I'm working my way through a 1954 Hamond C2 organ. The tone generator would not maintain speed, so after weeks of adding oil didn't work, a replacement motor was installed. One of two windings in the original motor had gone open circuit.
The audio output level was very weak. Tracing through the preamp found there was no gain and lots of DC offset from the old capacitors leaking. So a new set of caps were installed this week.
Now I'm working through the capacitors in the LC tank resonators on the tone wheel generators. Rows of capacitors to be replaced. Values are selected to match each LC tank circuit to each tone wheel frequency.
Preamp in the organ.
New capacitors installed in the preamp. Now working properly. 50 mV input gives 3 V output.
Disconnecting the wires from the tone generator.
Tone wheel generator with 91 individual permanent magnet generators. Six capacitors replaced and a whole bunch more to do.
Measuring the resonant frequency of one LC filter.
The audio output level was very weak. Tracing through the preamp found there was no gain and lots of DC offset from the old capacitors leaking. So a new set of caps were installed this week.
Now I'm working through the capacitors in the LC tank resonators on the tone wheel generators. Rows of capacitors to be replaced. Values are selected to match each LC tank circuit to each tone wheel frequency.
Preamp in the organ.
New capacitors installed in the preamp. Now working properly. 50 mV input gives 3 V output.
Disconnecting the wires from the tone generator.
Tone wheel generator with 91 individual permanent magnet generators. Six capacitors replaced and a whole bunch more to do.
Measuring the resonant frequency of one LC filter.
Yes, I am considering removing the HV secondary winding and customizing the primary for some 'Super mH Inductors'.
Until I got out the schematic and started on the restoration I did not appreciate the complexity. It's a polyphonic machine with adjustable levels for the subharmonics, fundamental and upper harmonics. Pressing one key closes eight switches that connect the appropriate set of tone generator outputs for that key to the main bus and then through attenuators ( draw bars ) and then to a summing transformer. So by adjusting the relative levels of the subharmonics, fundamental and upper harmonics the sound of various instruments can be synthesized. For brevity the schematic for a single key is presented in the manual and it is a few pages wide.
There are capacitor kits available to restore the tone generator. These were just a single value that was too low for the job. I bought my own set of capacitors from an amazing web store, Tony's Capacitor Corner, and I'm sorting and combing two or three capacitors to tune each resonator to the frequency generated, just as they did at the factory. I believe the factory changed the windings to match the capacitor values, but I can't do that. I have the advantage of running impedance sweeps with each capacitor combination I try, so I can really nail the resonant peak. So when complete this should play as good or better than it did from the factory in 1954. Unfortunately this takes hours and hours to get right which is why I've seen nobody else doing it.
There is a repair shop dedicated to Hammond organs in Seattle, but the owner has not been able to open the shop for months as he is caring for his wife. So I'm winging it, watching the videos I've found on youTube and websites.
For anyone else doing this I recommend
https://ssl.tonewheelgeneral.com/ for the preamp capacitor kit.
https://bentonelectronics.com/hammond-generator-filters/ great drawings and explanations of the circuits and construction
I created a list of the exact frequency for each tone wheel in the organ as I was unable to find this information. Fortunately I did find the calculation documented so it was easy to perform using the motor rpm, gear ratios and number of "teeth" on each tone wheel. See the attached .pdf.
I will likely have to sell this organ in the next few months along with the Leslie as I don't have room to keep it long term, and I don't actually play the organ.
There are capacitor kits available to restore the tone generator. These were just a single value that was too low for the job. I bought my own set of capacitors from an amazing web store, Tony's Capacitor Corner, and I'm sorting and combing two or three capacitors to tune each resonator to the frequency generated, just as they did at the factory. I believe the factory changed the windings to match the capacitor values, but I can't do that. I have the advantage of running impedance sweeps with each capacitor combination I try, so I can really nail the resonant peak. So when complete this should play as good or better than it did from the factory in 1954. Unfortunately this takes hours and hours to get right which is why I've seen nobody else doing it.
There is a repair shop dedicated to Hammond organs in Seattle, but the owner has not been able to open the shop for months as he is caring for his wife. So I'm winging it, watching the videos I've found on youTube and websites.
For anyone else doing this I recommend
https://ssl.tonewheelgeneral.com/ for the preamp capacitor kit.
https://bentonelectronics.com/hammond-generator-filters/ great drawings and explanations of the circuits and construction
I created a list of the exact frequency for each tone wheel in the organ as I was unable to find this information. Fortunately I did find the calculation documented so it was easy to perform using the motor rpm, gear ratios and number of "teeth" on each tone wheel. See the attached .pdf.
I will likely have to sell this organ in the next few months along with the Leslie as I don't have room to keep it long term, and I don't actually play the organ.
Hot glue for the win!My wife's shoes. Methyl hydrate to clean and a hot glue gun saved me $100.
When I learned that hot glue could be removed when cold after a bit of rubbing alcohol was applied it became really useful for prototyping as I could now take things apart if needed. I learned this watching the paintless dent removal videos on youTube.
Off to YouTube I go. I need to remove a ding from the lid of a Weber kettle and would definitely prefer not to repaint. **Cue future post here with a restored, repainted Weber...
Nice job on the restoration!
I once had a C3 and sold it for the very same reasons; not a keyboard player. There's a guy I connected with on ebay, who had/has a business restoring these and his customers are outside the US. He was driving a moving van around the country "American Pickers" style and loaded the C3 up into it himself. There were several other organs in there and I noticed he had vintage horn drivers tucked under the front seat. I had a pair of JBL cabs he made a good offer on, so I let those go to him same day, over 10 years ago...
RE tuning the tank circuits- a decade cap might speed the process up a lot. And this is quite a good deal: https://www.ebay.com/itm/2669357523...R3ob3F1MD/KWfJR85PDQojqQ==|tkp:Bk9SR_yU_vzxZA resonate the coil at the right frequency and read off the display what you need for a cap. The temperature coeffients will be a possible issue but would mostly affect the amplitude as the tuning shifts.
A decade box would have been good. After about 12 hours of working on it I installed the final capacitor this afternoon. I got pretty good at guessing the value I needed to add or subtract after measuring the resonant frequency using the nominal capacitor value.
Next I need to fire up the motor and check the relative levels of all the generators. If needed I can adjust the pickup coil gaps to the tone wheels to get a good waveform and balance the levels. I wish I had some sort of micro positioner.
I found an error in my frequency calculations that were in the pdf I uploaded previously. I am attaching the corrected spreadsheet here. I had used the wrong gear ratios to calculate the top seven frequencies. That became obvious when trying to tune the capacitors for those notes.
Next I need to fire up the motor and check the relative levels of all the generators. If needed I can adjust the pickup coil gaps to the tone wheels to get a good waveform and balance the levels. I wish I had some sort of micro positioner.
I found an error in my frequency calculations that were in the pdf I uploaded previously. I am attaching the corrected spreadsheet here. I had used the wrong gear ratios to calculate the top seven frequencies. That became obvious when trying to tune the capacitors for those notes.
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@olsond3 I think your soldering iron is period correct to attempt this repair. It looks like a Weller but I don't recognize the base. Maybe it was even before my time.
You might consider to remove the DMM from the bench and use a proper AVO. Preferably type 7.
It is a wonderful job you have undertaken. It would be a shame to see this thing being unused or worse being sent to the landfill.
You might consider to remove the DMM from the bench and use a proper AVO. Preferably type 7.
It is a wonderful job you have undertaken. It would be a shame to see this thing being unused or worse being sent to the landfill.
I repaired my glasses. The nosepad had broken off its support. The material is a fixture for a toilet flush mechanism which I eventually did not use but it came with the kit. Although that is a waste I did save it. As I save everything. Yes I am planning to buy a second 20 ft sea container for storage.
We get them at the spectacle shop...about 4 for 10 cents...and I have at least four shops in my city repairing spectacles.
No charge for regular customers..it is a two minute job.
They will even change the spring loaded hinges if needed and possible.
But then my city is a famous center in India for spectacles, (lenses etc. also), corrugated boxes and distribution transformers.
In any case, a commendable effort, making it from solid in a soft material.
No charge for regular customers..it is a two minute job.
They will even change the spring loaded hinges if needed and possible.
But then my city is a famous center in India for spectacles, (lenses etc. also), corrugated boxes and distribution transformers.
In any case, a commendable effort, making it from solid in a soft material.
My "IWork" leaf vacuum finally died. It's a clamshell assembly with a lot of screws. Sudden motor malfunction; hums strongly, turns at about 1/10 usual RPM. Rotor spins freely. I'm guessing a stator winding short / open, which I'd likely not find so easily. Anyone recognize the symptoms in brushed AC/DC motor? Big hum / 60 cy vibration, rotor turns relatively slowly maybe a couple hundred RPM. One moment running as usual, the next this.
The commutator probably has something lodged in there shorting adjacent windings. I’ve had brushes disintegrate on my Porter Cable router and short the works out. Threw a lot of sparks before it died. Cleaned the commutator, new brushes and continue making MDF dust.
That's what's weird - no sparks, no grinding. More like a 60 cyc vibration along with much slower turning. No scritchy feel when rotated by hand, like there might by when chunks of brush / brass are welded between the commutator contacts. I thought something jammed the impeller and it let go from the shaft mechanically, like a shear pin - it was that quick. But nothing did that and it's still fastened to the motor shaft as its always been.
It's AC powered, like a blender or vacuum appliance motor. It will - apparently - start to smoke if I run it for more that a few seconds, so I didnt do that a, er, 4th time.
What would the motor's operation feel like if one of the two series connected stator windings depicted below became shorted, with the commutator still in good shape? Run some, but not so well? Vibrate in a strange way?
I'm hoping to call it dead by consensus of experience and not have to take it apart only to discover I cant fix it unless I'm willing to unwind and rewind one of the stator windings. Got 10 years of service, bought used, maybe time to give it a permanent rest.
Well, I would quickly pop it apart and look to see.
You need to know something before making the right decision from a position of knowledge. It may just need brushes and a cleaning.
You need to know something before making the right decision from a position of knowledge. It may just need brushes and a cleaning.