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Post subject: Fender Hot Rod Deluxe
Posted: Tue Nov 04, 2008 10:19 am
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Hi guys,

first post. I've recently bought a Hot Rod deluxe a few months ago and I'm trying to diagnose a problem that's come up.

The best I can describe it is there is a resonant rattle in the pre-amp tube when I play a B note. Is 'this' tube rattle? I don't notice any microphonic tendencies unless if got the amplifier dimed out.

Should I replace the preamp tubes or is this a totally seperate issue? I don't notice a tonal or volume degradation - just a resonant sound. It's not coming from the cab or anything in the room - just sounds like a tube is rattling it's little heart out.

Is tube rattle the guts of the tube rattling (ie. filament/cathode) or is the actual whole tube rattling in the socket?

Thanks so much,
Andy.


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Post subject:
Posted: Tue Nov 04, 2008 7:01 pm
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Most tube rattles come from the power tubes. Occasionally you get a microphonic preamp tube, but usually it's a power tube. You'll probably save money and time by taking it to a qualified tech. Voltages in tube amps are very high, (typically 150 to 250 VDC on preamp tubes, double that on power tubes) and if you don't know what you are doing, there is a possibility of getting a lethal shock.


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Post subject:
Posted: Wed Nov 05, 2008 7:31 am
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Yeah, I understand the potential is there to get fried, it's like my shop teacher said "never stick you finger...."

It's just wierd that it's resonant on just one note. I tried to find any rattles in the cabinet or head and it diminishes when I apply some pressure on the back of cabinet just above the power tubes. I'm planning on taking it in to get the tech to look at it (it's still under warrenty). I was hoping it was a quick fix.

I haven't had the greatest luck with Fender amplifiers - my 300t's XLR line output just refuses to work even though the TRS line out works like a charm and I sent that in all the way to California. The compression op-amp crapped out on it. This noise in my guitar amplifier makes it impossible to do any tracking.

It's good that Fender has the three year warrenty, that's it's biggest selling point, IMHO. Every fender product I've bought has went back to the shop to get surgery. I can't say the same about Peavey or Yamaha. Although the Fender sure sounds good.


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Post subject:
Posted: Wed Nov 05, 2008 9:08 am
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This sounds just like my mates amp, he had an odd rattle at high volumes and took it to the tech.
Tech could not locate the cause of the issue and sent the amp back to Fender.
Still waiting for it to come back, guess it will be weeks before it comes home, hopefully fixed.

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Post subject:
Posted: Wed Nov 05, 2008 2:02 pm
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Did your bud's amp make the rattling sound only on the distortion channel or was it apparent on the clean channel?


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Post subject:
Posted: Wed Nov 05, 2008 2:33 pm
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It made the rattle with anything loud enough to shake windows :)
Either channel.

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Post subject:
Posted: Wed Nov 05, 2008 4:17 pm
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Interesting. I'd remove the back of the cab, keeping in mind the high voltage exposure, and see if it rattles. If it still rattles, you may be pushing on the pc board or tube sockets when appling pressure with the back of the cab on. I'd check the sockets for cracks and screws for tightness. If thats okay, it's probably on the pc board. Once again, I recommend a tech with some soldering skills.


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Post subject:
Posted: Thu Nov 06, 2008 9:58 am
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That's a really good suggestion.

When I apply pressure on the bottom of the powertube (the one farthest away from the pre-amp tube) the rattle goes away. I took the tube out and couldn't notice anything. I'll have to take the back off and poke around.


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Post subject:
Posted: Sun Nov 09, 2008 11:46 am
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Get yourself some good power tube retainers.


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Post subject:
Posted: Sun Nov 09, 2008 1:57 pm
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Retainers usually won't stop tube rattle. Tube dampers may help. Try the silicone "O" ring type. You can find them on Ebay cheap.


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Post subject:
Posted: Mon Nov 10, 2008 7:52 am
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I brought it into the amp 'guru' and he assured me that it's a powertube rattle, and that it's not uncommon for it to develop a resonant frequency.

Problem solved - I was kind of leaning towards that way anyway. Just too bad it's so damn expensive.

Thanks for all the help.

Andy


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Post subject:
Posted: Mon Nov 10, 2008 10:54 am
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It's a common problem with tube combo amps. It's even worse with the HRDlx because of the tubes close proximity to the speaker.

Eurotubes has JJ's that are manufactured with that problem in mind for the HRDlx.


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Post subject:
Posted: Mon Nov 10, 2008 10:54 am
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It's a common problem with tube combo amps. It's even worse with the HRDlx because of the tubes close proximity to the speaker.

Eurotubes has JJ's that are manufactured with that problem in mind for the HRDlx.


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Post subject:
Posted: Sun Nov 16, 2008 10:59 am
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Here's whats happening so far - it's so brutal.

I took my amplifier into the tech @ L&M in Saskatoon. He's a really super guy and kind of a guru on this stuff. I explained my problem and he said he'd look into it. I came back and he explained that the pre-amp tubes were really bad and he replaced them. Ok, great. $60. Moral of the story? TEST THE AMP BEFORE PAYING!

Brought it back home, plugged it in, played a nice big fat powerchord on the seventh fret of the low E string and the rattle was STILL awful. Needless to say I'm REALLY unhappy about the money I spent, that's why I've got no problems naming the store. Frustrated, I took the back off of the cabinet (saying to hell with safety!) and took a look into the chassis trying to see if it was a vibration from a loose circuit board, or perhaps a wire rattling against the back. Nothing seemed out of place, playing through the amp with the back off makes it really apparent it's the powertube itself rattling. When my old lady plays the guitar if I keep pressure on the tube the rattle goes away.

So, I'm going to look into the JJ powertubes, and perhaps get the machinist at work to rig a dampner that I can bolt onto the chassis to keep pressure on the tubes.

Here's my question - could I take just a single powertube out and run the amplifier like that just to be 100% sure it's a tube rattle? I live out in a rural area and I can't just swap tubes wth a friend - and it's an hour and a half drive to get new tubes. I really don't want to blow anything up either.

Thanks,
Andy


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Post subject:
Posted: Sun Nov 16, 2008 11:34 am
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Swap the tubes around and see if it moves with the tube. You can pull a power tube out. Instead of a push pull power amp you'll have a single ended amp. Not sure I would run it this way for a long time, the output transformer is rated for 40 watts.


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