Fender HRD Randomly switching channels

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MatthewShredderyMatthewShreddery Frets: 861
edited June 2021 in Amps
My HRD is randomly going from clean to the drive channel all of it's own accord - I don't even have the foot switch for the thing!
I know this is a fairly common problem with these amps - was wondering if there was a simple way to completely detach the drive channel from the amp so there's no possibility of it switching to it?

I've noticed that if I half plug a jack lead into the foot switch socket, the problem seems to go away, but I want piece of mind in case I wish to use this amp at gigs in the future.

Thanks in advance
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Comments

  • ICBMICBM Frets: 71956
    It will be a broken solder joint on either the footswitch jack or the resistor which feeds it, which gets hot enough to cook the solder. It's easier to fix it properly than to disable the switching, although it does mean getting the PCB out.

    The resistor in question is the large peach-coloured one at the top left of the PCB. Even at this photo resolution you can see a brown patch at each end of it where the board has started to cook...


    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • Which photo mate?
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  • ICBMICBM Frets: 71956
    Link not showing? It's working fine here... on computer and phone.

    Or Google image search 'fender hotrod pcb' and look at the second pic, at studiorepair.com.

    If you can't see it, just take the back off the amp, you'll easily find it - it's a large-ish pinky/peach-coloured resistor on the edge of the board just below the footswitch jack.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • Cheers ICBM. I'll take a look next weekend
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  • 26.226.2 Frets: 519
    They all do this eventually. Maybe it’s fixed on Mark 4?
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  • ICBM said:
    Link not showing? It's working fine here... on computer and phone.

    Or Google image search 'fender hotrod pcb' and look at the second pic, at studiorepair.com.

    If you can't see it, just take the back off the amp, you'll easily find it - it's a large-ish pinky/peach-coloured resistor on the edge of the board just below the footswitch jack.
    Would I need to get a new resistor, or just resolder?
    I hear that the big white relays are often dodgy too - is there a kit I can buy to get all the bits I need to do the job, or do you reckon I should just send it to a tech? @ICBM ;
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  • Also - do you think it would be possible to completely remove the channel switching capability?
    I only want the clean channel anyway.

    I'm guessing there's no simple way to do this. I imagine they're all linked together somehow
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  • ICBMICBM Frets: 71956
    Also - do you think it would be possible to completely remove the channel switching capability?
    I only want the clean channel anyway.

    I'm guessing there's no simple way to do this. I imagine they're all linked together somehow
    I can’t remember for sure which way round it is, but I think that if you remove the resistor completely it should stay on the clean channel.

    You can’t remove the low-voltage supply entirely since you need that for the reverb and FX loop.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • So I can completely remove the big peach-ish coloured resistor and that should solve the channel switching issue?
    Like I say - I'm not bothered about being able to switch channels, I just want the clean channel to be solid
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  • ICBMICBM Frets: 71956
    So I can completely remove the big peach-ish coloured resistor and that should solve the channel switching issue?
    No, I've just checked the schematic and unfortunately I was wrong, it's the other way round - removing the resistor would leave you on the dirty channel only. You're going to need to fix it properly. Sorry!

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • Haha no worries! 
    Wish it was simple!
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