Amp dropped by Fedex with weird doubling octavia noise

[louiss]

Hi everyone !......my first post,

Here I need your tech ears '
this is a well knowned beautiful Plexi like amp
dropped by Fedex when it was shipped from the builder's
place after full check up and update.

Now the amp is at my friends who his also
an amp builder but is trying hard to find whats
going on with the amp,...I made a clip where we
can hear the amp having a doubling kind of octavia sound,
anyone had that kind of problem?

Thank's!

Louis

http://youtu.be/9vY4mmISR-0

Here's what my friend noticed today,

Plate resistor at V3 via the 82K is low, 110vdc
(will raise the cap there see what happens),
should get above 200vdc, plate via the 100k is at 310vdc kinda high

all other voltages are in range, no leaks at first glance.
.nice B+ of 460vdc, screens voltages are good,
power tubes aren't pulling any current (normal)

Grounds are good but will redo some for better loop ground noises, ex.
presence should be alone

No scope here for now.....

[JazzGuitarGimp]

I don't mean to offend, bur based on what your friend has said, he is definitely not an amp tech. Take the amp to someone reputable.

[Phil_S]

...Grounds are good but will redo some for better loop ground noises, ex.

If it ain't broke, don't fix it. If you had a ground loop from the builder, he isn't much of a builder. I doubt this is related to any problem you've got or that it's a problem at all.

Take the amp to someone who will fix what's broken and not fix it until it's broken, and file a claim with Fed Ex to pay to fix it.

[louiss]

Thank's !

I know that my friend is not a professionnal
technicien or electronic engineer but he will do is best,
so that's why i'm here to ask
if the sound the amp makes is something
one of you have heard before .

Louis

[Meat&Beer]

I'm no awesome at amps guy, but I sure like to mess about with them. I've never experienced this problem before, and can't recollect actually hearing what I'm going to speculate on, but I'll throw a thought out there.

The choke?

From what I remember reading, ghost notes are heard, the tech goes nuts trying to troubleshoot and diagnose forever, and it's the choke being faulty. I think attack has a lot to do with power supply also. I doubt that a drop or a fall will debilitate a choke, however. (Being that it's mounted to a chassis that was assumed properly packaged for shipment) Perhaps the choke is underrated? Tell us some actual specifics on the components! Gut shots?

Did you hear this specific particular amplifier before buying it? Or, did you order it sight unseen/unheard? Was it a custom one-off order? I trust you've tried different guitars and speakers, cables, etc. Just because a guitar or speaker cab is known good, doesn't always 100% equate to good results, or "playing nicely" with other (unknown) equipment.

Maybe I'm way off! There is a plethora of amazing minds here that will make my theory null and void, if so.

Good luck with everything! Definitely +1 on filing a complaint on FedEx. Also, +1 on DO NOT MESS WITH IT if you aren't fully capable and well versed in all of the caveats that come with mucking around in tube amp guts. Oh, and +1 on IF IT AIN'T BROKE, DON'T F*** WITH IT. A ground loop has nothing to do with this issue.

[Milkmansound]

I've heard it before.

Once I accidentally put a 470k resistor where the 470R resistor goes in a long tail phase inverter (fender values)

I would suspect something in the Phase inverter based on my experience.

[martin manning]

One phase inverter plate low and the other high indicates the current in the one with the high Va is low. Try a new tube and check all the solder joints and the values of the resistors in the PI.

[louiss]

Again , thank's everyone ! .... I know it's not easy
not having the amp on your bench but I'm sure
that it will help !

I will try to post gut shots but this is
what this amp sounds like when healthy.

http://m.youtube.com/watch?v=rzBxYtUqhD8


Louis

[Structo]

First suspect is always tubes.
Especially if the amp has been rough handled.

Check mechanical things first like loose circuit boards or jacks.

Also, are you running the amp on a Variac?

[M Fowler]

Yup always tubes first and solder joints next. How are the pots they get hurt in most tumbles I've had to deal with.

[louiss]

Thank's again !

I found a good tech with a scope
near me so I should be able to drop
the amp on monday so I'll keep posted
on what the problem is or was !

Louis

[louiss]

Just came back from my friend to get
the amp to bring it on monday at the
tech's place and he found that the green wire
ground was loose so now the amp is a lot
better but still has a weird sound ,
he said the phase inverter V3 on pin 1 reads
120 and is suppose to be 225 and pin 6
reads 330 so he thonks somethings wring
in that area.

Louis

[JazzGuitarGimp]

Did he try replacing the PI tube? Given the amp was dropped, that would be the first thing I'd do.

[stephenl]

I've heard it before.

Once I accidentally put a 470k resistor where the 470R resistor goes in a long tail phase inverter (fender values)

I would suspect something in the Phase inverter based on my experience.

+1

[Leo_Gnardo]

pin 6
reads 330 so he thonks somethings wring
in that area.

open filament would do that. that's what I thonk.