Home › Forums › Help/Technical Questions › Repairing Holier Grail – Voltage converter and R1??

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  • April 5, 2012 at 9:08 pm #82288
    beedoola
    Participant

    My buddies’ Holier Grail stopped working, I was assuming it was his power supply that went out and caused the pedal to blow – I tested the PS with my multimeter and it was reading like 25v – supposed to be 18v.

    I opened up the pedal and the area around the voltage converted was browned. I but in a new converted but still get nothing – no LEDs and no reverb.

    I started to test the power path with my multi-meter – starting at the positive LED coming from the jack to the board, from there to R1.

    At the power going to the board I get 18v (i rigged up an 18v supply by combining 2 other jacks on my Voodoo labs pedal power 2).
    At the first leg of R1 I get 18, on the other leg I get nothing….

    Browsing around here I saw another thread I found this:

    https://www.ehx.com/forums/viewthread/1876/#15558

    One poster claims R1 is a 4.7ohm 1/2watt – this true? I opened mine to find a 22k…

    Anyways, I put another 22k in there and no luck with voltage coming through on the other side. Am I doing something wrong here?

    Is R1 4.7ohm?

    April 5, 2012 at 9:13 pm #117266
    The EH Man
    Moderator

    According to the Holier Grail schematic I have, it’s 4.7ohm 1/2watt resistor. It’s also possible that the main chip is bad and will need to be replaced. If it goes bad, it draws a lot of power and will easily fry R1.

    April 5, 2012 at 9:51 pm #117267
    beedoola
    Participant

    yeah I just tried a 10ohm 1/2 and it blew it… Which is the main chip – the big one? or is it a chip that can be replaced?

    April 5, 2012 at 9:57 pm #117268
    The EH Man
    Moderator

    Yeah, it’s the big one. You’ll probably need to send it to EHX for repair (link in my sig). I had no luck trying to find a chip to buy.

    April 5, 2012 at 10:10 pm #117269
    beedoola
    Participant

    ehhh ya my buddy won’t want to do that.

    I tried just jumping R1 – got the bypass LED and GATE LED to work. But no reverb and maximum blend yields no sound… I also replaced the voltage converter and that seems to be working – 18v on one side, 4.9v on the other side… Could a power spike or wrong power adapter blown the main chip? I thought thats what the voltage converter could protect against? There is a brown spot on the rear side of the PCB around where the VC goes – its not like burned black/brown, you can just tell something went on there cause its darker than the green of the PCB.

    April 5, 2012 at 10:23 pm #117270
    The EH Man
    Moderator

    I don’t know what causes it. There’s a lot of heat generated by the regulator and that’s likely causing the brown spot. I would’ve mounted it offboard using the chassis as a heatsink.

    April 5, 2012 at 10:24 pm #117271
    beedoola
    Participant

    I mean; is it common that IF the VC goes bad – as I’ve seen in other posts, that it will likely kill the main chip?

    April 5, 2012 at 10:26 pm #117272
    The EH Man
    Moderator

    I think the chip goes bad and pulls too much current, frying R1.

    April 5, 2012 at 10:28 pm #117273
    beedoola
    Participant

    Ahh damn, well thanks a lot for helping me out :)

    I have a Boss RV-3 I want to sell, maybe I can persuade my friend to buy it muhahaha

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