Need help with fixing the inside Monolith III transformers in the Hi freq. path ....

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yo9frj

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Hello to the group!

I've got a pair of ML Monolith III speakers from eBay. Soon as they arrived I found out they're damaged ...

Long story short, at a first check, they were abused with power! Inside each speaker, the internal crossover transformers were damaged, together with the trafo's secondary protections made by Dale's 2k and 50k 50W power resistors installed on the heatsink.

Could manage easy to outsource both Dale's resistors, but I'm having issues in finding a replacement for the transformers, or the correct data to rebuild them in a transformer factory in EU. At a first view, transformers are 1:50 ratio, with two identical windings in serial connection.

Funny enough, one of the transformers is completely burned in, and the other one has a different resistance of one of the half opposite secondary winding (1.6 ohms against the other half of the winding at 18.6ohms).

Any advice and help with additional data about rebuilding the transformers, or a supplier for selling both transformers, would be more than welcomed!

Thanks in advance!

Adrian
 
contact Martin Logan and ask for Scott Gribble excellent person to deal with. i am sure he can help you. Good luck and enjoy your speakers once they are fixed.
 
Old thread, I know, but just in case it helps anyone, here is a good replacement for the audio step-up transformer in the Monoliths:
http://shop.plitron.com/specs/413300.pdf

These Plitrons are great. At $350/ea, not cheap, but worth it.

I'll be upgrading my Monoliths to these this fall.
 
Old thread, I know, but just in case it helps anyone, here is a good replacement for the audio step-up transformer in the Monoliths:
http://shop.plitron.com/specs/413300.pdf

These Plitrons are great. At $350/ea, not cheap, but worth it.

I'll be upgrading my Monoliths to these this fall.

Hi John, long time no speak. These Plitron transformers? correct me if I'm wrong but it says the step up ratio is 4:50 that's around 1:12. The original ones in the Monolith III's are 1:50.

Cheers George
 

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I believe that's a misprint on the pdf page.
The prices & specs are here: http://shop.plitron.com/search_new.asp?Action=Search&SearchTerm=1:50&Search=Search

More specs: http://www.plitron.com/standard-toroidal-transformers/electrostatic-speaker-step-up-transformers/

Another common problem with the Monolith-III speakers is that internal binding post tips can break off under the PC board and the solder connections will break loose just below those resistors. If this occurs you can just swap them around with the woofer terminals or order some new binding post from ML.
 

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Old thread, I know, but just in case it helps anyone, here is a good replacement for the audio step-up transformer in the Monoliths:
http://shop.plitron.com/specs/413300.pdf

These Plitrons are great. At $350/ea, not cheap, but worth it.

I'll be upgrading my Monoliths to these this fall.
I like the idea of using a toroidal coil step-up transformer because they are a more efficent design than conventional transformers but the Plitron's output is only rated at 80-watts and there are only three small 22-guage wires for the panels. I'm not certain of the wattage ratting used for the Monolith-III transformers but they have much thicker gauge wire size with a six wire output bridged at the PC board into three sections going to the panels. Maybe you could use more than one transformer in each speaker to increase the wattage rating but that might get real expensive.

I'm just curious but what's the cost of the stock Monolith-III step-up transformer and the power rating? Also what's purpose of that 50W Dale 50K-ohm 1% resistor wired across the stators and the 2K-ohm 1% resistor wired in line with the ESL diaphragm? Are those used for arcing protection within the panel to safeguard the amplifier?

Also would it hurt anything on the Monolith-IIIs speakers to increase the turns ratio slightly because the JRM brand M299B 1:100 step-up transformers have a 6-dB increase in output over the standard M99B 1:50 ratio model and the M399B 1:125 ratio step-up transformers have a 9-dB increase in output for their ESL panels? http://www.justrealmusic.com/content/transformers.htm According to this page and the Plitron specs the transformers with a higher turns ratio have a better lower frequency crossover response with a slight reduction in the higher frequency maximum bandwidth.

Turns ratio effect on frequency bandwidth:

Plitron 1:50 = 1Hz to 26KHz
Plitron 1:75 = 0.5Hz to 23KHz

JRM 1:50 = 225Hz to 20KHz
JRM 1:100 = 150Hz to 20KHz
JRM 1:125 = 75Hz to 20KHz
JRM 1:200 = 6KHz Max
 
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Old thread, I know, but just in case it helps anyone, here is a good replacement for the audio step-up transformer in the Monoliths:
http://shop.plitron.com/specs/413300.pdf

These Plitrons are great. At $350/ea, not cheap, but worth it.

I'll be upgrading my Monoliths to these this fall.

I like the idea of using a toroidal coil step-up transformer because they are a more efficent design than conventional transformers but the Plitron's output is only rated at 80-watts and there are only three small 22-guage wires for the panels. I'm not certain of the wattage ratting used for the Monolith-III transformers but they have much thicker gauge wire size with a six wire output bridged at the PC board into three sections going to the panels. Maybe you could use more than one transformer in each speaker to increase the wattage rating but that might get real expensive.

I'm just curious but what's the cost of the stock Monolith-III step-up transformer and the power rating? Also what's purpose of that 50W Dale 50K-ohm 1% resistor wired across the stators and the 2K-ohm 1% resistor wired in line with the ESL diaphragm? Are those used for arcing protection within the panel to safeguard the amplifier?

Also would it hurt anything on the Monolith-IIIs speakers to increase the turns ratio slightly because the JRM brand M299B 1:100 step-up transformers have a 6-dB increase in output over the standard M99B 1:50 ratio model and the M399B 1:125 ratio step-up transformers have a 9-dB increase in output for their ESL panels? http://www.justrealmusic.com/content/transformers.htm According to this page and the Plitron specs the transformers with a higher turns ratio have a better lower frequency crossover response with a slight reduction in the higher frequency maximum bandwidth.

Turns ratio effect on frequency bandwidth:

Plitron 1:50 = 1Hz to 26KHz
Plitron 1:75 = 0.5Hz to 23KHz

JRM 1:50 = 225Hz to 20KHz
JRM 1:100 = 150Hz to 20KHz
JRM 1:125 = 75Hz to 20KHz
JRM 1:200 = 6KHz Max



I know this is off subject, but have you Jon or you Zero ever tried a beam splitter behind the curved Monolith pannel amde out of some thin stiff material to disperse the rear beaming?

Cheers George
 

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I know this is off subject, but have you Jon or you Zero ever tried a beam splitter behind the curved Monolith pannel amde out of some thin stiff material to disperse the rear beaming?

Cheers George
They work well if you need to place your speakers closer to the rear wall but you will need at least three feet or more from the room side walls or there will be a nasty early reflection. http://www.avsforum.com/t/1486626/diy-hybrid-electrostats

Old thread, I know, but just in case it helps anyone, here is a good replacement for the audio step-up transformer in the Monoliths:
http://shop.plitron.com/specs/413300.pdf

These Plitrons are great. At $350/ea, not cheap, but worth it.

I'll be upgrading my Monoliths to these this fall.

Here is some more info & specs on the Plitron toroidal coils and the purpose of the 50W resistors after the transformer. It appears as if the 50W 50K-ohm resistor is for secondary magnetic inductance and the 50W 2K-ohm resistor is for secondary leakage inductance. If you install the toroidal type transformers you may want to jump or lower the value of the 2K-ohm resistor because the toroid transformers have less leakage flux and therefore they have significantly less leakage inductance. http://home.kpn.nl/verwa255/esl/ESL_English_2011.pdf
 

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