One of my script panels quit functioning. Did the basics, switched power supplies and the panel worked fine. Narrowed it down to the power supply. Started with the 6 10k resistors on the board. A few were out of spec, so replaced them. They were not far out of spec, the worst being 11.47 and 10.67 and 10.53. New values are all within 5%. Next went to the transformer. I followed some of Bolserst's great troubleshooting advice. I was reading through his posts and his knowledge is amazing....
I measured the voltage output of the power transformer that feeds the HV multiplier. This seems high at 274 Vac, so not sure on that.
Next I measured voltage at c12. Did this with music being fed to the speaker. If I turn on the power and immediately test, it jumps to 1227 Vac and then steps down to zero. One second later it jumps back up, and steps back down. It does this for a couple mins and then holds steady at .90. Maybe I should be testing DC? I do not have a super expensive DVM, but I have always found it reliable.
The red light comes on and stays on for about 2 mins, then goes off with music being fed. Dont know if this is important.
Really love these and cannot afford $300 for a new board, so trying to DIY, but its beyond my knowledge at this point. Can anyone point me at other things to test? I would be extremely grateful. If I can isolate the bad part, I have enough skills to replace it.
Thanks for any help you can provide.
I measured the voltage output of the power transformer that feeds the HV multiplier. This seems high at 274 Vac, so not sure on that.
Next I measured voltage at c12. Did this with music being fed to the speaker. If I turn on the power and immediately test, it jumps to 1227 Vac and then steps down to zero. One second later it jumps back up, and steps back down. It does this for a couple mins and then holds steady at .90. Maybe I should be testing DC? I do not have a super expensive DVM, but I have always found it reliable.
The red light comes on and stays on for about 2 mins, then goes off with music being fed. Dont know if this is important.
Really love these and cannot afford $300 for a new board, so trying to DIY, but its beyond my knowledge at this point. Can anyone point me at other things to test? I would be extremely grateful. If I can isolate the bad part, I have enough skills to replace it.
Thanks for any help you can provide.
Had some time to do more testing. Originally, I thought it was the board, but switching them out between the 2 made no difference. Both panels are fine and verified both Bias boards are fine. It appears something in area with the crossovers. Switching cases replicates the problem. I can hear sound from the panel very, very faintly from the panel when using the bad case. There is a transformer in there with the model 486-07109 and under that 486-2000. Can anyone tell me what this does? I do not have a schematic for the Scripts, so trying to sort this out.
The Script seems to be a model where the schematic isn't around yet.
If you snap a pic of the overall board/speaker interior it would help.
From your previous descriptions, the one you're talking about is most likely the step-up transformer for the electrostatic panel. The step-up transformer converts your amp's output to the high voltages needed for the panel. This is typically something around a 1:70 ratio for midrange-and-up panels. So 10 volts from your amp would be transformed to 700 volts.
Martin Logan designs their own transformers, so the part number you're seeing is likely unique to that particular speaker model, and an internal Martin Logan number.
If you snap a pic of the overall board/speaker interior it would help.
From your previous descriptions, the one you're talking about is most likely the step-up transformer for the electrostatic panel. The step-up transformer converts your amp's output to the high voltages needed for the panel. This is typically something around a 1:70 ratio for midrange-and-up panels. So 10 volts from your amp would be transformed to 700 volts.
Martin Logan designs their own transformers, so the part number you're seeing is likely unique to that particular speaker model, and an internal Martin Logan number.
Hi ddikeht,
Sounds like you have been methodically swapping parts between working and non-working speaker to isolate the problem.
Problem is not the HV supply, panel, or step-up transformer. Not much left but the passive crossover parts.
To help people searching for information on the Martin Logan Script in the future, I'm responding in this thread rather than your other one you started to ask about the 2ohm resistor.
https://www.diyaudio.com/community/...f-possible-still-learning.381876/post-6910482
Based on the pic you posted in the other thread(attached below), I drew up the crossover schematic.
To confirm if the 2ohm resistor is your problem, just jump a wire across it. If you have an alligator clip terminated wire that would be an easy way to do it.
The 2ohm resistor really only affects things in the top octave, but just to be safe keep the volume low and play some music to see if the panel is now working.
Let us know your results.
Also, let us know what country you are from so we can better help you locate replacement parts.
Sounds like you have been methodically swapping parts between working and non-working speaker to isolate the problem.
Problem is not the HV supply, panel, or step-up transformer. Not much left but the passive crossover parts.
To help people searching for information on the Martin Logan Script in the future, I'm responding in this thread rather than your other one you started to ask about the 2ohm resistor.
https://www.diyaudio.com/community/...f-possible-still-learning.381876/post-6910482
Based on the pic you posted in the other thread(attached below), I drew up the crossover schematic.
To confirm if the 2ohm resistor is your problem, just jump a wire across it. If you have an alligator clip terminated wire that would be an easy way to do it.
The 2ohm resistor really only affects things in the top octave, but just to be safe keep the volume low and play some music to see if the panel is now working.
Let us know your results.
Also, let us know what country you are from so we can better help you locate replacement parts.
Attachments
Bolserst! So honored to have you respond, you are what I want to be when I grow up! Threw a jumper across the resistor, and the panel sings again. You are amazing! I have scrubbed the internet, but cannot locate the resistor as it is probably "vintage" at this point. I will try calling ML and Milwaukee Resistor tomorrow and report back. If you know of something that could replace it, I am open to options. I am in the United States.Hi ddikeht,
Sounds like you have been methodically swapping parts between working and non-working speaker to isolate the problem.
Problem is not the HV supply, panel, or step-up transformer. Not much left but the passive crossover parts.
To help people searching for information on the Martin Logan Script in the future, I'm responding in this thread rather than your other one you started to ask about the 2ohm resistor.
https://www.diyaudio.com/community/...f-possible-still-learning.381876/post-6910482
Based on the pic you posted in the other thread(attached below), I drew up the crossover schematic.
To confirm if the 2ohm resistor is your problem, just jump a wire across it. If you have an alligator clip terminated wire that would be an easy way to do it.
The 2ohm resistor really only affects things in the top octave, but just to be safe keep the volume low and play some music to see if the panel is now working.
Let us know your results.
Also, let us know what country you are from so we can better help you locate replacement parts.
Thanks again everyone for the support!
Great! that is good news...glad I could help out and that it wound up being a simple fix. It is unusual for power resistors to fail without obvious signs of overheating. But, I have experienced a similar issue once where the termination clamping band was no longer conducting electrically with the resistive wire element.
As mattstat already mentioned, one of the easiest places to get replacement crossover parts in the US is Parts Express.
I'd recommend the 20W version of the 2ohm resistor to match power handling and mounting method of the OEM part.
https://www.parts-express.com/Dayto...0-Watt-Precision-1-Audio-Grade-Resistor-007-2
As mattstat already mentioned, one of the easiest places to get replacement crossover parts in the US is Parts Express.
I'd recommend the 20W version of the 2ohm resistor to match power handling and mounting method of the OEM part.
https://www.parts-express.com/Dayto...0-Watt-Precision-1-Audio-Grade-Resistor-007-2
As a follow-up, straight from ML.
We don't have those individual components.
The schematic does not have detailed part specs
It is 2 ohm 5% 20watt wire wound
here is the closest match available today - https://octopart.com/b20j2r0e-ohmite-145495?r=sp
Thanks to all for the help with this!
We don't have those individual components.
The schematic does not have detailed part specs
It is 2 ohm 5% 20watt wire wound
here is the closest match available today - https://octopart.com/b20j2r0e-ohmite-145495?r=sp
Thanks to all for the help with this!
Here's what digikey has, sorry for the insane link:
https://www.digikey.com/en/products...CuetgW+AC0cNB2UPqJzkSQpHxKliDp0tn2eQWuEKXm5kA
Sheldon
https://www.digikey.com/en/products...CuetgW+AC0cNB2UPqJzkSQpHxKliDp0tn2eQWuEKXm5kA
Sheldon