M9 no sound hardware repair experience

[uedat125]

I thought I’d share my experience with a non-working M9 which I successfully repaired myself.

I auctioned off a M9 described as faulty, no sound,. The owner used it for a long time and when he powered it on for the first time in about a year, it failed to produce any sound.

Uppn receiving I pluged in and confirmed the condition where the LCD and switch indicators light up normally and function as expected but no sound. However the sound would come through when the effect was bypassed via tru-bypass, but not a humming noise when it’s on, so I figured the input/output and their relays are okay, and on an assumption that the trouble was somewhere around the DSP, I began probing the test points for voltage. I found +12V power was not there in the analog amp section and spotted the DC regulator “2SC1623-L4” (D23) was faulty. However it’s an old transistor rather hard to find. Eventually it was found at a Chinese parts shop Aitendo in Akihabara where I’d been a few times, but they only had “2SC1623-L6.” Crossing my fingers that the circuit design wasn’t so strict I bought a strip of them and managed to replace the faulty one with a new one which is smaller than a grain of rice. Having seen the correct voltage at the test point,  I connected the guitar and amp to hear colorful sound fly out of the box. It was worth the perseverance in the research and craft. 

[gabe_gonzalez]

Nice work I had the same problem on my m9 and got the transistor L6 and replaced it and it work now I have a question I have the same problem on my m13 the very same tried to look for the d 23 transistor but on this unit d23 is a diode is the analog amp section under the ic chip 2374 A ? Any help would be awosome thx 

[uedat125]

Hi pepethebull,

 

Congrats on successfully repairing your M9. I have an M13 which is a working unit, I haven't gone far as to opening it up,  but I'd examine voltage around the audio section by checking out all the test points, as the circuit design may vary. While you have the power on, check the test points, then if all check out okay,  check the semi-conductors visually for any indication of burnout. Also make sure that the tru bypass is working to eliminate possibility of relay or coil burnout. I've had a faulty inductor in a Tonecore, FWIW.

 

Best of luck!

[Wtfusay]

Hi uedat125,

i have the same problem with my m9,so i check the pcb,i see there is 2 ic jrc2374 burnt,so i replace them with good one,but problem still, no effect sound,blank light screen.

L4 seems good , and +12/-12 test  normal,i dont kown what to do next,would you help ?thank you.

[uedat125]

Hi Wtfusay

 

I would try to separate issues.

First check the connectors between PCBs.They can come loose over time and quite often the problem.

 

If the sound is there but no display, make sure the display driver has the right voltage. 

 

If there’s no sound, check the input/output for potential disconnect, or any indication of small piece of metal/solder  bridging input and the ground. 

Chances are that the IC/transistor you’ve replaced had fault in itself or  not in good contact.

 

Check all test points for correct voltage. 

 

Check any indication of dead IC/transistors. It could be resistors or caps, by the way.

 

If there’s a faint sound coming from the output, check the op amps and power amps.

 

All these things will require patience, but remember that the circuit once worked well and there’s probably one disconnect in the path of the guitar signal. 

 

Good luck!

[Wtfusay]

Wow, thank you very much, that's very nice of you, i'll try.

[edgibbs]

A Correction to the D23 part identification by uedat125 - D23 is a BAT54 Schottky Diode, Not a 2SC1623 Transistor :)

Hello to All and a hearty THANK YOU to uedat125!!!

uedat125 is potentially saving me $100-200!!! His sharing of this info is a gift from God through uedat125.

As with uedat125s unit, everything functions but there is no effected-audio coming through at all. I reflashed the unit with V2.04.00 firmware yesterday afternoon and there was no change - I was hoping that would fix it and it did not.

Last night, I did a google-search for "Line6 M9 mainboard" and ran across this post. I just took my M9 apart again and I can see that D23 is burnt and possibly R120 as it looks to have smoke residue on it although I haven't grabbed my meter and verified that yet.

I found the schematic for this unit and it says that D23 is a BAT54 schottky diode with SMT marking of L4. I looked up the part number that uedat125 found and it too is marked L4 for the lower Hfe version...he chose the L6 medium-Hfe version of the transistor as I can see that in the second photo. The proper SMD marking should be L4P as shown in On Semi, Vishay, and International-Rectifier datasheets but, some manufacturers are only putting L4 on the diodes which caused uedat125 to think that it is a transistor.

I have attached a photo-snip of the schematic showing D23 in the upper right.

Again, a great-many THANK-YOUS to uedat125 for sharing his repair-finding on this,

Dan Gibbs :)

 

[PedroHesse]

I recently discover an issue with my M9, it seems that is not picking signal from input{(mono) or stereo, when i disconnect the unit from power it by passes and signal goes through to the amp with no issue.

 

is this something that may help ?

 

i know is years after this post, hopefully somebody is able to help, i look through the community with the same issue as mine but they never got a response.

 

thanks

[uedat125]

On 1/17/2021 at 5:39 AM, edgibbs said:

A Correction to the D23 part identification by uedat125 - D23 is a BAT54 Schottky Diode, Not a 2SC1623 Transistor :)

Hello to All and a hearty THANK YOU to uedat125!!!

uedat125 is potentially saving me $100-200!!! His sharing of this info is a gift from God through uedat125.

As with uedat125s unit, everything functions but there is no effected-audio coming through at all. I reflashed the unit with V2.04.00 firmware yesterday afternoon and there was no change - I was hoping that would fix it and it did not.

Last night, I did a google-search for "Line6 M9 mainboard" and ran across this post. I just took my M9 apart again and I can see that D23 is burnt and possibly R120 as it looks to have smoke residue on it although I haven't grabbed my meter and verified that yet.

I found the schematic for this unit and it says that D23 is a BAT54 schottky diode with SMT marking of L4. I looked up the part number that uedat125 found and it too is marked L4 for the lower Hfe version...he chose the L6 medium-Hfe version of the transistor as I can see that in the second photo. The proper SMD marking should be L4P as shown in On Semi, Vishay, and International-Rectifier datasheets but, some manufacturers are only putting L4 on the diodes which caused uedat125 to think that it is a transistor.

I have attached a photo-snip of the schematic showing D23 in the upper right.

Again, a great-many THANK-YOUS to uedat125 for sharing his repair-finding on this,

Dan Gibbs :)

 

Congratulations on your excellent job finding the right part and the schematics, edgibbs!

You just proved that my sharing of the repair experience made a bit of contribution to Line 6 users, which is the whole purpose of the post.

BTW, where did you find the schematics? I'd very much like to take a close look!

[uedat125]

12 hours ago, PedroHesse said:

I recently discover an issue with my M9, it seems that is not picking signal from input{(mono) or stereo, when i disconnect the unit from power it by passes and signal goes through to the amp with no issue.

 

is this something that may help ?

 

i know is years after this post, hopefully somebody is able to help, i look through the community with the same issue as mine but they never got a response.

 

thanks

Hi PedroHesse,

 

Copy/Pasting my previous comment here, knowing that your problem sounds similar to what I had:

 

I would try to separate issues.

First check the connectors between PCBs. They can come loose over time and quite often the problem. Also there may be corrosion in the contacts.

If the sound is there but no display, make sure the display driver has the right voltage. 

If there’s no sound, check the input/output for potential disconnect, or any indication of small piece of metal/solder bridging input and the ground. 

Check all test points for correct voltage. 

Check any indication of dead IC/transistors. It could be resistors or caps, by the way.

If there’s a faint sound coming from the output, check the op amps and power amps.

All these things will require patience, but remember that the circuit once worked well and there’s probably one disconnect in the path of the guitar signal. 

 

Good luck!

[edgibbs]

Hey All :)

Again, another round of big thanks to uedat125!!! I'm back to contribute my help and pay it forward too :)

 

I finally got my M9 repaired last Thursday after work on my workbench there. I took me about four hours bench-time over a handful of days since my last post to weed out what was all wrong inside of my M9. My original problem was that the unit looked and acted fine but there was no throughput audio when any effect was enabled - only bypass audio when the true-bypass option was selected in the setup menus.

 

So what happened was some sort of large signal or impulse came in through the Left (Mono) guitar input which shorted U9 TL074 which then took out the -12Vdc rail U19 NJM2374A regulator & D25 BAT54 schottky-diode, the +12Vdc rail D23 BAT54 schottky-diode, the CODEC IC U17 CS42432 which shorted out it's +5VA IC U20 LM7805.

 

So, whatever the errant signal/impulse was, it poked quickly through to the CODEC IC a.k.a., analog-to-digital and digital-to-analog converter IC and knocking out the associated power regulator circuitry.

 

I bought all of the repair parts through Mouser.com :) Google: "line 6 M9 schematic" :)

 

Enjoy,

Dan Gibbs :)

[BoggianoSoy]

Hi All!

i am from Chile and apparently I have the same problem, but i have an M5, everything seems fine but there is no sound... my pcb schematic is different i don't know if it's the same "d23" or any clue what it could be in my case? and by the way what piece or part should I get , I'm not very good at electronics, that's why I ask you to tell me any clue of the exact name of the part, "L4P" ??? is that the technical name or BAT54 schottky-diode?? sorry if my question is very ignorant but i need to find it.

 

If you can help me 

[uedat125]

5 hours ago, BoggianoSoy said:

Hi All!

i am from Chile and apparently I have the same problem, but i have an M5, everything seems fine but there is no sound... my pcb schematic is different i don't know if it's the same "d23" or any clue what it could be in my case? and by the way what piece or part should I get , I'm not very good at electronics, that's why I ask you to tell me any clue of the exact name of the part, "L4P" ??? is that the technical name or BAT54 schottky-diode?? sorry if my question is very ignorant but i need to find it.

 

If you can help me 

Hi BoggianoSoy,

 

Yes, L4P is the package label for BAT54 series schottky diodes. FYI, I've attached a datasheet for them. 

As to the problem of no sound with M5, I have a unit that has a similar issue where there's a faint sound when the effect is switched on, and at the time of finding the issue I was suspecting one of the op amps but will have to look again when I have time, as I stowed it away and haven't gotten around to fixing it. 

In the meantime, once again I'd suggest you go through all the test points, marked TP and see for any failure in order to narrow down which part of the circuit is causing the issue.

Good luck!

https://datasheetspdf.com/datasheet/BAT54C.html

 

uedat125

[BoggianoSoy]

 

Thank you very much for the answer and that is exactly what I was doing, checking point by point and so far I have not found something obviously burned or something, approximately where are those "op amps"? maybe can i found something

THANKS

[uedat125]

On 2/14/2022 at 11:47 AM, BoggianoSoy said:

 

Thank you very much for the answer and that is exactly what I was doing, checking point by point and so far I have not found something obviously burned or something, approximately where are those "op amps"? maybe can i found something

THANKS

Hi BoggianoSoy,

 

Excuse me for writing off of my memory but I seem to remember those are near the DSP on the other side of the board.

Good luck, and if you get it fixed, please post how you did it!

 

 

[pdk972]

I have a similar issue where my M5 will make normal sound when I change the setting to true bypass (as opposed to DSP bypass) and switch the effect off, but when it's engaged the volume drops dramatically.  Distortion models don't drop volume as much.  I just replaced those BAT54 diodes (D13, D14 on the M5), but the problem persists. Any insight would be much appreciated.