Baldwin 632 (1979) Organ pitch adjustment

[Guest]

I received a query from a lady asking for instructions on adjusting the pitch of their 632 organ. I happen to have an original Technical Manual, but I cannot find any specifics on a pitch adjustment.</P>


Does anyone know of such adjustment, or is it locked in by the microprocessor?</P>


Thanks for any advice.</P>

[OrgansR4Me]

Re: Baldwin 632 (1979) Organ pitch adjustment

This is definitely a JBird question. I'm kicking this question up into the active file in hopes he will see it. I'm sceptical about any procedure that wasn't covered in the manual. Did the lady you mention give any specifics that the organ is out of tune with another instrument. Additional information on what problems she has experienced will help alot in finding the practical solution to your question.

[jbird604]

Re: Baldwin 632 (1979) Organ pitch adjustment



Pat,</P>


All Baldwin analog organs have some sort of tuning adjustment. The 632 is one of the "T-pulse" models using a master oscillator with several Top Octave Synthesizer chips. One of the chips is directly driven by the master clock, and that master clock will have a tuning coil associated with it. </P>


I don't have the 632 manual at home, or I'd look at the picture for you. But you have a manual, so look for the section on "tone generation" which is analog-speak for "frequency generation" .... It should describe the frequency generators in detail, and tell you where to look for the tuning coil.</P>


You will HAVE to get a plastic hex-end adjustment tool to do this. Don't even think about doing it with a screwdriver or even a metal Allen key, though you could use a set of Allen keys to find the exact size of the hex slot and then go out and buy (from Radio Shack) the proper plastic hex tool.</P>


A screwdriver will quickly destroy the fragile tuning core, even though you might fool yourself into thinking you are tuning it. You will need to be careful with it, because if you damage it you won't be able to tune the organ and it may be further off pitch than it was before you started.</P>


Anyway, I'd start by determining if you indeed need to tune the organ. It's possible that the customer has a piano that's out of tune and the organ is being blamed. You'll need to use a stable and reliable pitch source or meter. If you have a I-Phone there is a great tuning program that costs very little. Other tuning devices are equally useful.</P>


To do the actual tuning, insert your plastic hex tool into the tuning coil, draw the great 8' principal, and play a note in the middle octave. Use your tuning meter and adjust to correct pitch. If you are using an outside source rather than a meter, play the source note simultaneously and "zero-beat" the organ to it. Getting that one note (whichever one you use) in tune will automatically tune the entire organ, as all the generators are dependent on that single clock.</P>


Note that after you tune this central octave of the 8' principal, other octaves and other stops will not be exactly in tune with it. That's because Baldwin used a system of slight detuning to produce frequencies slightly sharp and slightly flat for various stops to more closely simulate a pipe organ, which would rarely be "perfectly" in tune.</P>


Also, if you have a sharp ear you may find the actual note to note intervals (the "temperament") of the organ not quite "even tempered" as Bach would have wanted. Baldwin (and everybody else that used TOS chips) settled for getting the notes "in the ballpark" and to my ear at least some of the intervals are a little sour.</P>


Hope that helps a little.</P>


John</P>
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[Guest]

Re: Baldwin 632 (1979) Organ pitch adjustment



John,</P>


Thanks for your insight and technical expertise. I found in the manual the generation circuit and it appears that there is afrequency adjustmentPot on the Celestial Vibrato Oscillator which is stated to be the source frequency for the TOFG circuits. I also find a tunable coil on what appears to be the same board near a circuit identified as signal apmplifier. I understand the sensitivity of tuning coils and have a tuning hex wrench in the box. I will need to study this write up and circuit board more before I mess around with it.</P>


I do appreciate your direction. It helped alot.</P>


Pat</P>

[jbird604]

Re: Baldwin 632 (1979) Organ pitch adjustment



Pat,</P>


I'll try to remember to bring home the 632 manual so I'll know what I'm talking about. My guess is that the pot on the Celestial Vibrato board is not what you're looking for. I think it only provides a modulation frequency that creates a tremulant for all the TOFG circuits. I believe the actual tuning coil will be on the board identified as the "transposer" board. That is where it's located on theBaldwin 626 I have in my house, which is closely related to the 632. This board may be mounted on the side wall of the console or it maybe at the back of the motherboard in the center (the "logic" motherboard).</P>


There is another tunable coil in these organs, and that is on the CPU board. But it has nothing to do with the frequency generators. It produces the clock for the CPU and tab action circuits. It should not be adjusted.</P>


John</P>
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[Guest]

Re: Baldwin 632 (1979) Organ pitch adjustment



John,</P>


I studied the manual and found the Master Oscillator adjusting coil. It is on the side board just above the Transposer Board. I forwarded your email and pictures of the assembly to the lady, highlighting your warnings on the sensitive iron core. I asked her if a HAM radio operator was a member of the church as he would know how to adjust a coil. In any event, your guidance pointed me in the direction I needed and I went straight to it in the manual.</P>


Thanks again for your counsel.</P>


Pat</P>

[Beebs]

Still have the manual?

Hi there I know this is a very old thread, but figured it was worth a shot asking the question! I'm looking for a technical manual for the Baldwin 632. We have one at my church, have played it for the last 30 years, but it's starting to act up. She's been a legend up to this point. Sound on lower manual cuts in and out randomly for no apparent reason. Upper manual no problem, pedals all good. Have had someone out to take a look but no success in fixing it. Have found another fellow willing to take a look, but he would like to see a technical manual. Does anyone have one available? I'm in Australia, so that could be another problem, unless you have an electronic version you can email me... Many thanks in advance!