Ehx deluxe electric mistress power repair (24v)

Started by perfectlyfineusername, July 25, 2023, 04:11:57 PM

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perfectlyfineusername

Hi, I have an ehx electric mistress with the boss style jack that takes a 24v. I replaced the broken jack that it had when I got it but now it won't turn on with the 24v plug even though it does work with a 9v though. I did plug in a wrong polarity supply by accident and it gets noisy at 9v, I'm almost certain I will have to change op amps but does anyone have any idea what else could be wrong?

POTL

here is the link to the schematic.
http://www.metzgerralf.de/elekt/stomp/mistress/images/deluxe-electric-mistress-v5-schematic.gif

24 volt models actually run on 12 volts. Several EHX devices had this solution. The difference between 12 and 9 volts will not be too critical. To work correctly, you will need to remove the voltage regulator and biasing BBD.

Apart from the increased noise, what else happened?
1) From 9v, the voltage stabilization microcircuit will not work, it is strange if the pedal is turned on.
2) Many things could break from incorrect polarity, stabilizer, operational amplifier, BBD, electrolytic capacitors, etc.

perfectlyfineusername

Quote from: POTL on July 25, 2023, 04:37:40 PM
here is the link to the schematic.
http://www.metzgerralf.de/elekt/stomp/mistress/images/deluxe-electric-mistress-v5-schematic.gif

24 volt models actually run on 12 volts. Several EHX devices had this solution. The difference between 12 and 9 volts will not be too critical. To work correctly, you will need to remove the voltage regulator and biasing BBD.

Apart from the increased noise, what else happened?
1) From 9v, the voltage stabilization microcircuit will not work, it is strange if the pedal is turned on.
2) Many things could break from incorrect polarity, stabilizer, operational amplifier, BBD, electrolytic capacitors, etc.

It seems to work totally fine with 9v and doesn't turn on at all with 24, I'll have to take it apart sometime soon to see

Kevin Mitchell

Quote from: POTL on July 25, 2023, 04:37:40 PM
1) From 9v, the voltage stabilization microcircuit will not work, it is strange if the pedal is turned on.
I'd guess it's not the V5 then.

A photo of the PCB may help sort this out.
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Rodgre

Pardon me for stating the obvious, but I assume you replaced the DC power jack with a plastic one, not metal, and I assume the lugs are wired correctly.

Roger

idy

One reason 9v might work and 24 not is... the barrel plugs come in various sizes. these sizes are not discernible to the naked eye. They *look* exactly the same. Really they do. Maybe the same dimension outside and different inside? But one is too small and delivers no power.

Only thing I can think of.

Hope to gods you didn't fret anything rarer than an opamp...

Kevin Mitchell

Quote from: idy on July 26, 2023, 03:42:41 PM
One reason 9v might work and 24 not is... the barrel plugs come in various sizes. these sizes are not discernible to the naked eye. They *look* exactly the same. Really they do. Maybe the same dimension outside and different inside? But one is too small and delivers no power.
POTL's concern was because in the V5 there is a 12v regulator. It's a dropout regulator and requires a couple volts over it's rating to even work. 9v in means no supply voltage to the rest of the circuit. Again, assuming it's the V5.

I'm not sure what you're getting at about barrel sizes. That's irrelevant to the voltage they're plugging into it.
2.1mm barrel jack is standard and comes with all of the EH pedals that moved away from internal transformers.
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idy

I thought the original post said it was
Quoteit won't turn on with the 24v plug even though it does work with a 9v though.

Opposite of what a regulator problem would do. Maybe he has it mixed up?
But he said he replaced the power jack (most of us keep jacks only for the 9v plugs we all use..). and now a normal 9v adapter works. But the (original ehx?) 24v adaptor does not. If the jack and adapter don't agree that would explain it. I have found that problem before.

Confirm to us that the "24v" adapter works. Mine read 33v unloaded.
Then confirm that the 24v is getting to the terminals on your power jack.



PRR

Polarity? (right voltage wrong polarity is usually no-work or smoke.)
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idy

Magic words. EHX 24v adaptors are center positive.

MrStab

Wow, that's a big drop!! What's the reasoning behind the 24V supply if it's passing through a 12V regulator? Legacy? Availability? Standardisation across multiple products?
Recovered guitar player.
Electronics manufacturer.

idy

QuoteLegacy? Availability? Standardisation across multiple products?

Probably yes, yes, and yes.

They started with that and stuck with it. Expensive to buy more than one kind.  I wonder if all of their big box effects regulate down to 12v?

POTL

Quote from: MrStab on July 28, 2023, 12:23:41 PM
Wow, that's a big drop!! What's the reasoning behind the 24V supply if it's passing through a 12V regulator? Legacy? Availability? Standardisation across multiple products?

one word - MONEY! there is such a thing as proprietary, like Apple branded connectors. The manufacturer creates an ecosystem and sells accessories from which he earns more than from the main product (although in the world of musical equipment the margin is large everywhere). Simply put, create a non-standard need for a power supply, sell these blocks, because almost no one makes such ones, profit.

MrStab

#13
Seems only the Deluxe V5 edition started getting silly for no clear electrical reason. Given the ubiquity of 18V, centre-negative supplies, that does indeed seem like some sketchy propietary BS. Benefit of the doubt: 18V supplies probably weren't as widespread when the pedal was released.

http://www.metzgerralf.de/elekt/stomp/mistress/index.shtml

Sorry, I know the Electric Mistress has probably been discussed to death here, but this oddity is new to me. Though I had been looking for a fairly-common 24VDC adapter a while back, noticed this pedal had one, and was bummed out to discover the polarity! (i can't just flip the leads as it's for the intention of reselling)
Recovered guitar player.
Electronics manufacturer.

Rob Strand

Quote from: idy on July 26, 2023, 09:44:24 PM
Magic words. EHX 24v adaptors are center positive.
If the jack has been replaced and wired as center negative the EHX adaptor won't work.   So the repair is the problem not the adaptor.

I believe the positive center/positive tip thing on EHX pedals came about back in the day when there was metal enclosures and sockets with nuts which naturally wired the "outside" to ground.   Boss and Ibanez use the plastic connectors on the pedal side so they don't need to worry the power being wired to the chassis by the DC jack.

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