Hi everyone,
This is my first post here, so if I'm doing something wrong, I'm sorry!
I'm repairing an old organ, the previous owner tried to tune it and destroyed what was probably a trimpot (which is now totally missing).
According to the schematics, the part "number" or "name" is "23.515".
I've found pictures of the missing component: Infrequent Sound [sex.tex] technology: GEM Galanti Group Rodeo 49, made in Italy
My missing part is the bottom left potentiometer.
Does this "23.515" refer to something standard ?
Thanks for any advice!
This is my first post here, so if I'm doing something wrong, I'm sorry!
I'm repairing an old organ, the previous owner tried to tune it and destroyed what was probably a trimpot (which is now totally missing).
According to the schematics, the part "number" or "name" is "23.515".
I've found pictures of the missing component: Infrequent Sound [sex.tex] technology: GEM Galanti Group Rodeo 49, made in Italy
My missing part is the bottom left potentiometer.
Does this "23.515" refer to something standard ?
Thanks for any advice!
You show 22 pictures covering the whole organ, are we supposed to guess?
Show it clearly and what is it connected to.
That´s an internal/Factory inventory name, tells us nothing.
![GEM+Rodeo+49+made+in+Italy+[Galanti+Group]+[0010].JPG](https://4.bp.blogspot.com/-keZBHmqdIEw/T_wnJ9dobnI/AAAAAAAAAhE/W46sRnPIasQ/s1600/GEM+Rodeo+49+made+in+Italy+[Galanti+Group]+[0010].JPG)
No help, but maybe there are more copies of that subcircuit elsewhere in the schematic.
Can you post the entire schematic?
Can you post the entire schematic?
Here is the full schematic for the Rodeo 37 (which is a smaller version of the Rodeo 49).
Sadly there's no parts list index 🙁
Sadly there's no parts list index 🙁
I see two 30-some-odd gauge magnet wires going into that device. That suggests to me *variable inductor*, not pot. It might make sense in an oscillator circuit.
Could be a bridged-T feedback oscillator. Some organ fan will have to give you the info on the inductor.
It's adjustable to set the frequency. Might be possible to replace this with another oscillator circuit.
It's adjustable to set the frequency. Might be possible to replace this with another oscillator circuit.
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You're right, the missing component looks like a variable inductor.
The tone generator is a MK50241 which seems to expect a 2MHz Clock on pin 2.
I'll have to find reference schematics, close to this one and extrapolate a proper range value.. wish me good luck 🙂
No clue on Digital stuff, but IF that were a resistive trimmer , I see a "T" filter made out of C113 - C114 and both halves of said "trimmer"
IF an inductor, it would be a center tapped one, obviously adjustable, and in both cases presumably part of a tuned circuit, either RC or LC
I would expect to find 12 of them, so 11 other "23-515" parts elsewhere.
or very similar, perhaps 23-512/513/514/etc. if each note needs a different value one but same basic function.
Lots of brainpower here 🙂 , but I bet there must be a dedicated Italian or 60´s Organ Forum somewhere where even the guy who sweeps the floor will know "oh" ... 23-515? ... but of course! ..." he he.
PS: LOVED the hand applied crepe tape design PCBs.
IF an inductor, it would be a center tapped one, obviously adjustable, and in both cases presumably part of a tuned circuit, either RC or LC
I would expect to find 12 of them, so 11 other "23-515" parts elsewhere.
or very similar, perhaps 23-512/513/514/etc. if each note needs a different value one but same basic function.
Lots of brainpower here 🙂 , but I bet there must be a dedicated Italian or 60´s Organ Forum somewhere where even the guy who sweeps the floor will know "oh" ... 23-515? ... but of course! ..." he he.
PS: LOVED the hand applied crepe tape design PCBs.
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Thanks for all your replies !
I'm still investigating and I found this (the place where the 'guy who sweeps the fooor'.. 😀)): Generalmusic Spare Part Codes – GEMClub | Generalmusic Owners Club
There's no reference to a 23.515 (nor 230515) component, but around "23-something" we have the
- 230521 : "Yel Dot Tuning Coil 10-20uH"
- 230526 : "Blu Dot Tuning Coil 1.2-4.6uH"
According to photo, the 230515 is progably the "red dot" version 🙂
I'm still investigating and I found this (the place where the 'guy who sweeps the fooor'.. 😀)): Generalmusic Spare Part Codes – GEMClub | Generalmusic Owners Club
There's no reference to a 23.515 (nor 230515) component, but around "23-something" we have the
- 230521 : "Yel Dot Tuning Coil 10-20uH"
- 230526 : "Blu Dot Tuning Coil 1.2-4.6uH"
According to photo, the 230515 is progably the "red dot" version 🙂
Sometimes, you need luck ...!
Since I know that the Blue dot tuning pot is around 5uH and the Yellow is around 20uH, I can guess that the red one is probably something between 1uH and 100uH.
I have a few K102 inductance in stock (1000 uH), so I tried to use two of them and replace the missing adjustable inductance. My plan was to measure the output Clock frequency (which is supposed to be precisely at 2MHz), and guess a more approriate inductance value.
And.. it works ! Clearly not in tune (middle C is at 446Hz), a few octaves too low, but well, it plays sound !
Since I know that the Blue dot tuning pot is around 5uH and the Yellow is around 20uH, I can guess that the red one is probably something between 1uH and 100uH.
I have a few K102 inductance in stock (1000 uH), so I tried to use two of them and replace the missing adjustable inductance. My plan was to measure the output Clock frequency (which is supposed to be precisely at 2MHz), and guess a more approriate inductance value.
And.. it works ! Clearly not in tune (middle C is at 446Hz), a few octaves too low, but well, it plays sound !
The 2MHz target suggests a "Top Octave Generator", did the divisions to turn 2MHz into nearly equal tempered 12 tones. While the pitches are not quite right, they are never very wrong, and the user can't mess-up much (except as in this case, by breaking stuff off).
TOGs and their app-notes used to be common but are now rare. The hits that Google is finding are mostly about duplicating the function in PICs. Or old-old CMOS plans that "I know" will be super-fussy about the CMOS you put in them.