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Vintage threads from the first ten years

Re: MXR Envelope Filter

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9/7/1999 2:40 AM

Re: MXR Envelope Filter

Not too many suggestions to make, based on the info you provide. A few possibilities to consider, though.

1) Because of how the EF is designed, a break in either the attack or sensitivity control wiring leaves it nonfunctional. Check to see if there is continuity from the board, through the pot, and back to the board for each of these controls. Given the struggle to get batteries inside the teeny box, it's always possible the connecting wires got cracked.

2) One of the chips got zapped. The EF uses 2 CMOS hex invertor chips (4069) and a CMOS switch chip (4066) which are both static sensitive. Once installed, normal use is unlikely to result in blowing one of the chips, but you never know. These things are cheap like borscht, easily found, and nothing that could be remotely called "vintage" (such as some germanium transistors in certain distortion devices), so you can always desolder them, stick in sockets, and pop in some new chips. There are two caveats here to consider, the first of which is pretty obvious: desoldering these chips will be painstaking, and requires diligence to avoid destroying the pc traces that are crammed together (it's no P2 motherboard, but it's crammed tight). The other caveat is to make sure you get UNbuffered 4069's, with the UBE suffix (or any equivalent).

9/7/1999 3:48 AM

quote:
"desoldering these chips will be painstaking, and requires diligence to avoid destroying the pc traces that are crammed together"

Take a look at http://www.geofex.com/remvdip.htm." target="_blank">http://www.geofex.com/remvdip.htm">http://www.geofex.com/remvdip.htm.

9/8/1999 6:18 AM
Mark Hammer	Sage advice. Another piece of sage advice is to WRITE DOWN THE ORIENTATION OF THE CHIP BEFORE YOU PULL THE DAMN THING OUT!! The well-experienced can often deduce where pin 1 goes, even if they pull this particular sort of blooper, but the novice may be seriously impeded in repairing the item without taking such measures.

9/8/1999 2:46 PM

quote:
"Another piece of sage advice is to WRITE DOWN THE ORIENTATION OF THE CHIP BEFORE YOU PULL THE DAMN THING OUT!!

"

Oh, sure - do it the simple, easy, quick way instead of thrashing around and getting it wrong a couple of times. That takes all the fun out of it.

*< 8-)

8-)

9/10/1999 4:44 PM
Rick	I've replaced all three chips but the 4069 replacements I got don't have the UBE suffix. That may be the problem, I'll try to find some unbuffered chips today. Thanks for all the input everyone.

9/16/1999 6:26 AM
Tracy	Re: what's a T-wah? I really like the old Electro Harmonix Doctor Q . You can control the opening and closing effect with your right hand picking intensity. Also it compresses lightly. Expressive pedal.

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