Monitor 5 upgrade

dpage

I read through the other threads on this same topic but have some questions I didn't see addressed. I picked up some Monitor 5's from '85 and want to upgrade them and use one as a center with my Monitor 10's (RDO-198's).

The SL3000 upgrade schematic adds a polyswitch that I assume replaces the fuse. I don't understand how/where to add that on the crossover. Also how do you change the inductor from .23 to .27mH. I don't have any testing equipment to measure. Can I just unwind it a specified amount?

And finally, to keep things easier I could just replace with same values and throw in an RDO-194 but wondering if that would be a bad idea since my Monitor 10's have 198's. Thanks, I appreciate any help.

westmassguy

The Polyswitch replaced the fuse. The resistor downstream was reduced to compensate for the added resistance of the Polyswitch. The SL3000 Mod is easy. You'll add the 5.8uf shunt cap. The .23mh shunt Inductor can be replaced with the Jantzen # 255-216 .27mh inductor. You'll need to pad it with a .27 or .3 ohm resistor to maintain the required .5 ohm resistance of the shunt. The holes for the added resistor should already be there.

dpage

Thank you! Will the Raychem RXEF050 0.50A Polyswitch from Parts Express work? Also, and forgive my lack of knowledge, if I decide to use Clarity PX caps and Dayton caps should the 12uf cap be the Clarity and the 34uf the Dayton? And what would you suggest for the 5.8 cap? Thanks again.

dpage

Also I was going to use a 2.0 Ohm Mills resistor but the only .27 Ohm I can find is a cheap one from PE. Is it ok to mix them?

westmassguy

Don't add a Polyswitch if your 5s have fuses. Polyswitches suck.
Sonic Craft carries all the values for Mills resistors. Go with 10 or 12 watt.
Clarity has the 5.6uf and 12uf in the PX line. Solen or Dayton for the 34uf. Dayton has the 33uf which is fine.

dpage

I just ordered all the parts but just realized since I'm now keeping the fuses and not replacing with polyswitches I probably ordered the wrong values for the resistor. Wasn't the resistor changed to compensate for the resistance of the polyswitch?

I ordered the Jantzen inductor you recommended, 2.0 ohm Mills, .27 ohm Mills, 5.6uf and 12uf Clarity PX, and 33uf Dayton. Was I supposed to keep the 2.7 ohm resistor if I keep the fuses? Thanks again for your help.

westmassguy

The 2.7 should have been replaced with the same value, you didn't change the fuse.

dpage

I received all the crossover parts. One last question...I'm not sure where to add the .27 ohm resistor to pad the new inductor. To the holes I marked with arrows below? Thank you!

dpage

And can I just solder the 5.8 uf cap leads to the 2.7ohm resistor leads?

westmassguy

On either side of the existing inductor is a hole. One has the inductor lead going through, the other is empty. Once you remove the old inductor you'll see it. The .27 ohm resistor mounts parallel to the 2.7 ohm resistor. One hole you have marked, the other is where the long lead from the inductor is going now. You'll have to drill two new holes to mount the new inductor. The winding must go in the same direction as the old one. The old inductor is a bobbin type, and they used a belly band to hold it in place. The new inductor is larger, and you'll loop a new wire tie through it, instead of over it, like this:

dpage

Ok finished the crossover. Just waiting on the tweeter. Thanks again. You're a huge asset to this forum.

vmaxer

dpage wrote: »

Ok finished the crossover. Just waiting on the tweeter. Thanks again. You're a huge asset to this forum.

Good luck, I hope it works out for you.