering, but just need to be sure which parts need to be replaced.

    I noticed in this first photo the capacitor on the far left seems to have some discolouration. Other than that nothing jumped out at me right away.






    I take it that the blue cap in the picture below is the "death cap" that Phantomman mentioned?




    As for the filter cap can in the photo below, am I correct that the four blobs of solder around the outer edge are holding down four tangs to the chassis? Is this filter can replaced as a complete unit and available?


    I really appreciate the help everyone.

    Thanks again.

    Sam

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    Re: Help with Fender Princeton?

    Quote Originally Posted by phantomman View Post
    The bias cap should also be replaced, along with the power-rail resistors on the main board.
    Thank you for sharing your knowledge Phantomman.

    Are you able to point out the bias cap? Also the power rail resistors on the main board?

    Is it good practice to replace all of the capacitors shown here or is that not necessary?



    Thanks in advance.

    Sam

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    Forum Member Michael Smith's Avatar
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    Re: Help with Fender Princeton?

    Those yellow paper covered electrolytic caps are original, from 1964, and should be replaced. I can read the date code on one of them. And yes, the 4 blobs of solder are holding the can cap to the chassis. It takes a pretty big soldering iron to melt that solder. Some techs leave the can cap in place, but disconnect the wires and install a terminal strip somewhere inside the chassis and mount modern caps in place of the can cap. If you are able to unsolder the can cap, replacements are still available. I get most of my parts from Amplified Parts.

    I believe the 3 resistors I have circled are the power rail resistors. You can upgrade them to metal film 2 Watt, or use carbon composite as are in there now. I have also drawn a line pointing to a negative bias resistor that should be replaced, along with the old bias cap. The positive lead on the bias cap may be a long lead and soldered to ground near your pilot light holder. If this is the case, you can clip out the old cap and J-hook the new one to the existing positive lead, so you can continue to use the existing ground. Of course observe the polarity of all of the electrolytic caps as you install the new ones.

    Last edited by Michael Smith; 03-29-2022 at 02:13 AM.
    "When You're Riding Down the Highway at Night, And You're Feeling that Wild Turkey's Bite" ZZ Top

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    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by Moxsam View Post
    The bias-supply cap is that large electrolytic on the small circuit board adjacent to the pilot-lamp assembly. The power-rail resistors are just to the left of the filter-cap can -- those actually look to be in pretty good shape but I would check them just the same to be certain. You've correctly identified and located the "death cap".

    If you're A&P-certified you should have little problem refurbishing this amp but holler if you find yourself in a pinch. There'll always be someone here to lend you a hand.
    "When injustice becomes law then rebellion becomes duty."

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    Forum Member Michael Smith's Avatar
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    Re: Help with Fender Princeton?

    Your multi section can capacitor actually contains four 20 microfarad, 450 volt caps. Amplified Parts has a similar replacement (20 microfarad, 475 volts). I have also circled in yellow the 3 power rail resistors, one 1K ohms, 1 Watt, and two 18K ohms, 1 Watt.

    As I stated in my earlier post, some techs upgrade the resistors to 2 Watt Metal Oxide. (I think I may have said Metal Film).

    "When You're Riding Down the Highway at Night, And You're Feeling that Wild Turkey's Bite" ZZ Top

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    Forum Member NTBluesGuitar's Avatar
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    Re: Help with Fender Princeton?

    Antique Electronics has the Cap Cans - I used these in my BFPR repro, and I think way back when I replaced Phantomman's with one too:

    Click here for the CE Mfg Cap Can

    "...pray do not imagine that those who make the noise are the only inhabitants of the field;
    that, of course, they are many in number; or that, after all, they are other than the little,
    shriveled, meagre, hopping, though loud and troublesome, insects of the hour."

    -Edmund Burke

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    Re: Help with Fender Princeton?

    I am always amazed and pleased with the amount of serious amp knowledge that you guys so kindly share in this forum.

    I don’t remember having seen such in depth info elsewhere, regarding forums.

    I’m not the op but thank you!

  21. #21
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by Moxsam View Post
    Is it good practice to replace all of the capacitors shown here or is that not necessary?

    Leave those Blue Molded caps in situ as they are largely responsible for the amp's magnificent tone and seldom require replacement. Any of the original carbon-comp resistors that appear "crispy' or discolored should be closely examined and measured for value. Deep-six any that are significantly out of tolerance.
    "When injustice becomes law then rebellion becomes duty."

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    Re: Help with Fender Princeton?

    (following)
    T 'n W

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    Forum Member Don's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by Moxsam View Post
    Thank you for sharing your knowledge Phantomman.

    Are you able to point out the bias cap? Also the power rail resistors on the main board?

    Is it good practice to replace all of the capacitors shown here or is that not necessary?



    Thanks in advance.

    Sam
    That's beautiful!

    Note that when you install the grounded power cord, attach the hot lead to the tip the fuse holder, then go from the side of the fuse holder to the switch, and then from the switch to the PT, NOT the switch on the one lead and the fuse on the other like Fender did it back then and how they showed in their schematics.

    Also, leave the ground lead on the power cord longer than the hot and neutral leads and do not connect it to a transformer mounting bolt/nut.

    You can leave the disconnected ground switch in place and use the terminals to hold wires.

  24. #24
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by Don View Post
    You can leave the disconnected ground switch in place and use the terminals to hold wires.
    That switch may also be used to add a "standby" function to extend the life of the power tubes.
    "When injustice becomes law then rebellion becomes duty."

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    Re: Help with Fender Princeton?

    Hello again,

    Thank you all for taking the time to share your knowledge of these old amplifiers.

    I do like the idea of having a standby switch. I will provide an update when the parts arrive.

    This truly is an amazing forum!

  26. #26
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Princeton's are marvelous amps, both in stock trim as "porch weasels" or as the basis for any number of conversions. I converted this 1980 example into a 2 x 12 piggyback configuration via new cabinetry and a pair of JBL K120's. World's loudest 12-watt amp!

    "When injustice becomes law then rebellion becomes duty."

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    Forum Member DanTheBluesMan's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by phantomman View Post
    Princeton's are marvelous amps, both in stock trim as "porch weasels" or as the basis for any number of conversions. I converted this 1980 example into a 2 x 12 piggyback configuration via new cabinetry and a pair of JBL K120's. World's loudest 12-watt amp!

    OMG - I want that so much. How much does a head shell like that cost? Could I use the two speaker outputs to the two 8 ohm inputs on my 1960A cab?
    "Live and learn and flip the burns"

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    Forum Member Michael Smith's Avatar
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    Re: Help with Fender Princeton?

    What impedance speaker is the Princeton designed for? The speaker jacks on Fender amps are wired in parallel, so if you use both of them, the impedance is halved. If the Princeton is designed for an 8 ohm load, you could plug into one of the jacks on your 1960a, put it in stereo mode, and use 2 of the 4 speakers in the cabinet. That is probably the safest thing to do, although Fender uses output transformers capable of handling 100% impedance mismatch. I always match the impedance of the speaker to what the amp was designed for.
    "When You're Riding Down the Highway at Night, And You're Feeling that Wild Turkey's Bite" ZZ Top

  29. #29
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    The Princeton's O/T has a single-tap secondary intended for an 8Ω load so I used a pair of 16Ω speakers wired in parallel to match the source to load.

    I built a smaller 1 x 15 cab for it as well, containing a JBL D130F. It's a nice little package for smaller, more intimate venues......

    Last edited by phantomman; 04-02-2022 at 03:57 PM.
    "When injustice becomes law then rebellion becomes duty."

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    Forum Member Michael Smith's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by phantomman View Post
    The Princeton's O/T has a single-tap secondary intended for an 8Ω load so I used a pair of 16Ω speakers wired in parallel to match the source to load.

    I built a smaller 1 x 16 cab for it as well, containing a JBL D130F. It's a nice little package for smaller, more intimate venues......
    Lol, I didn't know the D130F came in a 16 inch size.
    "When You're Riding Down the Highway at Night, And You're Feeling that Wild Turkey's Bite" ZZ Top

  31. #31
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by Michael Smith View Post
    Lol, I didn't know the D130F came in a 16 inch size.
    Caught and corrected.

    Sorry 'bout that.

    :
    "When injustice becomes law then rebellion becomes duty."

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    Forum Member NTBluesGuitar's Avatar
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    Re: Help with Fender Princeton?

    If anyone would be able to find a 16" JBL it would be Phantomman
    "...pray do not imagine that those who make the noise are the only inhabitants of the field;
    that, of course, they are many in number; or that, after all, they are other than the little,
    shriveled, meagre, hopping, though loud and troublesome, insects of the hour."

    -Edmund Burke

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    Re: Help with Fender Princeton?

    Amazing looking amp Phantomman! I love that colour grill cloth

    I have another question about capacitors for my Princeton non-reverb.

    I've found a few places that sell kits but I'm noticing that the values of the capacitors are different than what is in the amp now. Further reading has sent me down the rabbit hole of learning that different capacitors are going to change the tone of the amp.

    I REALLY like the sound of this amp as it is. Here is one of the kits I found:
    1 CE Mfg 20uFX4-475V
    3 Sprague 25uF-50V
    1 F&T 100uF-100V
    1 1K-2 Watt Resistor
    2 18K-2 Watt Resistors

    Is this a good kit to buy? If not do you have any other recommendations?

    Thanks in advance.
    Last edited by Moxsam; 04-05-2022 at 08:10 PM.

  34. #34
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    That looks like a great kit, with top-notch components. However, I believe you'll be better served by replacing the cap can with a like item instead of individual electrolytics which would require alterations to the chassis. Antique Radio Suppy regularly stocks these parts.
    "When injustice becomes law then rebellion becomes duty."

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    Re: Help with Fender Princeton?

    Quote Originally Posted by phantomman View Post
    That looks like a great kit, with top-notch components. However, I believe you'll be better served by replacing the cap can with a like item instead of individual electrolytics which would require alterations to the chassis. Antique Radio Suppy regularly stocks these parts.
    Sorry I made a mistake copying and pasting the items from the kit. I missed the filter cap can that was recommended previously by NTBluesGuitar. I've edited the original post to show it now.

    So I believe the complete kit and the parts they are replacing are:

    1 CE Mfg 20uFX4-475V (Filter cap can)
    3 Sprague 25uF-50V (to replace the 3 yellow paper electrolytic caps on the main board?)
    1 F&T 100uF-100V (to replace the bias cap?)
    1 1K-2 Watt Resistor (to replace power rail resistors)
    2 18K-2 Watt Resistors (to replace power rail resistors)

    Do I have this correct?

    I think it was also recommended to replace the resistor next to the bias cap as well.

    I must say it is VERY difficult NOT playing this amp right now. :) Luckily the weather has been improving here and the days are longer so I've been extra busy outside. I also just pulled my old 1971 Plymouth Valiant out of long term storage so I have lots to keep me distracted at the moment.

  36. #36
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    LOL, my mom had a '67 Valiant. Then she "graduated" to a '74 Duster.

    Yeah you've got the right components lined up, Sam. Be sure to maintain the correct polarity when replacing the bias-supply cap. Treat that Princeton like a vintage Stearman PT-17 owned by a CFI who signs your paycheck and it'll last another two or three lifetimes. With good parts the TBO for a Fender amp is usually a decade or more.
    "When injustice becomes law then rebellion becomes duty."

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    Forum Member Michael Smith's Avatar
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    Re: Help with Fender Princeton?

    At a minimum you should measure the bias resistor to see how close it is to it's original value. If it's off by 10% or more, replace it. Personally, I would replace it regardless, because once I get my soldering station and supplies out, it's just as easy to replace the bias resistor when replacing the bias capacitor.
    "When You're Riding Down the Highway at Night, And You're Feeling that Wild Turkey's Bite" ZZ Top

  38. #38
    Forum Member phantomman's Avatar
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    Re: Help with Fender Princeton?

    Quote Originally Posted by Michael Smith View Post
    At a minimum you should measure the bias resistor to see how close it is to it's original value. If it's off by 10% or more, replace it. Personally, I would replace it regardless, because once I get my soldering station and supplies out, it's just as easy to replace the bias resistor when replacing the bias capacitor.
    +1

    Metal-oxide resistors may be used in lieu of the original carbon-comp types -- such substitution in no way affects the amp's tone (same with the power-rail resistors).
    "When injustice becomes law then rebellion becomes duty."

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    Re: Help with Fender Princeton?

    Quote Originally Posted by phantomman View Post
    LOL, my mom had a '67 Valiant. Then she "graduated" to a '74 Duster.

    Yeah you've got the right components lined up, Sam. Be sure to maintain the correct polarity when replacing the bias-supply cap. Treat that Princeton like a vintage Stearman PT-17 owned by a CFI who signs your paycheck and it'll last another two or three lifetimes. With good parts the TBO for a Fender amp is usually a decade or more.
    Haha old Mopars run in my family too. Plymouth Fury, Valiants, Super Bee. My old mentor was a Stearman owner as well.

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    Re: Help with Fender Princeton?

    Quote Originally Posted by Michael Smith View Post
    At a minimum you should measure the bias resistor to see how close it is to it's original value. If it's off by 10% or more, replace it. Personally, I would replace it regardless, because once I get my soldering station and supplies out, it's just as easy to replace the bias resistor when replacing the bias capacitor.
    Thanks guys. I will replace that one too.

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