I have serviced few pairs of 300 on electronic. he best thing is to remove all the power board with trafos.
Then clean all things and change all the parts, diodes, cap and resistors.
It is take time but not complicated.
Check with the tester the Resistance of each winding of the trafo and must be same for both channels.
The diode can be UF4007 as improvement and the little can be Wima that you can buy from Digikey, Farnell
the resistors placed on the chassis outside the power supply area are almost all burned. They are two pairs of 5 for each speaker and only one group of 5 have continuity and a value of 136.7.
These resistors are not for the power supply but for the filtering/segmentation. The power supply is on the membrane, not on the stators.
The element is divided in three segments, one is the center 8 wires and the other two both sections left and right of the center section. The outer segments are wired in parallel. The center segment is connected directly to the audio transformers and emits the full audio spectrum. The outher ones are connected via the resistors. They form a low pass filter together with the capacitance of the ESL element, so the outer sections only radiate lower frequencies. This is to improve horizontal dispersion and to even out the frequency response. It also reduces the load on the amplifier.
With the resistors open, only the middle section will still work severely limiting output. Replace them and see what that brings.
Since the audio transformers output well over 5kV and standard resistors struggle above 200-300 V and will become non-lineair there, best is to use special resistors rated for high voltage. I know Vishay and Dale produce them, rated for several kV. But just for initial testing, you're fine with just putting some some standard stuff in there. Nothing will blow up.
I wonder what killed them. Moisture? It's almost impossble to kill them by overdriving.
The element is divided in three segments, one is the center 8 wires and the other two both sections left and right of the center section. The outer segments are wired in parallel. The center segment is connected directly to the audio transformers and emits the full audio spectrum. The outher ones are connected via the resistors. They form a low pass filter together with the capacitance of the ESL element, so the outer sections only radiate lower frequencies. This is to improve horizontal dispersion and to even out the frequency response. It also reduces the load on the amplifier.
With the resistors open, only the middle section will still work severely limiting output. Replace them and see what that brings.
Since the audio transformers output well over 5kV and standard resistors struggle above 200-300 V and will become non-lineair there, best is to use special resistors rated for high voltage. I know Vishay and Dale produce them, rated for several kV. But just for initial testing, you're fine with just putting some some standard stuff in there. Nothing will blow up.
I wonder what killed them. Moisture? It's almost impossble to kill them by overdriving.
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it's very strange indeed. now I have defined the left and right speaker, the left has the two pairs/rows of 5 burned, the right only one row of 5. I also performed the measurement of the points that you indicated on the board - the left 1.005 and 1.008 - the right 1.001 and 0.996
Some differences at the transformer secundaries. At least they are not open, but this could indicate shorted windings, let's hope for the best. If you have the equipment, you could disconnect the esl, feed a very small (!) 1kHz signal to the interface and exactly measure the current draw. However if something is wrong you'll find out very soon anyway once you start using them.
For now I would replace all 47k resistors with whatever you can source and see what that brings.
For now I would replace all 47k resistors with whatever you can source and see what that brings.
Color code looks like yellow-purple-orange-gold, that is 47k with 5% tolerance. Makes sense, other models use 4 or 5 resistors of 27k-47k. Depends on the segmentation and the panel size.
Given their size, they will be rated for 1 or 2 Watt so order 2 Watt.
Given their size, they will be rated for 1 or 2 Watt so order 2 Watt.
ok, updating the values.
after separating and measuring them, the value of each is 26.8 each - only one is burned and therefore the reason that there was no continuity of all placed in line. probably that the others also have only one faulty.
after separating and measuring them, the value of each is 26.8 each - only one is burned and therefore the reason that there was no continuity of all placed in line. probably that the others also have only one faulty.
I looked once again, could it be red-purple-orange-gold instead? That would be 27k. Makes more sense with the measurements too.
For a test you could just bypass the bad ones, so use only 4 per section. Saves you the trouble of ordering.
Yes, they will be fine I think.
Another good choice is Vishay VR68 series. These are special high voltage resistors, rated for 10kV and 1 Watt.
Another good choice is Vishay VR68 series. These are special high voltage resistors, rated for 10kV and 1 Watt.
today, i'm going to unplug all the resistors, separate them and measure them - just to see how many are burned/broken, then i'll take the 10 good ones and assemble at least one of the two ES and do an audio test. if it works, tomorrow everyone to mass to pray.
It's perfectly ok to use only 3 or 4 resistors for a test. It's not very critical and chances are you will never notice the difference. Just use the same number on all 4 locations. That allows you to test both speakers and compare them in sensitivity and sound, which is very usefull for further diagnosis.
of the 20 resistors, only 14 are good. I resoldered two sets of 5 and turned on only one ES300
wow! after only 10 minutes of charging it was immediately clear that they worked.
after 1 hour, fantastic!
in the afternoon/evening I order all the resistors present, including those on the board and the large yellow capacitors.
wow! after only 10 minutes of charging it was immediately clear that they worked.
after 1 hour, fantastic!
in the afternoon/evening I order all the resistors present, including those on the board and the large yellow capacitors.
Happy outcome and incredible that the coating is still working after almost 30 years. Enjoy! It's worth experimenting with placement.
If you find the bass a bit resonant, consider adding an (open baffle) sub. That will take them to a whole new level. Next project 😉
If you find the bass a bit resonant, consider adding an (open baffle) sub. That will take them to a whole new level. Next project 😉