Home Forums Help/Technical Questions Dead Small Clone

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  • #83166

    Hello, I have an old Small Clone EH4600 Full Chorus that I’m trying to fix. The indicator light comes on and the signal passes through, but there is no chorus effect. Any ideas would be appreciated. I replaced the ‘big’ chip with a new 4047BE, but it didn’t make any difference. Thanks.

    #119388
    Scruffie
    Member

    Do you have a multi meter to take voltage readings? Should be possible to spot what’s wrong with them.

    #119392

    Hi, thanks for the reply. At this point, I’ve replaced the 4047, the LM358 and the MN3007 with no success. I don’t have a schematic and have run out of ideas. Any help would be appreciated.

    #119396
    Scruffie
    Member

    Replacing chips at random isn’t the best way to go about this.

    First off, is this a vintage unit or reissue? If you’re unsure, if there is a square cut out in the circuit board with a blue switch using more than 3 lugs, it’s a reissue.

    Second, do you have or have access to a digital multimeter? If you do, can you post voltages of all 4 chips in the pedal going in this direction…

    Chip
    Notch
    1 8
    2 7
    3 6
    4 5

    and the 3 (or 4 depending if vintage/early reissue or reissue) transistors.

    Third, since you’ve owned the pedal, did it ever work? If so did anything specifically happen to it before it stopped?

    #119400

    Guess what? I’m swirling again! I had mistakenly replaced the 4558 with the LM 358. When I realized my mistake, I replaced the 358 and bingo! I was given this broken pedal in the early 90’s when I was a tech fixing Hammonds, Leslies etc. Thank you for your help. My next EHX pedal project is my old Micro Synth that somehow died while in storage.

    #119401
    Scruffie
    Member

    Hmm, odd that didn’t work anyway, they’re both dual op-amps, unless you mean you replaced the 358 with the 4558, the LFO might not have kicked in. Besides the point, glad you got it working!

    The Micro synth I can help with too but you will need a multimeter if you’re going to attempt it unless it’s an obvious issue to the eye.

    In storage I would imagine either some damp got in and there’s some corrosion somewhere or if it’s 20+ years old some of the electrolytic caps have dried up from age.

    Hope that can be made to run again too!

    #119402

    Hey, thanks again. I’m not sure what the setting of the trim pot does? I know I’ve moved mine. As far as the Micro Synth, it was stored cleanly, it just went dead. Power light is on. It’s an old one. It was suggested some time ago by the E-H Man to check the voltage around the 2N6111 in the power supply. I have a schematic, but haven’t looked inside in a while. I got intimidated when I saw how it was put together.

    #119404
    Scruffie
    Member

    In the Small Clone? The Trim pot sets the bias of the MN3007, it shouldn’t really be adjusted unless it goes out with age. It works within a small range and at a point in that range will be set for optimum bias.

    You should tweak it for the least distortion with your guitar (you can run a constant signal through to make this easier, building an audio probe and probing just the output of the BBD will help further) or if you have an oscilloscope, do so on the outputs (pins 7 & 8) of it.

    The EH Man is known so for a reason, I’ve never worked on a MicroSynth but he’s probably seen that part fail a lot in his time if he’s brought it up.

    #119406

    Hey, thanks again. I haven’t went back into the Micro Synth yet. I have to free up my ‘bench’ aka kitchen table. Do you know where to get case screws for old E-H effects like the Small Clone? I couldn’t find any at the hardware store or the specialty fastener store. I figured they would be common, but I had no luck when I tried to find some.

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