[sdiy] 1970's organ repair and multi-capacitor PS caps

[John Speth]

Here's an oddity in my three metal can power supply. There is a half 
inch screw wedged end to end between the two tallest metal cans near the 
non-terminal ends of the cans. The screw is held in place due to the 
spring force of the spreading cans against the screw. It was placed 
there on purpose. I've seen that once or twice on such metal cans in old 
tube radios.

What do you suppose the function of that screw could be? Resonant 
vibration/buzz reduction?

JJS

On 6/7/2020 9:25 AM, John Speth via Synth-diy wrote:
>
> Hi experts,
>
> I'd like to attempt hum elimination on a 1972 Wurlitzer 4027 organ. 
> I'm pretty sure the bridge rectifier filter electrolytic caps are aged 
> to the point at which they don't filter so well anymore. The power 
> supply uses 4 inch tall multi-capacitor cans mounted on the PS chassis 
> with pins in the chassis and the cans external to the chassis. All 
> caps are employed for a total of 10 caps in three metal can packages. 
> Are these antique parts even available in new, recently manufactured 
> form anymore? If so, where?
>
> There are three cans comprised of:
>
>  1. 500uF/25V x 2, 500uF/35V, and 1000uF/25V (4 caps)
>  2. 1000uF/25V x 2 and 5000uF/25V (3 caps)
>  3. 3500uF/25V and 1000 uF/25V x 2 (3 caps)
>
> Ideally, using exact replacement of new parts would be best (and maybe 
> costly, I fear). Non-ideally, I could wire new single cap 
> electrolytics but that would end up looking like a frankenstein fix 
> (probably work but bulky). Furthest from ideal is buy a new current 
> technology PS and use diodes or something to drop the highest voltage 
> to obtain the multitude of lower voltages (22.5V --> 20.0V, 19.9V, 
> 19.5V, 17V, and 10V). That might solve the problem but any engineering 
> miscalculation could fry other parts of the organ.
>
> Another question: There is a 0.01uF/1400V cap across the PS 
> transformer primary coil. What is the function of that cap?
>
> Thanks, John Speth
>
>
>
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