A0-28 in M3 prolblems

[Joe marolda]

Despite all my carfull planning it didn't work out. A awful buzz was present, the organ sounded good with volume soft/loud, perc.and vibrato functioning as should until a sudden substantial volume drop happened with the buzz. I checked the tubes in an other organ, fine. Checked the leslie, cable's and combo pre amp all fine. Im sure I damaged the amp. Just had the caps changed too and know i had a good amp. I'm sure I have no business messing with this stuff. I did fill out all missing fold back on this and three other spinets with success.
Can't for the life of me figure out why it didn't work or what's creating the buzz and the subsequent dammage.

[Sweet Pete]

Just had caps changed? Look at that for sure. Do you solder? Or do any repairs?
Cold solder joint will hum.Bad ground also.Or a transformer too close to the vibrato line....

Combo pre amp pedals are noisy to begin with.Great for testing Leslie motor stacks when servicing.....
personally,I remove them from my signal chain.
AO28 right into a Leslie is the way to go IMO.

Have the tech review the work.Unbolt the expression and AO28 and move it around still wired up to see if its a transformer issue.
Not as much room in there as a B/C etc.

[Joe marolda]

The transformer is within 6 in. Of the vibrato line so that may be the noise. I will move the V line and see if that's the noise. The re build on the amp was done by a 50 year seasoned amp guy that rebuilt 9 amps including this one for me and no prolblems. I have sound but it's very low, something happened suddenly, what caused it is a mystery.
Thanks Pete, I'll pick up on troble shooting with moving the V line.

[Joe marolda]

Tryed moving the V line, No difference. It's a older wooden box so I could hold it in my hand and move it closer and far away with no difference. I cut the loud soft wires to see if the shielded wires I used was it, no.
What would cause a massive drop in volume yet still have everything function as normal other than a loud buzz?
Maybe the amp? The only thing I wasn't sure about was the ground terminal, I put it on the TG housing and removed it with no luck. Where should brown ground go?
I tested the amp in my A100 before I had the caps changed, maybe it's just in the amp. Can't see it in the simple wireing.

[Sweet Pete]

How is the expression hooked up? What position is the expression potentiometer 'dialed' in to? When they travel beyond the operating limit interesting unwanted noises occur.
Did you make a note of the expression 'travel' when installing the AO28?
Have you 'overshot' the runway?

[Joe marolda]

The expression pedal works the same way just upside down and is working

[Jaim]

Where should brown ground go?

The brown/ground is used in the A1xx series to provide a ground point for the other amps (AO39 and AO35/44). It is also used as a ground point for a Leslie kit or line out. Did you clean the shield ground tabs?

Jim

[Joe marolda]

Thanks Jim, I could see that on my A105 but wasnt sure. I'm having my guy look at the amp, I put the A0-29 back in the organ and it works fine. I guess one prolblem out of nine amps this guy rebuilt for me is good considering most of them are older than myself.