Good afternoon,
I'm working on this JP 43. Something is causing it to protect, shutting down the drive. Card removed, tested out of circuit, works great. I removed the diode, drive fires up no problem. Outputs, Output drive card and power supply fets are all removed. Input voltage is 12.5v
Problem is, I can't figure out for the life of me where the voltage is coming from. I can't seem to trace that 10v to any source.
Thanks in advance. Pictures coming.
I'm working on this JP 43. Something is causing it to protect, shutting down the drive. Card removed, tested out of circuit, works great. I removed the diode, drive fires up no problem. Outputs, Output drive card and power supply fets are all removed. Input voltage is 12.5v
Problem is, I can't figure out for the life of me where the voltage is coming from. I can't seem to trace that 10v to any source.
Thanks in advance. Pictures coming.
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No, and neither is Q225. Give me a few min here... think I'm onto something... cause with the power supply transistors in circuit, the protection voltage seems to be gone.
Yup. Power supply fets must be in place for drivers to work. Otherwise protection kicks in. On to the output section!!
I've seen drive protection on some amps but never with anything like this one... but I couldn't find a diagram with the 8 pin drivers in the power supply.
This is the first one I've worked on. They're fairly new. I'll be sure to finish mapping most of this out before sending it off, seeing as I was almost there but not quite in finding that issue. I'll send it to you once I do sir. 🙂
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The low side doesn't have enough amplitude. Post another scope image with the yellow on the negative rail.
Do you know how to use your scope in differential mode?
Do you know how to use your scope in differential mode?
Are you familiar with that output card Perry? I noticed with the card out of circuit, when I went to take readings... Pin 1 would dart to near neg rail, but then come up nearly immediately and settle at -43v... Where as all the rest stayed down at neg rail except pin 4... that one looks to be the -12v above neg rail.
I know some about the card. Pin 1 is shutdown. IT's connected to the pin next to it which is the negative rail. There is a small capacitor between them so that's likely why it's acting like it is.
The differential mode section is on the TT8 page, item #8.
From macro:
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.
The differential mode section is on the TT8 page, item #8.
From macro:
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.
Inverted probe on source pad of low-side FET. Normal probe on gate pad of the same FET. Post waveform.
Post the waveform.
Post the waveform.
The second image looks OK (for the red trace). When checking the output drive, you should be able to use 5v/div. Try to determine why it's displaying 3 traces. In differential mode, it should display only one trace and that trace should be the difference in the two probed points. As an example, if you touched both probes to the drains of a PS FET, the displayed trace should be a straight line at 0v (on the reference line in the center of the display).
To get a drive waveform on the output stage, you may have to drive a signal into the amp.
Going to be away from the computer for a while. I'll check the thread when I return.
To get a drive waveform on the output stage, you may have to drive a signal into the amp.
Going to be away from the computer for a while. I'll check the thread when I return.