Schematic for Roland KC-500 keyboard amp

[ClumsyFingers]

There have been threads on this in the past, but when I find them, the linked PDFs don't show up. There's a 14-page "service notes" document by "RJA", I suppose a roland employee...but all I can find is small images referring to it.

Utlimately, this is what I need:
Ch1 and Ch2 input pots (stereo, 100k I think) and a mid EQ pot. I'm hoping the service notes include the Roland part numbers

Thanks!


Dave

[Jazz P Bass]

Can't post the file.
It's 8Meg.

The Roland Part# is: 00905278
The Mfg's Part# is: RK09L12BO 100KBX2
PCB Designation: VR1, 2, 4, 5

[data river]

KC 500 too harsh?

The Roland kc-500 I purchased on craigslist had a strange problem. Each channel sort of worked – but the amp would go into oscillation if any knob was turned above about 40%. What I found was that ALL the pots needed to be replaced. Good thing Roland includes the ALPS part numbers on the schematic. Not easy finding these but Mouser had all but the CH3 250K pots. For the tone 50K (type B taper) pots I used the dual gang pots ( and clipped off the extra leads) because that’s all I could get. Fortunately, the CH3 250k dual pot was ok – but not perfect. But ALPS doesn’t appear to have a part for this anymore.
So after I got that all taken care of, I started using the amp, but, with any higher volumes it sounds awfully harsh – like a weasel is living in there.
To fix this:
Roland put some equalization circuits in the power amp. After much calculation and messing around trying to flatten the response, I removed the following capacitors:
C225 (.0047uF)
C207 (.068uF)
C211 (1uF)
Roland uses these capacitors (and some resistors) in some equalization method which, frankly, doesn’t work well, especially with the horn. Removing these caps gives a straight eq which helps tremendously.
I also changed C213 from 330pF to 220pF, but this really didn’t have much of an effect.
But to completely fix the problem, I substituted a bullet tweeter with SPL 106db that is 100% better than the Fostex 025H27. I used a Pyramid TW47 that I had laying around – mainly because it fit in the existing hole for the Fostex horn – I only had to drill 4 more bolt holes. Previously, I used the TW47 in a Nemesis bass amp with 4 10” woofers, and it too sounded much better than the included horn (and it fit in the existing horn hole).
I also added some fiber fill to the cabinet – which was bare wood inside – that was a lot of labor that I am not sure helped, but it is generally recommended for sealed woofers to reduce internal noise.

[Enzo]

Um... It isn't necessary to post the same thing several times, please pick one thread and stay with it.