Teardown: Mystery Soviet bit of kit (TU-100BU 4.2). - Page 1
Forum section: electronics / testgear

author: Refrigerator
author_rank: Super Contributor
timestamp: December 30, 2021, 08:14:57 pm
content: While driving past the usual e-waste bin i noticed something that looked like lab equipment and decided to pick it up.It's an old Soviet piece of equipment made in 1974 and that's about as much as i can tell because i don't speak Russian.The unit had a model number on the front panel so i decided to google it but didn't find anything at all.There's a bunch of plugs in the back and potentiometers in the front.Google translate helped a little and let me know that this thing had something to do with gain and tone, so it might be audio related.Opening it was as easy as loosening two recessed screws in each side and lifting the top and bottom, which sort of enclose the thing like a clamshell.There were two pieces of yellow fabric glued behind the vent holes in the top half of the enclosure.Inside the unit the first thing i noticed was the speaker, which confirms that this thing has to be audio related.The speaker was mounted to a piece of plywood and had some handwriting on it.There are also a bunch of cobwebs and bugs which is kind of expected from something this old.Other than the speaker there's only a single main PCB inside, which doesn't look very sophisticated.But it does have some vertical boards with two transistors each mounted upside down and suspended by their legs, which is not unusual for soviet tech.What's different is that there's a hole in the board for the transistor to poke through.Besides two transistors the vertical boards have only a few resistors and not much more.Coming out of the enclosure of the device is a pig tail with a plug on the end. This plug looks alot like the end of a vacuum tube.If i had to guess this is some kind of audio mixer that perhaps plugs into a tube socket in a tube amp?Anyways, i have no use for this thing so i salvaged the germanium transistors and kept the enclosure which will most likely be used for a lab bench power supply.The enclosure has some corrosion on it but a new lick of paint should bring it right up.PS: the "SONY" on the front is just a sticker, i doubt Sony made soviet equipmentEdit: also i just noticed that when these soviet transistors are mounted "conventionally" they look like flying saucers (last pic).

author: AVGresponding
author_rank: Super Contributor
timestamp: December 30, 2021, 08:40:28 pm
content: If you have a smartphone you can use the translate function in the Google Lens app.It looks to be some sort of home-made audio monitor, with various gain controls (the first 5 knobs), low and high tone controls (the last two), the first 3 switches are some sort of input selection/tone bypass(?) and the last switch maybe the main power?

author: Refrigerator
author_rank: Super Contributor
timestamp: December 30, 2021, 09:32:19 pm
content: Quote from: AVGresponding on December 30, 2021, 08:40:28 pmI doubt anything homemade would have a serial number of 8951 and a logo of (presumably) the factory it was made in.And i already tried the google lens thing and that's how i knew that the potentiometers had something to do with gain and tone.The rightmost switch translates as "net", which is often referred to as mains over at my side of the swamp, but there is no transformer inside so it can't be mains.I think power is derived from the pigtail but that plug looks like the end of a vacuum tube so i don't know what it would plug into.

author: AVGresponding
author_rank: Super Contributor
timestamp: December 30, 2021, 09:40:25 pm
content: Quote from: Refrigerator on December 30, 2021, 09:32:19 pmGah... and I'm one of the first to chide people for not reading the OP correctly!I wonder if it's checking for signals at a tube's pins? So it would be powered by the DUT via the tube socket...

author: Bobson
author_rank: Regular Contributor
timestamp: January 09, 2022, 01:41:39 am
content: This is definitely public address amplifier. Made in Kazakhstan.