Home › Forums › Help/Technical Questions › 1976 Attack Equalizer power supply

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  • December 21, 2015 at 9:38 pm #84198
    oscar1965
    Member

    Does this vintage pedal run on 9 or 18 Volts DC? And also: does use it negative tip as usual?
    Its three knobs are labeled: Fundamental, Blend, Attack
    Thanks
    Oscar

    December 22, 2015 at 4:39 pm #121117
    Scruffie
    Member

    I don’t think the originals takes a power supply, it runs on 2 x 9V batteries for bipolar +/-9V supply.

    December 22, 2015 at 8:16 pm #121120
    oscar1965
    Member

    You are right, I opened it today after unpacking at last: two 9V batteries, with a On/Off switch on the side where the input and output are. But on the same side there is also a plug for 2.1 dc power. The guy who sold it to me answered today also, he wrote that it accept 18 V Dc, yet he preferred batteries because they were less noisy. I’ll ask him if it’s original or not. This unit was originally sold in England I think, it has still the original box with a 40 £ label, but I bought it in Italy. So I’ll start using the batteries, meanwhile I’ll try to collect more infos. Thanks Oscar

    January 9, 2016 at 6:10 pm #121161
    oscar1965
    Member
    Quote:
    I don’t think the originals takes a power supply, it runs on 2 x 9V batteries for bipolar +/-9V supply.

    I’ll try to post two pictures: there you can see the inlet for the power supply (and also the On/Off switch that regulates it), anyway it’s not easy to see if it was manually added later (with the On/off switch too), it looks old as the pedal itself. If anyone might add some further opinions, I’m not even able to find the original manual
    One of the two batteries have a broken cable, I need to fix it, so I’have not been able to use the pedal yet, I haven’t bought a 18 V AC/DC adapter yet
    Oscar

    January 10, 2016 at 3:24 pm #121162
    Scruffie
    Member

    Hard to tell from those photos but it looks like a 2.1mm jack to me and EHX always used 3.5mm earphone style power jacks. All the photos i’ve found of originals don’t show a power jack.

    It’s possible the circuit was revised at some point to run on 18V instead of +/-9V or the owner modded it themselves so that it would work on 18V…

    January 12, 2016 at 8:18 pm #121166
    oscar1965
    Member

    Now I understand what “bipolar +/- 9V” means: the circuit was running between +9 and -9; sorry I didn’t get it at first.
    Yes the internal pin is 2.1 mm, quite common here in Europe I guess.
    So most likely it was modded to run between +18 and 0. I wonder if there were many pedals running on two bipolar batteries, if it was a regular practice to mod the circuit to run at 18V and also if this mod was difficult or was prone to damage the pedal.
    Meanwhile I have found a 18V transformer online and I’ll buy it, next week I’l bring the pedal to someone who can fix the broken cable of one of the batteries, it needs soldering
    Thanks
    Oscar

    January 12, 2016 at 8:32 pm #121167
    Scruffie
    Member

    There is the third possibility, someone attempted to mod it to run on 18V, assuming that’s what it required because of the 2 batteries but were mistaken and it wont work.

    Yes if it’s a 2.1mm jack it’s definitely a mod.

    Hopefully your repair guy will be able to give a definitive answer as to what’s happening inside as without clear photos of both sides of the board I can only speculate.

    January 12, 2016 at 9:38 pm #121168
    oscar1965
    Member

    ok thanks
    I’ll bring the pedal to the repair guy next week hopefully,
    and then let you know his findings.
    I posted these small pictures because of limitations of EHX’s posting rules,
    is there any way to overcome them?
    Oscar

    January 13, 2016 at 4:00 pm #121170
    Scruffie
    Member

    To overcome the size limitations you have to use an outside image host such as photobucket, imgur etc. and then link to the images there.

    January 25, 2016 at 9:02 pm #121228
    oscar1965
    Member
    Quote:
    To overcome the size limitations you have to use an outside image host such as photobucket, imgur etc. and then link to the images there.

    I brought the pedal to Nick (in Bellinzona, Switzerland):
    – one resistor is 1977, so probably it was built that year or the following;
    – the DC inlet is more recently, it was added probably 20 years ago (so the pedal was modded, definitely);
    – it is working using two 9V batteries ;
    – I haven’t yet bought the 18V DC adapter, I’ll think about it a little;
    – I uploaded two pictures on imgur, 960×1280 500KB :
    http://imgur.com/a/fP8G0
    (there is one side of the PCB only, sorry but to photograph the other side, I’d had to remove all three potentiometers)

    so everything looks well at the moment
    thanks a lot Scruffie for your help
    Oscar

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