Anyone come across 1 of these amps basically it’s a 4 channel Class AB Tip35 Tip 36 setup with class D sub
Anyway it’s a brand new amp but always had a fault on 1 of the 4 channels , best way i can describe it is it’s like connecting a 1.5 volt battery to a speaker and messing about with it , it can only be heard when the amp is very low and doesn’t affect the sound quality at all
I have e-mailed rang “midbass” whom are the parent company for advice / circuit diagram with no joy
Anyway it’s a brand new amp but always had a fault on 1 of the 4 channels , best way i can describe it is it’s like connecting a 1.5 volt battery to a speaker and messing about with it , it can only be heard when the amp is very low and doesn’t affect the sound quality at all
I have e-mailed rang “midbass” whom are the parent company for advice / circuit diagram with no joy
Have you tried to follow the circuit to see where the noise enters the circuit?
Photos of the board would be helpful. I doubt that there are many people here familiar with that amp.
Photos of the board would be helpful. I doubt that there are many people here familiar with that amp.
In all honesty i do not have a signal generator or scope the voltages on the TIP 35 & 36 collectors are a steady 25 volts volts to the base are wrong / all over the place , i need to do some more tracing and get back to you guys , I’m glad i have found this forum though
Thanks for your reply
Thanks for your reply
anyone familiar ........
IMG_2743.jpg Photo by semisheen | Photobucket
IMG_2742.jpg Photo by semisheen | Photobucket
IMG_2743.jpg Photo by semisheen | Photobucket
IMG_2742.jpg Photo by semisheen | Photobucket
I've seen similar class D circuits but can't see enough detail on the class B circuit.
It appears that you've removed the preamp board. Does the noise persist on the noisy channel without the preamp board?
It appears that you've removed the preamp board. Does the noise persist on the noisy channel without the preamp board?
IMG_2750_2.jpg Photo by semisheen | Photobucket
Thank you for your reply
I have uploaded a better picture of the Class AB part what’s got the problem (the rest of the amp is perfect)
The amplifier was crackling with NO preamp board connected, as i said earlier the base voltages or of the drivers the TIP 35 and TIP 36 were all over on the other 3 good amps they were something like 4 volts on the bad section there were between 4 and 19 volts in line with the crackling sound
The amp has since blown its drivers but i have also noticed R450 a 200 ohm resistor is measuring 140 ohms the capacitor i have removed C411 i cannot get any sort of reading from although i wouldn’t imagine it to be associated with the fault as all the other caps in that position i can’t get them to read anything either maybe they are less than 1Pf
Thank you for your reply
I have uploaded a better picture of the Class AB part what’s got the problem (the rest of the amp is perfect)
The amplifier was crackling with NO preamp board connected, as i said earlier the base voltages or of the drivers the TIP 35 and TIP 36 were all over on the other 3 good amps they were something like 4 volts on the bad section there were between 4 and 19 volts in line with the crackling sound
The amp has since blown its drivers but i have also noticed R450 a 200 ohm resistor is measuring 140 ohms the capacitor i have removed C411 i cannot get any sort of reading from although i wouldn’t imagine it to be associated with the fault as all the other caps in that position i can’t get them to read anything either maybe they are less than 1Pf
If the problem persists after replacing the defective parts, I'd suggest selectively heating and cooling the various semiconductors to see if a change in temperature of any particular component causes a significant change in the noise.
Replaced the parts on this amp ....still exactly the same 3 perfect channels 1 is still the same just constantly rustling hissing crackling , but very quiet, disconnected preamp board it’s still there , its NOT affected by the volume ie never gets louder and is drowned out by the volume , collector voltages are a constant 25 volts, base are floating so are voltages on the drivers , just can’t seem to isolate where it’s starting to go wrong , its puzzling me how the crackling and hissing is sooooo quiet & don’t increase with the volume , you would think with 3 identical amplifiers on the same bcb it would be easy to find but so far it’s been illusive , i can’t even see how i would find the fault with a signal injector or a scope any ideas anyone .....................its driving me mad
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