Hello all i received the new kit for the mx50 finished building it it ran for about 30 sec and the the gray 10ohm resistor burned. Any ideas why this would happen it looks like it’s on the out going to ground with a film capacitor I believe the value of the cap is 100nf . I’m really bummed I just turned them on and both same thing happened music was playing and then boom smoke from the gray cap everything else on the board looks fine !
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The resistor and cap look to be a conventional Zobel network at the output of the amp.
For the resistor to burn like that suggest high frequency oscillation. At this point its impossible to say what has happened. but it could be down to the way you have the wiring and grounds configured.
Have you measured the resistor to see if it has failed open circuit? You can test it in circuit.
(I'm assuming you had the transistors bolted to a suitable heatsink)
For the resistor to burn like that suggest high frequency oscillation. At this point its impossible to say what has happened. but it could be down to the way you have the wiring and grounds configured.
Have you measured the resistor to see if it has failed open circuit? You can test it in circuit.
(I'm assuming you had the transistors bolted to a suitable heatsink)
The 10ohm resistor is still showing 10ohms but it’s tuned a bit black and now on the output all I get is humming if I try and play something. Yes I had the output transistors on a heatsink . How would I go about troubleshooting it . I’m new to electronics so any help is welcome . Thanks
If it still measure 10 ohm then its fine to keep in place.
The humming.... that doesn't sound good. I suspect you will find the output transistors (one or both) have shorted because of the oscillation issue.
If you put your meter on 'Diode' range and measure from the middle leg to each of the other two legs I think you will find that you get a 0.00 reading which means a short. Also check those white stand up resistors to make sure they have not failed open circuit.
The humming.... that doesn't sound good. I suspect you will find the output transistors (one or both) have shorted because of the oscillation issue.
If you put your meter on 'Diode' range and measure from the middle leg to each of the other two legs I think you will find that you get a 0.00 reading which means a short. Also check those white stand up resistors to make sure they have not failed open circuit.
Actually they are not shorted I just checked I still get gain from the amplifier if I touch the input I get humming coming from the amp so the transistors still work! Anything else I can check ?
Well that's good 🙂
If you have the input floating that may well cause it to hum as it picks up stray noise and interference, or you may have an issue with the way you have it all wired up
I would suggest you wire just one module up. Make sure you return the speaker ground to the power supply ground at the power supply itself. As an initial test I would begin with the input connector shorted together and not connected to anything else.
The amp should be silent in that state. If it is silent then try connecting just that one input and make sure that one module plays correctly.
Correct grounding is very important for stability.
I'll look in again tomorrow.
If you have the input floating that may well cause it to hum as it picks up stray noise and interference, or you may have an issue with the way you have it all wired up
I would suggest you wire just one module up. Make sure you return the speaker ground to the power supply ground at the power supply itself. As an initial test I would begin with the input connector shorted together and not connected to anything else.
The amp should be silent in that state. If it is silent then try connecting just that one input and make sure that one module plays correctly.
Correct grounding is very important for stability.
I'll look in again tomorrow.
I tried connecting it again and something smoked again my guess is it’s that resistor because it’s even darker now ! I check the resistor and it’s still showing 10ohms . It’s very strange could it be a very high frequency oscillation above the audible range ?
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Deleted member 550749
If that's zobel network, then I think problem with Oscillation, check compensation cap , same problem happened with me in another amp , check it
Can you please explain which one is the compensation cap I’m really new to electronics thank you
The one that came in the link https://www.ebay.com/itm/2542706740...486&ssuid=&var=&widget_ver=artemis&media=COPY
That’s the one I’ve been using
That’s the one I’ve been using
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Deleted member 550749
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Deleted member 550749
Yes, check is that layout ok, base to collector 100pf , if layout ok then try with same value different cap