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  • April 25, 2014 at 2:51 pm #83453
    frances rhodes
    Member

    hey y’all!

    i recently bought an old 4 knob deluxe memory man featuring 4 SAD1024 chips on ebay and got it with a few problems that the seller never mentionned before. thing is that i cannot return it so i’m stuck with trying to fix it myself.
    i’ve had quite some difficulties finding the schematics for this unit and i believe it was modified some how in the past, so i’m coming here to seek some precious and helpful information.
    first, i don’t know if the switch (SPDT) works because whatever the position is, the delay is always heard but what seems to be the off position makes the sound very distorted and extremely low.
    then, there is some distortion and noise/hiss in the repeats and i think the repeats are also pretty subtle, as in really not loud, even with the gain and feedback maxed out, and thus the pedal will never self-oscillate.

    not all chips are original (SAD1024s and CRC4559s), so i’m not sure if it would be worth trying swaping them to TL072s or 5532s…

    i know there are 4 trimpots for all 4 BBD chips but i don’t know what the other trimpots are for, would some of them fix the low volume of the delay path?

    i’m a little clueless about what to do, so if one of you had the same problems, or knows where to look or what to do, i’d be pleased to hear from you!

    regards
    frances

    April 25, 2014 at 2:54 pm #119911
    The EH Man
    Moderator

    Some of the trimpots are for biasing the SAD1024A chips and some are for adjusting the gain, which will affect the feedback. I wouldn’t recommend messing with them unless you know what you’re doing.

    April 25, 2014 at 3:14 pm #119912
    frances rhodes
    Member

    thanks Ron!
    i believe the hiss i can hear comes from a bad bbd biasing because the “note” heard changes with the delay pot position, i think it is a “clock bleed”. i know this can be done by ear using a sound probe (it won’t be perfect but probably better).

    would the schematics of the early 4 knob version be close to the later version with 4 panasonic chips?
    i found the schematics that everyone already has, with 2 MN3005s and the documents showing how to modify the circuit to 4 MN3008s, but i don’t know how different the 2 versions are from eachother.

    April 25, 2014 at 3:18 pm #119913
    The EH Man
    Moderator

    That’s a completely different schematic. The 4 knob Deluxe always used SAd1024A and can’t be easily changed over to MN series.
    The SAD1024A is a noisy chip. You’ll have to learn to live with it because it’ll never be as clean as the MN3005.

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