From eslawson@juno.com Tue Apr 03 03:32:12 2001
Subject:Leslie Treble Driver vs. Leslie 6550 tubes

Thanks to everyone for their suggestions for 6550 tubes and other
diagnoses given to my ailing 122. I am now convinced that I might have a
treble driver problem vs. a tube problem.

When I first heard the distortion happening at any volume, I was so
excited to be playing the Leslie that I chalked it up to sensitive tubes
or something like that. Now that the initial excitement has subsided, I
have done some additional experimentation. The sound I have been hearing
is more like a constant buzz, coming only from the high end. The organ
sound comes through as well, but it is accompanied by this constant
buzzing which is like a cross between rattling window panes, bacon frying
and solid state overdrive. It is not the sweet tube distortion one would
expect from a Leslie amp. It is rather annoying. I cannot get a clean
organ sound. This buzzing occurs at all volumes and only emanates from
the high end. As I crank the volume, I began to get a mix of the true
amp overdrive mixed with the buzz. The low end does not buzz at all. I
checked this out at all volume levels using only the lower end of the
organ with 1 or 2 drawbars pulled out. As I pull out higher drawbars or
go to the upper half of the organ keyboard and the sound crosses over to
hit the high end speaker, I get the buzzing sound. Since I don't get the
buzzing sound in the low end, I think this rules out the 6550s as the
culprit.

I don't know how to tell if a driver is fried. I tried reversing the
wires going to the upper driver and I hear the same thing. I jiggled the
wires and no loose connections. I checked and there are no loose
components rattling around (I hoped to find a loose screw or something).
This racket is coming straight from the horn driver. I'm in kind of a
precarious situation because any "test" remedy is going to cost me money.
I was about to order a set of 6550s from Goff (they sell an entire
matched set for $79). Now I might need to order a new horn driver, which
is like $150. I don't want to guess at the problem and end up spending
hundreds of dollars and still have the same problem. Especially when I
am saving my pennies for an Anvil road case!

So now I will ask the group: does this sound like a driver problem and
what kinds of replacement drivers do you recommend? I hear the Atlas
PD60 is a good one.

Thanks again,
Eric