The light show going on inside my PR rectifier tube

[biker joe]

So lately, when I turn on my 64 Princeton Reverb, the rectifier tube has started to do a little light show. It will start to flash and sparkle inside but once it warms up it seems normal. The plates on the inside aren't glowing bright red or anything. The amp is still sounds fine. I'm just wondering if I am in danger of blowing a transformer if I keep using it like it is. Should I just find a different tube to throw in there (I don't have one on hand to experiment with). Or do you think it is time to just take it to a shop? I've owned the amp for 15 years and it gets played almost everyday (at home level volume not stage level). It does have old tubes and caps, however, there is no bubbling on the caps and there is no excess hiss. I love how it sounds as is. However, if this thing blew a tranny I would be very very sad.

[muchxs]

Originally Posted by biker joe

So lately, when I turn on my 64 Princeton Reverb, the rectifier tube has started to do a little light show. It will start to flash and sparkle inside but once it warms up it seems normal. The plates on the inside aren't glowing bright red or anything. The amp is still sounds fine. I'm just wondering if I am in danger of blowing a transformer if I keep using it like it is. Should I just find a different tube to throw in there (I don't have one on hand to experiment with). Or do you think it is time to just take it to a shop? I've owned the amp for 15 years and it gets played almost everyday (at home level volume not stage level). It does have old tubes and caps, however, there is no bubbling on the caps and there is no excess hiss. I love how it sounds as is.

Your rectifier is telling you it's all done. Writing is in the wall in ten foot tall letters, ignore it at your peril. At the very least replace the rectifier. You know your amp's history, if it hasn't had a good going-over in ten years or so it might be overdue.

Originally Posted by biker joe

However, if this thing blew a tranny I would be very very sad.

An arcing rectifier will blow transformers.

[woodman]

yes, replace the recto by all means — you can get an NOS one that will last maybe another 15 years for not much dough.

[biker joe]

Thank you guys for your input. I went ahead and picked up a new JJ this afternoon and swapped it in and it seems like I'm good to go for now. One of these days I know I'm going to have to bring it in for an overhall, but I think I just postponed that date a little while longer.

[Raybob]

Rectifier tubes don't just go for no reason. If you've had that amp for 15 years and never changed the cap can, get it changed ASAP. Cap cans don't bubble, they just quit doing their job.

[T Prior]

Although you should be prepared to get a new rectifier ( 5U4GB) , you need to be certain the caps are ok, especially the first one 20u/450. There are 4 caps, the first is to the right of the 6V6 and 12AX7 circuits , change the first one, test the amp for arching then change the other 3 either before you change the Rect or at the same time. The proper procedure would be to change the caps first, check the circuit,( see if the light show goes away) then change the rectifier if need be, in this way you will know for certain what the the fix was. Do the repair in steps otherwise you will never really know what caused the issue.

It may very well be the rectifier tube but it would be common maint. to change the 4 caps as well.

I recently had this exact same issue with an old Tremolux, the rectifer was arching then blowing fuses, the problem turned out to be the first cap in the circuit following the rectifier, it was wacked. I initially thought it was the rectifier.

here is the schematic for your amp, this link has both the layout and the schematic, give it a minute for the page to load.

ps, I am not an expert...just been there done that...

http://www.el34world.com/charts/Sche...ERB_AA1164.pdf

The DC is at 420, the cap rating is at 450, that's not really much wiggle room.

side note: I noticed that Weber kits are shipping with 500v caps for the first cap in the Power Supply circuits, that's a great move and says a lot about this issue.

t

[zook]

The Princeton has a 4-cap can. It stands up on the chassis, you can't change just onesection, you'd have to change the whole can.

I would leave the amp alone, your tube went bad, it should be fine now.

Winnie

[T Prior]

ok, 4 cap can, didn't know that.Thought they may be discreet. I am looking at schemtic's and have never had a PR open.

Just my take, it's an old amp, 1964, maintenance is not a bad thing especially if the 4x Can is original or perhaps as much as 10 years old. Rectifiers arch for a various reasons, a bad cap is certainly one of them and it is well known that the first cap in the circuit becomes the weakest over time.

Change the Rectifier, it is the easiest and fastest route to a solution.

I would agree.

[Raybob]

If it's ready for the cap can, don't forget to replace the bias cap as well.

[Mik]

Biker Joe,

Other than the light show was there any other symptom something wasn't right? You wrote that once the amp warmed up it seemed normal.

[biker joe]

Thanks for all the follow ups. Even with the light show and the old rectifier, the amp was sounding great- no other issues. Now with the new rectifier (I replaced an Amperex 5AR4 GZ34 for a JJ GAR4CZ), the light show has gone away and it actually sounds louder- something I actually don't need for this stay at home amp. But it still sounds great.

Yes I know it will eventually need maintenance, but since its been running like a champ for these last 15 years, I figure- if it aint broke... However, I do want to avoid any chance of a catastrophic failure. I'm hoping that it would blow its fuse before it took out anything more costly. And by the way- I've checked, it does have the proper fuse in there.

[Demo]

On a related, albeit somewhat different, twist I was tube browsing my cabinet the other day trying different NOS 6V6's (I think they were branded National) when I lost volume, and got INCREDIBLE GAIN.

The amp is a Vic tweed Deluxe that has been a stellar performer since I got it. The National (relabeled RCA's I think) power tubes were smoked glass, so I couldn't really see much, but one was pretty warm and the other wasn't.

I shut down the amp immediately (it was only idling), replaced both National
Tubes with other RCA's, and everything sounds fine. Could I have damaged something that I don't know about? Yet.

[Mik]

Originally Posted by Demo

On a related, albeit somewhat different, twist I was tube browsing my cabinet the other day trying different NOS 6V6's (I think they were branded National) when I lost volume, and got INCREDIBLE GAIN.

The amp is a Vic tweed Deluxe that has been a stellar performer since I got it. The National (relabeled RCA's I think) power tubes were smoked glass, so I couldn't really see much, but one was pretty warm and the other wasn't.

I shut down the amp immediately (it was only idling), replaced both National
Tubes with other RCA's, and everything sounds fine. Could I have damaged something that I don't know about? Yet.

There were National branded designated 6V6GT tubes in the 90s that were Russian tubes but not really 6V6, so I heard, dark smoked glass. I had one in a Vibro Champ, didn't sound bad but I replaced it long ago.

[T Prior]

Originally Posted by biker joe

but since its been running like a champ for these last 15 years, I figure- if it aint broke... However, I do want to avoid any chance of a catastrophic failure.

it's time ...

If you plan on using the amp on a regular basis change the caps soon, 15 years is a very long time, the normal "cap" life on a regularly used amp is approx 10 years. If the new rectifier is more efficient than the old one and putting out a bit more DC, the existing old caps may not be happy. Don't forget to clean the tube sockets as well with spray cleaner, remember, everything is based on good mechanical connections between the tube and the tube socket. This is a 1964 amp, those sockets are now 45 years old.

Glad to hear the tube fixed the light show. This is a great amp and with a little bit of maintenance there is no reason it can't go another 45 years !

t