| k200b-3 questions [message #11684] |
Fri, 28 August 2009 13:05  |
jccoombs
Messages: 2
Registered: August 2009
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Junior Member |
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Hi, I'm new to the board and to Kustom amps. I recently purchased a K200B-3 serial# 27081 with matching 2x15 cab. I purchased the head understanding it had some issues, mainly channel 2 was not functioning, the pilot bulb and lens was missing, and channel 1 had filthy pots and had some static. I opened up the amp when I got home and it was extremely dirty so I cleaned the pots and attempted to clean the dust out. It seemed to sound somewhat cleaner but still nothing from the second channel. In trying to work the second channel I noticed that working the selective boost knobs produces extremely loud pops. I left it at that yesterday and didn't mess with it anymore. Today I was playing through the first channel for maybe five minutes and the sound cut out and I was left with a loud, steady hum, almost like a shorted speaker. I ran another head through the cab and it sounded fine albeit a bit buzzy. I opened up the k200 and reconnected the cab and noticed a spark. My questions:
1) What could cause the sudden failure of the first channel?
2) Channel 2 seems like a bad input jack but what would cause the popping on the boost?
3) Does the missing lamp cause any issues other than appearance?
4) could the buzz in the cab be from a dirty jack? its noticeable across the full range and the speakers otherwise sound loud and full.
5) Am i correct that this cab would be 8ohm? the only markings are kustom by ross on the front and altec on the back plate.
Sorry for the long post and thank you for any help
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| Re: k200b-3 questions [message #11692 is a reply to message #11688] |
Sat, 29 August 2009 11:34  |
pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi
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Senior Member |
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Again, Welcome to the site. I'm not a tech but to help some of the other techs, they will first need to know what color your kustom is. LOL. You may want to state the channels as left and right channels. On your -3 head, left channel should be a straight volume, bass, treble, and bright switch. The right channel is the channel that has the selective boost and harmonic clipper. First off, if the amp is giving a loud hum, Seeing a voltage spark when you plug in the speaker leads me to think you have some serious issues with the power amp section, and may be pumping DC Voltage into your speakers and can fry them. Again I'm no tech and it may be AC Voltage, but I do know you can cook your speakers.
The popping sound when rotating the selective boost switch, is a issue that most have. In the few dash 4 heads I've owned they all did it, even after cleaning the 7 position switch. I really think you need to have a qualified tech take the amp and get the power amp working and then have him chase down why the pre amps are not working like they should. In any amps I have if I can't get something cleared up with some contact cleaner, I just take them to my repair guy and have him go through the complete amp.
Nothing worse that have the amp fail on a gig.
Don
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| Re: k200b-3 questions [message #11695 is a reply to message #11684] |
Sat, 29 August 2009 14:55 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Welcome!
The bright channel pre-amp PC203 is designed with an added bright boost circuit that uses a bypass switch for the bright knob. If the switch becomes intermittent and does not make clean contact it will kill the signal through the pre-amp. Try switching it back and forth a few times and see if the sound is restored.
The Boost channel board PC403 has the selective boost and the harmonic clipper circuit. If you hear the noise from the boost switch, then that circuit is probably working. The noise is probably caused by a cap that is switched in the circuit that has a slight charge built up in it. Turning the switch causes the cap to discharge as it is being placed in and out of the circuit.
Have you tried switching on and off the clipper control? The clipper circuit falls between the boost and the pre-amp input stage. If the switch on the control is not clicked off the bypass circuit will not work.
If you have dc on the output, you will need to have the power amp looked at. If you have a voltmeter, see if there is any dc on the output jack (no speaker hooked up). I don't know what you were doing when the spark happened, but you should not have the amp on while connecting the speaker cable.
As for the pilot lamp, it will not cause any problems if it is missing the bulb. Just be sure to replace it with the correct one when you want to.
Buzz in the speakers is rarely caused by bad jacks or wiring. It is possible, but unlikely. Do both speakers sound the same? Is it something loose in the cabinet that could be buzzing?
Hope this helps.
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