6G2 Princeton amp?

[chuckb]

Hey guys, i have a 64 Princeton 6g2 tube amp that is giving me problems. I plugged it in the other day and was playing it when there was some smoke coming from it. I immediately shut it down. I felt the power transformer and it was hot. I let it cool down and when I powered it up it was fine for a few minutes then it started again, so I shut it down again. I removed the chassis from the cab and upon inspection found the 1k/1w resistor feeding off the b+ was totally burnt. i replaced the resistor and tried the amp again and still the power transformer got hot. Any suggestion on what it could be? Is the power transformer shorted internally? This amp has a 2 prong power cord with a ground switch as well. I was intending on switching out the cord for a three prong anyways. Could the ground cap be faulty and this is why my trannys getting hot?

Chuck.

[JoeM]

When was the last time this amp had a cap job?

[chuckb]

The amp is totally original. i purchased it last wk.The only thing that is different is there are a set of jj's 6v6s in it instead of the 6v6gt's.

[Enzo]

yeah well, pull the 6V6s and see if the amp will sit there running without smoking. I bet it is fine like that. Your 1k resistor serves the power tube screens, and burning up a screen resistor is almost always a sign of a failed power tube. A burnt resistor is never the resistor's fault. Resistors are passive components.

Replace any burnt or damaged resistors, then try a different set of 6V6.


ANy tube can fail at any time, even new ones.


Transformers do run hot, any chance you never felt the transformer until you saw smoke? But having said that, whatever caused that rsistor to burn up - likely a bad 6V6, but regardless - put a much larger than normal load on the transformer, so that makes it run hotter also.

Chances are the transformer is just fine. It didn't burn up your resistor.

[chuckb]

ya enzo, I pulled the tubes and the tranny is still getting hot although no smoke. there is a sizzling sound coming from the tranny though.There is a strong smell coming from the tranny as well. The 1.5k resistors( grid stoppers) on p6&5 look like that may have some burn on them as well.Checked out all other resistors but they look to be fine.The guy that i got the amp from told me that one of the tubes were bad so he installed the new jj's. I'm guessing that the screen resistor was already damaged when he installed the new tubes. I only touched the tranny after i had shut the amp down and it was hot and sizzling. I have to install a properly grounded power cord tomorrow because I'm not comfortable with the two prong cord that's there now. i really don't trust the cap that is going to ground.Any other things i can check? The screen resistor was a 11k/1watt, I replaced it with a 1k/2watt,should I have went with a higher wattage one there? Also there is a 10k resistor next to the screen resistor, could that resistor be affect as well,although there doesn't seem to be any obviously damage. I get a reading of 9k across it.I know that failing power filters can cause the tranny and rectifier to get hot as well, could this be a possible problem? I don't have a cap can like the one on the amp but I di have a 50/50 uf cap can and i hve lots of 22uf caps that i can try?

[Jazz P Bass]

You really do need to identify what is pulling current.
You can remove the 'death cap' without affecting the amp.
I would suggest that you pull all of the tubes.
If the power transformer still gets hot, it is bad.

[chuckb]

Yes, I pulled all the tubes and changed out the filter cap can and the tranny still gets hot. So looks like the tranny is shot eh?

[Jazz P Bass]

Yup.

[chuckb]

Hey guys, i just replaced the old power tranny with a brand new Hammond. I haven't tried it with tubes in yet, I just wanted to see how it would react? well the transformer is still getting hot even with the new on? I already replaced the 1k screen resistor with a 1k/5w and was wondering if I should replace the adjoing 10k as well. Something else is goin on here for that new transformer to get hot like that. any help would be greatly appreciated before I go any further?

Chuck.

[chuckb]

Got a new Hammond replacement for the 6g2 and got it onstalled. but the tranny is still getting hot,Why?
I wired it up the same as the old one came out and I flcked the"on" switch with no tubes installed of course. and the darn tranny still gets hot. I've changed out the screen resistors,1k and 10 k, along with the grid stoppers 1.5k ea. I'v changed the power filter caps as well, and nothing.

Frustrated,
chuck.

[Bruce / Mission Amps]

Got a new Hammond replacement for the 6g2 and got it onstalled. but the tranny is still getting hot,Why?
I wired it up the same as the old one came out and I flcked the"on" switch with no tubes installed of course. and the darn tranny still gets hot. I've changed out the screen resistors,1k and 10 k, along with the grid stoppers 1.5k ea. I'v changed the power filter caps as well, and nothing.

Frustrated,
chuck.

Pull off the filament wires from the PT to the first place they go and remove the rectifier tube.
If it still over heats you have a simple wire shorting somewhere. If not, my first guess is the pilot light assembly or the filament string is chassis grounded somewhere that it is not supposed to be.

[Tom Phillips]

There are two simultaneous threads running about this exact PT problem.
It would be best not to do that.

[bob p]

Agreed. Let's consolidate things into this thread:

http://music-electronics-forum.com/t32755/

[chuckb]

sorry bout both treads. The two green filament windings for the heaters, has one going to the pilot light and the other is grounded to the chassis with the red and yellow center tap?

[JoeM]

sorry bout both treads. The two green filament windings for the heaters, has one going to the pilot light and the other is grounded to the chassis with the red and yellow center tap?

??? One of the green is connected to the red/yellow CT? Or the 2 green to the pilot and one red/yellow to ground?