Here’s an MP3 file of the noise the organ is making. It’s about 24 seconds:
- The pop of the power switch being turned on.
- Silence and the noise fading in as the tubes warm up.
- Loud noise.
- Faint notes — me playing on the keyboard. I could adjust the manual and pedal volumes to any mix I wanted; that’s just where they happened to be set.
- Fade out after I turned off the power.
Note that the noise is continuous the whole time the organ is on — not just when playing the keyboard or pedals. And my iBook’s internal microphone didn’t capture the lower octaves of the noise at all — the sputter goes down further than I can hear playing back this sample.
Maybe this helps?
Very much so. We’re getting static, since the static remains even when a tone isn’t being played, it smells like an issue with the amplifier. This can be bad connection or bad capacitor. Does the static volume change as you change the volume of the organ? I did some digging and found this Baldwin:
http://www.gibson.com/en-us/Divisions/Baldwin/
I’m not sure that they’re the same company, if they are, they may very well have the schematic for your organ in their archives. It would be worth a call to see if you can get in touch with the archivist.
The static volume gets louder when we press the swell pedal (overall organ volume) and when we increase the pedal volume pot on the amplifier board. It does not seem to change when the pedal stops are switched in and out — even when they’re all out.
I’ve been leaning toward the amplifier too, but I know so little about the circuit, I’ll entertain other suggestions too.
That would imply amplifier – the volume control will alter the gain in this amplifier. So we know that the static is being amplified by it, therefore the noise has to be arriving on it’s audio input. The pot that controls the volume will probably form a resistive divider with a fixed value resistor, this will be providing feedback for the amp. Remember with feedback, we’re taking a small amount of the output and putting it back in the input. So we want to look for a connection going from the wiper of the pot either to ground or the grid of a tube(IIRC), that should be the input to our audio amplifier.
I also found this little blurb that describes a little more info on the structure of organ’s circuit:
http://en.allexperts.com/q/Piano-Organ-Keyboard-650/Baldwin-45-HP2-electronic.htm
Also, this fellow appears to have service manuals for your organ:
http://www.mitatechs.com/spoon1.html
These would include the schematic.
We have a Baldwin model 45c or h2. Keyboard stopped working not a peep out of any keys. Pedals did fine. I have a manual with schematics. Tracing I went to preamp found one of 12ax7 bad. This one has 2 channel amp which some like to get as they like sound from tube units. Lucky this time but need 12ax7 tube. I have box of tubes and believe one may be in it.