Home › Forums › Help/Technical Questions › Anybody ever convert a vintage 110V AC powered Hot Tubes to 9/12/18/24V DC adapter?

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  • April 28, 2010 at 9:48 am #79239
    germanium mash
    Member

    Hi,i’ve just acquired a vintage Hot Tubes which has some issues… mainly a high pitched buzzing noise whether the pedal is bypassed,or not. I’ve read somewhere that the caps in these pedals have been known to fail,or should be replaced,along with the original SPST switch. Does anyone have a vintage Hot Tubes that has been repaired or modded?? Any tips on upgrading performance/sound,decreasing noise & what to look out for would be greatly appreciated. Am also curious to know if a vintage 110V powered EH pedal could be converted to external DC power supply,similar to modern pedals?.. Thanks

    April 28, 2010 at 11:01 am #96673
    The EH Man
    Moderator

    Looks like it could be easily converted to 9v.

    June 1, 2010 at 10:09 am #102963
    kilohill
    Member

    Hey guys this should be absolutely nice and interesting.
    Any help? I’ve got the same exact problem.

    Mine is the “european” version 220/230V AC powered, I attach a photo.

    How easy could it be converted?

    June 1, 2010 at 10:27 am #102954
    The EH Man
    Moderator

    Just as easily as the above unit.

    June 2, 2010 at 8:17 am #102908
    kilohill
    Member

    I can’t understand if you know this pedal or not, seems not…

    Anyway, after the factory AC => DC you got 24VDC on circuit, so is not true that is simple converting at 9V, it’s just quite wrong.

    I removed the AC/DC and now I’m running at 9V, but this is undervolted for sure and this affects sound effect.
    Should be surely better with 24VDC, or maybe trying with 18VDC.

    Anyone who (really) knows this pedal?

    thanks

    June 2, 2010 at 9:39 am #102903
    The EH Man
    Moderator

    After rectification and regulation, you should have about 9v going to pin 8 of the 4558.

    June 3, 2010 at 8:54 am #102893
    kilohill
    Member

    After rectification I’ve got 24VDC.

    I mean, it should be right that 4558 is powered with +9V, but this is just a leg of the circuit, I’ve got a lot of thing connected on the main leg at 24V, so I think the best way to convert the factory AC/DC is powering with 24VDC in the exact point where rectifiers end, then you’ll have 9V on 4558 and 24V in the other places where needed, as original factory!

    Anyway I’ll work this out deeper in the next few days.

    Actually I’m running at 9V where it was at 24V and it works, but I’ve got some strange behavior with volume that waves (this was my impression), maybe can be related with gain undervolting.

    June 3, 2010 at 10:01 am #102865
    The EH Man
    Moderator

    I’m looking at the original factory schematic right now and the 24v goes into the regulator and no where else.

    June 3, 2010 at 12:56 pm #102835
    kilohill
    Member

    Ookey, I found the 9V leg, you were right and as schematics there’s 9V.

    Now I’ve got a doubt about a purple wire starting from the 24VDC point going to the switch pin 2, something could be wrong in this configuration, or not?

    Thanks for your help, I’m a very beginner! ;)

    edit: here the image

    June 3, 2010 at 1:41 pm #102789
    The EH Man
    Moderator

    looks like they’re using the 24vdc to run an LED. That isn’t stock.

    June 3, 2010 at 1:44 pm #102791
    julian
    Moderator

    I found the schems at musique.com:

    hottube.gif

    June 4, 2010 at 12:12 pm #106801
    kilohill
    Member

    Ok, the series resistance that goes to the LED is designed to put down voltage from 24VDC, so maybe it’s quite heavy since now there are +9V, anyway this is actually working and the hum has absolutely gone, this was my very goal!

    Just a consideration about supply, now I have not really 9V but +10-11VDC from PSU, I read 4558 datasheet and this shouldn’t be a problem, right?
    http://focus.ti.com/lit/ds/symlink/rc4558.pdf
    18V is the max voltage, I’m about on 10V.

    Thanks for your help.

    Now, another to-do-mod should be the TB with a 3PDT, this should be “easy” ;)

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