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Old 18th January 2014, 10:20 PM   #21
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So here's an update.

I checked all the solder joints on the crossovers and fixed the bad ones I found hooked up the power supplies and reinstalled them into the speaker hooking them up the way they came out.

I hooked them up to a test amp I have and plugged them in, turned on the amp and turned on Pandora. At first nothing but then I jiggles the speaker leads and suddenly I had sound. Unfortunately it wasn't anywhere near as loud as it shows have been and it was only coming out of the panels. No bass. Hooking up the speaker leads directly to the bass leads I get music out of the bass drivers but not with them hooked up to the crossovers. Another thing is regardless of whether the speaker power supply is hooked up or not it makes no difference. Same low level sound. It sounds ok. Mid to upper frequencies but nowhere near enough volume. Flipping the "on/off" switch on the power supply also makes no difference.

Ideas?

Thanks

Eric
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Old 18th January 2014, 10:47 PM   #22
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It seems to me that the Bias supplies are not working.

You can get sound out of an ESL without them due to a very small charge that may be on the diaphragm, But it won't be very much as you have experienced.

You need to build a resistor divider in order to measure the high voltage as I had suggested earlier.

You can however do a simple arc test through a at least a 30megohm resistor (3 X 10megoms in series) from the output of the supply to ground.
If it is working than you should get an arc to jump about a 3-4mm gap.

Check the diodes in the supply for any leaky or shorted ones.

jer
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Old 18th January 2014, 11:18 PM   #23
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So it's a good sign that I get sound out of the panels, correct?

It doesn't surprise me that there are issues with the crossovers given the condition they were/are in. Hopefully taking them apart and checking the components will get them working properly.

I will check the diodes and do a spark test. Can I test the transformer in situ and if so how?

Thanks

Eric
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Old 19th January 2014, 12:09 AM   #24
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When you try a spark test make sure that you are holding the ground wire and NOT the HV wire.
Else be ready for a JOLT !!!!

I don't know enough about ML's power supply's in order to give you specific things to check.
From your picture they look quite a bit different then any of the pictures I have seen posted in these threads.

If they are line driven then this would be easy but typically they are driven from some sort of high frequency oscillator.
This is not an issue for me, I am just not familiar with ML's circuit is all.

If you can obtain the actual schematic to the board you have then this will greatly help.
Else I will help with what I can.

Getting some sound is a good thing as this shows that the Step-ups may be okay.
But, After being driven to the point of burning up the crossover their integrity still has to be in question.

Getting the Bias supplies to work is the first step.

It seems by your picture that they are line driven with 4 stages of multiplication.
You can go by CharlieM's design as a reference for trouble shooting.

The links are in post #2.

You should have about 600Vac to maybe as high as 900Vac out of the transformer feeding the multiplier stage.

jer

Last edited by geraldfryjr; 19th January 2014 at 12:16 AM.
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Old 19th January 2014, 01:15 AM   #25
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What watt rating resistors do I need to do the arc test?

Thanks

Eric
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Old 19th January 2014, 01:44 AM   #26
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I have used plain ole' 1/4 or 1/2 watt ones from Radio Shack before.

It is just used for limiting the current so that the diodes don't get over current and short out when a arc happens.

jer
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Old 19th January 2014, 01:48 AM   #27
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It looks like there is already enough resistance on the board already.

jer
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Old 19th January 2014, 05:08 AM   #28
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Quote:
Originally Posted by geraldfryjr View Post
It looks like there is already enough resistance on the board already.

jer
So I can run a pair of wires out of the blue terminal block and see if I can get an arc between the ends?

I do t want to fry anything

Thanks

Eric
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Old 19th January 2014, 10:24 AM   #29
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Should be able too, From the view of the top of the board it is pretty simple.


jer
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Old 19th January 2014, 11:37 PM   #30
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So I get 335 volts out of the blue terminal block and a ver small spark but it doesn't jump anywhere near 6-7mm. More like 1-2mm.

I checked all the diodes and they all measure within a few % of each other. All the black ones between the caps and the four in the group of 16 diodes measure about 670+-. The redish ones measure about 820 and the tan ones about 830.

Should I be concerned about the PS transformer?

Thanks

Eric
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