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Thread: Broken Stereo Modulation - HELP PLZ!

  1. #1
    Forum Member
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    Oct 2020
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    Broken Stereo Modulation - HELP PLZ!

    TL:DR:
    If there are any amp doctors in the house, for no known reason my stereo modulation is only running in mono and I'd like to DIY the fix if I can, with your kind guidance of course. Fender Ultimate Chorus circa 1993. Here's a link to the service manual. It reads like Greek to me.
    https://www.manualslib.com/manual/10...te-Chorus.html

    Preface:
    In the early 90's I got to watch a tight cover band practice every weekend and LOVED the sounds they squeezed out of their guitars. When I bought my first fiddle I only had cash enough for one of those mini Marshall amps with the two inch speaker. I learned very early while picking their brains that the bulk of their sound came from the amps they were using. My mind was made up that the first "big ticket" item in my music journey would be the same amp that the rhythm player employed...

    Issue:
    I have an original Fender Ultimate Chorus (pre-DSP garbage) that had been out of commission for years. Found a guy a year or so ago who said it would be a breeze to get it working again, and seemingly he brought it back to life. Everything worked perfectly for a couple months, but then out of the blue the chorus stopped running in stereo. In normal operation the light that indicates stereo modulation will flash red and then green, but now it stays green all the time and though there is still chorus it's most certainly not in stereo anymore. I took the thing apart and looked to see if any components needed a bit of solder but didn't see anything that looked suspect.

    Anyhow, I've been looking all over the place and it seems I'm the lone soul stuck with this problem, which doesn't happen often here in internet land and out of desperation I have joined this community. So hello everybody, and cheers!
    Last edited by The_dude; 10-21-2020 at 09:48 PM. Reason: Didn't know emoticons were auto

  2. #2
    Forum Member Offshore Angler's Avatar
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    Re: Broken Stereo Modulation - HELP PLZ!

    I guess if you can't follow the schematic you probably don't have the equipment you need either. All you can do is follow the signal and it will come down to a bad trace, a bad component or a bad solder joint.

    A good electronics tech should be able to locate the issue very quickly. Sounds like you need to take it to get it fixed.
    "No harmonic knowledge, no sense of time, a ghastly tone, unskilled vibrato, and so on. Chuck is one of the worst guitar players I know" -Gravity Jim

  3. #3
    Forum Member dirtdog's Avatar
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    Re: Broken Stereo Modulation - HELP PLZ!

    And if it’s too far gone to fix it (esp if it’s something on a PCB), these amps can be had for relatively cheap on the used market. If you like that tone, it’s worth it to have a backup. There’s a few specimens listed on Reverb right now.

    I had the little brother to that amp for a short while (Princeton Stereo Chorus). Jammed with a band and it was next to unusable for what we were playing. With guidance from the forum, I eventually jumped to a DRRI. That’s an incredible amp.

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