hi there
I have repaired another lambda owe to your kindness and to the fact that you told me what product to use to make the mylar conductive.
first, the driver will seem ugly and dirty to you ( and they are) it is due to the fact that I have been working on these ones again and again and they were close to the trash, as I could never succeed in mending them. but now they work very fine !
Georg, by the way, I nearly repaired the one with the broken stator I told you about, but I still have bad contacts sometimes, that give imabalance from time to time, and the imbalance goes away depending on the hand pressure I put on the recomposed driver, so I am wondering wether, on some stax, the imabalance could come from a ill position of the elements of the driver, and not only because of the membrane to be changed
so the parts of the driver you will see are ugly, because each time I finished a repair operation, I had to glue the whole with glue that melts with heat( don’t know the english word, then, as I probably will have to use it quite a few times in the explaination, I will call it hot glue. sorry, but I am still french and not on my way to become english nor american before a few decades) please correct me when you read. I insist on the fact that my other mendings are cleaner than what you will see.
my hands are dirty too, lol, because I am in a wide repairing moment, and one of my printers (I am a writer and I print my books myself), had a big issue. so I have black ink on my hands.(yes, the printer is repaired too, after a three days fierce struggle against the machine)
what I will show here is what I do, I offer no guarantee that you will be able to have the same result (seven lambdas repaired now out of eight I own) but I think it will have good results on many old lambdas that don’t work anymore, and it would be too bad to leave them in a box if you have some. In my opinion, as a sound engineer and french dubber for movies, they are the best headphones ever for monitoring. and a big pleasure to listen to.
well first, I will show how to replace the protective membrane. This is most of the time the only issue of a lambda, and the point is that when we use it a long time, the warmth of our head makes condensation, humidity, this humidity is not stopped by the membrane, which has holes, and makes short circuits that give the static noises about which many stax user are talking about. the statics can apparently also be given by dust. But I repaired the stax in a non dust-free room, and I had no static issue after mending, only for my last lambda, but I think it is coming from a bad contact.
if you want to be sure you have this very problem of the protective membrane, try your stax, use it long enough for it to sound static problems. Then, stop using it. If, the following day, at the moment when you put the headphones on your head, you have no static noises, it means that the humidity has gone, and then, no static problem. If you still have static problèmes, then, there maybe dust on the central (sounding ) membrane, or if you have an imbalance, you probably have dust on it, or a problem with it.
But for the time being, let’s talk about the protective membrane, that I will call the PM. ( and MM for the main membrane, the one that makes the sound)
To change your protective membrane is very possible if you are patient, attentive, and take care not to brake the copper pieces of the stator that are used to solder the wires. they are very fragile, don’t move them nor change their position.
first, you have to remove the cans, which is very easy, gently removing its attaches on the sides. Take a photo of your lambda before you dissassemble it, because there are possibilities to mix things when reassembling it, things must be put back in a certain way.
unplug your stax form the amp. and be very careful, there are 540 volts in there, said to be tethal. I advise to wear plastic gloves
No need to remove the pads, you have four screws on the corners here
then, to remove the parts that hold the driver, push on the part where you can see I do, This will make the part pop out, don't be too strong, but it needs to be firm anyway.
notice the position of the wires that you will unsolder and solder after the mending
the wire with a continus white stripe is the +, the center is very probably the 540 volts wire,
le last one on the left is the -.
Once unsoldered, maitain with a bit of tape the stopper next to the wires, or it can fall down somwhere, and you can make mistakes while reassembling
remove the driver from the parts on which it is glued. Insist, it will come.
the PM is this membrane which was on the side of your ear when you listened to the headphones. The MM cannot be seen at that time, so you cannot make a mistake.
the PM is held by a very thin metal ring, maybe a tenth of a millimeter, use a cutter to remove it, and you don't have to keep it or reuse it, it doesn't affect the sound.
here are two of these rings :
when you have removed it, the damaged PM came with it.
you have to remove, then, the ticker plastic ring that was just stick to the thin ring. still with the cutter.
on the picture, it is on the left. You must leave the driver intact, meaning the black-cooper-copper-black rings on the right. the left ring is just there to hold the PM.
Then, you will need new mylar. The best I found wis used in houses, on furniture, when one leaves for a long while. It is supposed to last, then. And even if I can't be sure of it, because my oldest repairs are only six month old ( The mylar is still perfect now)
I think it is a good product to use for that. it must be very thin, mine is 7 microns. but probably thinner could work,as originally, stax uses thinner. But when I listen to my repaired stax, if I compare the sound from an original driver to a repaired one, I cannot hear any différence.
and (maybe i am repeating myslef, hope not ?) I have very good ears.rather special. When I was at the information days of the army, long ago, they were very surprised, and told me that in a case of war, I would have worked in a submarine, listenig to every sound
I could then hear for 5 hz to 50 000. Know, I am fifty, so It must not be the same. But I still can hear quite good, and it is important to say that, I think, when you are explianing that you are repairing your stax.
so, on the picture just up there, you can see the side of the driver. there are two copper parts in the "center", these are the stators, and you will only have to separate them with a cutter if you have to change the MM.
to change this PM, you have to find a good glue. I tried many, and even another one, that I wrote about previously on the thread, but today, I could see that it was not the best glue for the lambda membranes.
here is the roller glue I am using
http://www.hobbylobby.com/Scrapbook-Paper-Crafts/Glues-Adhesives/Runners/E-Z-Runner-Vellum-Tape/p/13855
then, you have to glue the side of the plastic ring with this roller. You can replace the mylar in the first seconds, but after, you won't be able to do it without tearing it.
cut a piece of mylar a bit larger than the ring, and take care there is no hole in it, no noticeable dust on it. put the mylar on one side, then, turn the driver, mylar-glued side next to your belly. Block it on your belly, and stretch very gently the mylar, to put the opposite side of it on the glue. Your don't need to have a very strongly strecthed mylar. if you do, it will affect the sound on certains frequencies.
here is the result. you can stretch it a bit more, gently with your thumb on the ring. make sure there is no hole, or you will have to redo it.
normally, the glued spaces are white or grey when using the good glue I gave the link to. On this picture, I used another glue which was not good enouch, and I had to redo.
cut the remaining mylar with a cutter blade
glue the result on the edges of the ring , with the roller
once glued :
put the ring back on the driver
result
using a hot glue pistol, put glue all around on the sides, the edge of the whole and make it thin with the end of the pistol
result :
glue the ring that will be stuck against its standing part
result
put it back on its standing part
use the same hot glue to glue the driver back to its standing part.
result
re solder the three wires
when putting back in the can, take care that the thinner part of the pad must be in front of the thicker part of the can
put back the stopper
remount the screws and the cans, you're done !
If you still are expermienting sound problems, then the MM very probably is the source. here is how I change it
with the cutter, seperate the two copper parts, the stators, as shown here. Sometimes it is hard, sometimes easy. take care to the blade, don't get wounded !
you only can do that after you have removed the glue wich is originally on the sides of the driver, still with the cutter.
after that, be gentle with all your moves. it is very fragile inside.
the MM will appear here, mine is terribly damaged, because as I knew exactly what and how to do, I was not very gentle. Stax makes me suffer, I have to revenge somhow !
the MM is removed and the ring cleaned. You can clean the stator if needed, with something which will not leave humidity : alcohol, for instance, or an compressed air .
glue the copper (side) , take care not to put glue on the rest of the stator. if you do, clean it with alcohol
make sure the mylar is ok
put it on one length and press to glue well
do the same on the opposite side, stretching a bit
do the same on the other sides, one by one
put a bit of the static liquid on a handkerchief, and put the product on the mylar (one side is enough). don't spread the liquide on the whole mylar, only on the effective part of it (not on the sides, you can leave half a cm without product on the sides. if you put it on the whole, it will not work as well as partly.
glue the side of the ring with the roller. no glue on the rest of the mylar is much better !!!
stick it back. Don't wait too long to do this. Glue the other side of the stator wich will be stuck also back
then, glue the edges of the reassembled stator with the hot glue, and follow the same explainations as for the PM for the rest.
You're done !
. The heater supplies are four separate 12v switched mode power supplies. The four tubes are each supplied with it's own supply, where the heaters on each tube are powered in series at 12v and commoned on each cathode. With the potential difference between the ECC83 cathode and 5965 cathode being at about 283v it is far too big to use one heater supply per channel unless it is floating, which is something I don't like doing. The SMPS's on the heaters eliminate mains hum.
