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Post subject: Princeton reverb reissue. Tremolo not working.
Posted: Fri Jun 29, 2012 3:30 pm
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I got my brand new prr today and it seems something is wrong with the tremolo. In order to hear it at all i need to turn speed and intesity all the way up, its still not very present, if I then backoff (10 to 8 ) on the speed i can then hear the tremolo being present for some seconds before it fades away. My web searches suggest its biased related, but its brand new so I dont get why it should have problems like this.

Any help would be greatly appreciated. Been waiting almost two weeks for it to arive so this was quit a letdown.

Lars W.


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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Fri Jun 29, 2012 3:37 pm
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Hi LarsWest,

If everything else works fine, it could be V4 (12AX7), try a new tube there first. Tubes are typically the first suspect. Often, in cases like this, you can get a new tube from where the amp was purchased.

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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Sat Jun 30, 2012 3:59 pm
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shimmilou wrote:
Hi LarsWest,

If everything else works fine, it could be V4 (12AX7), try a new tube there first. Tubes are typically the first suspect. Often, in cases like this, you can get a new tube from where the amp was purchased.


+1

The V4B half of this 12AX7 controls the tremolo oscillator. But be advised, this type of tremolo relies on modulating the bias voltage for the power tubes to create the effect. If a new tube does not rectify the issue it's possible that the amp has a bias-supply problem. And if this is the case, the amp needs servicing from a qualified tech.

HTH

Arjay

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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Sun Jul 01, 2012 8:39 am
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Thanks for replaying.

I removed the metal covers from the 4 tubes. The second one from the the right doesnt light up, is this normal? How much force is needed to remove the tube from its socket? I tried but stoped cause i was afraid to break something.

Also the treble knob crackles when i turn it, can this become a problem down the line?

I bought this amp from Germany, I live in Norway, im hoping to avoid the hassle sending it back will be.

Thanks
Lars Westrebø


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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Sun Jul 01, 2012 9:33 am
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That is the reverb driver tube, it's a 12AT7 and it can be hard to see the glow, not as bright as the others which are 12AX7, that's normal. Does the reverb work? If so, that tube is likely OK.

While pulling on the tube, use a slight circular motion to walk the tube out. Tight sockets are a good thing, and you're not likely to break the tube while removing it, provided that you don't let it smack into another component (like speaker magnet) when it releases. Be sure that the pins are lined up when replacing so as not to bend any pins.

Noisy pots are no big deal, often you can just work the knob back and forth many times to get rid of the noise.

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Last edited by shimmilou on Sun Jul 01, 2012 9:38 am, edited 1 time in total.

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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Sun Jul 01, 2012 9:38 am
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Lars, that's the reverb driver tube (12AT7 or V2). You should not have any reverb either. To pull out a 9-pin tube... let it the amp cool down or use a insulated glove or towel. Grip the tube near the bottom of the tube (near the base or socket).

Now, pull STRAIGHT up. I use my pinky to brace up against the chassis and act as a lever. Try to keep the rocking back-&-forth to a minimum, as this can bend the pins and damage the socket. A little contact spray lubricant can help. I used Caig De-oxit D5 or GN5. Just a little, once the tube has lifted a bit from the socket.

When installing another tube... note the orientation of the gap or space between the #1 and #9 pins. All the 9-pin sockets should have same orientation on most Fender amps, with this respects.

You can put a LITTLE more lubricant onto the socket. And then press the new tube (or replacement) straight down into the socket. Keep wiggling to a minimum.

It sounds like you need to rotate several tubes in the amp, as there maybe more than one that has gone hinky. You can move 12AX7's around. But, do not put a 12AX7 into that 12AT7 socket. As this tube draws a lot more current than the usual 12AX7 can handle-- esp when the 12AT7 is in the reverb driver position.

Good luck! Tell us how it all works out.

EDIT: Sorry Shimmy, if I stepped on your toes.


http://support.fender.com/schematics/gu ... ematic.pdf


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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Sun Jul 01, 2012 9:47 am
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:lol:

No, great to have backup! 8)

I figured that you had already prepared a response before seeing my post, and posted anyway since you went to the trouble, not a problem. I am quick on the draw this morning, not always, but today.

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Mon Jul 02, 2012 8:50 am
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I replaced the v4 tube with a new one today, unfortunately it didnt help. A couple of seconds with tremolo before it fades is still all i get :( . Is it time to get it to a quallified amp tech? Will my warranty be valid with any authorised fender dealer?

On the bright side Im really liking the rest of the amp :)


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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Mon Jul 02, 2012 9:00 am
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Yup... time for a good tech. My bet is it's the board or the footswitch or both. Try this first. Pull the plug that goes to the foot switch. I believe the PRRI is like the original BF PR and that the Vibrato section will work with the foot switch disconnected.

If this test works, you may want to try pulling the rubber seal off the foot switch and spraying some good contact cleaner on the switch contacts. Try cleaning the speed and intensity pots with good contact spray made for potentiomenters. Worth a try, at least.


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Post subject: Re: Princeton reverb reissue. Tremolo not working.
Posted: Wed Aug 22, 2012 6:16 am
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Have finaly gotten this sorted out. The tech told me it was a broken speed pot meter. have spent the time without an amp learning to play lapsteel(trying at least) so it hasnt been all bad. thanks for all your help.

LCW.


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