Have a client who has a number of vintage musical instruments and amplifiers. Nobody else in the area will touch any of this stuff and you can understand why. Whenever I hear “Oh you like a challenge” I reach for my tactical weapon store. No, I don’t like challenges anymore, I like jobs I can do with my eyes closed and charge enough money to keep my 24 year car on the road and have enough in my pocket to buy some bread and cheese. However…
On power up, there seemed to be more than one fault. With a sinking heart I opened her up, lifting he top panel. The wiring looms are quite tight and you stand to create an additional fault just by looking at it. The F note was odd, covering all octaves. Now the reference oscillator running okay with all notes being available, so the fault was going to be with the odd IC divider chip providing the 5 octaves. This chip is an odd logic divider operating at a minus supply line, made especially for this organ and one or two others. These ICs have not been available for years. But, an enterprising company has made a PCB header with a programmable chip which emulates the original. A bit expensive, but works really well and if you want a working organ, it’s the only option. I bought a handful a while ago, just in case and here is a great example of “who else could sort this out”.
All was good, save for the 2nd E key was missing most of it’s tonal component. After loads of checking with the scope, I came to the conclusion we had a keyboard fault. I really hate these. With the keyboard in the service position (i.e. hanging in mid air) and all the screening off, you could see all the green plastic guides had broken away and or deformed over the years. These interfere with the tiny contacts of the key actuators on the bus bars. Hours spent sorting these out and realigning the contacts. Real pain. Once done and a few capdensors replaced, we had a nice sounding working instrument.
Tomorrow I will be fitting some plugs on kettles. Happy days.