[Texasrocker]

Music, I just noticed in your previous thread about the "thump" you are having on powerup of your model 15.
You stated, that you are "turning the amp on first" ..... then, turning on your preamp feeding the model 15?

Powerup your system in "reverse"! Always turn on your preamp first, then follow up turning on your amp secondly! "Thump" gone!! General rule of all-things in any type "component systems" hooked together.

The model 15s are very nice looking & sounding amps indeed! I repaired a mod 15 several yrs ago.If I remember correctly, Its basically 2 model 14s monoblocks in 1 cabinet? If so, it has a silicone type power supply?, and is prone to thermal-runaway. Keep your amp well ventilated when turned on! I may even still have a schemat here, but not sure. I do remember the large size caps. You can still find those if needed.

Bad capacitors go "humm",.... not "thump"!! Its always a good idea to change out the filter caps, especially due to age issues! However, your caps are still working fine unless you hear a "humm", especially since you have fired up the amp already, and let the caps charge themselves up since you purchased it.If the orig caps have changed orig shape anywheres, or look leaky on the ends,wait until you replace the electrolytic caps before using it on a daily basis. Bad electrolytics go "BANG" when they fry! Let off some nasty smelling smoke also!

The "thump" your hearing in your stereo system comes from "inverse powerup"... of turning your Marantz Mod 15 amp on 1st, then... turning on the power of your preamp feeding it!
Try turning on your preamp 1st,then your amp,.. betcha "thump" is gone!! Go stand-out in the sun for awhile,brighten-up abit,( just kidding music!) and get back to me? ( hee hee) ol Tx.