Vintage Mystery Equipment Random Ebay Score: <10€ Mini Teardown/look-inside - Page 1
Forum section: electronics / testgear

author: schwarz-brot
author_rank: Regular Contributor
timestamp: January 31, 2014, 11:54:12 am
content: Quote from: retiredcaps on January 22, 2014, 11:18:11 pmretiredcaps, I heard your call and found something the other day. Sold as non-working / untested for the seller being unable to figure out the function. Scored it for 3,50€, makes not even 10 bucks delivered. Looks ugly but I wanted the switches and hoped for some random equipment and maybe a large transformer, therefore it was a nobrainer. Since the function was unknown I did not know what was coming. First I give you the pictures of the outside, maybe you could have figure out what it is good for before buying?Pic 1: Overview frontPic 2: The front panel with the worn out printPic 3: On-Off-Switch on the back, not doing anything when turned on.Pic 4: The bottom sports just a diagram. I guess because the print was gone with time.Pic 5: Diagram in Detail

author: Fraser
author_rank: Super Contributor
timestamp: January 31, 2014, 12:06:06 pm
content: That looks like a loudspeaker impedance simulator for testing an AF Power amplifier. Carious loads may be brought into play by a combination of switch positions and links. Te BNC outputs are likely used to monitor teh test waveform using a oscilloscope.You will likely find some hefty resistors inside the unitbut a transformer is unlikely. If you look at the front panel with a magnifying glass you may be able to read the remnants of the lettering and impedance tables.Edit: I see that the unit is not passive as it has a power cable. It will likely have a small transforrmer but what it is powering is a mystery to me. The L ad R phono sockets on the front panel also have me puzzled. Could it be that it has a built in AF signal generator to drive the Power Amplifier that is under load test ? That would be pretty cool if a its a quality low noise source.

author: schwarz-brot
author_rank: Regular Contributor
timestamp: January 31, 2014, 12:38:56 pm
content: Wow, that was fast.You are exactly right, this is what I figured out, too. But I had to lift the hoodPic 6: Printing on the front reconstructed. Left section is doubled on the right sideI was able to reconstruct the printing on the frontplate. Picture 6 shows what I scribbled down. Only shows the left and middle section. The right side is exactly the same as the left. In combination with picture 5 from my last post this made sense. Now it is obvious what to expect inside.Pic 7: Overview of the insidePicture 7 gives an overview of the inside. Not much to see but air and very few but beefy parts.Pic 8: Large FanPic 9: beefy resistorsPic 10: Detail of one of the huge rotary switches.The beefy parts are mainly eight high power resistors (4Ohm/50W, Picture 9) and a large fan running straight on 230V (Picture. Last but not least there are those wonderful rotary switches with their two layers (Picture 10).This puppy is a complete independent two-channel setup, configurable for 1/2/4/8/16 Ohms. On any channel there are at least two resistors to be used, giving at least 100W per channel. Plenty for testing standard livingroom audio stuff, I think. The yellow jacks on the front are not connected, they are simply for storing the jumpers. The RCA and BNC jacks are for measuring, the springloaded terminals on the bottom are the inputs.Even if powered up the fan won't turn: it only starts when the resistors heat up to a certain level - then a bimetal-switch would close the contact and start the fan.Vintage is true by the way: The fan sports a 4-digit postal code which was used only until the early nineties in germany.Well, I wanted to kill this thing and rip out the parts. But I think I won't do. It is possible this is an original piece of measuring equipment from DUAL which was a famous German HiFi manufacturer back in the days, especially well known for their turntables but also any other hifi related gear. Coincidentally I specialized on repairing those turntables as a hobby. I did not know this was possibly Dual gear but sometimes you've got to be lucky.This thing may also come in handy when servicing HiFi-gear. So I think for that price it was a real score. But for you I think it was not too interesting. Sorry guys!

author: Fraser
author_rank: Super Contributor
timestamp: January 31, 2014, 01:15:37 pm
content: So the 240V was only to power a fan. Oh well, it is pity you did not get a signal source included.....but that is a very well built unit that must have been expensive to buy. The fact that it has individual bi-metallic thermal switches to monitor the resistors and control the fan is a sign of quality in such a device.If you work with audio amplifiers that would be a very useful bit of kit.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: January 31, 2014, 08:21:35 pm
content: Those power resistors are fancy!!! Heat sink fins and probably precision as well!Very nicely built and laid out.What makes you think it might be Dual? I have a couple of Dual turntables myself and like them alot! A 909 and a 1219.

author: Macbeth
author_rank: Super Contributor
timestamp: January 31, 2014, 09:37:58 pm
content: Quote from: Aurora on January 31, 2014, 01:15:37 pmYou have to be kidding me? I can't see any gold plated silver wire 99% OFC Monster(c)(tm) cables in that shitbox? How on earth can it be quality? I don't even see any crystals placed on top or those pieces of fancy tape with "holograms" on them either.

author: david77
author_rank: Frequent Contributor
timestamp: January 31, 2014, 09:57:53 pm
content: Nice score! Yes, what makes you think it might come from Dual? I agree it looks too well built for your typical home brew hack job. Just one thing I don't like at all is that they didn't earth the case. I'd replace the Euro plug lead with a Schuko lead, redo the outside with new lettering and thoroughly clean the thing.Btw. I've also got a 1219, beautiful player.

author: retiredcaps
author_rank: Super Contributor
timestamp: January 31, 2014, 11:12:43 pm
content: Quote from: schwarz-brot on January 31, 2014, 11:54:12 amGood find and great pictures again. Remember one person's junk is another person's treasure especially if you can buy it for cheap.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: February 01, 2014, 12:08:15 am
content: Quote from: Macbeth on January 31, 2014, 09:37:58 pmpicky, picky, picky!!!

author: TerraHertz
author_rank: Super Contributor
timestamp: February 01, 2014, 09:13:37 am
content: That box reminds me of a lucky acquisition of mine recently. A friend let me know a friend of his was about to toss out a "Big heavy 240V to 110V converter, did I want it?" Of course!I'd expected just a transformer, but no.... When I opened it up it was a nice surprise.It's a 'regulated' 240V to 110V converter, 2KW capacity.How does it regulate?A: By motor-driving a big variac, with a control circuit adjusting the tap position to give the set output voltage regardless of loading.

author: schwarz-brot
author_rank: Regular Contributor
timestamp: February 01, 2014, 10:31:11 am
content: Quote from: Macbeth on January 31, 2014, 09:37:58 pmSorry, Macbeth. No Voodoo stuff neither in my hifi gear nor in my measuring equipment. Only into turntables and vinyl because I love those laaaaarge covers and the whole look and feel of this medium. Not because it may sound betterAnd maybe because I am a vintage freak for unknown reasons. Can't help it.pomonabill221, david77:I realized the other day the very same seller had several other measurement devices which were actually labeled with the late Dual logo. I did not know about any equipment other than audio gear made by Dual and posted a question about this on thegerman dual forum. There I learned the dual measuring equipment was actually built by an own department called "Dual Vorrichtungsbau" ("Appliance manufacturing department").So by now I know the same seller offers more audio related stuff that all came from the original Dual factory in St. Georgen. I tried to contact him to confirm this but have no answer yet.There are some more hints. The professional quality of course is obvious, especially the thermally controlled fan is a sign of professional gear and the modular construction is, too. I did not point that out in my earlier posts. The Resistornetworks and fan sit on an own folded piece of sheet metal that also takes the fan. It can be unscrewed from the bottom of the case and taken out as a hole piece. The Resistornetworks are easily to be removed per channel, no wires would come in the way. Even the wiring of the bi-metallic switches is routed underneath the construction and could not come in the way. So this is also constructed for easy servicing and repair. The very long hex-rods that give the case its stability are very professional, too.Next hint is the fan. It is made by Papst, which were based in St. Georgen, too. Dual and Papst is a very close relationship as Hermann Papst started as engineer for Georg Steidingers Dual. He eventually left Dual to start his own business back in 1937. But as far as I know nearly every motor in Dual equipment is made by Papst, it is just labeled Dual. Papst is now EBM-Papst, of course, and still well known. Of course it may be coincidence there is built in a Papst fan and of course it may be coincidence the same seller has to offer more (and only) audio related measuring equipment made by Dual.Only his answer can clarify this. Until then I cannot say for sure my device was made or at least used within the Dual factories.Quote from: david77 on January 31, 2014, 09:57:53 pmI too found the missing earthconnection a bit strange, to say the least. First thing that came to my mind was they possibly double insulated every mains related voltage. But this is obviously not the case. So yes, I think I am going to earth the case if I am going to use it with the fan attached.Interesting to see you all recognize Dual all over the world. Did not know they were that well known overseas. And very interesting you all like the turntables with idler wheel drive! So do I - my most loved one is the 1229 which I got as my very first turntable passed down from my father who thought for unknown reasons his belt-driven plastic box could be any betterI specialized a bit in repairing those idler wheel driven devices as I love the all-mechanical construction and the gorgeous built quality. They look a bit oldschool but somehow are kind of a definition for that famous "german quality". I think it is especially overengineered consumer goods like these turntables or other consumer goods from different companies that gave this reputation. Too bad it is nearly lost nowadays

author: Co6aka
author_rank: Unknown
timestamp: February 01, 2014, 03:42:41 pm
content: Quote from: schwarz-brot on February 01, 2014, 10:31:11 amWell, FWIW, even I had a Dual 1219 turntable...(Yes, even canines own turntables!) Sold it to a friend a couple of years back, so it's still in a good home.(Gotta have a good turntable to play the classic Berliner-schule elektronische!Ja!)

author: david77
author_rank: Frequent Contributor
timestamp: February 02, 2014, 01:25:52 am
content: Quote from: schwarz-brot on February 01, 2014, 10:31:11 amSorry, a bit OT:My feelings exactly. I used a JVC plastic box for years, wich was not a bad player by any means. But then one sunday I found this 1219 in near mint condition at a local flea market. I bought it out of an impulse because I used to have one when I was a kid. I immediately fell in love with it again - no crappy plastic, only solid metal.I built a new enclosure for it and went a bit OTT with the RIAA amp. I decided the tiny signal of the pick up coils shouldn't have to travel so far to get amplified, so the RIAA stage is now inside the case of the player. I also decided I wanted something really nice, not just your standard RIAA. So I built up the preamp section used in the EMT 938 studio decks, using better opamps, though. Not the crappy 741. Now the thing's got balanced and unbalanced line outputs conforming to german broadcast standards. Yeah, talk about over engineered...I can hear the hum and noise of the studio equipment where the records were produced. Not sure if that's desireable, though.

author: G7PSK
author_rank: Super Contributor
timestamp: February 02, 2014, 10:41:24 am
content: That voltage controller/ stabiliser/ inverter thing reminded me of a unit I had from a cinema in the late 70's much bigger than that one, weighed several hundred kilos, I think it was used for the house lights and dated from the 40's or 50's inside was a huge auto transformer and a motor to turn it, there was a couple of meters on it and a large dial to alter the output voltage, the motor was driven by valves/tubes so there was electronic stabilisation for the output. As I had no use for it at the time I sold it on.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: February 10, 2014, 12:54:06 am
content: Thank you schwarz-brot for the excellent history of Dual and Pabst!I have several Pabst fans and when I worked at Hughes Aircraft, they used them also.Interesting that Pabst and Dual are (were) so closely related!Gotta love that vintage vinyl equipment!