[HAM] Leslie 122 Amp Question

[Jim Shanks]

> At 10:37 PM 6/3/2008, Jim Shanks wrote:
>>Hi All,
>>I have a Leslie 122R amplifier that's been subjected to some very
>>creative repair.  Looks like whomever fixed it couldn't find the
>>30/30/30/10 can cap so they just wired in a bunch of 22mf caps.
>>Following the schematics, it looks like one of them is even wired
>>wrong.  Plus wires were moved from original locations to accommodate the
>>mods and other components a just plain wrong.  Not surprisingly, it
>>doesn't sound like it should.
>>Anyway, I have the right parts, and service instructions and
>>schematics.  What I don't have is a photo of a 122 amp that's put
>>together correctly.  A picture or diagram would be real helpful in
>>properly placing the correct components as well as getting the right
>>colors on the wires.
>>Anyone know of a source or have a high res digital photo of the
>>underside of a 122 amp?
>
> Jim, there are a couple of problems with this approach. If this amp has
> indeed been modified so irresponsibly, the wire colors could well have
> changed. What if, for example,  you were to see an orange wire in the
> picture hooked up to C56 +, but the orange wire was now doing something
> else? And, no matter how beautifully photographed, I don't think I would
> be
> at all comfortable with following what I think I see in such a photo. The
> only way to wire this amp right, in my humble opinion, is with a complete
> understanding of what you see on the schematic.
>
> The first, and easiest part, is that a terminal trip long enough to hold
> the three or four largest electrolytics can have the ground side bridged
> across the lugs with grounding wire.

Hi Steve,

What I'm planning on doing is putting back to original specs and
components.  I'm sure some of the wires are now wrong, or at least the
wrong color.  I ordered a rebuild kit which included the 30/30/30/10
capacitor as well as other common components (diodes, caps, resistors and
one pot).  I don't plan on trying to copy a picture to get mine right
except to the extent that I would like the color codes and position of the
components to match an original as closely as possible, mostly for the
next poor slob that has to work on this thing.  I do plan on tracing every
wire and connection to make sure it's to spec.

Mostly, it looks like the power supply side of this one was modified.  I
followed a few other circuits using the schematic and the only other thing
I see that's out of spec is the DC motor brake circuit was disabled by
clipping one lead of the capacitor.  I guess I would have just pulled the
jumper, but whatever.  The cap is getting changed anyway.

I also noticed that the output tubes, while matched on brand, are not
matched.  That doesn't mean they aren't biased correctly, but I doubt it.

Guess the point is, I'm worried enough about this one to check everything.
 The amp isn't that complicated, so a few hours and beers and it'll be
going again.

Thanks for the help,
Jim

>
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