Good day. I am working with a Deaf Bonce AAP 800,2D which has a flashing protect and clipping mode. I just found out that 2 output FETS are shorted, Removing it, then
the blue light is on and out from protect mode, As you all know the power supply and output FETS on some of the design of Deaf Bonce have their FETS re faced which is
difficult to know the correct part and written only H1 (power supply FEts) and H8(output FETS). I tried fixing with 200v ,104A (IRFB4115) Fets for the output, from Stetsom 3000EX but no luck because they are getting hot without load although gate signals are correct. Can anybody know the correct part number of these Fets? Thank You.
the blue light is on and out from protect mode, As you all know the power supply and output FETS on some of the design of Deaf Bonce have their FETS re faced which is
difficult to know the correct part and written only H1 (power supply FEts) and H8(output FETS). I tried fixing with 200v ,104A (IRFB4115) Fets for the output, from Stetsom 3000EX but no luck because they are getting hot without load although gate signals are correct. Can anybody know the correct part number of these Fets? Thank You.
yes, in seconds it gets hot. The Stetsom 3000EX has a 1ohm gate resistor while the Deaf Bonce has 47 ohm gateresistor.
Using the 4115 output FETs tried with a 5ohm then 1ohm gate resistor r , but they can not drive the outputs continously. The signal goes On and off in the gates. The gate resistor originally is 47ohms, which has a normal gate signals but the outputs are getting hot. 4115's are good enough I beleived in htis amp which has 134vdc rails, is there a better FETs I can replaced with?
What do the drive signals on the low-side look like?
Do you know how to use your scope in differential mode?
Do you know how to use your scope in differential mode?
unfortunately i don’t know Perry how to use in differential mode. The drive in low side is the same compared to the the signal when i am using the 47ohm gate resistor, but with 5ohm it’s going on /off , and FEts are more pretty hot quickly.
Are you looking at the signal directly on the leg of the FET?
A differential input uses two inputs to produce a single waveform. The simplest way to get a differential input is to use a differential probe. A differential probe has two signal leads and a mixer amplifier built into it. It feeds the scope a normal signal (a composite of the two signals input into the differential probe). The problem with differential probes is that they're expensive.
The alternative is to use two scope probes and and both inputs of your oscilloscope. This is how you have to set up your scope:
Two probes
Both scope inputs used
Input set to add
Both channels set to DC coupling
Both channels set to 'cal'.
Both vertical amps set to the same voltage
Ch2 input set to invert
Bandwidth limited (works best for most measurements in car amps)
Trace aligned to the reference line on the scope's display
Ground leads for both probes connected together (not always necessary)
After setting up the scope, you need to confirm that it's working as it should. With the vertical amp set to 5v/div, touching the probe that's connected to Ch1 to the positive terminal of your 12v power supply should make the trace deflect about 2.5 divisions up from the reference (like it always does, seen below). Doing the same with the probe connected to Ch2 should make the trace deflect down about 2.5 divisions. Touching both probes to the positive terminal of the 12v power supply should cause no deflection. If it does, something isn't right.
I know that this may not be as simple as the isolated scope but if you take the time to learn it one time (even if it takes an hour or more of your time), you have that knowledge and this tool to use for the rest of the time you need to use a scope. Using the analog scope will give you much larger and cleaner waveforms.
A differential input uses two inputs to produce a single waveform. The simplest way to get a differential input is to use a differential probe. A differential probe has two signal leads and a mixer amplifier built into it. It feeds the scope a normal signal (a composite of the two signals input into the differential probe). The problem with differential probes is that they're expensive.
The alternative is to use two scope probes and and both inputs of your oscilloscope. This is how you have to set up your scope:
Two probes
Both scope inputs used
Input set to add
Both channels set to DC coupling
Both channels set to 'cal'.
Both vertical amps set to the same voltage
Ch2 input set to invert
Bandwidth limited (works best for most measurements in car amps)
Trace aligned to the reference line on the scope's display
Ground leads for both probes connected together (not always necessary)
After setting up the scope, you need to confirm that it's working as it should. With the vertical amp set to 5v/div, touching the probe that's connected to Ch1 to the positive terminal of your 12v power supply should make the trace deflect about 2.5 divisions up from the reference (like it always does, seen below). Doing the same with the probe connected to Ch2 should make the trace deflect down about 2.5 divisions. Touching both probes to the positive terminal of the 12v power supply should cause no deflection. If it does, something isn't right.
I know that this may not be as simple as the isolated scope but if you take the time to learn it one time (even if it takes an hour or more of your time), you have that knowledge and this tool to use for the rest of the time you need to use a scope. Using the analog scope will give you much larger and cleaner waveforms.
Yes I am looking directly on the gate and drain leg of the FET simultaneously. I have also an analog scope GW Instek GOS-620 20MHz Dual Channel Oscilloscope, let me go and study the differential mode, Perry with my analog scope. Thank you as always for your help and helpful informations. If i have success in putting my scope in differential mode, shal I carry the same point in measuring the signals in the legs of the FETs? What is the purpose of the differential mode?
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With a mains-powered scope, you can't ground the scope to anything with voltage since the scope ground is connected to the mains ground. This means that, to look at the signals (low-side, for example), you have to look at the full negative rail voltage, as well as the drive signal (using DC coupling, which is important, AC coupling, is mostly useless). This leaves you with a tiny, low resolution signal on the scope.
In differential mode, you can see the signal in much greater detail because you use one channel of the scope to, basically, subtract the rail voltage from the equation. The huge advantage is that you can see the DC component of the drive signal. If the problem is that the FETs are heating, it could be that the drive isn't going back to 'ground'. Differential mode with DC coupling allows you to see that. In AC mode (remember, generally useless), you can't tell if the drive is going back to the signal ground (back to the voltage on the FET source leg).
For the high-side FETs, it's even more useful because they're floating (for all N-channel FET amps) on the rail to rail carrier waveform and subtracting that from the signal makes the displayed waveform much more useful.
The same thing (DC coupling, eliminating the DC rail voltage or the carrier waveform from the displayed signal) can be done with battery powered scopes but they generally have a very low resolution display so using a mains-powered scope is preferred for many people. For someone who absolutely hates the display on virtually all LCD scope displays (me), using an analog scope (with a beautiful, clean trace with no Donkey-Kong pixelation) in differential mode is a wonderful option.
Also understand that the scope can be left in the differential mode configuration most of the time, especially when one channel of the scope is all that's typically used (all that's needed for most testing).
In differential mode, you can see the signal in much greater detail because you use one channel of the scope to, basically, subtract the rail voltage from the equation. The huge advantage is that you can see the DC component of the drive signal. If the problem is that the FETs are heating, it could be that the drive isn't going back to 'ground'. Differential mode with DC coupling allows you to see that. In AC mode (remember, generally useless), you can't tell if the drive is going back to the signal ground (back to the voltage on the FET source leg).
For the high-side FETs, it's even more useful because they're floating (for all N-channel FET amps) on the rail to rail carrier waveform and subtracting that from the signal makes the displayed waveform much more useful.
The same thing (DC coupling, eliminating the DC rail voltage or the carrier waveform from the displayed signal) can be done with battery powered scopes but they generally have a very low resolution display so using a mains-powered scope is preferred for many people. For someone who absolutely hates the display on virtually all LCD scope displays (me), using an analog scope (with a beautiful, clean trace with no Donkey-Kong pixelation) in differential mode is a wonderful option.
Also understand that the scope can be left in the differential mode configuration most of the time, especially when one channel of the scope is all that's typically used (all that's needed for most testing).
Thanks bro, i've manage to use the IRFB4115 , it is getting a little hot as my main concern but all drive signals are normal, then it happened I had another Deaf Bonce amp for repair with the same Fets H8 marked on it, but with another issue then after repair on it, I found out that the H8 outputs are also going moderately hot as well when out of the heat sink body without load. So i believed this is normal on this design of the this amp. With the IRFB4115 replaced , until now surprisingly the amp is working fine as feedback from the owner, used it surviving the torture in the audio competition.