Princeton 1964 problems - weak tremolo and not loud enough

[Guitarman555]

Hi, everyone,

I have just bought a nice princeton 1964, with original circuit (according the seller untouched, but who can be sure, I haven t checked it yet), nice patriot cajun 10 speaker, which is one of louder speakers. Amp has 2 problems:

1.first problem is very weak tremolo, even at max level 10 is very weak.
2. Second problem is that the amp is not loud enough.

I have vibrochamp from the same year and I tried to put its tubes into my princeton (I replaced the fender marked 2 ax7 to 2 GT´s ax7 (which I have in my great working 64 vibrochamp), and I had only one available black glass tube 6v6 from my 64 vibrochamp that I put firstly instead of the first position RCA 6v6 tube and secondly to the second position 6v6 tube where amperex tube was ). After those swaps nothing changed significantly. Neither loudness nor vibrato.

Unfortunatley I don´t have onether GZ34 for princeton(I cannot take the 5Y3GT from Vibrochamp and put it into princeton instead of GZ34 to try the difference. Do you think this could be the reason for vibrato? I want to order TAD 5AR4 GZ34 Rectifier Tube Amp Doctor TAD PREMIUM SELECTED(which is promoted as a copy of Mullard/VALVO GZ34.)

Does anybody knows if this rectifier is good for 1964 vintage blackface princeton? Or any other advice? Many thanks!

Luke

[Squirrel]

The GZ34 is probably fine, there's no way it could stop the vibrato from working correctly. Could be a lot of things but if the circuit is untouched I'd definitely replace all of the electrolytic caps. That'd be my first port of call anyway.

[Embenny]

The GZ34 is probably fine, there's no way it could stop the vibrato from working correctly. Could be a lot of things but if the circuit is untouched I'd definitely replace all of the electrolytic caps. That'd be my first port of call anyway.

Yep, first step in using a 54 year old amp is to replace all electrolytic caps and then see what you're dealing with.

[Guitarman555]

Hi Squirell, many thanks for your quick reply, I have just plugged it in again and noticed that the problem number two (volume is already solved by replacing 2xax7 and one 6v6), but problem number 1(week vibrato) is still the same..
So also vibrato could be the caps?
Well for GZ34 I am sure it is fine for princeton 1964 in general but I dont know the particular product TAD 5AR4 GZ34 Rectifier Tube Amp Doctor TAD PREMIUM SELECTED, if it should be fine and will not burn the amp...

[Guitarman555]

The GZ34 is probably fine, there's no way it could stop the vibrato from working correctly. Could be a lot of things but if the circuit is untouched I'd definitely replace all of the electrolytic caps. That'd be my first port of call anyway.

Yep, first step in using a 54 year old amp is to replace all electrolytic caps and then see what you're dealing with.

Hi Squirell, many thanks for your quick reply, I have just plugged it in again and noticed that the problem number two (volume is already solved by replacing 2xax7 and one 6v6), but problem number 1(week vibrato) is still the same..
So also vibrato could be the caps?
Well for GZ34 I am sure it is fine for princeton 1964 in general but I dont know the particular product TAD 5AR4 GZ34 Rectifier Tube Amp Doctor TAD PREMIUM SELECTED, if it should be fine and will not burn the amp...

[andy_tchp]

No.

In these, weak vibrato = Power tubes need to be properly biased and are probably running too 'hot' at the moment.

Don't go replacing the rectifier tube just yet.

And yes, if those electrolytic caps are all original from 1964 get them replaced ASAP. I'd be hesitant to use the amp much until that's done.

[Guitarman555]

No.

In these, weak vibrato = Power tubes need to be properly biased and are probably running too 'hot' at the moment.

Don't go replacing the rectifier tube just yet.

And yes, if those electrolytic caps are all original from 1964 get them replaced ASAP. I'd be hesitant to use the amp much until that's done.

Many thanks for your answer! How to biase the two 6v6 powertubes? How about just buying a pair of black glass 6v6 and putting into the amp? And for caps, do you think am I able to change them at home by myself? Do you have some recommandation which caps/website where I shoud search for? Many thanks to you all! Great points, I really appreciate it!

[derekstudt]

It's certainly possible to change them yourself if you know what you're doing, however If you don't have a good understanding of working high voltage electronics, I would advise against attempting to replace the capacitors yourself. Those things can store voltage for quite a long time after being powered off.

This can be widely debated, but don't assume you must change out ALL of the capacitors at once. There's a chance some of them are still functioning properly. Will they need changed at some point? Yes. Will it be cheaper to have a tech change them out all at once? Likely. It just depends on which school of thought you subscribe to...keep it functional while being as original as possible (meaning change only the malfunctioning caps), or just give it an overhaul now because it will eventually need it.

[andy_tchp]

Take it to a reputable tech and have them carry out both jobs and give it a general once over.

Simply buying a 'matched' pair of 6V6s won't be enough; it's possible that the old tubes that came with it are fine and it just needs electrolytic caps and a bias. Tubes from that era are much more resilient/long-lived than current production items.

[Ursa Minor]

No.

In these, weak vibrato = Power tubes need to be properly biased and are probably running too 'hot' at the moment.

Don't go replacing the rectifier tube just yet.

And yes, if those electrolytic caps are all original from 1964 get them replaced ASAP. I'd be hesitant to use the amp much until that's done.

This.

Get the amp serviced. Cap can and all electrolytics should be replaced. The power tube bias controls how deep the trem is. So if it's weak, chances are the tubes are just running too hot. These amps are pretty simple, shouldn't take a tech too much effort to get it running

I take it this is a BF Princeton, with treble and bass tone stack and not the earlier brownface (6G2) circuit?

PS - lets' see some pics!

[Guitarman555]

No.

In these, weak vibrato = Power tubes need to be properly biased and are probably running too 'hot' at the moment.

Don't go replacing the rectifier tube just yet.

And yes, if those electrolytic caps are all original from 1964 get them replaced ASAP. I'd be hesitant to use the amp much until that's done.

This.

Get the amp serviced. Cap can and all electrolytics should be replaced. The power tube bias controls how deep the trem is. So if it's weak, chances are the tubes are just running too hot. These amps are pretty simple, shouldn't take a tech too much effort to get it running

I take it this is a BF Princeton, with treble and bass tone stack and not the earlier brownface (6G2) circuit?

PS - lets' see some pics!

Many thanks for your answer, it is black face (november and december 1964), NOT the brownface circuit. I will make some pictures as I come back home today.

[Guitarman555]

Unfortunately it is not possible ad images here, no"insert image", no upload, just "insert url"...

[Ursa Minor]

The non-verb Princetons are really cool. I only asked since I'm a huge Princeton fan. My main amps are a '72 SFPR and a '64 6G2 - brownface circuit but with blackface / tuxedo cosmetics.

Unfortunately you'll have to upload your pics to an image hosting site like imgur or flickr and then paste the image link into your post in order for them to show up.

For reference: Ye olde how to post an image on OSG thread.
viewtopic.php?f=5&t=202

[Witchburner]

The non-verb Princetons are really cool. I only asked since I'm a huge Princeton fan. My main amps are a '72 SFPR and a '64 6G2 - brownface circuit but with blackface / tuxedo cosmetics.

Why do you mention that? I'll pull up the schematics to see what you mean

I heard the head room and break up was completely different, I've never played a reverb version actually, so have no idea

What's your experience?

[sookwinder]

The BF Princeton has one less gain stage than the BFPR. similar amps but effectively different amps.