Home › Forums › Vintage EHX › 1976 Electric Mistress – Help me get it working.
- This topic has 11 replies, 3 voices, and was last updated 10 years, 4 months ago by guedzilla.
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June 1, 2013 at 10:47 pm #83021GplayerMember
I picked up a 1976 Electric Mistress as an impulse buy without being able to test it out and now that I have it it has problems. When I turn on the pedal there is the volume drop that was expected but I can’t hear much of any effect other than a very faint leslie kind of sound. It’s barely audible though.
I found some info on youtube about the trim pots. One guy said the left one had something to do with the voltage regulation and the other I don’t recall. Anyway I noticed distortion so I turned the right one (pedal facing down obviously with three pots on the top) to the right a bit and the signal cleared up. As for the other one I tried turning it to the left and it squealed so I quickly turned it back to where it is in most pictures I see of the unit.
I found a previous post regarding a 78 EM and I was wondering if the trim pots have the same functions, delay IC on the right and feedback on the left? Is it normal to have distortion if the right trim pot is turned to the right?
I opened up the case and there was a blob of solder that’s flat on one side but I can’t see any spot where it came off so I don’t know if it’s part of the unit or just an extra blob that wasn’t part of the unit’s functioning parts.
I really want to get this thing working for the great sound it makes and because I spent quite a lot of cash to get this thing. Any steps I can go through to safely set this thing up again will be greatly appreciated. (I have rookie electronic skills but not much)
Edit: pictures are now up!
June 2, 2013 at 1:40 am #119124The EH ManModeratorYou can alwayts post pics at flickr or photobucket and link to them.
June 2, 2013 at 3:35 am #119125GplayerMemberOk here are the pictures, whew!
June 2, 2013 at 11:24 am #119126The EH ManModeratorYes, like the earlier post, left is Feedback and right is Bias for the delay IC. The right one should be adjusted so it’s in the middle of it’s usable range (where the signal is strongest and clearest). The left one is turned till it feeds back, then backed off a bit.
Really, if you don’t have any skills you’d be better off sending it to a tech.
June 2, 2013 at 5:19 pm #119127GplayerMemberHi, thanks for the reply. I’ll give that a try.
By rookie skills I meant that I do have some experience but I don’t have an oscilloscope or anything fancy to use. I am familiar with soldering and I have done some mods on power jacks and the odd capacitor and resistor. I have a few electrical meters as well.
June 2, 2013 at 8:31 pm #119128GplayerMemberUPDATE! SUCCESS! I hear flanging!
The only thing is I still have a fair bit of distortion now along with the flanging that I need to deal with. Could this be caused by a weak battery? One of my 9volts is at 9 and the other is at 7volts.
I have a few spare 9v power supplies and 9v power plugs along with some barrel power jacks so I was going to set them up so I can just plug in a 9v power supply to each 9v plug on the unit. These power supplies are 650ma each so will that be safe to use?
Thanks!
June 2, 2013 at 9:38 pm #119129The EH ManModeratorCould be weak batteries or even the bias isn’t quite right yet.
Those power supplies probably aren’t regulated so I wouldn’t use them. If you had some 9v, 100mA supplies I’d be OK with that.June 3, 2013 at 12:52 am #119130GplayerMemberIt turns out that dialing this in is a bit trickier than I thought it would be.
Can you suggest a good starting point for the rate, range and color knobs before I try to fine tune the trim pots?
June 3, 2013 at 1:44 am #119131The EH ManModeratorRange and Color at max. Rate at 1/2.
June 3, 2013 at 3:17 am #119132GplayerMemberThe thing is now dialed in and sounds beautiful! The final trim pot configuration ended up like most pictures I see of the unit. The left one at bit past ten oclock and the right one a bit past 1 oclock.
It is also dead quiet while on with humbucker pickups. With single coils I can hear a faint swirling in the background when nothing is being played but there is always slightly more noise with the single coils. I am playing at a fairly low volume but some pedals are noisy even at low volumes. This one seems quiet.
I’ve decided to just run batteries in order to preserve this in its vintage condition because it seems to be one of the earliest models made apart from the blue box one. I’m going to pick up a Boss LS-2 line selector so I can balance out the volume.
I really appreciate the help getting this working and I hopefully these posts will help anyone else that comes across the same kind of problems.
June 3, 2013 at 9:40 am #119133The EH ManModeratorGood to hear! Glad it was nothing major.
July 15, 2014 at 1:49 am #120106guedzillaMemberNecro-ing this one-year old thread (instead of the two-year old where I last wrote about my EM issue)…
I followed the steps on that other thread on lining the pots up (have no access to an oscilloscope and I’m not really comfortable with sending my unit all over the world to Howard Roberts) and I managed to point my issue better: I have no problem whatsoever with the unit as long as I keep the range between 0 and the first mark. If I got any higher, I start getting some scratchy noises on a part of the oscillation. It’s almost as if most of the range had some kind of problem, but as long as I don’t go there, it’s all right… any ideas on what this could be?
PS, the other thread I’m referring to is this: https://www.ehx.com/forums/viewthread/5489/
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