Thank you to all the replies. There are a number of issues with the organ which I hope to fix one by one. I have to say: everything functions, every single key, every single tone generator, every single effect, just some things function less well than others. Those issues I will be working on in the future. And also, despite using germanium transistors, research tells me that many common soviet components are used here, should I need to source anything, I am not worried, as I even speak russian).
But the biggest multifaceted issue is to do with the "action" of the keys. The 5 contacts associated with every note are not activated simultaneously as the key is pressed down, but rather one by one, I think this is because the contact surface is not clean. I can confirm this visibly (as in, I can see what a clean section of contact looks like, and what a dirty section looks like).
the contacts are held in place by precise pieces of plastic, so contacts being "bent" or anything like that is no excuse. And due to the fact this issue occurs with all keys to a varying extent, I think this is just due to built up gunk from years of having "contact cleaner"-type stuff sprayed on the contacts. My thesis is that a slightly "better" than typical connection needs to be made now, before the electrical contact happens, as in the contacts need to be pressed up against the rod slightly harder, with slightly more surface area, that pressure is granted as the key is pressed deeper, resulting in staggered activation. Just a thesis.
Yeah, a pretty niche issue, with what hopefully will be a pretty niche solution.
I am going through the original service manual quite slowly (it's in german, I do not speak german), it even has a section on "common troubleshooting", maybe I will find something. It is a few weeks still before I get a soldering iron. So by that time I hope to be otherwise prepared.
See those 5 thicker rods in the keybed in th 1st picture from my previous post? Those are the rods the contacts touch when a key is pressed. I have no idea what the other 5 rods skinnier rods are for, but I can tell you now they are far less electrically involved, to my knowledge they serve the purpose of helping hold the 5 octaves together in a line (each octave has it's own circuit board). Following the wires, I believe they just ground to a metal component inside the organ. After a small amount of soldering, they should just slide out (they're almost a metre in length each, i'd say).
They are what is stopping me from getting a q-tip soaked in isopropyl between each contact and it's associated "big" rod. So yeah, all this work just to clean some contacts.
And after that point, i'll already have all the means (not necessarily the knowledge!) to work on the tone generators and whatever else.
I have soldered before (in a fun, let's-see-how-this-works, not-gonna-care-about-the-outcome scenario, supervised by a professional), and the circuitry inside this organ does "appear" less complicated in some ways (back then I remember trying to solder a chip with about 12 legs on each side, modern component, all the legs closely together, yikes, whereas here there are resistors, transistors, and things are spaced out quite nicely). I plan to practice for at least 2-4 months before seriously doing anything to the organ, practicing: soldering, de-soldering, working accurately, using a solder-sucker, operating quickly, working out some solution for ventilation (i'm only going to ever realistically use leaded solder). Not quite on scrap-electronics, but with things that can at least give me a response or indication as to whether the electrical connections I made were successful. I think there exist kits specifically for this educational purpose, I will likely start there.
Here's a zoomed out picture of the keybed, (
) with all keys removed. You can see I have made a start on taking out plastic components from the left hand side as part of the process of getting better access to the contacts. Ignore the annotations.
I have to restrain myself quite strictly as I'd love to ask more (related) questions but I am aware it is the rule of forums not to go off on tangeants.
Thanks to everyone for the replies. I will take my own advice (ha!) and make sure I am careful when working on things *inside* the organ. But before i got the answers I did here, I didn't even know that was allowed!