There are two identical regulator circuits - the one with transistor Q9 produces a positive (relative to ground) voltage rail and the one with transistor Q10 produces a negative voltage rail (relative to ground). Between these two rails is a total of 24 Volts. The fuse F2 supplies -45 volts to Q10 but Q10 is not regulating the voltage and bringing it down to the required -12V as it should. Now I would compare the two circuits side by side. for example check R41 against R42, R2 against R1 and so on. I would not reconnect the faulty negative rail to the rest of the circuit until you have repaired it and it is producing -12V. -45V is much higher than the rest of the circuit is designed to receive and might cause further damage, Do you know how to test a transistor with a multimeter? It is easy and I'm sure there are videos on YouTube explaining how to do it better than I can here. Also, remember that you cannot really check components when they are wired into a circuit because you are also measuring other components. For example if you check R44 in circuit you are also measuring across C31. In other words you often need to take components out of the board at one end so you can measure it independent of other components.
Good luck!

Hi bro , thank you so much for all your suggestion, that's help me a lot!!! finally I found the problem, the cause was diode D3! Replace it and I have 12vdc on both side, also the noise are gone. but still not able to get the lines in high and low to work, If I connect the guitar no sound come out! But mic1 mic2 works perfectly...I assume that the high voltage make problem to the mixer? Honestly I don't know where to start with the mixer I don't see any visible damaged..I member of the forum post the schematic of the mixer, if you could help I will appreciate. Thank you in advance

 

Only inputs 1 and 2, I would have guessed the entire mixer would have gone down.
Those 4560 chips are rated at + and - 18 volts max.
I would start with voltage readings on U1 and U12.
I have to leave shortly but can resume this conversation in a few hours.

Sorry bro for not reply, I haven't see your message till now!! thank you for the int, I will do, but I will do it tomorrow, now is too late. I'll let you know what I will read on U1 and U12, but U1 and U12 are Mic 1 and Mic 2, those channel works perfectly what doesn't work are CH3 Hi sense, and CH4 low sense, so the equivalent on this 2 INPUT should be U5A U5B ? please tell me if I'm correct, good night bro, speak to you soon tho

 

Hi. Could you take a good quality pictures this area, I have a burned PCB

 

on this 2 INPUT should be U5A U5B ? please tell me if I'm correct, good night bro, speak to you soon tho

That's correct my mistake, U5 and U13 to be exact. What equipment do you have for trouble shooting?

 

That's correct my mistake, U5 and U13 to be exact. What equipment do you have for trouble shooting?

Hi bro, I solve all the problem now, a part from this: When you play guitar, it play nice for a bit, but intermittently it fart it does brrrrr brrrrrr only on the high note, when volume is bit high. This is what was originally the problem with this amp, and that's why I change the TDA which make all the other problem! So been spend all my time to sort the other problem that come with the TDA, but I realise that the thing still make that intermittent noise...

The mixer was ok I found a dry connection and a bit of oxidation I clean it, and it's fine, all channels works now! What I have for testing is a multimeter....Could be the big capacitor the "fart" problem? Is the only thing I haven't check..I want to thank you again for your help, It's much appreciate!!!! Sorry if make gram mistakes, english is not my firs language

 

.Could be the big capacitor the "fart" problem?

Are you referring to C1 and C2?

 

Hi. Could you take a good quality pictures this area, I have a burned PCB
View attachment 268207

Here, how did this happen? what your problem? This pictures are before been fix it burn 3 times after changing TDA, weird...

 

Here, how did this happen? what your problem? This pictures are before been fix it burn 3 times after changing TDA, weird...

I bought burned, i must repairing broken traces , I removed parts from that area. i checked both TIP137 and TIP132, one is broken. I ordered new parts ... to be continued. Regards

 

postscript: Thanks for pictures!!!

 

I bought burned, i must repairing broken traces , I removed parts from that area. i checked both TIP137 and TIP132, one is broken. I ordered new parts ... to be continued. RegardsView attachment 268253

My board on the left side was similar, the track with number c6 c3 print on top of it, is connected to the middle leg of tip127, I did scratch the trace to reveal the copper and solder the R2 right leg to thats track! But I'm sure you already find out..Those amp have very good sound for electric classic guitar and cost about £800 pound! Worth to be save!! Good luck bro

 

Are you referring to C1 and C2?

Yes bro, could it be?

 

Could be, although from your photo they appear OK.
This "brrrrr brrrrrr" sound do you hear it out of both speakers?

 

Could be, although from your photo they appear OK.
This "brrrrr brrrrrr" sound do you hear it out of both speakers?

Good morning! Yes it's on both speakers, I test it with another speaker, it does the same..(it has 2 speakers but in the same channel, it's guitar amp) Sorry for late reply but I don't see notification! If was you having this issue, what would be the first thigh you would start to check?

 

(it has 2 speakers but in the same channel, it's guitar amp)

There are two separate power amps. The TDA drives the smaller speaker. If the noise is in both speakers it might be in the mixer circuit and/or related to the power supply which is common to both amps.
Personally I would use an oscilloscope to trace the signals through the mixer and monitor the power supply voltages for poor filtering.
With only a multimeter I would try and monitor all of the supply voltages first when the noise is happening.

BTW the power amp schematic you listed in post #2 is for the JAM 150 not the JAM 150 Plus. The mixer schematic is listed as a JAM 150 Plus. There does appear to be some discrepancies between the two. Not sure if it will make any difference or not.

 

There are two separate power amps. The TDA drives the smaller speaker. If the noise is in both speakers it might be in the mixer circuit and/or related to the power supply which is common to both amps.
Personally I would use an oscilloscope to trace the signals through the mixer and monitor the power supply voltages for poor filtering.
With only a multimeter I would try and monitor all of the supply voltages first when the noise is happening.

BTW the power amp schematic you listed in post #2 is for the JAM 150 not the JAM 150 Plus. The mixer schematic is listed as a JAM 150 Plus. There does appear to be some discrepancies between the two. Not sure if it will make any difference or not.

Hi, the speaker are connect together, the rise only 1 exit for the speaker + & - then they are connected in parallel.

I don't have oscilloscope, I will try to monitoring as suggested
The capacitor mentioning before as to do with power supply, that's is why I been thinking of them, the problem is that I can't check them properly with multimeter, I can only see if they working..
I have notice that the schematic is different, but only the mixer one, the board schematic is the same of the board I got, the wrong one is the mixer one! I did receive 3 file today from schertler, they send me the board which is for the JAM150 an the mixer for the plus! I will ask why....

 

Hi, the speaker are connect together, the rise only 1 exit for the speaker + & - then they are connected in parallel.

According to the schematic each speaker has it's own amp they should not be connected together, maybe that's your problem.

but only the mixer one, the board schematic is the same of the board I got, the wrong one is the mixer one!

So which model amp do you have the 150 or the 150 Plus?

 

According to the schematic each speaker has it's own amp they should not be connected together, maybe that's your problem.

So which model amp do you have the 150 or the 150 Plus?
[/QUOTEGood morning! The one I have is the plus, I think the difference is only the mixer, the board is the same
How it's possible that the speaker where connected separately? I don't have any other connection for the speakers

According to the schematic each speaker has it's own amp they should not be connected together, maybe that's your problem.

So which model amp do you have the 150 or the 150 Plus?

Good morning! The one I have is the plus, I think the difference is only the mixer, the board is the same on both..(but not sure)
How it's possible that the speaker where connected separately? I don't have any other connection for the speakers, it has only 1 exit for the speaker on the board. I guy here is fixing his amp which is like the one I got! I will ask him how they are connected on his amp and lI will et you know

 

I bought burned, i must repairing broken traces , I removed parts from that area. i checked both TIP137 and TIP132, one is broken. I ordered new parts ... to be continued. RegardsView attachment 268253

Hi, could you please descrive me how the speaker are connect on yours prior to dismount it? A friend here said that the boards has 2 exit, one for high and the other for low! Could please post some picture of the speaker connector inside the case and on the board? Thank you in advance

 

Good morning! Yes it's on both speakers, I test it with another speaker, it does the same..(it has 2 speakers but in the same channel, it's guitar amp) Sorry for late reply but I don't see notification! If was you having this issue, what would be the first thigh you would start to check?

Hi, could you please descrive me how the speaker are connect on yours prior to dismount it? A friend here said that the boards has 2 exit, one for high and the other for low! Could please post some picture of the speaker connector inside the case and on the board? Thank you in advance

red and white on the bottom.

 

View attachment 268432red and white on the bottom.

What do you mean by withe on the bottom? I'm interest to know if the speaker are connected together inside the box and if has 1 exit only for both high and low, could you confirm that only 1 connector is present on the board and both speakers are connect on the same connector? I can see from the picture that they are connect on only 1 exit (as on my) But I have been suggest that the low and high are connected separately. Did you fix yours?Thank you for the picture!