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Old 19th April 2005, 08:10 PM   #1
gothika is offline gothika  United States
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Default Janszen electrstat questions

I've got a apair of the old Janszen speakers with the electrostatic tweeters.
The 5 inch square flat panels in a quad array with the 12 inch woofers.
I've stripped all the components out of the boxes as they're pretty much trash and want to use the electrostats in another speaker project I'm working on.
Problem is one of the panels was cracked a bit on one edge.( the original owner tried prying them out.)
I removed the panels and the cracked one did flex back and seems ok, though if it works will remain to be seen.
All are grimey from long term storage and need to be dissasembled and cleaned.
Does anyone here have any working knowledge of how to take these things apart or how to do any service checks on them?
Any info or links to any sites on repair of Janszen electrostats would be greatly appreciated.
thanks in advance.
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Old 19th April 2005, 08:47 PM   #2
JohnL is offline JohnL  United States
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I knew I remembered seeing some info on audioasylum. This link is a bit old, but worth a try. BTW, RTR and Jantzen are pretty much the same thing.

http://db.audioasylum.com/cgi/m.mpl?...eakers&n=34334
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Old 19th April 2005, 11:38 PM   #3
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If these are like the RTR units I have, they are not serviceable. The RTR ones are glued or plasti-welded together. Have you checked out the p/s and step-up transformers?
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Old 20th April 2005, 07:28 AM   #4
gothika is offline gothika  United States
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The power supply and transformer should be ok. The speakers were some I sold to a customer through one of my hifi shops way back when.
He'd used them for a week or so and wasn't happy with the bass response so brought them back for a swap up.
The veneer had a big scratch so I just had them warehoused all this time.(along with a ton of other hifi gear that I've held onto over the years.)
As for breakdown. They should come apart. I took a closer look at the panels, peeled off some of the mylar chrome laminate cover strips and saw it had three brass rivets along the bottom holding it together along with the three machine screws/contact lugs at the top.
There might be some glue or sealant along the facing seams but that should not be a problem. I'll pry very carefully and use a solvent sparingly to loosen up the halves after drilling out the rivets and unbolting them at the top.
I'd really like to see a exploded diagrahm if anyone has one of these on these units.
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Old 23rd April 2005, 04:31 PM   #5
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Suggest you might post a picture of the unit(s).

The Janzen cells (square, black) are not going to be serviceable.
They are solvent glued and are a molded piece that has "sawtooth" molded in to accept the stator wires... tough to get apart, and tough to get to go back together.

I have tried.

Once apart the sawtooth pattern will likely not fit back again, so the distances between the diaphragm and the stators can't be recreated.

For a blow up view and all the technical details, JAES Audio Anthology Vol I has the full original Janzen article from the JAES journal. A well stocked library will have issues of the JAES from the 50s as well...

IF only one or two of the cells are bad, then you might consider a reconfiguration of the remaining cells and incorporate them into a new speaker design.

The JanZen cells do best when X'd over higher rather than lower... which is sometimes problematic. They have limited capabilities for output and distortion as they get lower in freq... 1.5kHz. being pretty low for them...

The diaphragms are graphite rubbed. The failure point is *often* but not always from the center most brass screw that contacts the diaphragm. This can be tested by taking a standard pin, held in an alligator clip, sharp side held, crown side down, and inserted between the stator wires on the side that has the graphite layer... if the contact is bad then the speaker will play when energized with signal and by applying the B+ via the pin...

Some seem to be fixable by getting some graphite into the hole with the screw head (nut losened) and sometimes on the diaphragm closest to the screw, trying to get some to flow down the sawtooth area to the screw... blow out the excess subsequently.

These "fixes" do not always work or result in entirely satisfactory or long lasting operation.

Taking them apart makes for situation where they really do not fit back together, as far as I can see.

BTW, the diaphragm is internally clamped only in one axis, so effectively there are vertical strips side by side corresponding to the width of the squares in the plastic grid.


_-_-bear

PS. the cracked cell could be repaired with judicious use of solvent glue, making sure it does not run to the diaprhagm...

the only thing you need for any ESL to work is B+ here it is probably between 700v and 1500 vdc MAX, usually they were adjustable with a "level" or "sensitivity" control on the back (a pot in series with the B+ transformer) and + & - signal swing via a step up transformer that is usually fed via a simple cap as an xover... you can run a single cell at a time with no problem for testing.
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http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- [...2SJ74 Toshiba bogus asian parts - beware! ]
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