# Transformer inside a strat cavity?



## knight_yyz (Mar 14, 2015)

I have a potential client who sent me these pics. No battery or power source other than the current provided by the pups. Anyone have any idea what's going on here? Bty also has two toggle switches. It's a rats nest in there but you can see what looks like a mini transformer bolted in the cavity


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## Milkman (Feb 2, 2006)

Seems like mad scientist shit to me.

No battery or other power and a transformer? 

Flux Capacitor?


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## gtrguy (Jul 6, 2006)

Could be using the transformer as a dummy coil to cancel the 60Hz hum or maybe it's being used at the output for changing the impedance to a lo-z output. Hard to tell how it's wired.


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## greco (Jul 15, 2007)

I'm voting for dummy coil.

@mhammer has discussed this many times in the past and could confirm.


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## Paul Running (Apr 12, 2020)

Reverse-engineer to a schematic drawing...that should indicate where and why it's there. The colour code of the TFM wires is standard plate to voice-coil. Characterize the TFM with a sig. gen and scope.


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## CathodeRay (Jan 12, 2018)

Long shot, but if there's an associated capacitor, it could also be part of a varitone circuit experiment. Ie a notch filter. Doubtful though, just throwing it out there.


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## greco (Jul 15, 2007)

Paul Running said:


> Reverse-engineer to a schematic drawing...that should indicate where and why it's there.


That would certainly help immensely. A lot of wires happenin' in that pic!


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## Verne (Dec 29, 2018)

Fire. That'll fix it. It would end that way for me if I were to try and figure that out. Also, 40oz of Forty Creek. Looks like a major headache about to happen


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## mhammer (Nov 30, 2007)

The Hammer says that Cathode Ray nailed it. It is a time-honoured trick to use a cap+inductor (and transformers are another kind of inductor) to turn a Tone pot into a midrange cut. The only other possibility is that the transformer is being used to provide a buffered output for DI purposes and plugging directly into a mixing board. But I don't see anything in the wires visible in the pictures to suggest that.


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## Paul Running (Apr 12, 2020)

The Bench tone stack, when using active PUPs:


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## knight_yyz (Mar 14, 2015)

I don't have the guitar. It's in another province. I also did some reading and found out that this could also be adding or subtracting impedance on the coils. Never heard of it before.

There is no battery so they are not active pups


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## tomee2 (Feb 27, 2017)

It has 4 wires, so I'm guessing a transformer for impedance change, maybe a step up transformer? Bump the output voltage up to overload an amp input stage? Just guessing, because I've often thought of doing this just to see what would happen, but figure if it did anything useful it would be common place by now. Or, it's a 1 to 1 to isolate the guitar?


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## knight_yyz (Mar 14, 2015)

I'm going by this 






Wiring a pickup thru a transformer???? - Seymour Duncan User Group Forums


All pickups. All the time.



forum.seymourduncan.com


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## tomee2 (Feb 27, 2017)

knight_yyz said:


> I'm going by this
> 
> 
> 
> ...


Page 2of that thread is interesting... what were talking about?


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## mhammer (Nov 30, 2007)

tomee2 said:


> It has 4 wires, so I'm guessing a transformer for impedance change, maybe a step up transformer? Bump the output voltage up to overload an amp input stage? Just guessing, because I've often thought of doing this just to see what would happen, but figure if it did anything useful it would be common place by now. Or, it's a 1 to 1 to isolate the guitar?


Possibly, but note that if one is using it as an inductor for a mid-cut, then changing the inductance by swapping primary and secondary, or putting them in series, can move around where the mid-cut occurs. Alternatively, bear in mind that it is a Strat-type guitar, which will have two tone controls, so conceivably one coil is for one of the tone pots, and the other coil is for the second tone pot.


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## tomee2 (Feb 27, 2017)

mhammer said:


> Possibly, but note that if one is using it as an inductor for a mid-cut, then changing the inductance by swapping primary and secondary, or putting them in series, can move around where the mid-cut occurs. Alternatively, bear in mind that it is a Strat-type guitar, which will have two tone controls, so conceivably one coil is for one of the tone pots, and the other coil is for the second tone pot.


I did say it was my best guess. It wasn't a criticism of your analysis.


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## mhammer (Nov 30, 2007)

Absolutely no offence taken. I figure that in the absence of better pictures, we're all just riffing here.


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## knight_yyz (Mar 14, 2015)

There are 2 toggles wired to the transformer


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## keto (May 23, 2006)

knight_yyz said:


> There are 2 toggles wired to the transformer


To make it do this:


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## dtsaudio (Apr 15, 2009)

I see the black wire of the tfm is connected to the ground. This more or less tells me it isn't in a tone circuit, but being used as impedance matching


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## b-nads (Apr 9, 2010)

keto said:


> To make it do this:


Exactly what I was thinking....is it in its robot stage as a Strat, or is that it's street outfit?


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## tomee2 (Feb 27, 2017)

keto said:


> To make it do this:


That's just awesome


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## Granny Gremlin (Jun 3, 2016)

Yeah that's my vote - it's (beng used as) a choke coil (inductor) rather than a transformer. Often for a bass cut or to create a mid control. See the Gibson varitone.

If so it should either be humbucking (2 coils reverse wound to each other just like a pickup but without magnets and poles) and/or in a shield can (60s Gibsons had a can; 70s were 2 coils humbucking). 


Another possibility is level matching - onboard passive DI (or to co.nvert to HiZ if LoZ pickups - essentially a DI backwards), but it doesn't look like it.


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## SWLABR (Nov 7, 2017)

My brain hurts just wondering how that all fits in there! There's not enough room for the pots to sit *on top* of that transformer.


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## greco (Jul 15, 2007)

This thread is drivin' me nuts. I am insatiably curious and hate mysteries.


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