Drawbar and Chorus troubleshooting

[ELB]

Hello,
I got a 1952 B2 with leslie 142.
The instruments. is in good shape. It has a TrekII preamp and percussion unit installed.

There's a few thiing not working as it should.
1- One drawbar is very quiet. I hear something but the sound is very faint. Can somebody could point me in the right direction for possible repair or what to look for.

2- vibrato-chorus. They are working but the effects are really not pronounced enough i find when i compare to other instruments (c-3 for exemple). Again any pointers will be greatly appreciated. Should I rebuilt and cleanup the scanner ?

I am very handy, so im looking foward to make repairs on my own.

Thanks

[David Anderson]

On earlier organs like your B2, the Chorus Mix Resistor, R38 on schematics, was 22k. It was 22k into the early 3-series. In 1957, that value was changed to 12K, making Chorus more pronounced (by making it electronically closer to the full Vibrato settings). You can either change this resistor value or attach a potentiometer to dial in the depth of Chorus you want. This is not a scanner issue. If the resistor change does not give you everything you want, you might try rebuilding the vibrato delay line box, though that is a fairly involved procedure on these early line boxes.

I'm not sure about your drawbar problem.

[ELB]

David,
What is the wattage of the 12K resistor I would need ?
I when to an electronic parts store and rhere's different ones to choose from.

[muckelroy]

I'm fairly certain R38 is inside your vibrato line box, but there are many different versions of this box. Follow the wiring diagram and schematic, and it should be apparent which it is when you drop down the line box and look inside. On the wooden frame large vib line boxes it's one of the resistors mounted just behind the terminals on the front.

As for your drawbar problem, there are several possibilities. Remember that one drawbar on the upper manual is disabled completely when percussion is turned on. Make sure the wire is securely soldered to the back side of the drawbar contact. Press down firmly on the appropriate preset key. If the sound is strong when pressing down but weak when you let go, the preset mechanism may need adjustment, or dirty bus bar contacts may call for shifting your bus bars.

Check that the Trek II unit is correctly installed. Tell us which drawbar is the problem, and whether it's the upper or lower manual (or both.)

[Hoaxel]

Trek ll Perkussion uses one drawbar permanent, For the Set ist Always " online"

[ELB]

Yes, the quiet drawbar is the one for the upper manual, second set, the 1 1/3'' one. If you tell me that the percussion steels one drawbar, I'm guessing that's the one.

[handyczech]

Tonewheel General Hospital, in my experience.

[muckelroy]

Your “quiet drawbar” is really a “dead drawbar”? Yes, it's expected for the Trek II to work that way. If you must have that harmonic, use the other B preset set of drawbars ;)

[ELB]

Thanks everybody for your inputs.
Problem solved :
- Rebuilt the vibrato delay line box.
- Swapped the old 22k for a new 12k located in the switch box near the knob.

Now I hear the difference between the different vibrato and chorus selectors. And the chorus is more present.
Plus, It was fun and easy to do.

Now I think, I will recap the tonewheel generator.