Hi,
I recently acquired a pair of SL3 in poor condition.
They've been slightly water damage and will require woodwork and reshaping.
one speaker is working fine, the other one has very limited sound coming from the panel. the sound produced is identical regardless the power is on or off.
I swapped the panels, both panels work fine, the issue is related to the electronic in the faulty SL3 speaker.
I opened it , it has a MLPS103 rev h board.
Both exterior and interior leds are on.
Thanks to the shared knowledge on the forum, I could find the board diagram and started investigations.
the D26 diode was visibly in bad shape , I replaced it with a spare one.
I also measured the bias supply voltage at 260v, between D26 and D27.
I'll continue researching but my electronic skills are very limited, any help on how to diagnose the issue is very welcome !!!!
Many thanks in advance and kudos for the friendship and knowledge shared on this amazing forum.
I recently acquired a pair of SL3 in poor condition.
They've been slightly water damage and will require woodwork and reshaping.
one speaker is working fine, the other one has very limited sound coming from the panel. the sound produced is identical regardless the power is on or off.
I swapped the panels, both panels work fine, the issue is related to the electronic in the faulty SL3 speaker.
I opened it , it has a MLPS103 rev h board.
Both exterior and interior leds are on.
Thanks to the shared knowledge on the forum, I could find the board diagram and started investigations.
the D26 diode was visibly in bad shape , I replaced it with a spare one.
I also measured the bias supply voltage at 260v, between D26 and D27.
I'll continue researching but my electronic skills are very limited, any help on how to diagnose the issue is very welcome !!!!
Many thanks in advance and kudos for the friendship and knowledge shared on this amazing forum.
Good troubleshooting so far 
Measuring 260VAC verifies that the HV transformer and zener regulator string are working properly.
Verifying that both LEDs are on confirms that the auto-ON/OFF is working properly.
The next likely culprit is one of the bias resistors R21, 22, 25, or R26 have failed open. They should each measure about 15Mohm. If you don't have a meter that can measure that high of a resistance, you can test by connecting a jumper clip across each resistor, one at a time, to see if the panel will spring to life.
Another possibility is that the Triac is not functioning.
If the resistors all test good, I will add or point you to a test for the Triac.
Measuring 260VAC verifies that the HV transformer and zener regulator string are working properly.
Verifying that both LEDs are on confirms that the auto-ON/OFF is working properly.
The next likely culprit is one of the bias resistors R21, 22, 25, or R26 have failed open. They should each measure about 15Mohm. If you don't have a meter that can measure that high of a resistance, you can test by connecting a jumper clip across each resistor, one at a time, to see if the panel will spring to life.
Another possibility is that the Triac is not functioning.
If the resistors all test good, I will add or point you to a test for the Triac.
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Hi Bolserst !
Wow, I did the test you recommend and indeed R25 was showing ∞ resistance.
I reconnected the board , did the jump test and the panel went back to life !
Thank you so much !!!!
I'm going to order 8 of them ...
These SL3s are from 97', I looked at the Caps, none seem bloated.
I'm always tempted to not touch what is functioning, but would you recommend changing the mainboard caps or other components that may affect the sound power or quality ?
Thanks again !!
Wow, I did the test you recommend and indeed R25 was showing ∞ resistance.
I reconnected the board , did the jump test and the panel went back to life !
Thank you so much !!!!
I'm going to order 8 of them ...
These SL3s are from 97', I looked at the Caps, none seem bloated.
I'm always tempted to not touch what is functioning, but would you recommend changing the mainboard caps or other components that may affect the sound power or quality ?
Thanks again !!
That is good new! 
In general, I don't replace additional components during a repair unless they are a known weak spot. I have never heard of this power supply board failing due to electrolytic caps going bad. Also, unless you have experience with component replacement, it is possible you might accidentally damage the board doing the extra replacements. But if you are confident in your soldering/de-soldering skills, it isn't much added cost to replace the electrolytic caps while you are in there. Often people do it for peace of mind, which is not a bad reason. Just be aware that C3 and C8 are non-polar electrolytics.
As far as the affect on the sound quality, all the electrolytic caps are used in the auto-ON/OFF circuitry; none in the actual HV bias supply portion of the circuit.
In general, I don't replace additional components during a repair unless they are a known weak spot. I have never heard of this power supply board failing due to electrolytic caps going bad. Also, unless you have experience with component replacement, it is possible you might accidentally damage the board doing the extra replacements. But if you are confident in your soldering/de-soldering skills, it isn't much added cost to replace the electrolytic caps while you are in there. Often people do it for peace of mind, which is not a bad reason. Just be aware that C3 and C8 are non-polar electrolytics.
As far as the affect on the sound quality, all the electrolytic caps are used in the auto-ON/OFF circuitry; none in the actual HV bias supply portion of the circuit.
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