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Author Topic: ots 100w hrm buzz/hum problem  (Read 2755 times)
trauko
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« on: March 29, 2010, 10:00:46 PM »


I have a little problem with an HRM 100. There is a loud Hum/Buzz present at all times with or with no guitar plugged in. I checked all voltages and they are pretty close if not the same as the ones from the Voltage Chart. I did some tests to help me close in on the problem. Ran the preamp of a Peavey Classic 30 through the power amp of the HRM and there's no hum/buzz at all. Ran the preamp of the HRM through the Classic 30 and the hum/buzz is present. Tried different tubes and no change. I did check for cold solder joints at all ground connections as well as continuity tests with a DMM and they all check out fine. I've looked at all the wiring a couple of times and they all look good. So my question is, what can i do next? are there any other obvious things I should check? ground loops maybe? Have someone else run into this problem before? I guess I ran out of ideas and I'm hoping you someone can help me out with that. Also, does the volume control of the clean channel affect the volume of the drive channel?? If I turn the volume of the clean channel fully counter clockwise while in the drive channel, the volume drops completely. Also, the master volume only affects the clean channel too right??

Thanks


* DSC03701.JPG (2099.26 KB, 2592x1944 - viewed 285 times.)

* DSC03712.JPG (1653.89 KB, 1944x2592 - viewed 267 times.)
« Last Edit: April 05, 2010, 02:35:18 PM by trauko » Logged
erwin_ve
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« Reply #1 on: March 30, 2010, 03:46:47 AM »

Check your wiring to the relays; obviously there's something wrong there.
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trauko
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« Reply #2 on: March 30, 2010, 04:15:03 PM »

Check your wiring to the relays; obviously there's something wrong there.

Thanks for the advice. What makes it so obvious though? The channels and boost switch fine by the way. Signal passes through too, it's just this loud hum/buzz somewhere in the preamp section.
« Last Edit: March 30, 2010, 04:22:28 PM by trauko » Logged
erwin_ve
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« Reply #3 on: March 31, 2010, 03:17:34 AM »



Also, does the volume control of the clean channel affect the volume of the drive channel?? If I turn the volume of the clean channel fully counter clockwise while in the drive channel, the volume drops completely. Also, the master volume only affects the clean channel too right??

Thanks
If you meant the master clean volume; the relays are wired wrong.
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trauko
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« Reply #4 on: March 31, 2010, 12:42:23 PM »

The master Clean volume is normal. I knew it was but I checked with Nik himself and he verified it.

Thanks.
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trauko
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« Reply #5 on: April 02, 2010, 05:52:14 PM »

With the Main On only there's no signal passing from the guitar plugged in. It's just hum but the master volume does have an effect on the hum. When the standby is on then signal passes through. Also, I was using the continuity setting on my DMM to check all of grounds in the amp. The amp was off and unplugged. Out of curiosity I checked on the power supply board and they showed continuity!. So I checked on the secondary taps (HT and Bias Taps) and they also show continuity. Something else I also noticed is that the filter caps drain waaaaaaay too fast, like really really fast. I not sure but for some reason this doesn't sound correct to me.
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hywelg
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« Reply #6 on: April 03, 2010, 04:42:42 AM »

It might be  a good idea to run checks against the voltage chart.

And just to clarify what you are saying, with the amp on Standby you are getting a hum?

* OTS Pin Voltages.pdf (6.96 KB - downloaded 393 times.)
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