Rodgers 755, service manual?

[zuulmusic]

I am looking for a 755 service manual. I might obtain an organ that "has bad amplifiers" so any thoughts specific to that would be appreciated. I'm hoping I can locate the proper audio signals and bring them into a some modern power amps.

I have a 750B so am a bit familiar with the inner workings. Anyone know if the 755 sounds any better, or is it the same analog tech? I'm considering the "upgrade" because the 755 has MIDI and a 32' pedal stop.

Thanks!

[myorgan]

I think I may have seen one on *Bay recently. Try checking there.

Michael

[toodles]

I have the 755 technical manual as 2 pdf file and can email them to you if you will send me a PM (private message) to include your email address.

Even though the tone generation technology is analog like the 750B, the 755 is still a bit of an upgrade to the 750B. Though a similar stop list, it has a few more stops and I would say it sounds better. It has the 32' Contre Bourdon, a Trompette keyer that is spectacular, alternate mixtures, a harpsichord, and it includes principal chiff. It is analog tone generation but uses a microprocessor for keying and effects (like chiff and alternate mixtures). It also includes a Festival Trumpet on the Swell (that does not incorporate tremulant). It does note, however, have a Krummhorn in the Great, and instead has a Trompette at 8 borrowed from the Swell. Most stops have dual volume levels, so the Swell Trompette can be set for loud and the Great set for soft (or vice versa).

If the organ's MIDI is Rodgers MIDI Implementation II, it's very desireable, and incorporates a lot of advanced MIDI functionality, such as being able to save stop changes to the MIDI voices with the combination action.

I am parting out a 755, so might be able to provide you with some things like the amplifiers. The 755 was available as a 3 or 4 channel model. so you'll need to figure out which you have.

You'll need a subwoofer speaker and 2 or three midrange/treble speakers. In particular, Walker TP3 speakers work nicely for the midrange/treble. This had 2 each 6x9 speakers plus a tweeter. I mention this because if the organ has original Rodgers speakers, they tend to be overly large for a home installation, and smaller speakers work fine for the non-subwoofer channels.

755.pdf

[zuulmusic]

Toodles, thanks very much for the help and service docs.

Update: I did pick up the organ. It looks to be in very good shape. It came with 3 very bulky speakers, 3 smaller ones, and a very large subwoofer cabinet. Most need re-foamed.
You could faintly hear things through the speakers, but its VERY faint. Is that an indication of anything particular? I would have thought a bad power amp would be silent.
I won't get into digging into things for a month or two.

Thanks!

[toodles]

Try using headphones--it'll tell you whether or not the signal out of the preamp is good, and let you narrow down your diagnosis.

The audio system in the 755 (and other models in this series (605, 625, 640, 645, 650, 655, 705, 740, 745, 755, 760, 770, 780, and 840) uses full range channels with bass roll off so that you could (if you bypass the bass roll off) just use the regular channels and not the pedal channel if your speakers can cover the frequency range. The pedal channel is full range, limited by the frequency response of the woofer. It is a sum of all the channels, but they have independent volume level settings for the summing. The organ also uses "bypass" channels (summed into the regular channels) with some phase shift between the regular and bypass to create the chorus. So, it's entirely possible that you get some bleed through of any and all signals even if a channel or two is dead, though the sound might be very soft.

Or it could just be that the volume settings are really low.

[BobBell]

In several posts on this forum, I have seen offers to email the Rodgers 755 manuals. I don't know what is available, but I just acquired a 755, and it may need some work. Having the manuals would be a big help. I am both an organist and an electrical engineer, so this kind of work doesn't scare me. I think it was tootles that offered these manuals, but I need to know how to get in touch. Thanks.

[myorgan]

Click on Toodles' name above, and make sure you send a Private Message (not visitor message) to him with the request.

Welcome to the Forum, Bob!

Michael

[toodles]

Point of grammar: It really should be "Toodles's", as though I am overweight, I am not yet plural! The "apostrophe s" for posessive is only for plurals that end in s, not for singulars.

[myorgan]

Point of grammar: It really should be "Toodles's", as though I am overweight, I am not yet plural! The "apostrophe s" for posessive is only for plurals that end in s, not for singulars.

So, if your name is Toodles, isn't it supposed to be an apostrophe only for the possessive?

[From Google]The possessive of a plural noun is formed by adding only an apostrophe when the noun ends in s, and by adding both an apostrophe and s when it ends in a letter other than s.

These multiple personalities are quite confusing!;-)

Michael

[toodles]

When you send your Private Message, be sure to include your direct email address in the text of the message. Files are too large to attach to posts and private messages.