HPPR build, got issues, rattle/buzz at high volume RESOLVED!!!

[dwp]

http://s304.photobucket.com/albums/nn191/dwpatte/

I just completed the HBPrinceton Reverb Build, no master volume. I get a, oscillation/feedback/rattle at high volume, cannot find error on the board or bad solder joints. Have been tugging wires to no avai. Can someone please review the pics in my photobucket and tell me where it looks like I mighr have gone wrong with lead dress?
Thanks in advance, dwp

[JayB]

Look for any grid wires crossing another previous grid wire. That's usually the culprit at high volumes.

[sluckey]

Whenever I hear the words 'feedback/oscillation' associated with a new build that uses NFB, the first thing that enters my mind is to eliminate the NFB loop as a possible source of the feedback/oscillation. May not be the problem but it needs to be eliminated. You have a 50/50 chance of connecting the OT primary plate leads correctly the first time around.

[dwp]

thanks Sluckey, how do I eliminate the NFB? you mean just lift the wire from the 2.7K resistor?

thanks JayB, I don't see any Grid crossing another grid at the preamp section. This problem has to be at the preamp end, yes?

[sluckey]

you mean just lift the wire from the 2.7K resistor?

Yes. Or, swap the OT plate leads.

[dwp]

swapping the leads I get a constant low pitched FB.......
will put back and try lifting the lead on the NFB resistor?

[sluckey]

swapping the leads I get a constant low pitched FB.......
will put back and try lifting the lead on the NFB resistor?

No need to lift the NFB now. You had the phase correct to begin with. Sorry, now you gotta find the real cause.

[dwp]

thanks. first time ever doing a request build for a customer too. Think I'm safe to figure lead dress issue at second stage or beyond? I have sone wires intertwined with the board components going to V2 and V3. am trying to free those up now, bring over and accross? checking solder joints as I go. Only hear it at High volume, like 7-8 and above. need to be able to dime this build, yes?

the feedback wouldn't be unpleasent if it didn't drop in and out while holding a note. snaps in, snaps out.....

[mick]

I have had oscillations at high volume because of my lead dress from the volume pot back to V1 pin 7.   I was getting coupling at high volumes across the wire even though I was using shielded wire.   When the amp starts to feed back, see if adjusting the treble control reduces the oscillations.   If so, you may reconsider the lead dress from the volume pot back to V1 pin 7.  I now run shielded wire under the board and have not had the problem since.

[dwp]

I had a cold solder joint right at the 470 K resistor to the Reverb pot. I looked at it 100 times thinking there's no way that's a cold solder joint. I wrap the lead to the pot around the turret, usually solder the component at that time, this one had visible solder but not a dome. I also started looking harder at Reverb section when I pulled the reverb driver tube and the problem stopped.
Thanks everyone, for your help and advice.