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K200-B5 - One channel is dead. . . [message #13581]

Fri, 07 May 2010 16:48

Optyk
Messages: 125
Registered: August 2006
Location: Texas

Senior Member

OK, this happened the other day. Channel 1 went dead on my K200B-5. I have a Kasino Club that's functioning but has some hum in it. According to ChicagoBill, the channel board is theoretically the same between the two units so I could yank a board from the Club and put it in place of the Channel 1 board (barring mounting issues). This would just be a board swap and shouldn't be a major adventure.

However, what are the chances that the hum I'm getting on the Club is from something on the channel boards and I'd only end up trading a bad board for a bad board and wind up having to yank it out and repair the thing anyway? I don't use the Club for anything, so parting it out isn't going to affect my life in any meaningful manner.

So, would I be better off repairing the existing Channel 1 board on the K200B-5 (with some help from the gurus here!) or should I roll the dice and just do the board swap? I think I'm capable of doing either. I know how to solder, have a digital multimeter, know a transistor from the pinion gear on a '57 Dodge station wagon and can read and comprehend a fair amount of the english language.

All advice is welcome and appreciated.

Rod

There's only two kinds of music. . . . blues and zippity doo dah.

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Re: K200-B5 - One channel is dead. . . [message #13582 is a reply to message #13581]

Fri, 07 May 2010 17:13

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Is the hum on the Kasino constant or does it change with the volume and tone controls?

If the hum is constant, it probably needs filter caps. If the hum changes with the controls, then it could be a problem with the preamp board.

Personally, I'd try to fix the K200B-5 head preamp board. There really isn't that much to them, and then you could always fall back to the board swap idea if you can't get it working.

Do you have a copy of the schematic for that board?

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Re: K200-B5 - One channel is dead. . . [message #13583 is a reply to message #13582]

Fri, 07 May 2010 17:40

Optyk
Messages: 125
Registered: August 2006
Location: Texas

Senior Member

> Is the hum on the Kasino constant or does it change with the
> volume and tone controls?

I couldn't detect any change in the hum by changing the volume
or tone controls.

> Do you have a copy of the schematic for that board?

I do have a copy of the schematic. I don't consider myself a board-level technician, though, although if you're just talking about changing out a transistor or capacitor or whatever, I believe I'm capable of locating the part and making the switch without butchering the board. I guess my shortcomings would be more in the circuit tracing/diagnostics arena.

Thanks for the quick response, Bill.

Rod

There's only two kinds of music. . . . blues and zippity doo dah.

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Re: K200-B5 - One channel is dead. . . [message #13584 is a reply to message #13581]

Fri, 07 May 2010 18:19

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Having the schematic will allow us to communicate easier, as long as you can figure out what part on the board is what part on the schematic.

Start by listening to the background noise that the dead channel makes. If you turn up the different controls can you hear the sound/hiss change? If you can, then the problem is at the front end of the board. If you can't then the problem starts at he back end of the board.

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Re: K200-B5 - One channel is dead. . . [message #13585 is a reply to message #13581]

Fri, 07 May 2010 18:19

pleat
Messages: 1452
Registered: June 2004
Location: Belding, Mi

Senior Member

Why not unsolder the board from the kasino, and if the hum goes away, you've located the problem. If the hum remains, then it could be in one of the other three pre amp boards or the other boards in the Kasino but at lest you have a good board to install in the kustom.
pleat

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Re: K200-B5 - One channel is dead. . . [message #13586 is a reply to message #13584]

Fri, 07 May 2010 20:11

Optyk
Messages: 125
Registered: August 2006
Location: Texas

Senior Member

> Start by listening to the background noise that the
> dead channel makes. If you turn up the different controls
> can you hear the sound/hiss change? If you can, then the
> problem is at the front end of the board. If you can't
> then the problem starts at he back end of the board.

OK, i listened to the background noise and could detect no change at all when diddling with either of the 4 controls, so the problem is at the back of the board, I presume.

Rod

There's only two kinds of music. . . . blues and zippity doo dah.

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Re: K200-B5 - One channel is dead. . . [message #13628 is a reply to message #13581]

Mon, 10 May 2010 12:09

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

That would be a good place to start your search, test Q103 and Q104 and check C113.

If you need help in testing the transistors let me know and I'll take you through it step by step.

If you can do it safely, check the voltages on the transistors and compare them to the voltages listed on the schematic.

Remember to use caution when working on an amp that is plugged into the wall and turned on.

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Re: K200-B5 - One channel is dead. . . [message #13645 is a reply to message #13628]

Wed, 12 May 2010 13:52

Optyk
Messages: 125
Registered: August 2006
Location: Texas

Senior Member

I'm not ignoring you, Bill. This week has just gotten wayyyyy too hectic for me to get time to get to this. I'm hoping I'll have time over the weekend.

Rod

There's only two kinds of music. . . . blues and zippity doo dah.

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Re: K200-B5 - One channel is dead. . . [message #13648 is a reply to message #13581]

Wed, 12 May 2010 17:20

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

No worries! I've got plenty on my plate as well.

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