Gulbransen Rialto K: help me identify these parts

[pedropol]

Hello,

I've open my Gulbransen Rialto K in order to understand how it works, helped for that with Jan Girardot's service manual. There are parts I can't identify and I'm not sure they are genuine or added later. Can you help me identify them?

1) In the back of the organ, connected to the 1135 Solo Voicing card, I have two cables terminated by sound jacks.

One of these cables has the jack wrapped in duck tape.

2) On the front of the organ, behind the front panel and under the accompaniment manual, on the left side, there is a grey metallic box with a plug for a jack.
According to the service manual, the Rialto had a headphone adapter that was plugged into one of the speaker sockets (page 25 of Jan's service manual). Could it be that this circuit has been "optimized" on my version of the Rialto, and plugged directly onto the Solo Voicing card?


3) Under the lower keybed, I have a black metallic box with a folding lever. I suppose it allows the organist to do some sound effect pressing the lever with his knee. I haven't found a mention of this part elsewhere. For what can it be used?


Thanks
--
Pierre

[indianajo]

I also do a lot of customization of electronic audio equipment. when my heirs or receivers (in case of bankrupcy) sell this stuff off, the "legendary" bits with known resale value are going to perplex the buyers.
Organs sound better with the sound bouncing around the room off various surfaces. This give phase shift. Perhaps in addition to the silencing headphone jack, a previous owner has tapped into the power amp circuits to provide power to other speakers. On those jacks, I would 1 buy a monaural and a stereo plug of the proper dimension.
2. Get a DVM with a 20 vdc and 200 v dc scale. I would use the plugs to determine if the jacks are mono or stereo. You can tell by feel, also by number of terminals soldered up. Then, with the right plug, I would set some sound going on upper manual, lower manual, and pedals, simultaneiously. Use rolls of nickets. Then check from the center to the back ring, also front ring to the back ring, for DC voltage. If there isn't any, or if it is under 1 vdc, then I'd later wire up some cheap speakers to the jacks to see what audio is coming out. The reason for the DC check, DC voltage will melt voice coils of speakers and sometimes tear the surrounds.
Note many phone jacks switch off the AC voltage (sound) from the source to the normal speaker. So when sound is dead, oxidized contacts in phone jacks is one of the first things to check for and clean off (power off) with a bent tip pick.
I would suspect the knee lever is something to provide separate volume control lower manual versus upper manual, or manuals versus pedal or something. If a pot and inserted in the pedal signal, a dirty wiper contact could be killing your pedal signal.
My organ has a foot switch to turn vibrato off after the tab is selected. I find this is a useful feature for using vibrato as an accent effect instead of a constant throbbing like the Bugs Bunny cartoon opera singer had. Maybe the knee lever is that. More exotic would be a depth or speed of vibrato control with the knee lever, but I kind of doubt of there is that kind of electronic expertise out there. You don't know, though.
Best of luck with this premium analog organ. One previous owner has reported his was not impossible to repair with parts from the distributor.

[andyg]

Those two cables would probably be inputs, rather than outputs, allowing the owner to plug in something like an external rhythm box. The plug in the large view is clearly mono, I'd guess that the other would be the same. Holding the plastic part of the plug, lick your finger and place it on the tip of the plug. Do you hear a slight hum? Then you have a pair of inputs. If your Rialto K is Isomonic and has two (effectively 'stereo') stationary channels, then you have a stereo input pair.

Knee lever. Does your Rialto K have the Electro-Mute tab? If so, I think you'll find that the knee lever operates the mute for this voice.

I assume that the silver/grey box is the headphone adaptor.

We do have a couple of Gulbransen experts on here who have, or have had various models in the Rialto series, I'm sure they'll be along later to help with this thread and your other one. If things get split up too much between the two threads I will merge them for you.

[pedropol]

Answers

Hello,

Here are partial answers. The previous ones were deleted by the server crash... My previous post contained mistakes as it was uneasy to trace the cables in the organ.

1. The two jacks are connected to the two Solo output channels according to the following schematic. They were probably used by a previous owner to plug the organ output to an external amplifier.


2. George Reynertson from Dave's Electronics told me that I have probably a model K reference 1107-101 and that this grey box should be a plug for headphones. I've tried with a stereo headphone and it muted output to the Leslie but I didn't received the sound in the headphones. I have to confirm it, either with a solo headphone or tracing the cables.

3. George again explained me that this is probably the waa-waa knee lever on the Solo Tuba stop.

These two last items were options on that model.
--
Pierre