KB300 sound cuts out intermittently

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lakejumper
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KB300 sound cuts out intermittently

Post by lakejumper » Fri Sep 26, 2008 9:25 pm

I have an older KB 300 and it is cutting out on all 3 channels intermittently. Does anyone have an idea what can be causing this and how I can fix it?

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Enzo
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Re: KB300 sound cuts out intermittently

Post by Enzo » Fri Sep 26, 2008 9:37 pm

Without me looking, the amp has either an insert jack, or effects loop jacks, or a power amp in jack. I'd bet one of those is dirty. If it has insert, plug something in and out of that jack a fefw times. Does it help? Does it start the problem? Inner contacts should be cleaned.

If there is an effects loop, plug a cord from send to return. if that cures it, the return jack needs service.

If there is a power amp in jack - and a preamp out next to it - plug a cord from pre out to power in and see if it helps. If so, the power amp jack needs service.

Other possibilities are loose speaker wiring, and in particular the little white connector that connects the blue and yellow wires to the circuit board might have a loose pin.

ANd the amp itself could have problems in which case, a tech should see it.

lakejumper
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Re: KB300 sound cuts out intermittently

Post by lakejumper » Sat Sep 27, 2008 9:06 am

Thanks for the quick reply. I will try those things today and also look at the connector and speaker wire. It makes sense that it may be a loose speaker wire. I bought this amp used and you never know how it's been handled.

hammond435
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Re: KB300 sound cuts out intermittently

Post by hammond435 » Sun Jun 05, 2011 12:17 pm

Something similar is happening to my kb300. All three channels play at a very low volume (even when cranked) and when I max out the volume they get distorted. If I plug a cable from the preamp out to the power amp in, then all three channels work fine.

I sprayed the jacks with deoxit but that didn't help. I pulled the chassis out and checked the soldering on the preamp and pwr amp jacks and they appear to be fine.

Do you have any other ideas? Could I have blown something? Thanks

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Enzo
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Re: KB300 sound cuts out intermittently

Post by Enzo » Mon Jun 06, 2011 3:03 pm

Your power amp in jack is not working correctly. If cleaning it doesn't help, then replace it. PV parts will sell you a new one.

Or just leave a little jumper cord in place, it won't harm the amp in any way to operate it that way.

hammond435
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Re: KB300 sound cuts out intermittently

Post by hammond435 » Thu Jun 09, 2011 12:47 am

Thanks Enzo!

I figured out what the problem was. After buying a new panel mount 1/4" Mono Phone Jack (closed circuit) from radio shack, I compared it to the broken jack. The broken jack had somehow been bent so that the circuit wasn't closing. This is why it only worked when I had a cord plugged in from the preamp out to the power amp. So, I bent it back and it works perfectly now.

Thanks again for your help

RedRob
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Re: KB300 sound cuts out intermittently

Post by RedRob » Thu Nov 03, 2016 11:38 am

hammond435 wrote:Thanks Enzo!

I figured out what the problem was. After buying a new panel mount 1/4" Mono Phone Jack (closed circuit) from radio shack, I compared it to the broken jack. The broken jack had somehow been bent so that the circuit wasn't closing. This is why it only worked when I had a cord plugged in from the preamp out to the power amp. So, I bent it back and it works perfectly now.

Thanks again for your help

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