Behringer vtone gmx 212 no output

[gongoose1]

Hi,i am new to the forum and would be gratefull for any help please.Ive had the gmx212 for a while,bought used but working.I have been using a Boss gt 8 plugged into the rear panel return socket.All was ok untill i powered up one morning,and heyho no output just a crackly sound when i turned the master pot up!
So,i tried plugging into the front socket and still no sound.Ive now stripped the amp apart and being old school was not impressed by all the subminature components!Forgot to mention that the power amp section seems fine as slave inputs work.....loud.
So,feeling around the ic's and v,regs for heat,one of the v,regs is pretty warm on the power amp board,also a very hot one on the dsp board.So ive turned off!
The front panel switches and dsp display and switches are all functioning.Im just wondering if i may have overdone the input to the return socket?And damaged the ic's on the rear board..uld be really appreciated,thankyou.

[Jazz P Bass]

As you have noted, this amplifier is chock full of surface mount components.
So, unless you have the equipment & the experience to work on SMT boards, you really should take it to a good tech.
I have attached the schematic for reference.

[gongoose1]

As you have noted, this amplifier is chock full of surface mount components.
So, unless you have the equipment & the experiance to work on SMT boards, you really should take it to a good tech.
I have attached the schematic for reference.

Many thanks for your advice,i do have the basic test gear,but not a scope,i did do electronics in my younger yours lol.

[gongoose1]

Many thanks for your advice,i do have the basic test gear,but not a scope,i did do electronics in my younger yours lol.

Just found out that the lead used to connect the Boss gt8 to the amp return input is either faulty or dead shorted,now im wondering if the dead short has damaged the inputs board in the rear panel???As stated the v,reg on the dsp board and one of the v,regs on the main power amps are pretty hot!!

[Enzo]

Vregs normally get hot. If they are making the 15v or whatever they are rated for, then they are probably OK.

[gongoose1]

Vregs normally get hot. If they are making the 15v or whatever they are rated for, then they are probably OK.

Many thanks Enzo,i will check all the rails for voltages.But it is possible i may have either overloaded or shorted out the return jack.Im guessing ive damaged the op amp/s on the rear panel.Shame i cant retrofit these ic's.

[Enzo]

You may be old school. I am old school, I have been soldering close to 60 years now. But the tiny surface mount parts is how things ar made today. It is not substandard, it isn't cheap workmanship, it is state of the art. Your cell phone is made that way, your computer is made that way.

There exists all kinds of specialized gear, but for the low volume user, they make something called "Chip QUick" or something like that. Might be spelled Qwik or something. It is easy to use and works well. I use it here. SO changing out a surface mount TL074 is not much different from changing out and old one with through-hole legs. It's a fact of life, so we have to deal with it.

Bad signal cords don;t kill amps.

If the slave ins work, the power amps are OK.

Do the AUX in or TAPE ins work?

You have INSERT jacks - the FX loop - is that the rear panel jack you refer to?

PLugging the guitar into the insert retirn doesn;t work?


If I read the schematic right, there is a cutout on the main inoput jack that will silence the 4053s. Try plugging something in there while you also try injecting signal at the insert retirn.

Once we isolate just where the signal path is broken, we will probably find a bad TL074.

[gongoose1]

You may be old school. I am old school, I have been soldering close to 60 years now. But the tiny surface mount parts is how things ar made today. It is not substandard, it isn't cheap workmanship, it is state of the art. Your cell phone is made that way, your computer is made that way.

There exists all kinds of specialized gear, but for the low volume user, they make something called "Chip QUick" or something like that. Might be spelled Qwik or something. It is easy to use and works well. I use it here. SO changing out a surface mount TL074 is not much different from changing out and old one with through-hole legs. It's a fact of life, so we have to deal with it.

Bad signal cords don;t kill amps.

If the slave ins work, the power amps are OK.

Do the AUX in or TAPE ins work?

You have INSERT jacks - the FX loop - is that the rear panel jack you refer to?

PLugging the guitar into the insert retirn doesn;t work?


If I read the schematic right, there is a cutout on the main inoput jack that will silence the 4053s. Try plugging something in there while you also try injecting signal at the insert retirn.

Once we isolate just where the signal path is broken, we will probably find a bad TL074.

Many thanks Enzo for your advice,really appreciate this.Yes it is the rear panel i am refering to,also the main front input is not working!!The tape and aux inputs are yet to be tested,fortuneatly i have found someone with a scope,who is now testing it,so i am waiting with fingers crossed.Regards Rich.

[Enzo]

Those other untested things enter teh signal path at different points than the things we have tested, so trying them helps isolate which part of the circuit has the problem.