Conn Rhapsody 627 Issues

[Matt Sabo]

Greetings All, Just picked up an old Conn Rhapsody 627 and fell in love with it. It has some problems that I would appreciate any advice on how to handle:
1) After moving it home (not when I first heard it prior to move) when I turn organ on there is an audible static that begins after its been turned on about 10 seconds and stays at the same level regardless of whether the volume pedal is all the way forward--it has quieted down for short periods, when I turned it on and off
2) Three of the pedal notes do not sound their intended tones, but are actually sounding other tones instead (example: high Bb pedal sounds Ab, F# pedal sounds G octave below, low G pedal sounds D fifth above). I tried to change this with the tuning screws although it seems that they were not made to alter the tones that significantly?

Otherwise its in good working order. I have ordered contact cleaner (although not sure where to start on this one) and service manual, and I'm planning a good vacuuming.

Any suggestions on handling the above issues would be MUCH appreciated!

Thanks,
Matt

[xbidela]

Hi Matt - funnily enough I just picked up a Conn Rhapsody 627 as well last week (and also fell in love with it).
Mine does seem to be in tune (or at least close on a fairly quick inspection), but has a couple of distinct issues.
Since I'm completely new on the forum and have as of now no knowledge of the Conn, I won't be of much help at this point, but maybe in future we can help each other.
The issues that mine displays are the following:
- All pedals seem to work, but intermittently. I think a good cleaning of the contacts should help here. All registers seem to work and individual pedals seem to be in tune.
- On both the upper and lower manuals several F and B are not functioning. This issue repeats itself for the different registrations at the expected corresponding octaves higher and lower (i.e. 16' registration displays same issue 1 octave higher than in 8' registration). This makes me think that certain tone generating circuits are defect.
- Some D# and B flat keys exhibit unintended sustain (tone rings on after release).

So some significant issues to be sorted out, but I'm hoping that there are common causes to at least the non-functioning keys.
Apart from that the organ sounds lovely: quite low back-ground noise levels and the built-in Leslie sounds great.

Where did you get the service manual?

Thanks
Alex

[JQA]

Hi Matt and Alex,

I don't have a Rhapsody 627 (nor the service documentation), but from what little I have found online, it appears similar in overall design to my Conn "Caprice" 430, in that it uses tube oscillators and amplification, and transistors for keying those tones with "sustain". So, I will try to help assuming the designs are reasonably similar.

1) After moving it home (not when I first heard it prior to move) when I turn organ on there is an audible static that begins after its been turned on about 10 seconds and stays at the same level regardless of whether the volume pedal is all the way forward--it has quieted down for short periods, when I turned it on and off

It sounds like the static is coming in as the tubes warm up. Because it remains at the same level no matter the pedal position, that greatly narrows down the problem to the either the power amplifier or power supply sections. The most likely fault would be a bad tube in the power amp, especially considering it didn't occur before moving, and comes and goes. So, you would want to identify which tubes are in that section (probably a 12AX7 or two, and a pair or quad of 6L6s), then try substituting them. It could also be a bad connection/solder joint, or another type of bad component. A local tech familiar with tube guitar amps could be helpful.

2) Three of the pedal notes do not sound their intended tones, but are actually sounding other tones instead (example: high Bb pedal sounds Ab, F# pedal sounds G octave below, low G pedal sounds D fifth above). I tried to change this with the tuning screws although it seems that they were not made to alter the tones that significantly?

If the pedals are designed similar to my Conn 430, the tuning potentiometers are grouped in series strings of three, with fixed resistors also inserted in series on both ends. These strings are placed across a regulated 75V supply, and used to provide appropriate control voltages for each pedal to the pedal oscillator. Since the other pedals are OK, and all tuning strings are across the same power supply, and assuming the pots truly cannot tune the notes within range, the fault must be in the relevant strings. Fixed resistors can drift, and pots can drift or make bad wiper contact. It is possible that all 3 bad pedals are part of the same string.

Although the circuitry may be difficult to physically access, it should be quite easy to determine the problem with an ohmmeter once access has been gained, referring to the service manual for locations and values of components. The usual precautions for working on tube equipment should be taken, of course.

All pedals seem to work, but intermittently. I think a good cleaning of the contacts should help here. All registers seem to work and individual pedals seem to be in tune.

Yes, cleaning of the contacts would be the first (and perhaps only) step.

On both the upper and lower manuals several F and B are not functioning. This issue repeats itself for the different registrations at the expected corresponding octaves higher and lower (i.e. 16' registration displays same issue 1 octave higher than in 8' registration). This makes me think that certain tone generating circuits are defect.

This is almost certainly a bad tone generator tube, considering that in each 1-octave tone generator section, the same tube provides both F and B pitches! All you need to do then is identify which tube is bad, which could be as easy as looking to see which one of the F-B tubes is not lit, since most likely it has an open heater/filament. If it's like my 430, the tubes are all 12AU7, which is a very common type still made by multiple factories to this day.

Some D# and B flat keys exhibit unintended sustain (tone rings on after release).

This would indicate problems in the associated transistor keying circuits for those tones. Again assuming the circuit is like that of the 430, probably bad neon bulbs are the culprit, since those are really the only things making the difference between sustain and no sustain. Neons are known to have their leads break off due to vibration.

A service manual can be purchased here (I have bought from Mike before without problems): https://www.mikesmanuals.com/Manuals_Details_5974.htm
I have scanned the Conn 430 service manual, which may be of some help, though don't count on it being identical. You can download it here: http://crasno.ca/articles/doc/Conn_430_SM.zip

Jesse

[Matt Sabo]

Wow, this is extremely helpful Jesse, thank you for all the tips! I ordered the 627 manual from Mikes manuals but he's been having trouble finding the original so I have not received it. I will definitely take a look at that Conn 430 manual—thank you for that also Jesse!

[JQA]

Wow, this is extremely helpful Jesse, thank you for all the tips! I ordered the 627 manual from Mikes manuals but he's been having trouble finding the original so I have not received it. I will definitely take a look at that Conn 430 manual—thank you for that also Jesse!

You're welcome. Too bad you haven't got the manual yet; I couldn't locate any other source for it, so hopefully Mike finds his copy eventually.

Feel free to ask if you have any other questions, and keep us posted!

[Matt Sabo]

Hi All, I finally received the Rhapsody 627 manual from Mike, and after following directions for tuning pedals, determined that two of the pedals (3-D1 and 8-G1) sound the same note—a high C#, and the tuning screws are not changing the pitch for those, so I am unable to tune them correctly. I followed directions for the master tuning of that octave, however this only confirmed that when I turn those two screws it does not alter the pitch. Interestingly, the two resistors are on the same line on the schematic R156 & R157. I sprayed some contact cleaner around the screws and tried to reach the pots from below, but could not access them easily due to the metal frame in the way. Any thoughts?

[JQA]

Hi Matt, good to hear that you received the manual after all!

My suspicion was correct about all faulty tuning pots being on the same voltage-divider string. Assuming that higher voltage = higher pitch (which is true on my model 430), there is probably no current flowing through this string due to an open circuit "below" or inside R157. Both pedals sound the same high pitch because the control voltage line is being pulled to the same upper supply voltage, since no matter how the pots are adjusted, the control voltage line draws basically no current through them (thus resulting in no voltage drop, and hence no lowering of pitch). Anyway, R156 clearly has a good resistive track, and R157 is good at least between the "upper" lug of the track, and the wiper.

This narrows down the problem to basically three possibilities:

• R158 is open
• Connection is bad on either side of R158 (due to bad soldering, etc.)
• R157 is open on the "lower" lug of the resistive track (and thus would measure open across the entire track)

Check these possibilities, and let us know what you find.

Jesse

[Matt Sabo]

Hi Jesse, Thank you for your thoughtful assessment. Appears that the circuitry is behind the metal frame, so not sure how to access it other than following what it says in the manual:
Feeling a little nervous about removing the power supply and Leslie. Any tips would be appreciated!
Thanks again,
Matt

[JQA]

I'm afraid I am not familiar enough with the 627's layout to know whether or not there are any quick and easy ways to access those parts, so unless you can spot some way, you will have to remove the pedal switch/generator assembly based on the procedure in the manual.

My main recommendation is to take your time, working carefully and following the service manual to the best of your ability. If it hasn't already been done, unplug the instrument and wait some hours after it was last powered on before working on it. Wear gloves if you have them, and clothes that you wouldn't mind getting a bit dirty. Keep track of where all screws go, since length and type may vary. Also keep track of all connectors, making sure to plug them in the same way during reassembly. Pull them out by the base, not the wires.

As long as you are careful and follow the given procedure, things should go well. Once the pedal switch/generator assembly is out, it should be very easy to check the offending resistor string with an ohmmeter. Before starting, consider that you may have to keep the assembly out for some time while waiting for a replacement part - this may affect where you decide to do the disassembly.

Jesse

[edkennedy]

Pedal Access, Sounds like its the same as my Conn 645 (Tube oscillators and amps, except mine has 32 pedals). The power amp comes out easily, and the Leslie comes out very easily. While the Leslie is out, oil its motors. The pedal switch and electronics assembly simply slides out between the legs after the screws are removed. When I got mine, the pedal tuning was way out on the lower octave, which turned out to be a dirty tube socket.
Contact Cleaning, I don't like spraying the cleaner into the assembly. The overspray leaves a mess. I normally spray it onto a business card or stiff piece of paper, slide the paper between the contacts, gently close the contacts with the key or pedal, and slide the card in and out to clean the contacts. Use a plastic safe cleaner, especially for the pulse rods on the keyboards. I use DeOxit F5 which is made for plastic volume controls.
Dead keys, are they dead on all the stops? If so, look at the oscillators (Bad tube?). if only on the Tibia stops, look at the keyer circuits.

General Comments, It always helps to give a basic description of the organ; e.g. Tube Oscillators and Amplifiers, Console with 25 pedals, etc. Pictures are always helpful also. Conn has many models, but most of the same vintage use the same components and assemblies. That way, those of us who don't know the model numbers, can help if we have knowledge or information for a similar organ.