screeching

[youDEVILyou]

my model t just got new power tubes new pre amp tubes and SCREEEEECHES!
above 3 gain and 3 volume

i mean IT WAILS HORRID BLOODY MAYHEM.. and not the good kind..
i took out the new tubes and placed them all into a carvin mts 3200 and it soudns liek god on wheels. so im pretty sure none of the tubes were bad.

what could be up guys?



p.s im glad this place is back.

[tube]

if the screech has a rythym to it (tuh, tuh, tuh, tuh......) check for a small tube that has gone lame. you call that "motorboating."

 if the screech is like a siren that gets a little louder when it goes into full howl mode, the bias is incorrect on the output stage. that could be a mis-adjusted potentiometer or a bad solder joint in the bias circuit. you really need to carefully dial in the amp when it's re-tubed. it's not really cool to indiscriminately plug tubes into different amps without checking voltages and dialing things in.

 time to bust out the old simpson meter and plastic wand.

 best regards, tube

[Anonymous]

yea
i dont jsut pop in tubes to the sunn i got it biased. and all matched quad.

but the carvin has a fixed bias..so it figured it wasnt going to hurt it.

so ill take it to a guy and ask him to check the bias circut.?

[Anonymous]

Did you replace the metal shield covers on the Model T?  These are essential.

[Don T.]

Hello:
 You may have a microphonic preamp tube. Depending on the gain structure or placement it may not squeel in another amp.
Don T.

[Anonymous]

i replaced the metal sheilding and i switched the tubes aroudn in all positions.

you see i DID have microphonic pre amps before i could tap the top of the amp and hear it reverberate through teh speakers but ive tested all of the positions (not all but i have put all the tubes i have in to v1) and it still squeals.

[tube]

yea
i dont jsut pop in tubes to the sunn i got it biased. and all matched quad.

but the carvin has a fixed bias..so it figured it wasnt going to hurt it.

so ill take it to a guy and ask him to check the bias circut.?

  dude,

 i didn't mean to offend you, i would have been more correct in saying that "one" shouldn't arbitrarily swap tubes instead of inferring that "you" had done so.

 other shielding issues could be checked point to point.

  best regards, tube

[Anonymous]

thanks every one.


other sheilding issues?

like what?

i like the idea of it being my bias circut becaus it answers alot of querstions.


like when i put a voltometer in the self bias section NO MATTER WAHT i never get any signal.


any specifics on what could be wrong with my out put bias section that i could mention to my tech

[briann]

is your reverb turned up? this is a long shot... but i got a horrid screeching sound when the ground from the reverb came unattached. the sound was actually kinda cool, like a oscillating fuzz scream or something...

[Anonymous]

no its FMIC no reverb on it.

[youDEVILyou]

i just found ou tthta doug roctofore lives up the road form me and im probobly gona pay him to make it alllll better.



thanks people i apreciate the help.

[Anonymous]

This is a Fender Model T?  Sorry, I thought you meant a real one

[youDEVILyou]

i wish

i really love this amp though.


unique sounding