(solved) what is is it? a milliampere meter? - Page 1
Forum section: electronics / testgear

author: whitevamp
author_rank: Regular Contributor
timestamp: September 18, 2016, 05:30:24 am
content: 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%20EQEDIT2: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.

author: Brumby
author_rank: Unknown
timestamp: September 18, 2016, 06:01:48 am
content: 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 Ihadto make a guess.... a Geiger counter?

author: whitevamp
author_rank: Regular Contributor
timestamp: September 18, 2016, 06:37:24 am
content: Quote from: Brumby on September 18, 2016, 06:01:48 amUpdated first post with a link to 9 pics.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: September 18, 2016, 08:34:50 am
content: 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.

author: tatus1969
author_rank: Super Contributor
timestamp: September 18, 2016, 10:28:28 am
content: 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?

author: EEVblog
author_rank: Unknown
timestamp: September 18, 2016, 10:31:22 am
content: Quote from: alsetalokin4017 on September 18, 2016, 08:34:50 amYep, we need to know what that part under the top grill is. Assuming the front grill is a speaker?

author: Fungus
author_rank: Super Contributor
timestamp: September 18, 2016, 10:37:13 am
content: Looks like a uBeam prototype to me.

author: tatus1969
author_rank: Super Contributor
timestamp: September 18, 2016, 11:06:24 am
content: 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.

author: testmode
author_rank: Regular Contributor
timestamp: September 18, 2016, 01:17:39 pm
content: 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.

author: Fungus
author_rank: Super Contributor
timestamp: September 18, 2016, 01:24:44 pm
content: Looking closely at the coil near the top I'd say it was some sort of ghost detector (evil spirits).

author: NottheDan
author_rank: Frequent Contributor
timestamp: September 18, 2016, 01:36:07 pm
content: Am I seeing that correctly? That cable to the thing up front is coax and core and shield are shorted out?

author: whitevamp
author_rank: Regular Contributor
timestamp: September 18, 2016, 02:27:01 pm
content: Quote from: alsetalokin4017 on September 18, 2016, 08:34:50 amupdated first post.

author: SeanB
author_rank: Super Contributor
timestamp: September 18, 2016, 02:49:57 pm
content: 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.

author: whitevamp
author_rank: Regular Contributor
timestamp: September 18, 2016, 02:55:03 pm
content: Quote from: SeanB on September 18, 2016, 02:49:57 pmnop no holes just soldplasticaluminum casing.

author: tatus1969
author_rank: Super Contributor
timestamp: September 18, 2016, 03:20:19 pm
content: Quote from: whitevamp on September 18, 2016, 02:55:03 pmdo 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?

author: Fungus
author_rank: Super Contributor
timestamp: September 18, 2016, 04:32:33 pm
content: Quote from: SeanB on September 18, 2016, 02:49:57 pmLike I said, it's a ghost detector. Very popular in the 1970s.

author: tatus1969
author_rank: Super Contributor
timestamp: September 18, 2016, 05:03:50 pm
content: Quote from: Fungus on September 18, 2016, 04:32:33 pmfound something veeeery similarhttp://hackedgadgets.com/2009/12/07/electromagnetic-field-detector/

author: testmode
author_rank: Regular Contributor
timestamp: September 18, 2016, 06:25:56 pm
content: 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?

author: whitevamp
author_rank: Regular Contributor
timestamp: September 18, 2016, 06:37:23 pm
content: Quote from: tatus1969 on September 18, 2016, 03:20:19 pmI wish I did.I have no scope, or lcr meter.

author: Fungus
author_rank: Super Contributor
timestamp: September 18, 2016, 07:13:41 pm
content: Quote from: testmode on September 18, 2016, 06:25:56 pmMaybe 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.

author: whitevamp
author_rank: Regular Contributor
timestamp: September 18, 2016, 07:19:21 pm
content: Quote from: testmode on September 18, 2016, 06:25:56 pmyeap 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 massahere is the data sheet for the tr-89B mines just tr-89http://www.massa.com/wp-content/uploads/2016/01/TR-89-Datasheet-151227.pdf

author: testmode
author_rank: Regular Contributor
timestamp: September 18, 2016, 07:42:45 pm
content: Quote from: Fungus on September 18, 2016, 07:13:41 pmIt wouldn't be a ghost detector for nothing, now ain't it?Quote from: whitevamp on September 18, 2016, 07:19:21 pmKidding 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.

author: StillTrying
author_rank: Super Contributor
timestamp: September 18, 2016, 09:45:16 pm
content: 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 massaI'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.

author: whitevamp
author_rank: Regular Contributor
timestamp: September 18, 2016, 10:52:03 pm
content: Quote from: StillTrying on September 18, 2016, 09:45:16 pmhere is the transducer pic... taken link from first post.

author: whitevamp
author_rank: Regular Contributor
timestamp: September 19, 2016, 03:08:33 am
content: 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.

author: Fungus
author_rank: Super Contributor
timestamp: September 19, 2016, 05:31:37 am
content: Quote from: whitevamp on September 19, 2016, 03:08:33 amThere's about $0.01 of parts there. I'd keep it as a conversation piece.PS: Does it still work?

author: Fungus
author_rank: Super Contributor
timestamp: September 19, 2016, 05:43:29 am
content: Quote from: testmode on September 18, 2016, 07:42:45 pmI originally said it as a joke.But ... the more I look at it, the more I think that's actually what it is. Theydoexist, so...

author: whitevamp
author_rank: Regular Contributor
timestamp: September 19, 2016, 05:54:02 am
content: Quote from: Fungus on September 19, 2016, 05:31:37 ampowered it on and wasnt getting any thing out but verry faint static from the speaker.and as for parting it out i was meany basically scrapping all of it but the case, and the meter.

author: Fungus
author_rank: Super Contributor
timestamp: September 19, 2016, 06:06:33 am
content: Quote from: whitevamp on September 19, 2016, 05:54:02 amThat's about right for a ghost detector. Now you have to walk around at night trying to find places where the static is louder.Quote from: whitevamp on September 19, 2016, 05:54:02 amWell...the case is full of holes and the meter is worth about $0.10.If you don't want it then try selling it on eBay. Somebody might pay good money for a genuine "1970s analog ghost detector".(bonus points for saying "tested and working" in the listing)

author: whitevamp
author_rank: Regular Contributor
timestamp: September 19, 2016, 06:19:30 am
content: Quote from: Fungus on September 19, 2016, 06:06:33 amgood one.but on a more serious note i will not sell on flebay agine, the first and only time i havesoldon there the person bought it and destroyed it, and then calmed that it was that way when they received it, and ultimately flebay sided with them and i was out a $700.00 item yes i got it back but its maybe worth 100 now.

author: tatus1969
author_rank: Super Contributor
timestamp: September 19, 2016, 06:27:34 am
content: how could that happen here again? You can only win. Even nobody will be able to prove that it is not working, ie. not detecting ghosts

author: whitevamp
author_rank: Regular Contributor
timestamp: September 19, 2016, 06:34:49 am
content: Quote from: tatus1969 on September 19, 2016, 06:27:34 amyea very true.49.95 working ghost detector.and curiosity looked on flebay and look at all the ghost detectors on there.even somebrass dousing rodserr excuse me ghost detector rods, for 15.00http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR3.TRC2.A0.H0.TRS0&_nkw=ghost++detector&_sacat=0

author: tatus1969
author_rank: Super Contributor
timestamp: September 19, 2016, 07:59:39 am
content: Quote from: whitevamp on September 19, 2016, 06:34:49 amgive it a go, and let us knowEven if it would have turns out that this one is a bat detector (I would vote for that), all it needs to do is crackling noise.

author: Fungus
author_rank: Super Contributor
timestamp: September 19, 2016, 08:16:28 am
content: Quote from: whitevamp on September 19, 2016, 06:34:49 am"942 Sold"Seriously, I'm doing thiswrong. A bigto me for not being on that bandwagon.

author: EEVblog
author_rank: Unknown
timestamp: September 19, 2016, 10:16:22 am
content: Sell it on ebay as a ghost detector.Insert phrases like "They don't make them like this any more".

author: StillTrying
author_rank: Super Contributor
timestamp: September 19, 2016, 12:44:13 pm
content: QuoteDid you try rattling some keys in front of it to produce some ultrasound, keys from a very old church might work best.

author: Brumby
author_rank: Unknown
timestamp: September 19, 2016, 03:11:04 pm
content: I wouldn't need old keys.I'd just mention to SWMBO that I'm looking at a new scope. If I want a higher energy response, I can mention a $2K budget.

author: BMack
author_rank: Regular Contributor
timestamp: September 19, 2016, 03:39:32 pm
content: Definitely a ghost bat detector from the 70s, it tells you if a bat is alive or a ghost.

author: tatus1969
author_rank: Super Contributor
timestamp: September 19, 2016, 07:21:29 pm
content: Quote from: BMack on September 19, 2016, 03:39:32 pm