| Schematics for K250 Amp head? [message #4110] |
Mon, 26 April 2004 04:41  |
VinceG2
Messages: 26
Registered: April 2004
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Junior Member |
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Does anyone have the schematics for the K250 amp head? Specify I have the K250-2 with the Tremolo/Vibrato but no Fuzz/Wah (K250-4).
I acquired the amp around 1982-1984 when my brother in law passed away. I had tried to learn guitar back then, but after a while, I just sorta settle into knowing a few chords.
Anyhow, recently I got the bug to want to learn again, so I took the amp out, and bought a Fender Stratocaster.
The amp had been sitting in the closet for almost 20 years (I know, such a shame!), but when I powered it up, THUMP! It has a nice clean sound to it!
But it does/did have a few problems. The mid control on the bottom channel was barely changing the sound, the amp would squeal badly when I'd plug or unplug a cord, and it seemed to have feedback when the volume on the top channel was around half way up.
Cleaning the jacks up and inserting a guitar cable a bunch of times seems to have cleared the oxide off enough, so it doesn't squeal anymore.
upon opening up the unit, I found that the parts seems to have been soldered tacked into place..very little solder used! I guess over the years, some parts became dislodged. On the top channel, 2 orange drop capacitors had a leg disconnected/in the hole but not really making contact. I soldered those in place and soldered a few other suspect areas.
On the bottom channel, it appears someone had worked on the unit. This amp seems to be from around 1971 (thanks Les for finding the approx date of this unit!), but the IC had been replaced with a Texas Instrument IC, and one of the transistors was replaced as well. It was pretty obvious, as the areas worked on all have brown rosin flux all over..the IC, all three transistors (I think they took them out, tested them, found one bad and reinstalled the two good ones).
A black part (electrolytic cap? Not sure, but it has a dot designating which way to install it..) had one of it's legs up in the air. Soldered that properly in place.
The blue and black wires to the input jacks had been resoldered..looks like whoever was soldering burned off the trace where the blue wire goes. So they had soldered it directly to the resistor it goes to. Ouch. I straightened out that mess and now it's back in the hole on the board and soldered from under like it should be.
After all that, I powered it back up, and the mid control is working great now! And I was able to turn the amp's volume full blast now without feedback! (I need to check that tomorrow, I only had the amp on for a few minutes because I didn't want the neighbors to complain!)
The thing is, I was pretty much working in the dark..schematics would have majorly come in handy!
I also heard that Kustom put out some service update/revision paper(s) as well? Anybody have these?
I do like the modular design on this amp! And the sound is very clean! It sounds tube-like. Wow, impressive!
Thanks for listening to a newbie to the guitar world ramble on. I am glad this Kustom is my first amp, I should have never put it in the closet for 20 years to begin with!
If anyone has the schematics and/or service info, please let me know. I'll gladly reimburse you.
Vince
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