Rodgers 800 Alexandria (1978)

[Guest]

Hello boys and girls,</P>


I have fairly recently aquired a semi-used Rodgers 800 which is generally working just fine tonally, but I'm having a problem with the combination action. This model has a dual memory capture system with 6 generals, and 4 divisionals on the Sw, Gt., &amp; Ped. Problem is that the stops will NOT set on the Swell and Great divisions. If you try and set them, they cancel whenever any general piston or divisional piston is pressed. I have replaced the two rechargeable batteries with brand new ones and still the same problem. Originally when I first got the organ about a month ago, all of the stops on the swell and great would come on when pressing any general or divisional piston, or the cancel piston. Doing some tracing, I disconnected one wire between the memory section and the driver section and now at least the cancel buttons works but the other problem still exists. Anyone got any ideas? I have a service/technical manual on the way, but thought one of you might have an insight into this system. I have sourced practically all of the IC's so would be able to obtain those is needed, but don't want to just start desoldering at random without first having better information.</P>


The organ is really quite amazing for having only one main generator, plus a 39 note celeste generator. It will shake the house with the four 100 watt amps and 6 speaker cabinets going. 32' Contra Bourdon really does the thing.</P>


Thanks for any help anyone might have on this salvaged gem.</P>


Harry</P>

[jbird604]

Re: Rodgers 800 Alexandria (1978)



Harry,</P>


I'm a tech myself and work on Rodgers, but have not attempted to repair one of these capture actions. I believe that action is part of the series that Rodgers called "CMOS" actions.</P>


IIRC, this action works in a similar fashion to the old magnetic core actions that Rodgers pioneered in the late 60's or early 70's. These core capture memories worked in such a way that each time a piston was pressed, the system would "read" the cores by actually DE-magnetizingthem all, in other words destroyingeach coresstored on or off bit! As each core was de-magnetized by the strobed pulse, the system would detect the presence of absence of a generated pulse caused by the collapse of the magnetic field on those cores that had been magnetized or not by the "write" cycle, the last time a piston was set.</P>


Now, to restore the correct magnetized/not magnetized condition of each core following this destructive read cycle, a fraction of a second after each "read" cycle, the system would query the stop rail to determine the position of each tab, and record that on the cores, so the memory would be ready for the next "read" of that piston.</P>


Sounds kludgy, and maybe it was, but it worked pretty well. Now, in these CMOS actions, the same thing takes place. The "read" cycle initiated by a piston press actually destroys the on/off status of the bits stored in CMOS memory (or I should say, it sets them all back to 0). Then moments later the system recovers the data by reading the positions of the tabs and re-storing that information to the memory.</P>


So, your memory system may in fact be working properly, but before you disconnected the wire, something on the capture board was malfunctioning, sending "go down" data to all the tabs. Now that you've cut the wire, all tabs are getting a "go up" instruction (or more correctly, "no data" which the tab interprets as "go up.")</P>


So, I'd look at whatever chip or transistor in the system sends that data to the tabs.</P>


If you are successful, please post in detail. As I said, I've not worked on one of these, but I know of at least one Rodgers of that era with a dead action, and I might be able to work with some information you are able to obtain in trying this repair.</P>


Thanks in advance!</P>


John</P>
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[Guest]

Re: Rodgers 800 Alexandria (1978)



Hi John,</P>


Thanks for the reply and info. Hopefully the tech manual will arrive this week and I can further diagnose the problem. It's probably something simple but difficult to track down without the proper drawings, etc. I had heard of the earlier type of action with the magnetic cores, and also think there was something else maybe earlier than that which used magnetic beads that actually moved back and forth. Everything was okay unless you happened to move the console and upset the arrangement of the beads. Kind of like the old setter board Virgil Fox used to have to fiddle with on the Hook and Hastings organ prior to the Aeolian-Skinner being installed. I guess the setter board was out in the hallway and there were little brass pins that would loosen causing the setters to fall out of place. So - Virgil had to take his little tack hammer and pound the pins back in place. BUT, at least the offending problem could be easily found by sight and repaired. And, even today anyone with good vision could fix the problem. Now a Rocket Scientist who is still familiar with "old" technology is required. Are we moving ahead or backward? </P>

[jbird604]

Re: Rodgers 800 Alexandria (1978)



Not sure that all "progress" is "forward progress!"</P>


John</P>

[Guest]

Re: Rodgers 800 Alexandria (1978)



Hello John,</P>


Would you believe. The tech manual arrived today in just a week from the UK. After studying the schematic for a couple of hours I had narrowed the problem to one or two IC's and the first one I replaced solved the problem. It happend to be U37 on the Memory board. Now I just have a couple of stops that either won't set, or the flip flop that controls the stop action magnet is defective, so will trace that down tomorrow. Other than that, all systems go. What I am quickly learning, however, is that many of these chips are soon becoming quite obsolete so stock up while you can! Fortunately, there are a number of places that cross reference this old stuff and some even still have a few lying around. I was lucky enough to find an electronics distributor down in San Antonio that had all kinds of chips for .25 to .50 ea. The socket cost more than the chip. So, for just over a buck I got the Rodgers 800 bach in service. The manual I got from the UK was a very good copy and contained everything I needed and covered about four different models, mine I guess being the top of that particular series. Still, I would again like to have a 3m drawknob, but not sure I could get it through the door! Used to have 2 large 3m Allen analogs with 5 and 6 generators. A little more warmth, depth, but also a LOT more space with the huge racks for the generators, amps, "Whind" supplies, etc. </P>


I've rattled on much too long, but thanks again for your information. In fact, this system must be quite similar to the "memory core" of earlier vintage you mentioned. </P>
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Harry</P>

[jbird604]

Re: Rodgers 800 Alexandria (1978)



Wonderful news! Keep up the good work. There is probably a lot you can do that organ as an on-going project. IIRC, the 800 series has a pretty extensive set of voicing controls, so you can customize the sound quite a bit.</P>


Keep posting your results.</P>


John</P>
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[Guest]

Re: Rodgers 800 Alexandria (1978)



Hi John,</P>


Yes, I've already "goosed" most everything up to the limit or at least so that it now is more aggressive which I like. Although this has a 32' Contra Bourdon which really shakes things, I'd like to had a 32' Harmonics to simulate a bombarde. It is basically just a wired mixture of the proper harmonic series. Not sure exactly what I'd have to do, but am going to investigate it. I'd also like to get the levels higher on the swell reeds, but haven't found an overall level control for that. There are individual level controls for every note, but not sure I want to go through that procedure, but may have to. I suppose one could say that if I were to put all of the levels higher on every stop you really haven't accomplished anything, however, it seems that as you increase the level the harmonics seem to change and get brighter. But maybe it is just that you can hear better at a higher level?? This organ had a "necklace" reverb tank, but I am using a DigiTech effects generator which gives me 99 different choices and types of reverb, chorus, echo, etc. Have it set on "Cathedral" now which is quite awesome. But in a tiny room such as I have, I need all the help I can get!</P>


Harry</P>