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Post subject: Help with an amp I bought today
Posted: Mon Dec 12, 2011 9:48 pm
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Hello,
I was incredibly favored by the amp gods today and found what I think is an 1966 Princeton blackface (AA964) on CList (at a price even my wife didn't have a problem with), which is great but there are some things about it I don't understand so I was hoping maybe someone has a .pdf of a manual. An example, on the back it has a switch labeled ground that I don't know what it does.

Also since this is my first tube amp, there are somethings I am not sure about. The tubes all appear to be original and sound fantastic, but again as an example, when I have the tremolo set, the tubes in the back seems to flicker which I am not sure if that is normal. It also makes a audible 'ticking' kind of noise that comes and goes with the tremolo set (usually after the tubes are good and hot), which again, I am not sure if that is normal or not.

Any help would be appreciated.

/Cheers
Jason


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Post subject: Re: Help with an amp I bought today
Posted: Mon Dec 12, 2011 10:47 pm
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Back when your amp was made, grounded 3-conductor outlets were a rarity instead of the rule. Thus, the AC receptacles of the day had only a "hot" and a "neutral" side. An amp using a 2-prong plug would operate regardless of how its plug were inserted into a 2-conductor wall socket but one orientation or the other would always produce some hum since components within the chassis were polarized and intended to operate more efficiently with the plug correctly inserted into the wall socket. Amps of cheaper construction and lacking the "ground" switch required the user to manually rotate the plug in the wall socket (ie: flip it over) to minimize this hum. The "ground" switch on your amp (which more correctly should be labeled as a polarity switch) accomplishes the same objective as manually flipping the plug in a wall socket.

In the interests of self-preservation you should immediately take this amp to a competent amp tech and have him convert the power cable to a modern grounded 3-conductor type. Lacking a true ground, the possibility exists for your amp to generate lethal voltages in this condition. Once converted, the ground switch may be ignored or even disconnected since it will be superfluous to the amp's operation.

The Princeton amp uses what's known as a bias-modulated tremolo circuit which actually switches your output tubes on and off temporarily at a rate dependent upon the setting of the front panel's "speed" control. The control itself actually regulates a tube oscillator that generates a gated pulse which is used to briefly suppress the bias voltage to the power tubes at a regulated interval. This system was Leo Fender's first tremolo design (he made a total of three radically different types) and was the simplest in terms of circuit complexity. The tremolo on these amps is always "on" -- to turn it off requires the footswitch or merely "zeroing out" the speed and intensity controls on the front panel. Power-tube flicker with the tremolo engaged is perfectly normal. However, the "ticking" is not; likely your oscillator tube (V2) is growing weak.

HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Help with an amp I bought today
Posted: Tue Dec 13, 2011 11:31 am
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Thank you Arjay, That information helps a lot.

As far as tube replacements go, the amp has tubes from West Germany, Great Britain & then some RCAs from the USA. I am not sure if these are made today. Is it better to buy new tubes from places like Musicians Friend, etc. or try and find these older ones? I have found some subjective & conflicting info on the web.

Just as a side note/question, the tremolo on this amp sounds 10x better than my pedal, it may be simple, but I like it, definitely more subtle. Does the turning off and on of the tubes reduce their life though?

Sorry for all the questions, I am just a little paranoid about taking care of this amp.
(I never had to worry about such things with my Behringer amp. But it doesn't sound like this Princeton so I am more than willing to learn).

Thanks again,
Jason


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Post subject: Re: Help with an amp I bought today
Posted: Tue Dec 13, 2011 12:17 pm
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rockdog2001 wrote:
Does the turning off and on of the tubes reduce their life though?


Arguably, yes. And no.

While it's a given that loading and unloading a tube's bias voltage in rapid fashion may decrease its service life, the fact that the heater and the plates remain "lit" under this circumstance ameliorates the condition to an extent. Frankly, I wouldn't give it a second thought (and I don't -- I own both a Princeton and a Princeton Reverb).

Contemporary tubes will never last as long as vintage bottles built in the USA, Europe, or Japan (especially the JAN/milspec types). That said, there are some very good replacements available from Russia and the former ComBloc nations that will deliver good tone for a reasonable price. They'll merely require replacement at shorter intervals than the NOS types (which generally command big $$$ now). Such new glass is made by JJ, TAD, EHX, SovTek, Red Ruby, and others. I doubt that you'll find them at your local GC but it costs nothing to take a look there.

If you can find a worthy amp tech familiar with vintage Fender architecture, ask about adding a "standby" function using the rear panel's ground switch (assuming you have the amp safely converted to a modern grounded 3-conductor plug). This simple mod requires no additional holes to be drilled and is totally transparent -- it could be reversed if desired in about fifteen minutes. The new standby switch will help extend the service life of your power tubes. Both of my Princetons have this feature.

Best of luck, HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Help with an amp I bought today
Posted: Tue Dec 13, 2011 2:17 pm
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I talked with the technician out our locally owned music shop about changing the AC cord on the amp. He said he could do replace the cord for about $40 parts and labor and that usually he just 'un-wires' the ground switch at that time.

I planned on taking it in after the first of the year so I will mention the standby switch modification to him then. If he is unfamiliar with the modification, is it something that can be done later by someone else? Or does it usually need to be done at the same time?


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Post subject: Re: Help with an amp I bought today
Posted: Tue Dec 13, 2011 2:56 pm
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Any qualified tech can perform the mod anytime -- all that's required is about six inches of AWG18 insulated wire. Essentially the switch will be wired to interrupt the B+ voltage supply to the power tubes.

When you take the amp in for its first service, have the filter cap can checked for a date code -- if it's ten years or older (or the original from the '60s) it should be replaced immediately. If one of those caps goes bad due to age, it will likely drag the power transformer and the rectifier tube with it to the "graveyard of vintage amp components". Save yourself some potential grief and a lot of $$$ (the power-rail resistors should be coincidentally replaced as well). A new cap can runs about $60 on Ebay, the resistors a couple of bucks each. This preventative maintenance might cause you some dismay but it's absolutely essential to keep these vintage amps running. And once serviced, you'll enjoy trouble-free performance for a decade or more.

HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Help with an amp I bought today
Posted: Tue Dec 13, 2011 6:12 pm
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Enough with the technical chit chat - we need to see some photos. :lol:


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Post subject: Re: Help with an amp I bought today
Posted: Tue Dec 13, 2011 6:19 pm
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phansford wrote:
Enough with the technical chit chat - we need to see some photos. :lol:


HEAR, HEAR -- WELL SAID!

:lol:

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Help with an amp I bought today
Posted: Wed Dec 14, 2011 12:10 am
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Here are the pics.

https://plus.google.com/photos/10345738 ... 2453848961


As far as I can tell it is all stock and seems in really good shape. The canister capacitor, transformers, serial # etc. all seem to date to '66. I was feeling pretty proud of my $100 purchase and the funny thing is, I was planning on buying the Fender Super Champ XD on payday because it is on sale for $200 right now.

That said, I am now a little afraid of the maintenance on this amp, after reading about capacitor failure, tube costs, needed mods and such, I am a little worried about it :!:

It does sound wonderful though. :)


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Post subject: Re: Help with an amp I bought today
Posted: Wed Dec 14, 2011 1:06 am
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She's all "there" and clean as the proverbial pin, rockdog. Her birthday's in October.

Magnifíque!

A hundred bucks?

Ya done good, kid!

Hey, the servicing is nothing to fret over. Just get it into the shop as soon as you can. You don't want any maintenance issues to spoil that cutie.

ROCK......ON!

8) 8) 8)

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Help with an amp I bought today
Posted: Wed Dec 14, 2011 6:46 am
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Great score! a beautiful example of a big sounding little amp...like Arjay said,service it and it will be a treasure...especially good for recording.


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Post subject: Re: Help with an amp I bought today
Posted: Wed Dec 14, 2011 9:28 am
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Rebelsoul wrote:
...especially good for recording.


+1

Of all the amps in my herd, when it's time for some studio work the engineer there prefers that I bring my '65 Princeton Reverb.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Help with an amp I bought today
Posted: Wed Dec 14, 2011 11:02 am
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rockdog2001 wrote:
I was feeling pretty proud of my $100 purchase and the funny thing is, I was planning on buying the Fender Super Champ XD on payday because it is on sale for $200 right now.


$100!!!!! and a gun wasn't used in the transaction? :lol:

Great find at an unbelievable price. A real beauty.

Let me assure you from experience (I have a Vibro XD) - this is by far a better use of your cash. My son and I have had a couple of modeling amps and I don't care who makes them, they don't hold a candle to the real thing. If I had the time, I would live at Guitar Center and keep people from wasting their time and money on the hybrids. :wink:

rockdog2001 wrote:
That said, I am now a little afraid of the maintenance on this amp, after reading about capacitor failure, tube costs, needed mods and such, I am a little worried about it


Don't worry about maintenance. I am not a techie and would probably solder my wedding ring to the chassis if I tried a simple repair. I use a local tech that really knows his stuff and I have never had any issues that cost big bucks to repair - I've had pots changed, filter caps replaced, grounded plugs installed. Bench time (labor) has always been under an hour. The most I have ever spent on repair was $75 on an amp I found in an old building that probably had been played for 20 year or more. Unless you are really hard on this gem, it really won't require a lot of maintenance.

These non-verb Princeton's are great amps. Mines a 1969 and my son has it in his room connected to a 2x12 cab. Fun Fun Fun amp.


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Post subject: Re: Help with an amp I bought today
Posted: Thu Dec 15, 2011 6:44 am
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I have to drive up north to BGSU today to get my son for Christmas break. I was checking out Lima and Toledo CL looking for targets of opportunity. (I'm looking for an old single pup, double cut, Melody Maker in Cherry - just like I had as a kid)


There's a 1965 (OF) Princeton on CL in the Lima area.

He's going to struggle trying to move that amp for $900 in Lima. Actually Fostoria.... which is even more isolated. He needs to be posting this in Columbus or Cincinnati. Then he might get some interest.


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Post subject: Re: Help with an amp I bought today
Posted: Thu Dec 15, 2011 3:25 pm
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Hey, that looks familiar. Mine might have a different speaker though as my end label is brown.

The man I bought mine from had evidently taken in some musical equipment (including the Princeton) as payment for some work he did and just wanted to get his $300 from selling all the gear together. He was disappointed that I only wanted the guitar amp, but said he would take a hundred for it. He didn't really seem to care what he had, just wanted his money back. I doubt I will ever come across such a deal again, but you never know. :)

I think I have a tech lined up that can do the work (cord, caps, switch) but he won't be able to get to it until after the new year. So for now it just sits in the corner of the room. When I practice and plug into my GM108, it bums me out a little I can't use the Princeton. Hopefully soon!

I do appreciate all the advice though - Thank you!


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