Hammond Organ, is it safe

[Lucien Nunes]

For buzzing that is certainly a possibility but we should call it signal ground instead of earth

 

[DPG]

For buzzing that is certainly a possibility but we should call it signal ground instead of earth

A fair point. In my defence I was trying to keep things simple.

 

[Mad collector]

Someone coming to look at the organ tomorrow, it seems he's been fixing Hammond Organs for about 150 years, he's no youngster lol

 

[Lucien Nunes]

I was just looking at the circuit. I suggest beginning by looking at the connections from pedal divider board to pedal mute tab and its associated wiring, as these lie between the keying diodes on the divider board (which aren't controlling the buzz) and the drawbar (which is). I would begin by linking divider board pin 1 (output) to pin 9 (ground) and seeing if that clears the buzz partially or completely. Then we can move forwards or backwards depending on the result.

Do you have a multimeter?

E2A Ah I see you have found someone to do this, hope it goes well. Also ignore previous incorrect reference to pin 6!

 

[Mad collector]

Yes I have an AVO model 8

 

[Lucien Nunes]

Hmm, well if you want to have a look at your own risk, try my suggestion, pedal div board link pins 1 & 9.
And/or confirm what effect the pedal mute tab has on the buzz.
Make sure the pedal div board can see ground properly, it might pass signal in the absense of a solid ground connection due to paths through the footage switch etc.
Service manual is available here https://medias.audiofanzine.com/files/hammond-xtp-series-service-manual-478272.pdf
It is missing a few pages and parts of it are specific to the XTP but the circuits for the cabinet T's are there.
P29/30 of the PDF shows the pedal divider schematic, 31 the PCB, 33 & 38 the wiring from divider to the pedal drawbar

 

[DPG]

I can't stop picturing the Viz comic strip 'Captain Morgan and his Hammond Organ'

 

[Lucien Nunes]

It's always possible to drag the tone of a thread downwards.

Actually the organ (the instrument) has always had a problem with its name. I'm sure there would be much less tittering in the back row if it were called the 'omniphone' or 'aerochord' or really anything but organ. Perhaps the piano could be renamed the plonker, to distract attention.

 

[DPG]

It's always possible to drag the tone of a thread downwards.

Actually the organ (the instrument) has always had a problem with its name. I'm sure there would be much less tittering in the back row if it were called the 'omniphone' or 'aerochord' or really anything but organ. Perhaps the piano could be renamed the plonker, to distract attention.

Omniphone - I like that.

 

[Lucien Nunes]

If you listen to some good orchestral-style playing on a big multi-genre civic organ, and in this domain there is no finer example than Richard Hills at the Southampton Guildhall Compton, you will get a sense of how apt the 'omni' is. Try these little samples from this instrument:

http://www.ssfweb.co.uk/silverst/The_Dancing_Years.mp3

http://www.ssfweb.co.uk/silverst/In_Malaga-1.mp3

http://www.ssfweb.co.uk/silverst/March_Heroique.mp3

And to return towards the original subject of the Hammond, this one features the Melotone electrostatic tone generator which is incorporated into the pipe organ.

http://www.ssfweb.co.uk/silverst/The_Girl_from_Corsica.mp3

The men at Compton who designed this had tried electromagnetic generators as used in the Hammond, ran into some of the same limitations as Hammond, and developed the more versatile electrostatic system instead that sounded more convincingly like a pipe organ. However, Hammond did a much better job of selling his invention and and although his tone generators didn't sound quite like a pipe organ (in fact there was a lawsuit in which it was questioned whether the Hammond instrument was, in fact, an organ) their signature sound was promoted, caught on and became a legend of its own.

 

[DPG]

If you listen to some good orchestral-style playing on a big multi-genre civic organ, and in this domain there is no finer example than Richard Hills at the Southampton Guildhall Compton, you will get a sense of how apt the 'omni' is. Try these little samples from this instrument:

http://www.ssfweb.co.uk/silverst/The_Dancing_Years.mp3

http://www.ssfweb.co.uk/silverst/In_Malaga-1.mp3

http://www.ssfweb.co.uk/silverst/March_Heroique.mp3

And to return towards the original subject of the Hammond, this one features the Melotone electrostatic tone generator which is incorporated into the pipe organ.

http://www.ssfweb.co.uk/silverst/The_Girl_from_Corsica.mp3

The men at Compton who designed this had tried electromagnetic generators as used in the Hammond, ran into some of the same limitations as Hammond, and developed the more versatile electrostatic system instead that sounded more convincingly like a pipe organ. However, Hammond did a much better job of selling his invention and and although his tone generators didn't sound quite like a pipe organ (in fact there was a lawsuit in which it was questioned whether the Hammond instrument was, in fact, an organ) their signature sound was promoted, caught on and became a legend of its own.

I will definitely look at those links later. Beer precludes me from fully appreciating them tonight.

 

[Mad collector]

Organ duly repaired and ok now loose wire near the pedals
Organ now working perfectly

 

[Lucien Nunes]

Good stuff, thanks for reporting back. Keep the generator oiled with the correct oil and it'll probably outlast all of us.