I picked up a Conn Serenade 633 Organ.....

[Paul789]

.....that someone left on the curb, and posted on Craigslist.

I paid someone $70 to move it to my house. I must be desperately
bored during this quarantine! :o

Anyways, some of the voices work, the keys are flakey, and the
volumes are all over the place, as I was warned about the vinyl
keying rods. Boy, those contact whiskers look very delicate!

And there is a warning: "Do NOT Spray Contact Cleaners or Lubricants
on Key Contacts of this Organ." WTF??? Lubricants, I can understand,
but why not some DeoxIT?

And where is the headphone output? Or the Line-level output, so I can
add an external reverb, and external amplifier?

I have a bad feeling I only got this for the 25-note foot pedal board,
which I might convert to MIDI. But I might also convert the two manuals
to MIDI as well. But before I tear all the guts out of this guy, I will try
to get it working as best as I can. And so I must ask:

1) What is that pop-corn sound that seems to randomly occur as I
hit the keys? On either manual? It sounds like the snare drum sound
is triggering on it's own, somewhat randomly? How do I get rid of this
irritating sound?

The humming sound I assume is due to the old, dried out electrolytics.
I won't deal with that, unless I decide this organ is worth saving!

:o

[Paul789]

The owner claims the bass foot pedals all play the same note, so I know
I have some troubleshooting to do.

But how about overall build quality and reliability, once I get it running well?

Good for playing Bach?

[Paul789]

A previous post by Don S:

"The Serenade series was the larger, better of Conn's 2 manual, 25 pedal organs. The 632 was introduced in l968 and was the stripped, churchified version of the Serenades with a locking top, finished back and legless church style cabinet and bench. It was the 2nd of Conn's switch to all transistor circuitry. The 633 is the home version with all the bells and whistles and more stylish cabinet designs. The 642 theatre model is based a lot on the 633 design except for the horseshoe cabinet and theatre styled bench. These were pretty well designed and built organs but time has probably taken its toll unless the one you play has had exceptional care and service. Unless the keyer rods have been updated with the gold type you can expect keying problems, sputtering uneven notes, dead notes etc. The flute based stop tabs used a gold rod all along so they rarely had the problem. The proper fix is to replace all the mylar type rods with gold or similar metal surface rods. But these had a lot of rods and its a nasty job. i did it once and would not care to do it again. You may have a similar problem with the pedals altho if you don't have the pedalboard properly seated it may mimic the bad contact thing somewhat. These were two channel organs 80watts total. The flutes/tibias went thru the rotor channel which had a 2 speed leslie, the main voices went thru a stationary channel. The low end of the flutes and main voices go thru a network crossoever unit to provide the pedal sound. So make sure your main amp dials are set the same or your pedal will sound weak or unbalanced. Don S."

[andyg]

Good old analogue technology throughout, the only real issue is the vinyl keying rods, for which there now seem to be no replacements at all. There are plenty of threads about Conn organs on here as I'm sure you've found - in Home Organs and Electronic Theatre Organs and Electronic Classical organs.

Of the various instruments you've mentioned like the Hammonds, the Kawai and the Yamaha, the Conn will be closer to a pipe like sound, of course.

[jbird604]

I would add that the pedals all playing the same note COULD be a simple fix or not. The pedal pitch is determined by a series string of resistors from end to end. If the string is broken by a faulty solder joint or bad make/break contact spring (one at each note location), all the pedals above the faulty one will sound the same pitch. That problem is fixable, though time-consuming. Another possibility is that the FET in the tunable oscillator is bad, and no longer responding to the varying voltages from the divider string, or that the capacitor in that circuit has opened up. Or some other critical component. So that could be a real technical problem.

This anomaly will only affect the 16' pedal stops though. The 8' stops are borrowed from the same oscillators that serve the manuals, and will sound correctly, though as mentioned, there could be issues due to the vinyl keying rods. Most likely, the organ will be playable, even if the 16' pedal stops have to be sacrificed.

The console is sturdy and beautiful, and a savvy hobbyist could convert it into a fine Hauptwerk organ, or perhaps just MIDI-fy the pedals and use an outboard generator for pedal voices instead of laboring over fixing the on-board pedal system with all its quirks and shortcomings.

[Paul789]

You called it! Most likely, the JFETs on both tone generators went bad! Shorted gate to drain.

[Paul789]

Good old analogue technology throughout, the only real issue is the vinyl keying rods, for which there now seem to be no replacements at all. There are plenty of threads about Conn organs on here as I'm sure you've found - in Home Organs and Electronic Theatre Organs and Electronic Classical organs.

Of the various instruments you've mentioned like the Hammonds, the Kawai and the Yamaha, the Conn will be closer to a pipe like sound, of course.

So the Conn will be the most pipe-like of all these brands? Perhaps the most Bach-like??? :-)

Ok, so I found the Serenade 633 (and Theatre 641) service manual on Ebay for $70, plus $15 shipping, from Canada.

Would anyone possibly know where I might be able to download them in PDF for free, off the internet?

:embarrassed:

[jbird604]

Conn would definitely come closer to mimicking a classical organ sound than Hammond or Kawai models that I've played. Because the Conn uses individual oscillators for each note or pitch, it has a very random and interesting "ensemble" effect, somewhat like a pipe organ. And the tones are created from various outputs of the oscillator which give either flute-like tone (sine waves) or stringy tone. So it's a system designed more like a small unit pipe organ, while Hammond and Kawai both have sophisticated ways of generating a variety of tone colors but don't really go for imitating the randomness and brilliance of pipes.

I've never seen Conn service manuals offered in PDF, mostly because the Conn company went out of business long before there ever was a PDF, even before there was an internet. So they only exist in book form, unless someone has gone to the trouble of scanning them into PDF. Unlikely, given the small demand for these nowadays.

[Paul789]

Ok, progress has been made!

Imagine have a pop-corn machine (that sounds like a snare!) going off randomly
as you are playing! That's what I had at first, but I found the darn drum-machine
board, and Conn had the foresight to place a guide on the cabinet, showing which
pots control the snare level, white noise level, and overall drum machine output
level. I set them all to ZERO! Problem solved! :->

And the manual voices? They sound pretty good for Bach, considering there
is almost zero reverb on this unit, even with the "Sustain Tibia Reverb" ON.
Some of the voices have uneven volume problems, but the Tibias sound good, and
seem to be the main ones I like.

The bass pedals pretty much play the same note from C1 to B1, and then
play a higher, more dissonant note, from C2 to C3 (This problem occurs for the
16 feet voices. The 8' Tibia sounds normal, but is too quiet). And it looks like
I will need to tune up all 25 bass pedal notes individually :



I'm not sure where to look for the bass pedal problem?

I sure wish I had a schematic. I might have to cough up the
$85 to get the Ebay Service manual! =-O

[tucsondave]

Maybe this will get you started. It's from a 634 but the pedals should be the same.
Pedal Generator.pdf

[edkennedy]

You can get a 632 service manual for $25 at mikesmanuals.com. It won't include the percussion unit, but the rest should be the same.
Keying Rods; First you need some plastic safe contact cleaner. I use Deoxit Fader F5. I don't spray it on the rods, I spray it on a piece of stiff paper or business card, slide the card between the contact wire and the rod, press down on the key, and gently slide the card in and out. This gets the dirt off the vinyl covered keying rod, and the tarnish off the wire.

[andyg]

There is a post somewhere from the late, great Jan Girardot about the keying rod issues. The other problem with them, and one that sadly cannot be cured, is that the vinyl sometimes comes away from the inner core and stops making contact internally.

[Paul789]

Maybe this will get you started. It's from a 634 but the pedals should be the same.
[ATTACH]n743858[/ATTACH]

Wow, thanks Dave. That's a HUGE help!

Ok, the main problem I found, was the +30 Volts Yellow wire
was only +22.9 V! And it was only +23.2 V when I disconnected
the source voltage from both generator boards.

So the question is: Where is the Yellow wire +30 V source coming from? The main
power supply I assume?

Because too low a source voltage is affecting all the other voltages:

The +20 Volt "keying" voltage is only +17.9 V with no keying, and +17.5 V with keying.

The +18 Volt tuning voltage is only +16.8 V, and +16.5 when a key is pressed.

The tuning voltage going to the Gate of Q18 of the first generator, is +16.8 V with no
keying, and +16.5 V with keying, no matter which key you depress! This must be
why the same note sounds in the first octave. (The same note also sounds in the
second octave, except it's a higher note)

Is it possible the only problem is the +30V source being too low? Why doesn't the resistive
divider ladder work still work? Shouldn't the wire #1 tuning voltage still vary, depending on
which key you press? :-P

[Paul789]

Ok, I just verified that the Yellow wire coming out of the main power supply, is only +22.9!

It should be +30V, correct?

I'm a bit surprise the Conn engineers had the foresight to only use Yellow for +30V! Some
companies aren't so disciplined! :-)

[edkennedy]

Just a quick note, If your organ is like my older 645, the complete pedal electronics assembly comes out easily as a unit. On mine, I had to remove the Leslie and the power amplifier to get to the mounting screws. Bonus - you can clean and oil the Leslie while it is out.

[Paul789]

Yes, I mine is a 633, and I had to remove the Leslie, and the power supply, to access the screws. Not very user serviceable, but they obviously made it easier to repair in later models. Clean and oil the Leslie? Good Idea! :)

[Paul789]

Dave, is the power supply for the 634 the same as for the 633? ;-)

[Paul789]

Ok, so the resistive ladder IS working, because if I measure
the voltage of the center wiper of each tuning pot, I measure
about +4.9 to +12.9 Volts, going from C1 to B1, with all
voltages for the notes in between.

And yet, the +16.8V (which should actually be +18 V) is
always present on voltage tuning wire 1, even when
nothing is keyed! This doesn't show up on the schematic.
If anything, wire 1 should only have a small floating gate voltage
from Q18, when there is no keying.

:-P:o