Amplifier noisy nothing plugged

[Colas LeGrippa]

Hola amigos ! It's been a while...


I have an old Traynor YBA1A which is noisy  even when nothing is plugged in with volume at 6 and over. Kinda hiss and hum mixed


I checked all voltages, bias, lead dress, unsuccessfully.


The heaters are elevated   , power tubes are good, .....so I dont know where to check now ,
my skills disappeared , too many hours practicing..


Thanx


Colad

[shooter]

start with the 1st tube after the input jack, remove, test, Noise still there?
IF so;
leave tube out, remove "next" tube in line, still noise?
STOP before the PI


hiss is "typically" noisy plate R's, but that just the beginning....

[kagliostro]

Ciao Colas

Is the switch on the female input jack OK ? Does it connects the input to ground when nothing is inserted ?

The same for the ground connection

Franco

[PRR]

Do you play un-plugged?

Why care about power tubes? Hiss/hum normally comes in a LOW level. Swap small tubes!!

Do any knobs do anything? (You gave a partial clue but more info helps.)

[Colas LeGrippa]

PRR,  I just want to reduce to minimum  the  noise of my amp. The tubes are good.that s the first thing I tried. While playing I don't hear it ( I am deaf anyway) but when I turn on my 12V tube stompbox which is near dead quiet on my high gain little amp,  the hum is just too loud on the Traynor because the amp is  unstsable.
I  swapped the 220k plate resistor.on V1 for a 100k which helped a bit.


Kagliostro,, I've redone the input jack and.discovered a noise when moving the  shielded cable from volume pot to V1 second control grid. Replaced the cable just to make sure that it is not the issue.


Shooter, tubes are good.


Overall noise has definitely diminished.
Thanks for tips .  Linda will  be happy too !!!


Colas

[shooter]

Shooter, tubes are good.

you're pulling the tubes to ISOLATE the noise, you can put them back when you figure out which stage is the problem child

when I turn on my 12V tube stompbox

without it being plugged into the amp?, just powering on?

[Colas LeGrippa]

Sorry  Shooter, I .meant to say the first stage was the offending one.  The amp is dead quiet without the first tube. I tried that tube in  another amp to make sure it was nott the issue.
In that sense I answered you that the tubes were good.


At first I thought it was a ground loop since I m' using two amplifiers  with 3 prong cords but it's not cause I am using a lineout with a transformer.

[Colas LeGrippa]

Layout is:


Hi gain low wattage amp------ transformer line out------regulated 12v 12au7 stompbox ------digital delay--------traynor 50w, in that sequence. Tonight, I have replaced V1 capacitor for a new one. Hiss and hum are reduced but still there at vol set to 7. When I switch off  V1  first cathode bypass cap,  the noise is almost gone at full volume. It s not too bad  but .I want the traynor to be perfectly noiseless so more investigation is goin on, while I have a bit of time ahead of me.




Colas

[tubeswell]

bad cable?

[Colas LeGrippa]

......very simple thing to check first, but I haven t thought of it.....


Nope, all  jacks are good thanks anyway.
It s very weird,  go back to the post "layout".
When the amp goes noisy and unstable, turning on the 12au7 stompbox makes a loud pop , otherwise we hear only the click of the switch itself. I think I'll do a cap job on the Traynor.
The stompbox is good, well filtered  and regulated 12V,  shielded signal cables , guitar ok too ...






Colas