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K-200B-2 normal channel [message #25325]

Thu, 28 July 2016 15:57

slk854
Messages: 192
Registered: January 2015

Senior Member

I just got a 200B-2 and the bright channel seams to working ok. When I connect to the normal channel I have nothing, but when I turn the volume knob back and forth on that channel I have some sound. It is just what is input sound. It is just more like a scratchy volume sound but it will not pick up anything that is plugged into it. Any suggestions are greatly appreciated

Steve

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Re: K-200B-2 normal channel [message #25330 is a reply to message #25325]

Fri, 29 July 2016 08:47

slk854
Messages: 192
Registered: January 2015

Senior Member

I just re read my post and I know it doesn't make a lot of sense. The bright side is working. The one with the reverb and vibrato. The normal side is not. It does not matter if you plug into the low or high jack. It does make a little scratchy noise if I turn the volume knob back and forth, but no input sound from a guitar. It will make the same noise when nothing is plugged into the jack. Need advice...

Steve

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Re: K-200B-2 normal channel [message #25331 is a reply to message #25325]

Fri, 29 July 2016 08:57

stevem
Messages: 4773
Registered: June 2004
Location: NY

Senior Member

There are many things that can make for this problem and they all get solved by removing that board to repair it!

One thing that I have seen more and more as these amps get older is people breaking the pots trying to free the rusted pot shaft nuts that hold the boards to the inside face of the amp.

Trying to bust loose a frozen on nut can break the connections on the face of the pot and make for a issue like you have, of course a failed first gain stage transistor can make for the same problem , so like I posted that board needs to be backed off the inside face of the amp to do anything.

Remove all the knobs by means of tree set screw and then get the shaft nuts loose, use some rust breaker if need be and let it soak for a day and try to remove it again.

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Re: K-200B-2 normal channel [message #25332 is a reply to message #25331]

Fri, 29 July 2016 09:18

slk854
Messages: 192
Registered: January 2015

Senior Member

Steve, thank you for the reply. Some things I am good at but some I am lost. When I get the board loose does it disconnect some how like the molex connectors on the 250 series, or will wires have to be cut. I am not too swift with electronic stuff. I can take apart and clean but that is about it unless it is pretty simple procedures. I do have some electronic skills but would never call myself a repair person.

Steve

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Re: K-200B-2 normal channel [message #25333 is a reply to message #25325]

Fri, 29 July 2016 09:52

stevem
Messages: 4773
Registered: June 2004
Location: NY

Senior Member

No, no easy connections like in a metal face Kustom , so you may need to tract down a repair tech?

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Re: K-200B-2 normal channel [message #25337 is a reply to message #25333]

Fri, 29 July 2016 13:05

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

If the volume control causes a noise in the amp, what happens to any of the background noise if you turn the tone controls or the bright switch? If the noises change with the tone controls, then the problem would be at the very input of the preamp.

Check the wires from the input jacks to the pc board. For that matter check the input jacks themselves. Make sure that the contacts are clean and that the little switching contacts that ground the input signal are opening when you insert a plug.

If you have a multimeter and a soldering iron and feel adventurous, you could try fixing it yourself. It could be a broken solder connection or a bad input transistor. Both things would be fairly easy for even a beginner to handle.

And if you really don't feel up to the task, you can always just remove the one pc board and ship it to Steve to fix for you.

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Re: K-200B-2 normal channel [message #25341 is a reply to message #25337]

Fri, 29 July 2016 17:24

slk854
Messages: 192
Registered: January 2015

Senior Member

Thanks guys. I will let you know what I find

Steve

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Re: K-200B-2 normal channel [message #25342 is a reply to message #25325]

Sat, 30 July 2016 06:29

stevem
Messages: 4773
Registered: June 2004
Location: NY

Senior Member

If you pull the board, to get more room to work on it you can undo the harness and cut it open so that you can butt splice / crimp it back together .

Boards get there needed circuit ground many times by being bolted to the chassis so do not fire the amp up with the board out until you have a ground in place.

If you look at the copper traces where the pots bolt to the board you can clearly see the ones that need grounding.

Like Bill kindly posted about checking the first gain stage transistor , new ones these days can be had for far far less then the cost of shipping them ,like far under 50 cents each and the ones made these days make less hiss than the original ones.

If you want yo drop off the board that is working you can use that boards first gain stage transistor as a fix for your bad board , but first do the checks that Bill posted.

Just note that the box type resistor off of the pilot lamp gets very hot so steer clear when the amp is on and for 3 minutes after the amp is off!

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Re: K-200B-2 normal channel [message #25360 is a reply to message #25325]

Wed, 03 August 2016 14:44

slk854
Messages: 192
Registered: January 2015

Senior Member

This was the culprit...

http://i1211.photobucket.com/albums/cc434/hunter12407/001_zpsywijqkpw.jpg

Steve

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Re: K-200B-2 normal channel [message #25361 is a reply to message #25325]

Wed, 03 August 2016 15:39

chicagobill
Messages: 2006
Registered: April 2003

Senior Member

That was simple enough wasn't it?

Tell us how did you find the problem?

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Re: K-200B-2 normal channel [message #25362 is a reply to message #25325]

Wed, 03 August 2016 15:58

slk854
Messages: 192
Registered: January 2015

Senior Member

If the transistor is good, you should get an open-circuit reading from collector to emitter.

And most of all thank you to Stevem & Chicagobill for pointing out exactly what stage to check out first.

Steve

[Updated on: Wed, 03 August 2016 16:01]

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