Home › Forums › Vintage EHX › Bad Stone Mummy Version 1 oddity?

Viewing 10 posts - 16 through 25 (of 25 total)
1 2
  • Author
    Posts
  • January 30, 2014 at 8:00 pm #119645
    dwmorrin
    Member

    I’m got one of these on the bench now.
    It appears to be the same version.
    The circuit board appears to read “EH 5800.” Pot date codes: 7407 and 7418 (1974)
    At max CW, the rate control goes into audio frequencies for a ring mod type sound.
    There is a small zone of rate control where it sounds quasi-normal, save for the lopsided/asymmetrical sweep.
    The lower speeds don’t seem to be working.
    The “COLOR” switch puts it into vibrato mode (pitch bending).

    It appears to have a replacement trim pot, and definitely has a very odd replacement quad op amp… someone has put two SIP op amps onto some perfboard and fit that contraption over the DIP footprint.

    A full trace of the pedal is on my to do list.

    l1MIHaNl.jpg
    nzmlpvjl.jpg
    S2Tr94Il.jpg

    January 30, 2014 at 8:14 pm #119646
    TheGroke
    Member

    Hey DW,

    Thanks for posting your info. Do you get clock noise at the high speeds when there is no signal being input (like on mine)? I never did figure out how to fix that (if it is even a fault – maybe you are saying it is intentional?) l

    Let me know if you need any readings off of mine.

    best – DT

    January 30, 2014 at 8:22 pm #119647
    dwmorrin
    Member

    Yes, there is some awful nosies when the rate is up.
    This one is definitely broken and modded.
    I was looking for any other examples out there to compare to, and I came across your posts.

    January 30, 2014 at 8:35 pm #119648
    TheGroke
    Member

    cool… but awful if not looking for cool :)

    On mine, on the slow settings, the noise is still present as a light click. But as the rate increases, this click becomes more like a hum.

    March 24, 2014 at 2:12 pm #119786
    The_Janitor
    Member

    Hi Everybody,
    Bumping this thread with a familiar story:

    I recently purchased a non-functioning Mummy Face Bad Stone – all of the parts appear to be there, but the PCB was not attached to the housing, pots, switch or footswitch. I found photos on this forum that got me 90% of the way there, but I still need some info:

    How is the Rate pot wired to the PCB? Would anyone be able to take a photo of these connections or point me to an accurate schematic?

    Second, related connection – what type and value should this pot be? The pot that came with the pedal is a replacement and I want to be sure that it’s the correct type and value before I solder it together.

    Thanks in advance for the help, this is a very cool and helpful forum!

    March 24, 2014 at 3:48 pm #119787
    The_Janitor
    Member
    Quote:
    I’m got one of these on the bench now.
    It appears to be the same version.
    The circuit board appears to read “EH 5800.” Pot date codes: 7407 and 7418 (1974)
    At max CW, the rate control goes into audio frequencies for a ring mod type sound.
    There is a small zone of rate control where it sounds quasi-normal, save for the lopsided/asymmetrical sweep.
    The lower speeds don’t seem to be working.
    The “COLOR” switch puts it into vibrato mode (pitch bending).

    It appears to have a replacement trim pot, and definitely has a very odd replacement quad op amp… someone has put two SIP op amps onto some perfboard and fit that contraption over the DIP footprint.

    A full trace of the pedal is on my to do list.

    l1MIHaNl.jpg
    nzmlpvjl.jpg
    S2Tr94Il.jpg

    For some reason the photo wasn’t displaying on my phone. Looks like outer legs of the rate pot are attached to the board at the upper right of the PCB (bottom image) – I’m guessing that legs 2 and 3 of the pot are tied together, then 1 and 3 attach to the traces on the upper right of the board. If someone could confirm or deny this it would be much appreciated. At any rate, I’ll wire it up and give it a go.

    March 24, 2014 at 8:06 pm #119788
    TheGroke
    Member

    Hi. Here is a pic of the rate knob connection. Two legs are strapped together, as you stated. The value is 1M, as on the schematic. Mine measures a span of ~180 to .9 M when in circuit.

    Let me know if you need anything else!

    Good luck,

    D

    March 24, 2014 at 8:26 pm #119789
    The_Janitor
    Member
    Quote:
    Hi. Here is a pic of the rate knob connection. Two legs are strapped together, as you stated. The value is 1M, as on the schematic. Mine measures a span of ~180 to .9 M when in circuit.

    Let me know if you need anything else!

    Good luck,

    D

    That’s very helpful, thank you! I’ll hopefully get some bench time tonight and get this thing put together.

    April 8, 2014 at 1:25 am #119861
    The_Janitor
    Member

    I was able to wire up the board of my Bad Stone to all of the jacks and switches, and it works!
    Unfortunately, this mummy is sick. The sweep of the phaser is not right, it sounds broken down and a little creepy rather
    than the lush sounds I’ve heard online. The rate pot is obviously the wrong value, so I’ll need to replace that. Is this ytan audio, logrithmic, reverse audio type pot?
    I adjusted the trimpot and it changed the lfo sweep a bit, but didn’t correct the problem. Will finer adjustment fix my sweep problem or should i go looking for a bad component? Everything on the pcb is still original, so the caps may not be good.

    The vibrato half seems to work mostly ok, but it still sounds a little off.

    Thanks in advance for any help you can provide! I’m enjoying this project and i just bought a broken big box Clone Theory that I’ll work on next.

    April 10, 2014 at 2:55 pm #119873
    The_Janitor
    Member

    Well, I ordered what I think are the right pots.

    No one has any idea how to fix my lopsided sweep?

    Does anyone know where I should set the rate and blend pots when I tweak the trim pot?

  • Author
    Posts
Viewing 10 posts - 16 through 25 (of 25 total)
1 2
  • You must be logged in to reply to this topic.