# Mistress Mystery — a repair blog



## Feral Feline (Apr 17, 2021)

Hello fellow Soldernauts,

I mentioned in the Boneyard that I came into possession of a Mint-Looking Electric Mistress. 

Alas the sordid tale in an EHX nutshell is that a friend bought it new back in the day, and while it still had its new-pedal smell, was left at a band rehearsal space where somebody tried to release the magic smoke. Thereafter it remained in a shoebox coffin for decades before being entrusted to me.

This past Friday night, I dismantled it and proceeded to go through the circuit with my mentor leading the way. I'm still not that great at trouble-shooting yet, but learning lots from my Amp-Dr friend. 

After poking and prodding our way through the circuit with schematic in hand: 

Re-attached a few wires
Replaced a transistor
Swapped out a faulty 4558
Trimmer supplying power to said 4558 is suspect/intermittent
Determined a definite problem with the $AD1024 😿.

Then we ran out of time.

It passes signal now, but without any jet-mojo from the heart of the unit. We looked through the stash of vintage pedals in his atelier for something we could borrow a chip from to test the circuit further, but all we could find was a Memory Man Deluxe. 


I'll try to get some pics up in a day or two, as soon as I have time, and of course will continue the saga in more detail and update after next Friday's search & repair session. 

Now to look for NOS Reticon chips, at ONS prices... 😸


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## Chuck D. Bones (Apr 17, 2021)

Do you have a scope?


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## Feral Feline (Apr 17, 2021)

Yeah, we put it on the scope, but as mentioned ran out of time.


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## Chuck D. Bones (Apr 17, 2021)

Did you check to see if the SAD1024 was getting a clock signal on pins 3, 8 10 & 14?


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## Feral Feline (Apr 17, 2021)

No, but we got thumping with the rate knob so there's some clock ticking away in there somewhere.

I'll make note of testing 3, 8, 10, & 14 this coming Friday. 

I recall my friend mentioning something about pin 6... an out.

Looking at the Datasheet, it says the 1024 is essentially two independent 512 ICs, though sharing a common ground. Are the 512s more common than the 1024? I could put a daughterboard together with two 512s...


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## Chuck D. Bones (Apr 17, 2021)

The two 512 stage BBDs are run in parallel multiplex configuration, which effectively doubles the sample rate for lower noise and more bandwidth.

If you're going to start hacking the Electric Mistress board, you might as well build a flanger using modern BBD parts.


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## Feral Feline (Apr 17, 2021)

True, I've got a few flanger builds in the ever-growing queue. 

This is a passion project though, besides, the SAD1024 or 2x SAD512 have mojo. 😹

What's weird is all the chips are socketed except one: TI LM339N.

The Reticon, the 4013, the 4558 and the 741 ICs are all socketed.


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## Chuck D. Bones (Apr 17, 2021)

I can understand socketing the SAD1024, they were expensive even back then.  The other chips, I don't get why they socketed them.
After you verify the absence or presence of clock to the SAD1024, then we'll have a better idea on how to proceed.  If in fact the transistor and 741 were blown, then my guess is some %$&^ hooked up the wrong power.  Maybe those two parts died to save the others or maybe all the semiconductors are toast.  You have a schematic, right?


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## Feral Feline (Apr 17, 2021)

Yup, the wrong power was hooked up and as mentioned in the Margin thread, the culprits denied culpability. 

We've got a schematic, Version 2 I think, it's a hardcopy with the pedal so I can't check right now. However...the pedal is a version 5, I believe, from 1980 as 1981's Version 6 was 9v, and this is 18v so 1980 also jives with when my friend purchased it.

Sifu & I swapped the original 4558 back in after mucking with the faulty trimmer pot and getting some signal. So the 4558 might not be faulty after all. It was all a blur... 


The 4558 is first in the signal chain... 
We were getting 13.33 volts where it should've been 12v, that's what lead us to the 4558 "problem" area; but looking at this other 1980 schematic now, 13.33 is still within the newer schematic's 12v–13.5v acceptable range. 

The transistor replaced was PN4354, we subbed a 2N5551 which seemed to work.

Can't tell you much about the scope other than I strummed a Strat while Sifu continued with the poking and prodding the guts of the circuit.



Gotta get some shut-eye, it's 8:30 am and  I'll be dealing with my niece and nephew in a few hours so need all the zeds I can get. I'll check back in later, ASAP.


As always, thank you for your time and wisdom, CDB.


Cheers,
FF


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## Gordo (Apr 17, 2021)

Fingers crossed that the SAD is ok.  Everything else is just parts.


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## Chuck D. Bones (Apr 17, 2021)

Here's the schematic I have, FYI. I imagine they are all pretty similar.


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## Feral Feline (Apr 18, 2021)

That’s the schematic we’re working from.
Other schems at this great site:





						The Electric Mistress Mystery Page
					

The Electric Mistress Mystery Page - Everything about the vintage Electric Mistress. Versions, schematics, identification, how it works, measurements, repair, maintenance, links.



					www.metzgerralf.de


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## Feral Feline (Apr 18, 2021)




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## Feral Feline (Apr 18, 2021)

Posting from my phone, which is a first for me — much easier to use the computer...😾


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## Feral Feline (Apr 18, 2021)

Looks a lot more like a ’79...


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## Gordo (Apr 18, 2021)

Looking back on those old boards it's amazing anything EHX sold ever worked at all.  Like a 5 yr old with a soldering iron.  When I was a kid I worked in a music store and we had boxes of Small Stones.  Failure rate was about 1 in 3.  Wish I'd kept all the bad ones...

I'd give that board a serious cleaning, it might make a few dodgy solder spots a bit more obvious.


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## fig (Apr 18, 2021)

Is that connected?


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## music6000 (Apr 18, 2021)

fig said:


> Is that connected?
> View attachment 11098


Looks like a Floater!


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## Feral Feline (Apr 18, 2021)

Thanks Gordo, & Fig — well spotted, however the photos above were taken immediately after disassembly and prior to any work of any kind being performed.

Music6000, the resistor in question is from the filter-flanger switch and was indeed re-attached; went over the whole circuit to make sure everything was connected — 't's crossed 'i's dotted — before putting some 18v fire in its belly.

Alas, I don't have better pics post-repairs. Will get some updated pics coming Friday.


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## Feral Feline (Apr 23, 2021)

FADE IN:

EXT.
A nondescript industrial-building surrounded by more of its ilk in the Tsing Yi enclave of old Hong Kong's New Territories…

CUT TO:
INT.
An atelier rife with tube-amplifiers of all manner stacked and stashed in every nook and cranny and amongst those stacks gaps are effects pedals, rack-units, mixing boards, even a synthesizer or two — some with their guts spilling, open gaping wounds, others upside down and their tubes jutting out, a few tagged “finished” or “fixed”. Entering further into the warren, we take what is barely a path, cleared from the door to two brightly-lit mobile work-stands made from old amp-cabinets with casters; on one, a vintage ’60s Telefunken multi-band radio, on the other a Mesa Boogie MKI, out of its chassis, and a reverb pan with fumes emanating from it — three men surround it, intently absorbed in the three springs’ wire-connections being soldered…

NARRATOR:​Last week, on Mistress-Mystery Theatre, the dynamic duo Dr Valve-Amp Sifu and his right-hand nurse-ratchet assistant, the Boy-Blunder Feral Feline, had cracked open a malfunctioning EHX Electric Mistress and vowed to return her to her former glory. They had but barely started to plumb the depths of her malignant-mystery and wished to wend their way through the rest of her circuit’s secrets this week to wrest the wayward whirling-whoosh of flangelic-waves from the Mistress’ womb —

But, wait! What’s this? An interloper interrupting the mending of the Mistress with a miscreant Mesa Boogie behaving badly? Ahh it’s Sifu’s long-time friend and guitar surgeon, just back from a storage-sale blow-out of four Mesa Boogies — what a score! Yet… Why so serious gentlemen, why the bad vibe? Is the MKI not picking up the reverb pan’s good vibrations? Could there be an output-transformer trepidation also preying upon their psyches as they suss out the signal’s incapacity to forthrightly sally forth? 
What gives, FF?

FERAL FELINE:​Oh, hello! Salutations fellow soldernaut-viewers. Sorry to break the fourth wall (4th today, anyways), but if I’m only good at one thing, it seems to be breaking things.
    Indeed, last week Sifu and I determined the Mistress’ 741 chip was hunky-dory and managed to find a suitable replacement for a toasted transistor. We messed around with the 4558 as well, but the problems it seemed to be having were negated. Checked some power and determined the pots were doing something, just no flangering was getting out. The one chip we’d not had a good look at was the 4013, so I said I’d check my stash as Sifu had none in stock. I had plenty, but Sifu had already gone out and picked up the little DIPer.

It’s been a heckuva week, and I arrived a wee bit later than usual this Friday night. Work was already well underway on the Boogie’s reverb conundrum; time was already tight so I thought it little-likely that we’d get another peek under the Mistress’ skirt, what with pressing amp repairs at hand. I assisted as best I could, swapping out 3 different reverb units, but in the end the transformer proved to be our biggest stumbling block.

In between reverbs, I had found an old answering-dicta-phone device amongst some amp transformers… the Reticon SAD1024 was used in such voice-activated units back in the day so with permission I made an exploratory recon — alas no magic-smoke-filled chip inside. We hit the wall with the Boogie’s transformer. Sifu’s second-in-command would be charged with transformer transformations for tomorrow. That left us about a half hour — barely enough time to bring the Mistress out and set her up, were it just me. However, Sifu works at a confident competent experienced speed.

So we swapped in the new CD4013 chips, checked voltages, checked SAD1024 pins and worked our way through the rest of the circuit. Seems the 4013 was not the culprit, it had 100kH+ going and that seemed crazy and wrong — not only beyond human ears but beyond dogs and probably bats, I dunno. So I checked the datasheet of the SAD1024 and its sample rate is 150kH, and so another piece of the puzzle clicked into place in my noggin — got to think beyond the human ear’s audible spectrum (I’ve zero previous electronics experience going into pedal building/repairing). Tick-tock said the clock, time’s a-wasting…

Sifu’s Mesa-Boogie buddy strummed the strangs of the Shop Strat while we probed every possible path. The clean signal was getting through, but somewhat distorted and muffled, not quite right, but there. The clock was tick-talking to the rest of the circuit and the whole 339 section was functional. Bit by bit we broke it down into its component parts and determined the circuit was operational up to, but excluding, the SAD1024. That was it. The last thing left. A defunct $AD1024; End of the delay-line.

We sat back and joked about how many more hours it would take to work through the circuit again with a fresh Reticon, if we could find one. Sifu’s more at home with amps, not as familiar with analogue pedals, but he’s as tenacious as a bulldog with a bone and Sifu wanted a taste of the Mistress’ marrow. Mulling over the reticent Reticon’s datasheet he pulled the chip and checked some of the socket’s pins and Godot knows what else as buddy and I chilled — Sifu popped the chip back in and with a test-signal blaring started probing again with a quick adjustment to a trimmer while monitoring the oscilloscope — I thought I heard a distinct blip of a difference at some point of the trimmer’s travel, but Sifu was too absorbed in prodding the underside of the PCB. So I dimed the controls and got buddy to strum strangs again while I fettled the Mistress’ trim…

Noting where the trimmer was parked, so I could get back to ground zero if need be, I started twisting the flat-blade into the Mistress’s guts. I hit her g-spot, she sighed, I squealed — there it was! At last! Zombie Alert! Back from the DEAD!

Buddy had never heard an Electric Mistress in person before, he was smitten with her charms and checking online prices within a heartbeat of handing off the Strat to me. Sifu had a mile-wide smile, and much trading of the Strat back and forth ensued while dialling in lush to lunatic-fringe… I think we were there for at least another half hour beyond when we were s’posed to make like a tree, branch off and leave.

EPILOGUE: EBULLIENT JUBILATION ! ! !

So, naturally I was too excited to keep last week’s promise and remember to take the pics this Friday-night. After more than 3 decades of slumber, Sleeping Beauty has awoke with a tender, long kiss. Mwah! … Mwah, dahlings, MWaH mwAH!

After being up since about 3am, I was bagged but so pumped I couldn’t sleep. Instead, took advantage of the time difference and chatted with my buddy who had bequeathed me the Mistress, but she’s always been his in my mind and still is. So, we’ll have a great ownership debate when I return to Canada. If it’s “mine”, I know a guy who might be willing to look after the Mistress, ;-) he’s been looking after my SG for the last couple of decades (didn’t want to risk theft/breakage/humidity-damage bringing it to HK). ’Twas 2am before I finally hit the shower, the tub’s resistance was futile.

Thanks for reading, thanks for your support, huge shout-out to ChuckDBones!


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## Feral Feline (Apr 17, 2021)

Hello fellow Soldernauts,

I mentioned in the Boneyard that I came into possession of a Mint-Looking Electric Mistress. 

Alas the sordid tale in an EHX nutshell is that a friend bought it new back in the day, and while it still had its new-pedal smell, was left at a band rehearsal space where somebody tried to release the magic smoke. Thereafter it remained in a shoebox coffin for decades before being entrusted to me.

This past Friday night, I dismantled it and proceeded to go through the circuit with my mentor leading the way. I'm still not that great at trouble-shooting yet, but learning lots from my Amp-Dr friend. 

After poking and prodding our way through the circuit with schematic in hand: 

Re-attached a few wires
Replaced a transistor
Swapped out a faulty 4558
Trimmer supplying power to said 4558 is suspect/intermittent
Determined a definite problem with the $AD1024 😿.

Then we ran out of time.

It passes signal now, but without any jet-mojo from the heart of the unit. We looked through the stash of vintage pedals in his atelier for something we could borrow a chip from to test the circuit further, but all we could find was a Memory Man Deluxe. 


I'll try to get some pics up in a day or two, as soon as I have time, and of course will continue the saga in more detail and update after next Friday's search & repair session. 

Now to look for NOS Reticon chips, at ONS prices... 😸


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## Feral Feline (Apr 23, 2021)




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## Feral Feline (Apr 23, 2021)

Above pic, lookin' at the 'scope off camera to the right.

Outside of home, my most favourite place to be in HK, the Amp Atelier.


I've got some short clips of the Mistress making wooshy, but I don't do FecalBrook and don't have a Ute-oob account, so no idea how to upload any of the clips. Besides, it's not like you've never heard an Electric Mistress before...


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## fig (Apr 24, 2021)

An epic tale indeed! I was "in the moment", feeling the friction resonate through the screwdriver as that trimpot turned _ever...so_...slightly.


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## Chuck D. Bones (Apr 24, 2021)

Great narrative!  So was the root cause a bad connection or demonic possession?


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## Feral Feline (Apr 24, 2021)

YES!


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## Feral Feline (Apr 24, 2021)

Well, personally I think it was a demonic connection to a bad possession ... once everything was hooked up and the fried transistor replaced, maybe it needed that little something extra — truthfully might've just needed to have her trim tuned up, but I think the real key was Sifu popping out the SAD1024 and re-inserting it — love always involves generating a little friction.

We'd already tried tuning it before the Reticon was pulled, but once the Reticon was re-inserted dialling it in was easier than tuning a guitar.


PS: I just noticed the Boogie Preamp (left of pic) that Sifu's friend had just picked up. That, and the MKI, but I don't know what the other two Boogies were that he got. I keep missing out on the deals — there was a shop that closed down and I really could've used the caps they were selling for my upcoming amp projects. Ahh well, the Mistress "Ain't Misbehavin'" anymore so I'm still counting my lucky stars.


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