Hi, I just receive a free Conn 640 theatre organ from a thieft shop who was going to throw it in the dumpster.
I need a complete schematic for the 640, which seems to use the same power amp as the 720 model, from what I've seen online.
I am into repairing and restoring old electronics, but not confident enough to reverse engineer a schematic set.
Thank you for reading this and hopefully responding.
I need a complete schematic for the 640, which seems to use the same power amp as the 720 model, from what I've seen online.
I am into repairing and restoring old electronics, but not confident enough to reverse engineer a schematic set.
Thank you for reading this and hopefully responding.
The Conn 640 was built in 1963 according to Jan Girardot's famous list.
It is a vacuum tube individual oscillator organ. It is a premium console with 25 pedals and 2 probably 61 key manuals.
People liked the tibia sound of Conn's particularly in 1963.
Most of these will have bad electrolytic capacitors particularly in the power amp, plus maybe a rectifier tube damaged by the above.
You could get custom help on organforum.com from a pro, tuscondave. I was criticised on that forum by the moderator for making the above statement about e-caps, and will not be participating. Dave likes to replace one part at a time based on his extensive experience. I replaced 71 caps in my H100, starting at the power supply, working through the power amp, then up to the feature and TG areas. Every couple I put in made it sound or work better. It was putting out about 1 watt when I got it, now 30 W bass channel and 13 watt two treble channels.
Conn's are also prone after many thousands of hours of practice (maybe 20000), to having the vinyl wrap on the bus bar of the keys wear out. This part is not available. If all of your keys work, and shut the sound off properly, the bus bars could be salvaged and sold if nothing else. Most home instruments were not played that much. Few churches & funeral homes (high use areas) had theatre organs. Before spending money, it is worth tipping the keyboard up and seeing if the bus bar has been robbed. I bought a Conn case from a dealer in 1988 to midi-encode the pedals, only to find out he'd kept the buss bar so I had no switches.
For a sample power amp schematic, search any number of threads here for conn tube organ amp, from people who have salvaged them for electric guitars. Most 1958-1965 will be very similar, some with bigger power tubes and rectifiers for more power, some with smaller.
The tone generators don't go bad much, especially in 1963 after they quit using paper dielectric capacitors. Resistors 100k and over can draw moisture and grow in value, although I think conn used the AB or Sprague ones with the military paint that didn't do that. My hammond & dynaco resistors from 1961 & 1964 are fine except the ones that the paint was burnt by too low a watt rating.
The tabs contacts can block sound and need exercising, and maybe spraying out with contact cleaner. Warning, proper contact cleaner is flammable no smoking open flame pilot lights or electricity on or off within 10 m. The non-flammable brominated hydrocarbon kind at the electrical supply dissolves PVC and styrene plastics and should not be used on consumer products. Only in factories with ABS or teflon plastic.
Read the safety thread under tube amps before touching any metal behind the cover. Very briefly, don't work with the power plug in the wall. Touch only with one hand at a time, current across your heart can stop it. Wear no jewelry on hand wrist or neck, 1 v with enough current stored can concentrate through metal and burn your flesh to charcoal. Electrolytic caps store charge, measure at <1v to chassis ground before touching metal. discharge with tool described on safety sticky thread on tube forum. Wear safety glasses soldering, solder splashes and can damage eyes.
Have fun. As you see I've got several organs, one Hammond H182 working very nicely. Do you play? what genre?
It is a vacuum tube individual oscillator organ. It is a premium console with 25 pedals and 2 probably 61 key manuals.
People liked the tibia sound of Conn's particularly in 1963.
Most of these will have bad electrolytic capacitors particularly in the power amp, plus maybe a rectifier tube damaged by the above.
You could get custom help on organforum.com from a pro, tuscondave. I was criticised on that forum by the moderator for making the above statement about e-caps, and will not be participating. Dave likes to replace one part at a time based on his extensive experience. I replaced 71 caps in my H100, starting at the power supply, working through the power amp, then up to the feature and TG areas. Every couple I put in made it sound or work better. It was putting out about 1 watt when I got it, now 30 W bass channel and 13 watt two treble channels.
Conn's are also prone after many thousands of hours of practice (maybe 20000), to having the vinyl wrap on the bus bar of the keys wear out. This part is not available. If all of your keys work, and shut the sound off properly, the bus bars could be salvaged and sold if nothing else. Most home instruments were not played that much. Few churches & funeral homes (high use areas) had theatre organs. Before spending money, it is worth tipping the keyboard up and seeing if the bus bar has been robbed. I bought a Conn case from a dealer in 1988 to midi-encode the pedals, only to find out he'd kept the buss bar so I had no switches.
For a sample power amp schematic, search any number of threads here for conn tube organ amp, from people who have salvaged them for electric guitars. Most 1958-1965 will be very similar, some with bigger power tubes and rectifiers for more power, some with smaller.
The tone generators don't go bad much, especially in 1963 after they quit using paper dielectric capacitors. Resistors 100k and over can draw moisture and grow in value, although I think conn used the AB or Sprague ones with the military paint that didn't do that. My hammond & dynaco resistors from 1961 & 1964 are fine except the ones that the paint was burnt by too low a watt rating.
The tabs contacts can block sound and need exercising, and maybe spraying out with contact cleaner. Warning, proper contact cleaner is flammable no smoking open flame pilot lights or electricity on or off within 10 m. The non-flammable brominated hydrocarbon kind at the electrical supply dissolves PVC and styrene plastics and should not be used on consumer products. Only in factories with ABS or teflon plastic.
Read the safety thread under tube amps before touching any metal behind the cover. Very briefly, don't work with the power plug in the wall. Touch only with one hand at a time, current across your heart can stop it. Wear no jewelry on hand wrist or neck, 1 v with enough current stored can concentrate through metal and burn your flesh to charcoal. Electrolytic caps store charge, measure at <1v to chassis ground before touching metal. discharge with tool described on safety sticky thread on tube forum. Wear safety glasses soldering, solder splashes and can damage eyes.
Have fun. As you see I've got several organs, one Hammond H182 working very nicely. Do you play? what genre?
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