Behringer GMX212 PS ?

[gtrplayr1976]

I do understand that part, but if it is in that state , what needs to be done to correct it , and if it isn't stuck what would the voltage be at the speaker ?

Thanks, Tom

[Enzo]

No amp should put any DC voltage on its speaker load. A small offset might be tolerated - a tenth of a volt perhaps. The mute should have no effect on that. If you have DC on the speaker, you have a problem, usually a bad 3886 or a missing power supply.

If it is stuck in mute, then the mute circuit is bad - look at T4, T5 there, plus there is a contact on the headphones jack that mutes the amps. It is a separate switched contact that swhould have a negative voltage on it until phones are plugged in.

[gtrplayr1976]

No amp should put any DC voltage on its speaker load. A small offset might be tolerated - a tenth of a volt perhaps. The mute should have no effect on that. If you have DC on the speaker, you have a problem, usually a bad 3886 or a missing power supply.

If it is stuck in mute, then the mute circuit is bad - look at T4, T5 there, plus there is a contact on the headphones jack that mutes the amps. It is a separate switched contact that swhould have a negative voltage on it until phones are plugged in.

Hey Enzo,
So i'm guessing T4-T5 are the transistors on the PS board side by side.
The headphone jack has about 8 terminals. Which ones am I checking ?

Thanks , Tom

[Enzo]

T4, T5 would be on the same board as the 3886s, and they would be small. Behr tends to print the part numbers in tiny letters next to each part, and they usually also label the type, so T5 should say T5 next to it and probably A06 as well. T4 is an A56.

I have no idea which terminal is which on the phones jack, it would be a terminal that gets grounded whenever anything is plugged into the phones jack. It would only be a problem if it were stuck grounded.

There is a special negative supply just for this. From the AC, D7,D8 make a negative DC, which feeds through paralleled R19,R20 (10k each, so about 5k measured), to little filter cap C12. Should be some negative voltage there. From that cap, R14 heads up to T4. I don't know what the voltage is, maybe 35-40 volts negative. Measured at C12 or the low voltage end of R19/20, whatever it is is likely either correct or missing. Plugging something in and out of the phones jack should make the voltage disappear and return. So: got V- on R14?

[gtrplayr1976]

T4, T5 would be on the same board as the 3886s, and they would be small. Behr tends to print the part numbers in tiny letters next to each part, and they usually also label the type, so T5 should say T5 next to it and probably A06 as well. T4 is an A56.

I have no idea which terminal is which on the phones jack, it would be a terminal that gets grounded whenever anything is plugged into the phones jack. It would only be a problem if it were stuck grounded.

There is a special negative supply just for this. From the AC, D7,D8 make a negative DC, which feeds through paralleled R19,R20 (10k each, so about 5k measured), to little filter cap C12. Should be some negative voltage there. From that cap, R14 heads up to T4. I don't know what the voltage is, maybe 35-40 volts negative. Measured at C12 or the low voltage end of R19/20, whatever it is is likely either correct or missing. Plugging something in and out of the phones jack should make the voltage disappear and return. So: got V- on R14?

Enzo,

From what i can see, I'm guessing most of these parts are on the bottom of the board. I do not see any resistors on top, and no T4,or T5.
I do see negative voltage on two of the terminals on the phone jack -9vdc.
From the PS board there are 3 wires R,B,Blk. Are there voltages on these?

Thanks, Tom

[gtrplayr1976]

Enzo,

From what i can see, I'm guessing most of these parts are on the bottom of the board. I do not see any resistors on top, and no T4,or T5.
I do see negative voltage on two of the terminals on the phone jack -9vdc.
From the PS board there are 3 wires R,B,Blk. Are there voltages on these?

Thanks, Tom

I did check the voltages on the phone jack, and they zeroed when I plugged a cable in.

[Enzo]

I have no idea in the world what should be on three wires. What connector do they spring from? Everything is labelled on those boards, isn't it? Where do they go? WHy do they seem suspect?

And yes, expect parts all over both sides of the boards. Those transistors will be those tiny three legged flecks you see here and there.

You just need to check for voltage at pin 8 of the 3886s. If you do not have a small enough clip lead to get on the pin, then tack some small wire onto one of them and trail it out to where you can get at it. DO all this connecting with powr off so you don;t short anything.

[gtrplayr1976]

I have no idea in the world what should be on three wires. What connector do they spring from? Everything is labelled on those boards, isn't it? Where do they go? WHy do they seem suspect?

And yes, expect parts all over both sides of the boards. Those transistors will be those tiny three legged flecks you see here and there.

You just need to check for voltage at pin 8 of the 3886s. If you do not have a small enough clip lead to get on the pin, then tack some small wire onto one of them and trail it out to where you can get at it. DO all this connecting with powr off so you don;t short anything.

I guess it would help if I gave you more info on the wires. The 3 wires feed from the PS board X2 ,and go to X19, X20, X21 on the board the speakers connect, along with most of the other inputs,and outputs. I'm thinking I checked one of the 3886s , but I will check again.

Thanks, Tom

[gtrplayr1976]

T4, T5 would be on the same board as the 3886s, and they would be small. Behr tends to print the part numbers in tiny letters next to each part, and they usually also label the type, so T5 should say T5 next to it and probably A06 as well. T4 is an A56.

I have no idea which terminal is which on the phones jack, it would be a terminal that gets grounded whenever anything is plugged into the phones jack. It would only be a problem if it were stuck grounded.

There is a special negative supply just for this. From the AC, D7,D8 make a negative DC, which feeds through paralleled R19,R20 (10k each, so about 5k measured), to little filter cap C12. Should be some negative voltage there. From that cap, R14 heads up to T4. I don't know what the voltage is, maybe 35-40 volts negative. Measured at C12 or the low voltage end of R19/20, whatever it is is likely either correct or missing. Plugging something in and out of the phones jack should make the voltage disappear and return. So: got V- on R14?

So ...I removed the PS so I could get access to the bottom of the circuit board. I found the T4, T5 ,and R14, 19, and 20. Problem now is that I see no voltage anywhere where I was. The only things that are connected are the PS. Everything else is disconnected.

Thanks, Tom

[gtrplayr1976]

ENZO

So...finally back to this , and got some voltages on the points you suggested.

The 3886s at pin #8 have .6 vdc. At one end of R19/R20 there is -25vdc, and the other side had -9 vdc. R14 has -9vdc on both sides. Anything else I need to check ?

I just checked T4 & T5 also. T4 had -9vdc at C,B,and E...T5 had 0vdc at C until I pushed on it some ...I could hera sound from the speakers...also noticed the voltage dropped on T4 to about half, and I could hear sound when I pressed on it... Bad solder joints?

Got it Enzo....T4 & T5 were both barely on the pads. I heated them up ,and repositioned them ,and now it works. Thanks for all the help.

Thanks, Tom

[sijobarteam]

Hello Guys!
I'm French so sorry for my bad english. I use a GMX212 from Behringer too.
It just turn off yesterday, since it does'nt work.
The fuse is ok, I checked the outlet and the switch, and there is a voltage of 230V which arrives correctly to the input of the transformer.
However, if I measure the pin X3 wich arrives in DSP, there is no tension.
How to measure the voltage at the output of the transformer?
Thanks guys!

[gtrplayr1976]

Hey, English seems ok too me. Have you checked for any DC voltage on the PS board where X3 connects...Like on the diodes ? just to see if anything is there..also take a look at post #4 of this thread.from ENZO

[sijobarteam]

Hey,
at the pins of X3 there is no current! There would be an AC voltage because it is directly connected with the output of the transformer!
Furthermore, between the 6 pins of the output of the transformer, I can't manage to measure any voltage!
So I think my transformer is dead?? I have ordered a new one on PMS electronics.com

[gtrplayr1976]

I think you need to read through this whole thread. Enzo explained some things too me about reading the voltages on these. I did the same thing you did.

[sijobarteam]

What do you mean? I have wrong about the transformer's fail?