Tube Amps / Music Electronics
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|9/2/1996 8:01 PM|
||EH - Memory Man|
I have an old Memory Man Delay/Chorus pedal.
It is obvious that the Bucket Brigade Chip is dead and I would like to replace it. Does anybody know of a source or a replacement. It is a MN40?? Which is a 4096 bit Bucket brigade analog delay. I heard they cost more than $ 50.00!! Is is there a cheaper replacement available
|9/3/1996 2:08 PM|
How certain are you that the delay chip is bad? If you have absolutely no delay signal at all, then there's a good chance your theory is correct, but there are other things that could go wrong in the delay signal path. There are actually two MN3005 bbd chips and an NE570 compandor, and each of these chips has trimpot adjustments that could be out of whack. If you get any delay signal at all, even though it may be very weak and distorted, then it could be that all you need is a tweaking of the input bias trimmers on each of the MN3005's.
|9/4/1996 7:57 PM|
|Daniel A. Lurie
I am pretty certain it is the delay chip because I get a direct signal no
matter if I bypass with the foot switch or not.
|9/6/1996 9:57 PM|
Analog delay lines need to have a bias voltage applied to their inputs
in order to work properly. Take apart any analog flanger/chorus/delay
and you will see a trimpot right near the delay chip(s). Usually, the
"sweet spot" on the trim pot is set and nail-polished (lacquered) in place
during production, but if this is the relic I think it is, it is feasible
that the trim pot has ventured away from the sweet spot. Because of the
way that analog delays work, you would still hear a straight sound even
if the delay chip was fine, IF the trimpot is off as the previous writer
suggested. Fixing it would simply be a matter of twiddling the trimpot
until the sweet spot is rediscovered. Typically, what you'll hear is
no delay at the ends of rotation of the trim pot, a grainy distorted delay
as you get closer to the midpoint, and then a clear delay signal. Don't
worry about damaging the IC with this procedure; all you are doing is
"conditioning" the signal to where the delay chip wants it.
Having said that, there IS always the chance that the delay chip has been
damaged by static electricity. (Remember, a BBD is just a chip with many
eensy-weensy FET's and capacitors with a lower voltage rating than what
you generate in a sweater). But, if the chip has remained in its socket
all these years, there is little chance of that happening.
I always thought that the Memory Man used a couple of SAD-1024's, but
then EH changed the design of many classic units over the years, so a
MN3005 wouldn't surprise me at all. These chips are relatively easy to
obtain, and last time I looked were under $20 a pop. If it turns out
you have one that uses SAD-1024's (assuming I remember this right), then
you may have a far more difficult time getting them since they are no
longer produced. R.G. Keen (www.eden.com/~keen) has some for sale at a
reasonable price. Last time I looked, Dalbani Electronics stocked the
complete line of Matsushita/Panasonic delay chips at fair prices. You
can usually find their ad in Popular Electronics or Electronics Now.
If anyone sees this and knows where a person can find MN3011's, the
chip that was used in the legendary A/DA Stereo Tapped Delay, I'd sure
|9/7/1996 2:07 PM|
The good news: Digi-Key" target="_blank">http://www.digikey.com/">Digi-Key has the MN3011" target="_blank">http://www.digikey.com/DDnt.qry?P=MN3011-ND">MN3011 in stock.
The bad news: They want $53.20 for single units.
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