Gulbransen Rialto II (Model 828)

[indianajo]

I've found some obsolete IC's at avnetexpress.com, jameco.com, or http://www.ceitron.com/products.html. I last bought from avnet in 1978, they have a $50 minimum, but on $38 IC's that would not be a problem. Jameco has a split shipping policy, watch the ship dates of what you order, you may pay for 2 boxes if you buy items involving 2 ship dates. cei I've never bought from but there website lists Dayton, OH.
The organ community can't help you find bargain IC's if you don't list the number. Somebody on diyaudio.com found the LM3080's for me at jameco. Saved me walking 1/2 mile to the payphone next to a diesel truck for a long distance call , and making a single item ($8 shipping) order to Peavey sound.

[Wayneh]

Many thanks for the info. So far I'm good right now. The IC's in question were:

Gulbransen Part no. 801816 (NC1184P) Top Octave Syn. C# - F
Gulbransen Part no. 801817 (NC1183P) Top Octave Syn. G - C

[indianajo]

Those IC numbers are too weird for my usual sources.. Sorry. Mr. Dave is earning his pay. I guess this organ verges on the custom IC era. Would take a little circuit board of IC's and a plug in header to the old socket to duplicate these dividers, probably.
Glad your new oscilloscope is helping you.

[Wayneh]

I have found a couple of sites for the Top Octave Synthesizers, one of particular interest is this:

http://www.organservice.com/crm/topdividers.htm

They have developed various replacements for the original TOS. If you scroll down you will find a section titled "Replacement Dual TOS Divider Retro For Organs Using Dual TOS IC's. This retro replaces both the 7-note and 6-note TOS IC's." This assembly replaces the two TOS IC's that work in tandem in the Gulbransen. The three octave independent tone generator uses a total of 6 TOS's for the three octaves. I guess this assembly replaces one pair. And the price for this assembly is close to what I paid for the pair. Plus these run cool, and don't need the negative power. So there's hope if you can't find the original

[indianajo]

A divider assembly of different IC's that runs cooler than the original but is a little larger. Well, great mind think alike.

[Wayneh]

The Octave 4', Flute 8' and Salicet 4' on the accompiment manual had the following dead keys:
Key 37 C
Key 39 D
Key 41 E
Key 43 F#
Key 45 G#
Key 47 A#

This was all of octave 4 of the C# channel. Using the block diagram in the Service Manual, I traced through the various circuits to the Main Bus Amplifier and Scaling PCB, then to IC2, a quad amp LM 3900. Signals going in, but not coming out. Replaced IC2 and cured the problem.

NOTE: There are errors in the schematic shown on page 11-2 of the manual. IC2 has four sections, and the pin-outs (8, 9, 13) are shown as the same for two separate circuits.

[indianajo]

Curse of the LM3900. Glad I don't have any.

[Wayneh]

The following keys were dead on the Solo 8' Tibia:
39 (4th octave) D
52 (5th octave) D#
55 (5th octave) F#

After some troubleshooting, I decided to swap the 8' DC switching matrix with another identical DC switching matrix board that is used on the 5-2/3 Solo Drawbar. All problems went with the 8' DC switching matrix, and all of the above keys now work. Since I don't use the drawbars very often, I'll let this work for now.

Then, whenever the Tibia sustain Tabs were selected, or the Chrysoglott or Glockenspiel Tabs selected, a high-pitched note would sound with no keys depressed. This was key 61 on the Solo Manual. After much troubleshooting, found a transistor (Q49) on the Tibia Gate board with a high voltage on the emitter. This would let the key sound, even though not pressed. Problem cured after replacing Q49 (a 2N3860).