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Post subject: Hot Rod Deluxe Hum!!! HELP!!!
Posted: Tue May 14, 2013 8:38 pm
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So I was an idiot and left my HotRod Deluxe on standby all night after one of our practices... (I know, don't say it). Came back the next day, it started out playing fine. All of a sudden, a very loud and sustained hum came on. Unplugged it for 15 minutes, turned it back on, the hum was still there. The hum didn't change with volume at all. Whether it was turned up, or completely down, the hum was still there. (On both channels 1 & 2). Here's the kicker. After leaving the amp off for a while, I unplugged it, and plugged it back in, turned it on, and played for about 20 minutes straight just fine. The next day we had a show. Got to the venue, during sound check, turned the amp on, the hum was there immediately. After turning it off quickly, I unplugged it from the power supply, plugged it back in, it played perfectly fine the entire night (3hrs). It still responds this way every time. The hum only happens if there is an instrument cord plugged into either of the channels, regardless of whether or not an instrument is on the other end. No idea where to start on this... you tube experts, help me out and with some thoughts!


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Post subject: Re: Hot Rod Deluxe Hum!!! HELP!!!
Posted: Tue May 14, 2013 9:15 pm
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Leaving the amp on standby has nothing to do with the hum.

Since you say the hum only occurs with a cable plugged in, I will assume that the amp is quiet with nothing plugged into any of the inputs. If that is the case, the problem is either with the cable or guitar. Try a different cable and different guitar. Or try the problem cable and guitar in another, known working amp. The input jacks are shorting jacks and will prevent noise from getting into the front end of the amp when nothing is plugged in. If you plug a cable in without a guitar, the cable acts as an antenna, picking up noise. The guitar, especially if it has single coils will do the same.

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Post subject: Re: Hot Rod Deluxe Hum!!! HELP!!!
Posted: Tue May 14, 2013 9:25 pm
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Another possibility is a faulty preamp tube, likely V1. As bluesky636 pointed out, the input is grounded with nothing plugged in, and after plugging in, the input ground is lifted and a noisy grid in a preamp tube can then be heard.

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Post subject: Re: Hot Rod Deluxe Hum!!! HELP!!!
Posted: Tue May 14, 2013 10:57 pm
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ive tried both different cables and different guitars, the hum is still there when that amp is turned on initially. when its unplugged and plugged back in.. usually its fine. sometimes i have to do this a couple of times until it works. that possibly a preamp problem still?


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Post subject: Re: Hot Rod Deluxe Hum!!! HELP!!!
Posted: Tue May 14, 2013 11:59 pm
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Maybe preamp tube, maybe solder joint(s), maybe even a faulty cap, hard to say. The easiest thing to do is to try a new preamp tube in V1, if you still have hum, put the original tube back in V1 and try the new tube in V2, then V3. This can at least confirm whether the problem is a preamp tube or not.

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Post subject: Re: Hot Rod Deluxe Hum!!! HELP!!!
Posted: Wed May 15, 2013 3:32 pm
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markdaisymusic wrote:
The hum only happens if there is an instrument cord plugged into either of the channels, regardless of whether or not an instrument is on the other end.


Is this statement true or not? Does the amp hum when nothing is plugged into the input?

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Post subject: Re: Hot Rod Deluxe Hum!!! HELP!!!
Posted: Thu May 16, 2013 7:02 am
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The amp does NOT hum when there is no cable plugged into it. (and wheb i say hum, its a real loud hum)


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Post subject: Re: Hot Rod Deluxe Hum!!! HELP!!!
Posted: Thu May 16, 2013 3:30 pm
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markdaisymusic wrote:
The amp does NOT hum when there is no cable plugged into it. (and wheb i say hum, its a real loud hum)


If you've tried different cables and guitars and it still does it, it could be a bad V1 but if not, I think the problem would have to be right at the input between the jack and V1 grid. Check for faulty components or bad solder joints in that area.

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