Mystery Mini Analog Scope(need help identifying) - Page 1
Forum section: electronics / repair

author: inkster
author_rank: Newbie
timestamp: December 06, 2023, 04:18:20 am
content: Hey everyoneI'm trying to identify this little scope, the fluke 187 is there for size reference.I have done some repairs and got it working but I would love to learn the make and model and if possible get schematics to get it working as good as possible.Thanks

author: tunk
author_rank: Super Contributor
timestamp: December 06, 2023, 11:21:57 am
content: Photos of the inside could possibly help?

author: Zenith
author_rank: Frequent Contributor
timestamp: December 06, 2023, 01:11:48 pm
content: Nothing I recognise. Years ago there were a few crude little scopes like that as part of a course on electronics, or used by a company for a specific test purpose, which would need a scope, but not a very high specification one. This may have had a graticule which has been lost, but it doesn't look like a measuring instrument.As tunk said, more photos would help.

author: GLouie
author_rank: Regular Contributor
timestamp: December 06, 2023, 06:37:27 pm
content: It looks like an old DIY kit project from a magazine, or like Zenith says, part of an electronics course. I found a couple of similar old projects on the web, but not this one. Is it tube or transistor?https://www.eeweb.com/1-inch-oscilloscope-known-as-tiny-scope/https://www.nutsvolts.com/magazine/article/build-a-one-inch-scope

author: BrokenYugo
author_rank: Super Contributor
timestamp: December 06, 2023, 06:56:03 pm
content: I'll hazard a guess it's a very basic recurrent sweep design, don't expect great linearity, bandwidth, or stability, it may not even have retrace blanking. If it will sort of lock onto a ~100kHz sine without much trouble it's probably good to go.

author: inkster
author_rank: Newbie
timestamp: December 06, 2023, 07:32:23 pm
content: Here's some more pics, this one is solid state(aside from crt of course)

author: inkster
author_rank: Newbie
timestamp: December 06, 2023, 08:09:34 pm
content: 300khz, drops off after that

author: floobydust
author_rank: Super Contributor
timestamp: December 06, 2023, 10:24:11 pm
content: The front panel font looks British but it's full of American parts.Waterman Products Co. Inc. Philadelphia did the Rayonic CRT fab and had a Pocketscope lineup as well in the 1950's. But I think they didn't make it to solid-state."Donald C. Harder Inc." custom transformer 91124 (they also made coil winding machines) San Diego.You could probably find itWorld Radio Historybut their search feature is terrible. I tried "rayonic" and got a zillion hits for rayon.edit: what is the part number on the can transistors on the CRT board?

author: fzabkar
author_rank: Super Contributor
timestamp: December 06, 2023, 11:23:54 pm
content: Can you find any date codes on the semis?

author: pickle9000
author_rank: Super Contributor
timestamp: December 07, 2023, 12:06:02 am
content: cool

author: CaptDon
author_rank: Super Contributor
timestamp: December 07, 2023, 01:57:07 pm
content: That looks like a 3WP1 flat face high sensitivity C.R.T., They are a nice tube to work with! much easier to deflect the beam with lower voltage than a 3RP1. I have a Dumont 3WP2A long persistance C.R.T. with a very sharp almost needle point trace. It looks good in a slow sweep spectrum analyzer.

author: Stray Electron
author_rank: Super Contributor
timestamp: December 07, 2023, 09:13:29 pm
content: Quote from: GLouie on December 06, 2023, 06:37:27 pmThe knobs looks like those made by General Radio. They weren't cheap and are usually found only on military electronics or other expensive electronics.

author: floobydust
author_rank: Super Contributor
timestamp: December 07, 2023, 09:42:13 pm
content: The enclosure, handle, front panel - look professional as if it was a commercial product. But... it has no manufacturer logo, model # etc. so I think it was a prototype, a one of.Solid-state was certainly a step forward and I think it would have been very expensive, too expensive in the end to use imported American scope tube and power transformers.That's why I'm wondering who made the transistors and their date codes.

author: inkster
author_rank: Newbie
timestamp: December 08, 2023, 07:22:42 pm
content: I'll dig a little deeper over the weekend and post whatever I find, there was some sort of identifying decal on the back but only the outline remains.

author: inkster
author_rank: Newbie
timestamp: December 08, 2023, 08:07:54 pm
content: Barely legible(doesn't show up in a photo) remnants of the label on the back read2501 Proto2502-10-63

author: MK14
author_rank: Super Contributor
timestamp: December 08, 2023, 08:21:33 pm
content: Looks a bit like the following, very approximately 1968 Tektronix 213 prototypes.The blue colour scheme, and handle, seem to remind me of Tektronix.Source:https://vintagetek.org/birth-of-the-miniscope-by-david-allen/Original image (first OP post), put into post, to make it easier to compare them side by side.

author: factory
author_rank: Super Contributor
timestamp: December 08, 2023, 08:23:29 pm
content: Quote from: Stray Electron on December 07, 2023, 09:13:29 pmThose are Raytheon knobs.https://www.tedss.com/DataSheets/2051/Raytheon-Knobs-MS91528-Series.pdfDavid

author: inkster
author_rank: Newbie
timestamp: December 08, 2023, 10:16:16 pm
content: Stamped on the enclosure under the motherboard is the #25004, PS PCB is marker 25100, and the other PCB is marked 25101.One of the REON pots is marked with the following code, 1K(value) and 88-15-60, the others I can't read without disassembly.The 2N2188 are marked 980 2N2188 320, the 2N2190 are marked 980 2N2190 310.I can read a couple ELPAC caps, one reads 1.0/100v VX1E105 263, another reads .18/200v 2X2A184K 1162.At some point I'll pull the CRT.The scope works pretty well after I recapped the lytics and replaced slightly burned resistors, the issue now is the loud whine from the voltage multiplier caps, it uses (6) .02 ceramics that originally had some sort of compound or material to dampen them which had flaked off...I used neutral cure silicon on them but it did nothing.Cheers

author: inkster
author_rank: Newbie
timestamp: December 08, 2023, 10:30:04 pm
content: I bought the scope along with a few other pieces of gear online from someone in Seattle...$100 shipped for everything, it included a nice old Dynatracer(curve or signature tracer) that I use regularly. In the photo for the tracer was the scope and I bought most of what he had.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 09, 2023, 01:01:07 am
content: My guess is something made up "in House" for a specific function.Some of those "One(or a few)-off" specials were very well made, rivalling stuff made by small manufacturers.

author: CaptDon
author_rank: Super Contributor
timestamp: December 09, 2023, 02:56:25 am
content: Could have been some sort of Tektronix prototype, Seattle isn't that far from Oregon, the home of Tek. Some of the 'proto' stuff I had a hand in developing was just to unique to destroy. It either had "Look what we did" value, or "This was my baby and made the company millions", or "This was the first one ever made". I think some of my co-workers still have the prototypes. Some were attached to a wooden display board with a commemoritive brass tag and a plexiglass enclosure for lobby showcase display and given to retirees of the team. We had some 'one off' development items on display in the training center also. I think a few of those 'walked off the property over the years'. Engineering labs I worked in always had tons of oddball stuff that people were sort of personally attached to and often 'grew legs and walked away'. More than once the 'Incredible Floor Monster' (they only come out at night) was blamed for the disappearance of prototype items (especially if they could enhance the operation of a ham radio station)

author: inkster
author_rank: Newbie
timestamp: December 09, 2023, 09:11:52 pm
content: That could explain why the tag was removed.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 10, 2023, 12:01:06 am
content: Heathkit also used the blue color at times. But I don't find any Heath that looks like it.The pics of the board look like it was a quality product.It looks like something that would be used for monitoring the quality of AM signal output on a transmitter.You don't even need any reference graticule for that. Was the guy a Ham?Just a guess.