| need some help with a hissy k100 [message #8906] |
Thu, 20 September 2007 19:10  |
ianb
Messages: 13
Registered: July 2007
Location: tennessee
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Junior Member |
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i picked up a charcoal plexi front k100/ 212 cab this week and the head is having some issues.
the seller told me it had some hissing issues but it was such a sick deal i jumped anyway.it's hissing loudly (not just the normal noise)on both channels and the hiss goes up with the volume.
i dropped the board today and there is quite a bit of oxidation on the traces but probing it didn't turn up any loose components and all of the resistors i've measure so far have been in tolerance. the hiss gets louder with the volume control but is present all the time to a degree.
i injected signal into the circuit right before the drivers and it sounds clean so i'm thinking it's not filters.
any of you guys got any pointers for me? i don't have a scope so i'm hoping there is a pretty common issue i just don't know about.
[Updated on: Sat, 22 September 2007 01:28] Report message to a moderator |
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| Re: need some help with a hissy k100 [message #8912 is a reply to message #8906] |
Mon, 24 September 2007 16:07  |
chicagobill
Messages: 2005
Registered: April 2003
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Senior Member |
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Unfortunatly, your problem is the most common among the Kustom amps, and also the most difficult to cure. Hiss and random popping can be caused by any of the following items, transistors, resistors or caps.
The best way to find it is to isolate the source and then start replacing parts to lessen the noise. Turn down all of the controls, then listen to the noise. What you hear now is the sound (mostly) of the power amp. Turn up each channels controls one by one and listen to the noise. If the noise increases when you turn up a control, then check that area of the circuit.
Most modern transistors are much quieter than the 60's versions.
Metal film resisitors are less noisy than the 40 yr old carbon comp resistors in your amp. Actually, Kustom used 1% carbon film resistors in many of their designs for their low noise qualities.
Hope that some of this is helpful, Bill
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| Re: need some help with a hissy k100 [message #9135 is a reply to message #8923] |
Tue, 15 January 2008 12:11 |
KustomBlues
Messages: 490
Registered: June 2001
Location: Michigan
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Senior Member |
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I know from personal experience that when you get into this amp repair--take the time to replace every resistor with the equivalent value, but use a METAL film one instead= extremely quiet.
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