I don't remember having anything like that on the site. Where was it?
If you run the amp full range, does it work properly?
Is there any significant DC voltage on the RCA shields?
If you run the amp full range, does it work properly?
Is there any significant DC voltage on the RCA shields?
Ok today I tested both MTX152, the ones that I adjusted bias to 1.5mv, both of them work and sound great, no distortion, nice clean power. However the last MTX152 with low filter on and low HZ adjusting pot set low the woofer destorts badly but at higher hz works fine. RCA are plugged in and stereo deck is at low volume. This does not happen with first MTX152. I already changed the OP amps, what could cause this?
If you move the body of any of the potentiometers does it make a difference?
Even if it doesn't, the pot could still be defective.
Don't try removing a pot from the working amp and installing it in the other amp. You have to take special care in removing the pots to prevent damaging them.
If you pull both boards and set the pots the same (various positions where the amp produces the noise), you can compare the resistance between the terminals on the pots to see if one varies significantly from the other.
Even if it doesn't, the pot could still be defective.
Don't try removing a pot from the working amp and installing it in the other amp. You have to take special care in removing the pots to prevent damaging them.
If you pull both boards and set the pots the same (various positions where the amp produces the noise), you can compare the resistance between the terminals on the pots to see if one varies significantly from the other.
I will test that 152 and I will let you know. I just got another 500D powers on but no output, the 150 ohm resistors look overheated.
How do you test MPSW42 and
MPSW56 when removed?
How do you test MPSW42 and
MPSW56 when removed?
Meter on diode check
MPSW42:
With the red probe on the center leg, you should read ~0.65v to both outer legs. With the probes reversed, you should read an open circuit.
MPSW56:
With the black probe on the center leg, you should read ~0.65v to both outer legs. With the probes reversed, you should read an open circuit.
MPSW42:
With the red probe on the center leg, you should read ~0.65v to both outer legs. With the probes reversed, you should read an open circuit.
MPSW56:
With the black probe on the center leg, you should read ~0.65v to both outer legs. With the probes reversed, you should read an open circuit.
Thanks, got that figured out.
On another 500D post I did not know the value of Capacitor C215 that is accross plus B+ and ground you told me this: "I don't know the value of the cap under the terminal block. If it's across the B+ and ground terminals, a 0.1uf mylar should be close enough." So I went and got 0.1Uf mylar 16v(asuming 12v supply power to amp)
http://www.diyaudio.com/forums/showthread.php?postid=1416348#post1416348
Well I got good 500d now and that capacitor has numbers Z5U 475M 50V so I asume that is 4.7uF 50V capacitor with Temperature Coefficient Z5U . I wonder if the one you told me before is totaly wrong cap to go there.
can you use radial instead of mylar ?
On another 500D post I did not know the value of Capacitor C215 that is accross plus B+ and ground you told me this: "I don't know the value of the cap under the terminal block. If it's across the B+ and ground terminals, a 0.1uf mylar should be close enough." So I went and got 0.1Uf mylar 16v(asuming 12v supply power to amp)
http://www.diyaudio.com/forums/showthread.php?postid=1416348#post1416348
Well I got good 500d now and that capacitor has numbers Z5U 475M 50V so I asume that is 4.7uF 50V capacitor with Temperature Coefficient Z5U . I wonder if the one you told me before is totaly wrong cap to go there.
can you use radial instead of mylar ?
The 0.1uf isn't the correct value but there will be no difference in performance with either, or none. There may be a measurable difference but you'll never notice the difference.
That said, you should replace the 0.1 with the correct cap now that you know the correct value.
That said, you should replace the 0.1 with the correct cap now that you know the correct value.
'Radial' means that both leads come out of the same end of the cap.
A film cap is probably the best option. There are already several large electrolytics across B+ and ground.. The Mylar/polyester film capacitor is used to bypass the high frequency noise (not audible) that isn't bypassed by the electrolytics.
A film cap is probably the best option. There are already several large electrolytics across B+ and ground.. The Mylar/polyester film capacitor is used to bypass the high frequency noise (not audible) that isn't bypassed by the electrolytics.
local electronics store does not have any 4.7uf50v caps, they have ones that are not polyester so I did not buy it. Right now I have in it what you told me the .1uf16v, but I got some .47j100, should I just put it there?
I see you don't want to answer my question. I asume that you already answered my question and refuse to elaborate further.
I forgot to reply but...
If the 'wrong' cap isn't causing a problem because it's value is too low, why replace it with another cap that's the wrong value? Wait until you order parts and order the correct part. Then replace the 0.1uf.
If the 'wrong' cap isn't causing a problem because it's value is too low, why replace it with another cap that's the wrong value? Wait until you order parts and order the correct part. Then replace the 0.1uf.
It is not about what correct parts fits that, I already know. But I want to learn about what does that capacitor do? Why is the value so high on that capacitor and why is the value lower on the same capacitor in different amps? Why not use another version of capacitor not mylar?
As I mentioned before, the capacitors shunt (bypass) high frequency noise to ground.
The capacitor is placed at the terminals so that's it's most effective at shunting the noise and prevents it from getting into/out of the amp.
Aluminum electrolytics are not as good as ceramic or film capacitors because they have relatively high ESL (Equivalent Series Inductance) and the loss (inability to pass efficiently pass current) at higher frequencies is greater.
When low impedance at high frequencies is needed and the total capacitance needed is not significant, ceramic, film or tantalum capacitors are used.
The value used is up the the designer, in most cases. You can vary the capacitance significantly and make no audible difference. If the amp must pass certain tests for noise (on the power supply lines), the designer may have to increase the capacitance to meet spec. 0.1uf is a good starting point. If the amp is generating too much high frequency noise on the supply lines (across B+ and ground), the designer may increase the value.
The capacitor is placed at the terminals so that's it's most effective at shunting the noise and prevents it from getting into/out of the amp.
Aluminum electrolytics are not as good as ceramic or film capacitors because they have relatively high ESL (Equivalent Series Inductance) and the loss (inability to pass efficiently pass current) at higher frequencies is greater.
When low impedance at high frequencies is needed and the total capacitance needed is not significant, ceramic, film or tantalum capacitors are used.
The value used is up the the designer, in most cases. You can vary the capacitance significantly and make no audible difference. If the amp must pass certain tests for noise (on the power supply lines), the designer may have to increase the capacitance to meet spec. 0.1uf is a good starting point. If the amp is generating too much high frequency noise on the supply lines (across B+ and ground), the designer may increase the value.
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