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K250-4 low g breakup [message #8158]

Sat, 03 February 2007 00:53

wsbb
Messages: 6
Registered: January 2007

Junior Member

My K250-4 has strange problem. After it warms up for a while the low g note or chord will cause signal breakup. Sometimes it will happen with a low d note too. Also if you move the guitar chords 1/4" jack around at the input it makes a very god-awful sound. Do the inputs with the nylon tab pressing against the pin have something to do with this?

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Re: K250-4 low g breakup [message #8167 is a reply to message #8158]

Mon, 05 February 2007 06:47

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

Hi, This sounds like two different problems. Your first problem sounds like a component connection. These amps use moldex type connectors to take the signal from each circuit board to one another, and in these connectors, sometimes the female pins make intermtant connectons. If you pull each connector apart and take a small finshing nail you can bend that female tighter for a better connetion.
Also on my own k250 I had a noise like you describe and it turned out to be that one of the large orange drop type caps on one of the preamp boards developed a bad solder joint at one end, and the noise only showed up after the amp warmed up a bit or if you taped the amp.
Your second question sounds like the input jack has to be cleaned, has a tip tension problem or both.
If you get some contact cleaner from raido shack and apply it to a Q TIP you can get in the jack and clean the tip connection and around the ring(the part where the long shank of a guitar cord makes contact)
Also if the tip tang in the jack is not putting enough pressure on the tip of the jack to load the shank sideways you will get that crackling sound becase with the cord in the jack, the switch in the jack is open so if your volume is up you are hearing a intermitant connection to the preamp.
The cure is to bend the tight curve of the tip tang out more to load the whole plug, but you have to do it carefull, if you bent the wrong part of the jack then the switch will not close when that jack is not in use.
It may be easyer to just replace the jack in question.

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Re: K250-4 low g breakup [message #8896 is a reply to message #8158]

Fri, 14 September 2007 08:39

davohilts
Messages: 40
Registered: August 2006
Location: Portland, OR

Member

I had a problem much like this with my Plush 1000S.
With the amp sitting on my 4x10 half stack the vibration from low chords and notes caused the jack to loose connection causing a horrible sounding crackle then back to normal. I cleaned the jack and the problem was solved.

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Re: K250-4 low g breakup [message #8897 is a reply to message #8158]

Fri, 14 September 2007 12:33

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

One of my k250s had a bad solder connection on a orange drop type cap on one of its preamp boards. I forget if it was the top channel or not, but it did make a horrible crackle on the right bass notes.

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Re: K250-4 low g breakup [message #17047 is a reply to message #8897]

Thu, 03 May 2012 15:56

RobbieNuke
Messages: 66
Registered: October 2006
Location: Baltimore

Member

My K250 had two issues;

1. Crackle noise when plugging/unplugging guitar cord-
a) A broken input jack @ Ch 2 (first time ever saw this).
b) Cold solder joints at the resistors on Ch 1 input jack.

2. Ch 1 has a replacement pre-amp IC. There is a weird 'Morse-code' kinda noise, very low volume but noticeable. I'm trying to locate a suitable replacement.

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