For whatever it's worth, probably not much, I have replaced crossover capacitor(s) in my my AMI F-120, but it was a long time ago. As far as I can remember, my experience agrees with everything Nigel says on the caps, including the part about not being born at the time!

The motor start caps were available at a relatively cheap price at the time. As long as your replacement is non-polarized, matches the original capacitance value reasonably well, and can handle the voltages in the given circuit, you will be fine.

Online calculator, back of the envelope calculations say a 20 watt amp can put ~18 volts through a 16 ohm load, and the voltage is lower for lower impedances, so I think 250v is *plenty* of safety margin. Someone else can tell me if I'm not thinking clearly about what voltages could be found in a crossover.

As far as the resistors go, I don't know what type of resistors were used originally. I am assuming you've checked your originals and they are out of spec? If the originals were not wire wound, I might be wary of potential magnetic coupling between the coils used in the crossover and the coil-like thing a wire-wound resistor happens to be. Something like that probably wouldn't cause any electrical dammage, but it could have odd effects on the sound.

Now that I think of it, the potential addition of inductance to the crossover circuit might have bad effects if you're substituting a wire wound resistor in place of something that wasn't.

NOTE THAT I'm self educated when it comes to electronics, I get DC circuits pretty well but am sketchy at AC, and this is nothing but AC. I'm well outside the boundaries where I probably should be chiming in, but I've already written it so I will inflict it upon the rest of you. :-) Take what I've said here with a grain of salt, and give heavier creedence to anyone else on this list who replies!

--> Steve Wahl

On Fri, Feb 09, 2024 at 02:43:52PM +0000, Nigel Pugh via Jukebox-list wrote:

Hi Joey,

Regarding the crossover caps. Ami / Rowe used those motor start types a lot around that time, and I believe it's because they were available in the values needed and for no other reason. You can happily replace with a 22uf standard np electrolytic, which will be about a tenth of the size.

I read, but wasn't born then so don't take my word for it, that caps were much bigger then and have reduced in size due to technology. Ignore the motor start bit completely.

Nigel, uk

...

On 9 Feb 2024 at 14:33, joeymcd via Jukebox-list jukebox-list@lists.netlojix.com wrote:

Looking at freshening up a few AMI F and G crossovers I have. AMI F manual page 17 of the sound section shows the schematic and parts. Both capacitors are the same rated the same. The original capacitor is labeled Dry Electrolytic Motor Starting Capacitor 18-22 MFD 115 VAC 60 Cycles and is quite large.

Why would AMI use this? Can something like this be used?

[ https://www.solen.ca/en/products/dmpc-20 | https://www.solen.ca/en/products/dmpc-20 ]

Second is the resistors used to attenuate. One is 18 ohm 4 watt and the other is 33 ohm 4 watt spec given on the parts list. Is resistor type and wattage a factor here? Can this be used? These are exact ohm rating but 10 watt.

https://www.solen.ca/en/products/solen-cement-type-wirewound-resistors-wwsqp... [ https://www.solen.ca/en/products/solen-cement-type-wirewound-resistors-wwsqp... | https://www.solen.ca/en/products/solen-cement-type-wirewound-resistors-wwsqp... ]

Thanks. Joey McDonald

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