ML Odyssey lower volume on 1 panel

[sumotan]

Hi Guys

Need help. 1 panel on my Odyssey has gone down in volume.
It still sounds normal just lower volume. I vacuum panels once a month
so dust should not be the problem. Have search the threads here & seems to indicate that bias voltage could be the issue. Question without a high voltage dvm or scope, is there a passive way to measure the bias board just with a Dvm

Thank in advance

 

[sumotan]

Problem solved

Thanks

 

[bolserst]

What did you determine the problem was?
From the PM you sent I wasn't sure if you solved the problem or not.

If you are still experiencing problems, the first thing you need to do is confirm if the problem is in the power supply, or in the panel. The easiest way to do this is swap the power supply boards between the two speakers. If the problem of lower volume follows the power supply board, you have confirmed you are dealing with a power supply problem. If the lower volume stays with the same panel even when swapping power supply boards, you are likely dealing with a panel that has a poor HV contact with the diaphragm coating or has developed some leakage paths which are loading down the HV bias supply.

 

[sumotan]

Hi Bolserst,

Thanks for the reply. Yes I have swap the HV bias board & indeed it sounds louder.
That's why I was asking for advice & guidance.

Thank you

 

[tyu]

Sumotan.....
I get ML Prodigy,Odyssey,Ascend I....SL3.....with bad or low output from one of the panels....thay all use the same HV bias...to day thay were $100.US..I have found more the one of these bias boards with the first one are two or any I think there 4-6... 15meg res is open,cooket there only 1/4 watt..right befor the panel bias red wire output......an that CANBe.....the cause, if your lucky...of the panel output drop...
if you can you may like too ck before you pay.....good luck

 

[sumotan]

Hi Tyu
Thanks for the reply. May I ask, are the stators easy to
to remove without destroying the mylar film for diy
recoating work ?

Thanks

 

[sumotan]

Hi Bolserst

Was searching through this forum on bias board issues. Came across
you mentioning of red led should be lit when sensing signal. Question,
my bias boards does not lit up at all but music was playing through the
panels.

Thanks

 

[tyu]

NO!....
Not on the ML Prodigy,Odyssey,Ascend I...there side reals are made with the panels as one peace....if you get new panels.... panels come as one peace...
ML made a big error on this type setup!...The panels can an have fell out of a 10k pr of .Prodigy... as well Odyssey,Ascend I..thats why I only pay $100 for a pr of any ML like this...must have been others befor the 10cent fix thay came up with...Nuts right....
You do have the FIX on your panels??....if not call ML an get it...free!...when panels slip down the wire gets ripet from the panels....people cant fix... call for new panels....you know...$1500-2000....NOT ....for most...who well thay get put the panels in?..thay just get new speakers....just what ML planed...most not new ml...

SL3 type with wood reals ezer...only way I would pull the other like your Odyssey... is if there not given output to match the other panels output then you have nouthing to lose...then its a shot in the dark if you can get the panels apart.with out riping the mylar......good luck

 

[sumotan]

Thanks again Tyu

 

[bolserst]

I have swap the HV bias board & indeed it sounds louder.
That's why I was asking for advice & guidance.

Ok, so you have narrowed the problem to the HV bias board.
The first stage of the HV multiplier is 300VDC, so you can test it with a standard DVM.
To measure, set your DVM to highest DC voltage scale and place probes to the C12 lead wires as shown in the attached top and bottom views of the board. Compare the voltage reading across C12 on both boards to see if they are similar or if the quieter board has a lower reading. Let us know what you find out.

If they both read close to the same voltage, the next likely suspect is the resistors that Tyu mentioned. I put a yellow box around them in the top view of the board. There are 6, and each should measure as 10Mohm. Sometimes one or more can fail and read a much higher resistance.

NOTE: For the 300VDC measurement, the power supply must be plugged in and music playing so the auto ON/OFF has been triggered to the ON state. Once triggered, it should stay in the ON state for 5 - 10 minutes even if the music is turned off.

 

[sumotan]

Thank you very much Bolserst,

Will verify the voltage. Yes I have
measured those strings of 10 meg resistors all reading above accept 1 which reads only 8 meg or so, wondering if it has any effect on lowering the volume.
My Odyssey is an old lady now. Since I’ve already open her up, do you have any suggestion on servicing the bias board Bolserst ? I do notice that on both boards
the side where the HV is located are all yellowed seems like it running hot.
Also the red led does not light up even when music is playing.

Many thanks again for your kind advice

 

[sumotan]

Hi Bolserst,
Dilemma time. Clean the board before re installing confirm that all connections were correct, power up only got distorted sound at high volume. Could not make any measurements at C12 cause voltage was just fluctuating all over. Would this have to do with the sensing circuit or ????

Thank again for for patients & help

 

[tyu]

These boards can,well go bad....I have had to replace, vary hard to work on ...but you see that...there also the chip on the board....can go bad.....I have had ML send new chip ....for free...
Never seen yellowed boards.....you may need to get two new boards.....if your sure it not the panel?...
good luck

 

[sumotan]

Thats bad news Tyu. Anyway since Im already trouble shooting, I was thinking I mignt as well prepare for resotration work on the panesl if possible.
Is it possible to remove stator without demaging the Mylar film TYU ?
Your the expert who appreciate your advice.

Thanks again

 

[tyu]

Well now geting the side rails off can done.... But.....I don't think you well ever get them back on.....each rail is full of sticky rubber type ...you well see....as for geting the panel apart..... Ive got more of these type panels apart with out riping...than the older sl3 type... as you may know panels are only glued togather at the top an bottem.....
So you are SURE its The panel that's bad??....
Only do pull the panels... IF you have.....nothing to lose....!.....if you have new panels you well still need bias.....or thay well not work...............good luck

 

[sumotan]

No panel aren’t bad. Just asking you from your experience.
If I were to restore the Odyssey I would try to do everyhing
at one go . Panels will go bad cause it’s already that old just
don’t know when.

Many thanks again TYU

 

[tyu]

Ok....got it..... an glad to help....
the one thing I would do is put the Ascend Xo in, an do change the setup transfourm secdairy...as well...an it should give the old panels...more better output....pull up a ML Ascend OX..have look..... same panel same stepup trans in the two speakers... just diff taps....have fun

 

[sumotan]

Yes Tyu you mentioned this to me before. I actually bought the parts to built the Ascent XO already. Lol Does changing that wire on the step up trans make alot of difference to the sound ?

Thanks again

 

[bolserst]

... confirm that all connections were correct, power up only got distorted sound at high volume. Could not make any measurements at C12 cause voltage was just fluctuating all over.

Hmmmm...sounds like I have missed something along the way. At the beginning of the thread you said one speaker was a little quieter than the other. Now you are getting very little output. Very little output(and distorted) sounds like you are not getting any bias voltage to the panel at all.

A few questions to help me understand:
1) Is one speaker still working OK?

2) Could you get a solid 300VDC reading from one of the speakers but not the other? or were both of them fluctuating. You will not get a solid reading if the auto-ON has not been triggered.

3) You mention that the LED on the board does not light. This LED lights when the auto-ON is triggered and the HV supply is activated. Does the LED light on one board but not the other? Had you ever seen the LED light on either board?

A preliminary step you might check is the output of the power transformer that feeds the HV multiplier. It should measure about 240-250 VAC when the power cord is plugged in. You should be able to measure this voltage at all times whether or not there is an audio signal or if the auto-ON has been triggered or not.

If you confirm you have this voltage present, I can show you how to temporarily bypass the auto-ON function to check that the rest of the HV supply is working OK.

 

[sumotan]

Yes Bolserst your reading correctly. Originally only lower in volume on 1 panel. Remove HV board from good speaker to test. Bad speaker sounded ok so confirm Hv board is problem area. Re install good HV board back onto the good speaker. Re install bad Hv board back into bad speaker just to varify again. Yep all not sound accept at almost full volume which is distorted. I understand what the music sense signal is suppose to do thats why I ask why do I get music playing even when red led is not lit. This is on the good speaker as well.

Thanks again Bolserst