МТХ-90~MTH-90 Keypad from eBay - What is it and how do I hook it up?
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Mac Doktor
Apr 1, 2021, 5:15:47 PM4/1/21
to neonixie-l
Recently these interesting little gadgets turned up on eBay (the following are all seller photos):
I bought two of the above. After some haggling, shipping, and tax it added up to just under $33.
It pays to look at all of the listings. The colors and numbers on the panel vary, and some don't have the cool red lenses. And some prices have already gone up. If you add them to your watchlist you may get an offer.
Starting with the seller I purchased mine from:
On to the fun part. It contains five MTH-90s. The metal "keys" don't move. They're touch-sensitive. They appear to be connected to the gates on the thyratrons through capacitors (see further down). Here are some interior shots:
The capacitors (or whatever) are about the size of the old 5% 1/4W carbon film resistors I bought at Radio Shack in the '80s, perhaps a little longer and thinner. There are two "dot and cosine wave" markings, one rotated 180°:
Unpolarized capacitors?? They're also marked "М22" and "ИВ9" (IV9). I couldn't find decent picture so you'll have to take my word for it.
In the photos from another listing the only thing visible (thanks to Photoshop) on three of them is this:
It appears to be "8", "K" inside a "C" or semi-circle, and "O" or zero.
OK gang, what were these things used for and how do I hook them up? I know there's 220V AC involved somewhere. I already have the data-sheet for the MTH-90s. I'm hoping that someone else has already figured out the rest for me. 8D
Terry Bowman, KA4HJH
"The Mac Doctor"
Q: Should car stereo speakers be pointed to the rear for more thrust or up for more traction?
A. On long trips, the 20- to 30% improvement in gas mileage you might get with speakers pointing to the rear is certainly worthwhile. On the other hand, if you drive on snow or ice, the extra traction of speakers pointing upward gives you added control.
"The Mac Doctor"
Q: Should car stereo speakers be pointed to the rear for more thrust or up for more traction?
A. On long trips, the 20- to 30% improvement in gas mileage you might get with speakers pointing to the rear is certainly worthwhile. On the other hand, if you drive on snow or ice, the extra traction of speakers pointing upward gives you added control.
Don Lancaster
Yohan Park
Apr 1, 2021, 7:53:29 PM4/1/21
to neonixie-l
Great timing :D
Just ordered 10 of these for $47 including shipping and all (seller agreed to put a low value on the package) after a bit of haggling.
Yours look cleaner but mine don't have the orange filters in front of the tubes which I prefer because you see the real neon orange.
I was wondering how to hook it up and what it was initially being used for too.
Funny how things can suddenly pop up after all these years. I guess they were seen as useless until someone discovered there was neon inside...
Just ordered 10 of these for $47 including shipping and all (seller agreed to put a low value on the package) after a bit of haggling.
Yours look cleaner but mine don't have the orange filters in front of the tubes which I prefer because you see the real neon orange.
I was wondering how to hook it up and what it was initially being used for too.
Funny how things can suddenly pop up after all these years. I guess they were seen as useless until someone discovered there was neon inside...
Keith Moore
Apr 16, 2021, 1:36:40 PM4/16/21
to neonixie-l
Did you get any more information on these?
Mac Doktor
Apr 16, 2021, 2:48:38 PM4/16/21
to neonixie-l
On Apr 16, 2021, at 1:36 PM, Keith Moore <nixie...@gmail.com> wrote:Did you get any more information on these?
I'm all ears as well.
This seller just put up three BIN listings. They appear to be identical (you may have to scroll down the page):
I wish now that I'd bought some of the ones with yellowed plastic. The light probably shines through unlike the white ones that are opaque.
Terry Bowman, KA4HJH
"The Mac Doctor"
"The Mac Doctor"
"If only you could see what I've seen with your eyes."—Roy Batty, Blade Runner
Dekatron42
Apr 17, 2021, 5:49:58 AM4/17/21
to neonixie-l
I had one of these many years ago and if I remember correctly now it is a resistor of some 100k, or perhaps it was closer to 1Meg, as it just limits the current flowing in the trigger circuit. You can google these and find circuits like the ones below:
https://tubes-store.com/images/mtx90_02.jpg (I can recommend a high value resistor from 100k and up on the trigger pin so you don't touch any live parts accidentally! It will also protect a little bit if the tube shorts out)
http://www.elektronika.lt/schemos/ivairios/61/jutiklinis-jungiklis-su-mtx-90/ (this is a Doorbell, use Google Translate from Lithuanian to English)
/Martin
Yohan Park
Apr 17, 2021, 11:34:17 AM4/17/21
to neonixie-l
There's something odd with the one in this listing:
https://ebay.us/8EtaeL
Check the 5th picture (close up of the tubes from the top).
They don't look like MTH-90 since they seem to have a nipple on the top of the tube (the side facing the lenses).
Also, the bottom part (where the terminals are) is different from an MTH-90.
So this one seems to use a different type of thyratron but the question is, which one?
Check the 5th picture (close up of the tubes from the top).
They don't look like MTH-90 since they seem to have a nipple on the top of the tube (the side facing the lenses).
Also, the bottom part (where the terminals are) is different from an MTH-90.
So this one seems to use a different type of thyratron but the question is, which one?
Dekatron42
Apr 17, 2021, 2:34:46 PM4/17/21
to neonixie-l
They are the same thryratron electrically but they have a different top, some come with this evacuation pip at the front and some come with a lens at the front and the evacuation pip at the bottom where the pins exit the glass.
/Martin
Yohan Park
Apr 17, 2021, 3:21:13 PM4/17/21
to neonixie-l
Ah yes I've found them. They're less suitable to use as an indicator.
Mac Doktor
Apr 17, 2021, 8:11:34 PM4/17/21
to neonixie-l
I did a quick search and these these things are for sale on Etsy and various other merchant sites I've never heard of. Similar pricing but eBay does give you something resembling a safety net.
White plastic with red lenses seems to be the norm.
On Apr 17, 2021, at 5:49 AM, Dekatron42 <martin....@gmail.com> wrote:I had one of these many years ago and if I remember correctly now it is a resistor of some 100k, or perhaps it was closer to 1Meg, as it just limits the current flowing in the trigger circuit. You can google these and find circuits like the ones below:
I finally dug a meter out and checked the component marked "M22". Sure enough it's a .22MΩ (220kΩ) resistor. It's connected directly to the touch-sensitive "key" on the front.
On Apr 17, 2021, at 3:21 PM, Yohan Park <w...@kitsunegari.net> wrote:Ah yes I've found them. They're less suitable to use as an indicator.
The tubes in the ones I purchased are identical. There's no part number and the only marking is "OTK 25". Apparently that means that quality control inspector number 25 has approved the lamp as military spec. Feel free to correct me if I'm wrong.
I still can't figure out what they were used for. Functionally they're just a box with five momentary sort-of isolated touch switches controlling a 220V RMS mains load. Cheaper than using mechanical switches?
Terry Bowman, KA4HJH
"The Mac Doctor"
"The Mac Doctor"
“...the book said something astonishing, a very big thought. The stars, it said, were suns but very far away. The Sun was a star but close up.”—Carl Sagan, "The Backbone Of Night", Cosmos, 1980
Yohan Park
Apr 17, 2021, 10:23:42 PM4/17/21
to neonixie-l
Yes, the ones I have also use an M22K (220K) resistor.
The tubes in mine aren't labeled at all but they're the more common MTH-90 tube without a nipple on top and the unit has clear lenses.
They come without any screws to attach the top cover to the lower part of the case so it seems they're meant to be screwed on to something else.
The tubes in mine aren't labeled at all but they're the more common MTH-90 tube without a nipple on top and the unit has clear lenses.
They come without any screws to attach the top cover to the lower part of the case so it seems they're meant to be screwed on to something else.
Yuriy Ovchinnikov
Apr 24, 2021, 11:01:27 AM4/24/21
to neoni...@googlegroups.com
If anyone is interested, then I have 50 pcs. MTX-90.
вс, 18 апр. 2021 г. в 05:23, Yohan Park <w...@kitsunegari.net>:
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Mac Doktor
May 8, 2021, 8:33:22 PM5/8/21
to neonixie-l
On Apr 17, 2021, at 10:23 PM, Yohan Park <w...@kitsunegari.net> wrote:Yes, the ones I have also use an M22K (220K) resistor.
The tubes in mine aren't labeled at all but they're the more common MTH-90 tube without a nipple on top and the unit has clear lenses.
They come without any screws to attach the top cover to the lower part of the case so it seems they're meant to be screwed on to something else.
I just received four more with clear lenses instead of red. The tubes have round lenses instead of nipples and are clearly marked "MTX-90" although that's difficult to see. The black plastic bases are identical. The lids are the same as the ones with red lenses although the plastic is slightly whiter. So far so good.
The big difference is the front panel. The plastic has the same whiteness as the lid but its surface is rough, not smooth, and the numerals are slightly different in shape. I suspect that it was made with a different die. There's another variant on eBay that has a gray panel and doubled numbers like this: "1(5)", "2(6)" and so on. I'm wondering if different panels were made for different applications.
If I get the chance I'll take some more pictures. I'm still wondering what their application was and how to wire one up.
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