(solved) what is is it? a milliampere meter?

[whitevamp]

OK so i have this piece of test EQ. and i am puzzled by what it is.
im use to seeing 2 probes not one, if it is a milliampere meter.
it has a single 2mm jack on it and a speaker and on the board is 5 lm741cn opamps,and a tip30, and tip29, and misc resistors, and some ceramic caps, and 2 1000MFD electrolytic caps.
 i tried to make a schematic for it but it was turning out to be a cluster f**k,( first time trying to reverse engineer.) so i thought i would just post a pick of it and describe it. but if need be i could try and finish the schematic for it.


the speaker is on the front, and on the top is a unknown part.

EDIT0:
and after think about it, this is probably a loaded question, with out the schematic.

EDIT1:
here is a slide show of the 9 pic's. the tape on the bottom right is for orientation.
http://s656.photobucket.com/user/whitevamp/slideshow/random%20things/unknown%20piece%20%20of%20test%20EQ

EDIT2:
here is some pics of the unknown part, yes there is a few dups.
 
pic of the speaker and the switches, and 2mm jack.


this is the back of the unknown part. it is a single strand shielded wire.


and a nother pic of the back of the unknown part.


this is a pic of the unknown part on its side for depth.




the supply is 2 9v batteries in series.

schematic of the wires.

[Brumby]

It would seem the meter is an off-the-shelf unit with the original scale it came with and the whole unit looks like a home-brew.  At this time, understanding what circuitry is involved and it's purpose is a matter of conjecture...

How about a photo of the inside, to at least give us half a chance?




If I had to make a guess.... a Geiger counter?

[whitevamp]

It would seem the meter is an off-the-shelf unit with the original scale it came with and the whole unit looks like a home-brew.  At this time, understanding what circuitry is involved and it's purpose is a matter of conjecture...

How about a photo of the inside, to at least give us half a chance?




If I had to make a guess.... a Geiger counter?

Updated first post with a link to 9 pics.

[alsetalokin4017]

Nice photos ...  of everything _except_ the "unknown part" at the top under the grille.   

And the power supply, and the connections at the meter and front panel controls....

And there are really only 4 unique photos, the rest seem to be duplicates.

[tatus1969]

the device on the top would be the most important one in order to find out what it does. Maybe a microphone? Maybe a sound meter? Or some ultrasonic gear?

[EEVblog]

Nice photos ...  of everything _except_ the "unknown part" at the top under the grille.   

Yep, we need to know what that part under the top grill is. Assuming the front grill is a speaker?

[Fungus]

Looks like a uBeam prototype to me.

[tatus1969]

uBeam... just read about this. Naahhh. Would that be a topic for Daves' next debunking video?

I worked with resonant 40kHz ultrasonic (although fully encapsulated) transducers some years ago for an air speed measurement system, and I remember that I had to drive the transmitter with tens of volts just to obtain a few ten millivolts at the reciever, sitting maybe 5cm away. Air is a quite good ultrasonic absorber.

[testmode]

I would have to go w/ the "some kind of a detector" guess as well.  Maybe the sensor is for some kind of a gas?  Does it have an opening in it (i.e. a hole or something)?  What kind of material is it made of?

The 2mm jack looks to be an option for external audio output or headphones as it seems to bypass the speaker when plugged in.

[Fungus]

Looking closely at the coil near the top I'd say it was some sort of ghost detector (evil spirits).

[NottheDan]

Am I seeing that correctly? That cable to the thing up front is coax and core and shield are shorted out?

[whitevamp]

Nice photos ...  of everything _except_ the "unknown part" at the top under the grille.   

And the power supply, and the connections at the meter and front panel controls....

And there are really only 4 unique photos, the rest seem to be duplicates.

updated first post.

[SeanB]

Potted item is a open bobbin ferrite with an inductor wound on it, likely used as a magnetic field detector. Then the board has an audio amplifier and probably a RF detector, so that you can hear the changing magnetic field. Input circuit looks like a limiting amplifier, then an audio amplifier ( with speaker output) and then the meter is used as a signal strength meter.

Otherwise the black part is an ultrasonic detector, and the rest is just a preamplifier and demodulator so you can hear the downconverted ultrasonic energy. If the black object has some holes in it and a diaphragm behind it it is a microphone.

[whitevamp]

If the black object has some holes in it and a diaphragm behind it it is a microphone.

nop no holes just sold plastic aluminum casing.

[tatus1969]

If the black object has some holes in it and a diaphragm behind it it is a microphone.

nop no holes just sold plastic casing.

do you have the tools to measure the electrical properties like L, C, R of that black "box"? Or power up the unit and attach a scope to it?

[Fungus]

Potted item is a open bobbin ferrite with an inductor wound on it, likely used as a magnetic field detector. Then the board has an audio amplifier and probably a RF detector, so that you can hear the changing magnetic field. Input circuit looks like a limiting amplifier, then an audio amplifier ( with speaker output) and then the meter is used as a signal strength meter.

Otherwise the black part is an ultrasonic detector, and the rest is just a preamplifier and demodulator so you can hear the downconverted ultrasonic energy. If the black object has some holes in it and a diaphragm behind it it is a microphone.

Like I said, it's a ghost detector. Very popular in the 1970s.

[tatus1969]

Potted item is a open bobbin ferrite with an inductor wound on it, likely used as a magnetic field detector. Then the board has an audio amplifier and probably a RF detector, so that you can hear the changing magnetic field. Input circuit looks like a limiting amplifier, then an audio amplifier ( with speaker output) and then the meter is used as a signal strength meter.

Otherwise the black part is an ultrasonic detector, and the rest is just a preamplifier and demodulator so you can hear the downconverted ultrasonic energy. If the black object has some holes in it and a diaphragm behind it it is a microphone.

Like I said, it's a ghost detector. Very popular in the 1970s.

found something veeeery similar

http://hackedgadgets.com/2009/12/07/electromagnetic-field-detector/

[testmode]

Isn't the unknown part a bit small for a "ghost" (i.e. emf) detector?  And why would they keep it inside the chassis with a grill as an opening? Why wasn't it designed like an antenna, I guess it would be more effective that way.

But it does look awfully similar to the ghost detector @tatus1969 has shown.

I wonder if by any chance OP has plans to tear apart the black part?

[whitevamp]

If the black object has some holes in it and a diaphragm behind it it is a microphone.

nop no holes just sold plastic casing.

do you have the tools to measure the electrical properties like L, C, R of that black "box"? Or power up the unit and attach a scope to it?

I wish I did.
I have no scope, or lcr meter.

[Fungus]

Isn't the unknown part a bit small for a "ghost" (i.e. emf) detector?  And why would they keep it inside the chassis with a grill as an opening? Why wasn't it designed like an antenna, I guess it would be more effective that way.

Maybe it's not a very good one. 

It's not as if it has to detect real ghosts or anything. All it needs to do is make crackly noises when you wave it around.

[whitevamp]

I wonder if by any chance OP has plans to tear apart the black part?

yeap i sure did desolder it to see who/why/what for.
and low and behold there a part# on it, and manufacture.
its a tr-89 Transducer made by massa
here is the data sheet for the tr-89B mines just tr-89

http://www.massa.com/wp-content/uploads/2016/01/TR-89-Datasheet-151227.pdf

[testmode]

It's not they they actually have to detect real ghosts or anything. All it needs to do is make crackly noises when you wave it around.

It wouldn't be a ghost detector for nothing, now ain't it?

... low and behold there a part# on it, and manufacture.
its a tr-89 Transducer made by massa...

Kidding aside...hmmm, so it is actually an ultrasonic transducer.  If I interpret it correctly, it seems that it is routed in receiver config in the PCB.  This further reinforces Fungus' ghost detector theory (operating in ultrasonic freq).  Makes me wonder if ghosts and spirits radiates in specific bands depending on their type.

[StillTrying]

Is it a home made bat detector. If it is, it won't be very good using 741s.

Ed:
its a tr-89 Transducer made by massa
I'm not sure I'm looking at the right photos, can't see any sensor, but if that's what's on it then still bat detector.

[whitevamp]

Is it a home made bat detector. If it is, it won't be very good using 741s.

Ed:
its a tr-89 Transducer made by massa
I'm not sure I'm looking at the right photos, can't see any sensor, but if that's what's on it then still bat detector.

here is the transducer pic... taken link from first post.

[whitevamp]

thank you every one that commented on this question i had about this item.
from the comments it ether a ghost detector or a i see one bat detector.
so not much use for anything.
so i think i might just part it out.