This Is wierd

St August · Post by **St August** » Sat Apr 08, 2006 7:56 pm

Today I decieded to put the Sovtek Back In the Head box .. Hooked it up and all of a sudden my amp sounded like SH*T.. I was like WTF so I took it back out and Low&behold it kicks ass again.... Is there something Im doing wrong?

Help!!!!!

Necrovore · Post by **Necrovore** » Sat Apr 08, 2006 8:35 pm

The amp no longer wants to be constrained in that Sovtek box?

JD · Post by JD » Sat Apr 08, 2006 8:57 pm

"Some birds are just not meant to be caged."

St August · Post by **St August** » Sat Apr 08, 2006 9:10 pm

SDM · Post by **SDM** » Sat Apr 08, 2006 11:06 pm

I like the above theories. Might be something shorting out or flexing a bad solder joint when the amp is flipped upside right. Could also be oscillation you sometimes get with a head placed upright over the speaker cabinet. Does your head box have a metal shield/screen stapled or glued to the bottom inside that would act as a cover for the open bottom side of the chassis? If not you could try putting one in, could aso try moving the amp away from the cabinet first, while it is upright, to see if oscillation could be the problem. If you do have a shield in the head box, make sure nothing is hitting on it to short anything in the circuit when the amp is sitting on it.

St August · Post by **St August** » Sat Apr 08, 2006 11:26 pm

Hey Steve it does have a shield.... how ever I did find a loose wire and I fixed that problem... but may be I have another.. When I turn up the the V2 pot past half way iget a real fast ossilation(if you remeber idid the one wire mod you helped me with) so if I could fix this other problem Ill be all set cause the amp is sounding real good but i would like to know that it isnt ossilating anymore..

SDM · Post by **SDM** » Sun Apr 09, 2006 12:07 am

There are a few ways that will likely kill any oscillation you have left, though some of them (if the oscillation is stubborn enough) could effect your high end a bit. Usually lead dress is the biggest culprit, and is the best to try to remedy first, as it won't alter anything tone wise. A signal wire passing too close to a plate lead in phase with it is a big culprit in oscillating problems. Might try the good old wooden stick with the amp on to move some wires around to see if you can effect the oscillation. Shielded wiring, do you have any in there, and where? If the above two don't get it, you can use small 100pf and up caps acrossed one or both of the 100K plate resistors feeding your first preamp tube. Of course cheap guitar cables and pickups can cause you squealing too, and shouldn't be overlooked. Got any good gut shots? Would be the easiest way to give any ideas on what may help.

St August · Post by **St August** » Sun Apr 09, 2006 11:57 am

Ok I finally found my camera.....Ok heres a couple of picsof the guts if you need more let me know.. I dont have a great camera so I dont know if these will help any... the black wire is sheiled cable going to the input of V1
the white w blue stripe is also shielded cable in use for the ground

SDM · Post by **SDM** » Sun Apr 09, 2006 9:05 pm

I said " good gut shots"

. Yeah a bit fuzzy there . Looks like your amp may has a shared cathode on V1, pin 8 jumpered to pin 2. Is that right? Seperating the cathodes will give you alot more options for tweaking the sound/gain of the first tube's 2 stages independantly, and help avoid oscillation. That aside, as to current circuit: The prominent white lead that looks to hit the long black lead is just a ground wire for the shielding on the black wire? If so the white ground lead doesn't need to be a shielded wire, doesn't hurt anyting that it is though. All shielded wiring is not created equally, and your long black wire could be causing you problems. Try moving that wire pretty much up and away from the inputs, and board. If this makes any difference, you can likely shorten it up, and run it more directly to V1. Can you tell me what the two thick white wires running to socket one are connected to. Is one just lying there disconnected from one of your inputs? Looks like you've got a very simple PPIMV there, try moving the purple wire near the yellow negative feedback wire (coming from the speaker jack) away from each other. Best to use short as possible wires to your PPIMV and preferably shield them. Try moving the negative feedback wire alone around a bit to see if that helps too. If it were me, I'd just go ahead and shield the PPIMV wires anyway, could solve the problem right off. Some ideas ideas to play around with first with anyway.

St August · Post by **St August** » Sun Apr 09, 2006 9:20 pm

steve im going to pm you with my fone # and we can talk....