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Thread: Hot Rod Deluxe loud noise when knock or tap on it

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    Hot Rod Deluxe loud noise when knock or tap on it

    Hello everyone, Im Simon and Im new here so I apologise if I do something wrong...
    I just bought a Hot rod deluxe and it make a very loud noise if you tap or knock on it...
    Is not the reverb, and is not the valves because I have another pair that I tried.
    Any suggestions on what is the problem?
    Thanks

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    Last edited by simonflower; 05-21-2020 at 11:31 PM.

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    Lifetime Member Enzo's Avatar
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    A loose connection or broken solder joint. Look VERY closely at the solder on the pins of the power tubes. I bet you see some cracks.

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    Thanks Enzo, Ill give a look.
    Also I forgot to mention that the filter caps (the big one) are probably gone because there are some sorts of stuff coming out from them. Could be that the problem?

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    Supporting Member nevetslab's Avatar
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    Quote Originally Posted by simonflower View Post
    Thanks Enzo, I’ll give a look.
    Also I forgot to mention that the filter caps (the big one) are probably gone because there are some sorts of stuff coming out from them. Could be that the problem?
    Welcome to the Forum!

    If you don't get results from going thru the tube PCB assy and repairing any suspect solder joints on components or tube sockets, I'd plug in a cable into the Power Amp input jack, which separates the Preamp section from the Power Amp section. See if the problem persists. If so, it's probably not in the preamp, though could also be there, if you find bad solder joints on the lower tube PCB.

    The Filter caps with goo coming out is not a good sign, and, the caps in the Hot Rod Series are known to go bad, so it would be wise to replace them. Extracting the main PCB is a bit tricky, as the O/T wires exiting below the bottom edge of the main PCB don't want to let the board come down enough to have the pot shafts clear the folded lip of the chassis. I always cut the cable ties on the wires exiting the O/T. You'll want to label all the Quick Disconnect wire terminals per their PCB position as you remove each of them so they go back the same place in reassembly. Leaving them connected hinders full access to the solder side of the PCB. Also, while the board is removed, grab hold of the round standoffs and give them a clockwise twist to insure they're tight again...they like to come undone!

    I regularly find solder joint fractures on the input jacks, pots across the full width of the control edge, fractures on the 5W zeners and 5W resistors in the +/- 16V supplies, as well as on the ribbon cable connections, and the filter cap joints. On some versions of the PCB, the solder mask openings for the filter cap leads is WAY TOO SMALL, disallowing good solder joints. I desolder those, then scrape away the solder mask over the large solder pads, then I can get a good solder joint on those connections. Take your time....use bright light and magnification to find all of the radial cracks on the bad solder joints. Pounding on the top of the amp sounds like you have more than one in the system.

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    Lifetime Member Enzo's Avatar
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    On the other hand, many times "goo coming out" in an amp is just glue used to hold larger parts steady.

    it makes a loud noise when you hit the amp. But when you are not hitting it, and it is not making the noise, is there excess hum? Excess hum would be the typical symptom of failed filter caps.

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    Thanks for the welcome, Nevetslab and for the tips.
    I'm going to follow your sugestions.
    Hope to find the faulty one, maybe I should just re-do all of the solder points... Is not a massive job I thinks,so I'll be sure to don't miss any of them..
    I'll let you now.

    Thanks

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    Quote Originally Posted by Enzo View Post
    On the other hand, many times "goo coming out" in an amp is just glue used to hold larger parts steady.

    it makes a loud noise when you hit the amp. But when you are not hitting it, and it is not making the noise, is there excess hum? Excess hum would be the typical symptom of failed filter caps.
    Hi Enzo,
    yes I see the glue you talking about, but this stuff is dark and it's from the connection on the actual capacitor.

    yes it make very loud noise like that it wanto to explode, even with the volume to zero and with no guitar jack in it. This Hum you're seing it come and goes while i tap it.. but i guess that is the caps to replace.. is that loud "explosion" that I want to fix.. it's scary...

    Thanks

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    Quote Originally Posted by simonflower View Post
    this stuff is dark and it's from the connection on the actual capacitor.
    If it's at the + (rubber) end, then yes that is bad. If it's at the - (metal) end, it's probably normal. Where the wire is connected ('welded') to the metal case at the minus end there is usually black discoloration.

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    Quote Originally Posted by simonflower View Post
    Hello everyone, Im Simon and Im new here so I apologise if I do something wrong...
    I just bought a Hot rod deluxe and it make a very loud noise if you tap or knock on it...
    Is not the reverb, and is not the valves because I have another pair that I tried.
    Any suggestions on what is the problem?
    Thanks
    I also found on some really high gain point to point circuits ( I apologize if Your amp has a PCB board as this may not apply...) If a particularly stiff and longish wire in the pre-amp stage is left to vibrate unsupported, it sometimes can create a low freq noise on tapping the chassis. I think Enzo pointed out bad solder joints, and I would check this first, but then chopstick long wires as well.

    Just had this "microphonic" wire issue recently and I put a dab of silicone to "mount" the wire between the tangs of a terminal strip. Worked like a charm to quite the noise. Also some caps in the early gain stages of some amps can be micro-phonic. The worst offenders are often older cheap ceramic caps I find. Some people ignore this cap microphonics figuring the signal passing through is much stronger, but remember low frequency noise will tend to modulate upper frequencies because of the relatively high energy to create low frequencies, and sometimes the resultant odd distortion is hideous.

    Other times it sounds cool !

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    I see more of this series of amps (Hotrod/Blues and Deville) than any other. Probably 9 times out of 10 if it has the grey Illinois caps there will be crusty residue around the + terminals of the main electrolytics and they need to be replaced. Even if they show no signs of leakage they're usually on their way and test marginal. The caps are usually well-glued to the PCB with silicone but I've had a couple where the solder joints around the cap leads have circular cracks.

    A favourite is, as mentioned, the tube socket PCB. In addition to the power tube pins the preamp tubes can crack the solder around the pins.

    I would plug your guitar into the 'Power amp in' socket and see if the noise happens then. This will point to whether it's a preamp, power amp or maybe even power supply issue. It could even be that you have a loose push-on terminal somewhere. You replaced the power amp tubes, but equally a faulty preamp tube could be an issue.

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    Quote Originally Posted by g1 View Post
    If it's at the + (rubber) end, then yes that is bad. If it's at the - (metal) end, it's probably normal. Where the wire is connected ('welded') to the metal case at the minus end there is usually black discoloration.
    Hi,
    yes it's at + ...
    What you you mean "is bad" ?
    Hope means that just need to be replaces..
    Thanks

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    Quote Originally Posted by Mick Bailey View Post
    I see more of this series of amps (Hotrod/Blues and Deville) than any other. Probably 9 times out of 10 if it has the grey Illinois caps there will be crusty residue around the + terminals of the main electrolytics and they need to be replaced. Even if they show no signs of leakage they're usually on their way and test marginal. The caps are usually well-glued to the PCB with silicone but I've had a couple where the solder joints around the cap leads have circular cracks.

    A favourite is, as mentioned, the tube socket PCB. In addition to the power tube pins the preamp tubes can crack the solder around the pins.

    I would plug your guitar into the 'Power amp in' socket and see if the noise happens then. This will point to whether it's a preamp, power amp or maybe even power supply issue. It could even be that you have a loose push-on terminal somewhere. You replaced the power amp tubes, but equally a faulty preamp tube could be an issue.
    Hi,
    yes it as the Grey Ic caps with stuff coming out at the + terminal...
    I going to replace them.
    Is it the Caps that make that loud "bang" when I tap on the amp or still can be a crack on a solder point?

    The "bang" is there always, with guitar plugged in and not, the volume of the "bang" is the same with volume at Zero or 10..
    Also any tips on any other "bad electronic component" to replace?
    I did, I used some spare ECC83 but stil the "bang" is there...
    What power issue could be? I'll check all the connection you said.

    Thanks!

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    The noise is most likely a bad joint. Bad caps will cause hum and other symptoms. Did you resolder the tube bases as cracking is very common? Rather than replacing parts right now, try to determine the cause of the problem. Power issues could be if you have a loose push-on terminal. There are quite a few in these amps. Another way of locating a problem is to 'chopstick' the amp but I would only recommend this to someone with experience of tube amps, as it needs to be powered on and therefore presents hazardous voltages.

    Just to be clear - did you plug your guitar directly into the 'power amp in' socket, and did it still make the same noise? What if you tap the tubes?

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    Quote Originally Posted by Mick Bailey View Post
    The noise is most likely a bad joint. Bad caps will cause hum and other symptoms. Did you resolder the tube bases as cracking is very common? Rather than replacing parts right now, try to determine the cause of the problem. Power issues could be if you have a loose push-on terminal. There are quite a few in these amps. Another way of locating a problem is to 'chopstick' the amp but I would only recommend this to someone with experience of tube amps, as it needs to be powered on and therefore presents hazardous voltages.

    Just to be clear - did you plug your guitar directly into the 'power amp in' socket, and did it still make the same noise? What if you tap the tubes?
    Hi,
    I'm going to resold the tube bases now, and I just noticed tha the PCB is darkers under the 2 white resistor diode.
    What can I do about that?
    Thanks

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    Lifetime Member Enzo's Avatar
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    Make sure the solder there is in good shape. Darker doesn't hurt anything until it turns black and carbonizes.

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    Quote Originally Posted by simonflower View Post
    Hi,
    I'm going to resold the tube bases now
    Thanks
    After you reflow check for continuity between the pins and next component. I had a HR Deville that had cracks in the traces themselves and had a gap right where the trace met the solder pad, and reflowing wasn't enough. I had to scrape the solder resist off the traces and use wire to bridge the gap.

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    Quote Originally Posted by Enzo View Post
    Make sure the solder there is in good shape. Darker doesn't hurt anything until it turns black and carbonizes.
    Hi Enzo,
    ok I'll have a look at the soldert there too.
    So I don't need to worry about that?
    This is a relief..
    Thanks

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    Quote Originally Posted by glebert View Post
    After you reflow check for continuity between the pins and next component. I had a HR Deville that had cracks in the traces themselves and had a gap right where the trace met the solder pad, and reflowing wasn't enough. I had to scrape the solder resist off the traces and use wire to bridge the gap.
    ...oh wow!
    Ok, I'll use a very strong torch and magnifying glass to check everything.. and the Tester of course...
    Thanks!

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    Supporting Member nevetslab's Avatar
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    Quote Originally Posted by simonflower View Post
    Hi,
    I'm going to resold the tube bases now, and I just noticed tha the PCB is darkers under the 2 white resistor diode.
    What can I do about that?
    Thanks
    When the component leads are long enough, you can re-install the components elevated above the board. Easier to do when the parts are new, as you can create a 'dimple' in the lead to keep the part up off the PCB, and still be able to fold the lead over on the foil side. Or, if you have any fishpaper, you could slip a cut piece underneath between the PCB and the part.

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