Hi,
Thank you for your time and help.
I have a MXB 4150i Crunch Black Maxx, when i switch it on the "Preamplifier" gets hot, the negative side switch a C1815 gets hot after some time the Emitter Resistor burns trough. No Signal on.
The Transistors are good, The Output Transistors are good.
The Supply is stable with +/- 30V.
Without the Transistors in the Circuit i measure the positive and negative Rail at the Collector Pin Positions. That seems fine.
Do I need to match the Transistors in some kinda way?
I will post some pictures tomorrow. (Schematic of a Channel, Voltages without the Transistors in the Circuit)
Please tell me when u need more infos.
Thank you for your time and help.
I have a MXB 4150i Crunch Black Maxx, when i switch it on the "Preamplifier" gets hot, the negative side switch a C1815 gets hot after some time the Emitter Resistor burns trough. No Signal on.
The Transistors are good, The Output Transistors are good.
The Supply is stable with +/- 30V.
Without the Transistors in the Circuit i measure the positive and negative Rail at the Collector Pin Positions. That seems fine.
Do I need to match the Transistors in some kinda way?
I will post some pictures tomorrow. (Schematic of a Channel, Voltages without the Transistors in the Circuit)
Please tell me when u need more infos.
![IMG_5147[1].jpg](/community/data/attachments/765/765735-04756fa832a58eeaecec054f9db862ba.jpg?hash=BHVvqDKlju)
![IMG_5146[1].jpg](/community/data/attachments/765/765755-f48cf65de67d7fd3aec0311465e1a368.jpg?hash=9Iz2XeZ9f9)
![IMG_5145[1].jpg](/community/data/attachments/765/765779-82404a70e1e0a3170c70951268142292.jpg?hash=gkBKcOHgox)
Rewrite this using different phrasing. Be very specific.
when i switch it on the "Preamplifier" gets hot, the negative side switch a C1815 gets hot after some time the Emitter Resistor burns trough. No Signal on.
Is the circuit below close to what you have?
when i switch it on the "Preamplifier" gets hot, the negative side switch a C1815 gets hot after some time the Emitter Resistor burns trough. No Signal on.
Is the circuit below close to what you have?
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Last edited:
Thank you for your answer,
When I switch it on the Current starts normal with about 1 Ampere, then it starts to rise.
Kept on the emitter resistor of the negative side starts to burn trough. Without the Output Transistors it just gets hot.
Said C1815 Transistor has a sinking BE-Voltage while it keeps getting hotter. The BC-Voltage keeps sinking too.
Only the negative side gets hot, do I need to match the Transistors in some kinda way?
It seems like the negative side is switching some kinda way when it should be idle. Not working.
Can the hfe of the Transisors make such a big difference? When all Transistors are of the same class/rating?
I need to look longer at the schematic to see if it is similar.
When I switch it on the Current starts normal with about 1 Ampere, then it starts to rise.
Kept on the emitter resistor of the negative side starts to burn trough. Without the Output Transistors it just gets hot.
Said C1815 Transistor has a sinking BE-Voltage while it keeps getting hotter. The BC-Voltage keeps sinking too.
Only the negative side gets hot, do I need to match the Transistors in some kinda way?
It seems like the negative side is switching some kinda way when it should be idle. Not working.
Can the hfe of the Transisors make such a big difference? When all Transistors are of the same class/rating?
I need to look longer at the schematic to see if it is similar.
The emitter resistors are the large white ceramic resistors. Are you saying that one of those burns?
Using the top half of the diagram I posted, which resistor corresponds to the resistor that burns?
Using the top half of the diagram I posted, which resistor corresponds to the resistor that burns?
The R169 but I don´t understand what you are meaning with corresponds.
Maybe you could explain the meaning of that?
Maybe you could explain the meaning of that?
I posted the diagram I did because I could not follow what you posted.
I don't want to know what resistor burns in your board. I want to know what resistor in your amp (that's burning) is the equivalent of the one in the diagram.
Why did you post a transistor number when I asked about a resistor?
I don't want to know what resistor burns in your board. I want to know what resistor in your amp (that's burning) is the equivalent of the one in the diagram.
Why did you post a transistor number when I asked about a resistor?
Is D102 open? Desolder to check.
Are all of the transistors in sockets?
If so, are they original?
Are all of the transistors in sockets?
If so, are they original?
In my Amplifier there is no D102.
I put sockets in there so that I don´t need to desolder to switch them.
Not a single one of them is original anymore.
I put sockets in there so that I don´t need to desolder to switch them.
Not a single one of them is original anymore.
I will check that Q109 at monday, but my memory says that it still gets hot, I don´t let it on for so long that the current can rise to that critical point.
2 years or so, my second amp. I put it away and am trying again now.
2 years or so, my second amp. I put it away and am trying again now.
Here's the thing. The current has to be coming from somewhere to burn that resistor. There are no other connections that I can see that could supply that current. All other paths have high value resistors. Through Q107/108? possible but less likely.
Solder bridge under the board?
Solder bridge under the board?
Thank you for your help so far, all 4 Channels are showing the same behaviour, I resoldered every part and measured every resistor.
I will measure a little bit more with the schematic you posted, makes things more clear than my scribble. And look how it behaves when I pull that Q109, somewhere it must come from. Especially the supply rails will be interesting.
Good Night.
I will measure a little bit more with the schematic you posted, makes things more clear than my scribble. And look how it behaves when I pull that Q109, somewhere it must come from. Especially the supply rails will be interesting.
Good Night.