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k200b1 bass head bright channel is DEAD...please help [message #9473]

Tue, 27 May 2008 21:52

raw-dogg
Messages: 13
Registered: January 2008
Location: nyc

Junior Member

Hi,
I just got my hands on a nice K200B head. The NORMALl (right) channel sounds great. Then when I plugged into the BRIGHT (left) channel...NOTHING...
Does anybody have any ideas about what the problem could be? I didn't look at the inside yet to see if it's a fuse or anything simple like that. Thanks in advance for your help.
Werner<font color=""></font>

[Updated on: Tue, 27 May 2008 22:29]

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Re: k200b1 bass head bright channel is DEAD...please help [message #9474 is a reply to message #9473]

Wed, 28 May 2008 13:07

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

If the amp works, and only the bright channel is doa, then the problem in on the bright channel circuit board located behind the front panel controls.

The two things to check first are:
1-Check for loose or broken wires. There will be red and green wires that supply the power to the board and a blue wire that sends the signal to the power amp. Also be sure to check the input jack wiring.
2-Check the bright switch. Unlike the normal preamp, this preamp actually switches in an additional circuit for the "bright" function. If this switch becomes oxidized or dirty, it will in some cases completely kill the signal to the power amp. Try spraying the bright switch out with contact cleaner and then turn it on and off a few times to wipe the contacts clean.

If the channel still doesn't work, then it will require circuit troubleshooting. I don't know what your skill level is, but it will require you to have a working multimeter and the ability to work on the amp while it is plugged in.

Let us know what you find out.

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Re: k200b1 bass head bright channel is DEAD...please help [message #9475 is a reply to message #9474]

Thu, 29 May 2008 00:54

raw-dogg
Messages: 13
Registered: January 2008
Location: nyc

Junior Member

Thanks for your help. I'm in the process of moving so it will be a couple of days bafore I can really give it a good look. I will definitely let you know how I make out. One thing I forgot to mention is that even though that channel seems dead I noticed that there is a sound when I touch the strings on the bass. It's not a "note" but it sound like a hum or like static, so there is something there but it's not what it's supposed to be. Thanks again and I'll keep you posted.

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Re: k200b1 bass head bright channel is DEAD...please help [message #9476 is a reply to message #9473]

Thu, 29 May 2008 12:30

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

That Static you be a indication that at least the first gain stage/transistor in that channels preamp is working.
Also you may be able to hear a increase in hiss when you turn the brite switch on, if so then the problem lies inbetween the first gain stage and the brite/boost circuit so let us know what you find.
Pack that k200 baby up well for the move!

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Re: k200b1 bass head bright channel is DEAD...please help [message #9480 is a reply to message #9473]

Sat, 31 May 2008 13:50

raw-dogg
Messages: 13
Registered: January 2008
Location: nyc

Junior Member

OK. This is ridiculous...but GREAT!!! I took your advice and looked over the wiring and switches for loose connections and what not. The "bright" on/off knob on the left (bright) channel was missing. I replaced it and turned it on and off a few times after putting the chassis back into the outside padded casing. I could hear a "pop" kind of noise (almost like some sort of grounding issue) and it started working perfectly. Not sure why but HEY it works. Now I just need to change the 2 prong power chord out for a 3 prong to avoid being shocked. I did this with my K100-2 head and it fixed the "shock" issue.
Thank you so much for your help and for getting back to me so quickly. Hopefully I can do the same for someone else.
Take care...

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Re: k200b1 bass head bright channel is DEAD...please help [message #9481 is a reply to message #9473]

Mon, 02 June 2008 06:17

stevem
Messages: 4774
Registered: June 2004
Location: NY

Senior Member

Well the good news is than its not a transistor, due to the fact that the only way they fail in a intermitant condition is when hot, so you are most likly look at a connection problem.
I would take Bill`s suggestion and go to radio shack and get a can of contact spray and clean up that brite swt and any controls that are scratchy or crackle.
Also tapping on that intermitant channels preamp board after the switch cleaning while the amp is out of the case with the plastic end of a small screwdriver might give a clue as to a bad circuit board solder connection.

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