The goal is to test the amp with Vgs 3V or less.
If the bulb stays off under those conditions then we are ready to go to the next stage
Just get to that condition and nothing else.
If the bulb stays off under those conditions then we are ready to go to the next stage
Just get to that condition and nothing else.
If the Vgs is less than 3V then the bulb should stay off and if it doesn't stay off then you have a problem.
From post #2338 and #2341 (meanie)
When I turn on with bulb tester,
PSU have + - 25V.
But 5-10seconds later, PSU down to +,- 10V.
The power supply hold full voltage (even with the bulb tester?) for 5 - 10 seconds then drops to 10 volts which seems to indicate a problem with the power supply (and/or that huge 2 x 75,000uF charge) - check the power supply with/without the "bulb tester" on two dummy loads ( 24v/(2x1.5A) = 24/3A = 8R)
The transformer primary thermistor/soft-start is working okay with this turn-on current surge? And, check the rectifier diodes too for failure or insulation breakdown.
When I turn on with bulb tester,
PSU have + - 25V.
But 5-10seconds later, PSU down to +,- 10V.
The power supply hold full voltage (even with the bulb tester?) for 5 - 10 seconds then drops to 10 volts which seems to indicate a problem with the power supply (and/or that huge 2 x 75,000uF charge) - check the power supply with/without the "bulb tester" on two dummy loads ( 24v/(2x1.5A) = 24/3A = 8R)
The transformer primary thermistor/soft-start is working okay with this turn-on current surge? And, check the rectifier diodes too for failure or insulation breakdown.
I think he doesn't know how to properly use a light bulb tester and the trimpots.
It could be a fault elsewhere but that is what I am trying to establish right now.
As yet we know nothing until he confirms:
Vgs <3V
Bulb stays off
He hasn't even confirmed that yet
It could be a fault elsewhere but that is what I am trying to establish right now.
As yet we know nothing until he confirms:
Vgs <3V
Bulb stays off
He hasn't even confirmed that yet
It doesn't tell us anything till he confirms what I have requested above.
Let's establish that first then we can move forward with some facts
Let's establish that first then we can move forward with some facts
I have to say this has been incredibly challenging just to get someone to adjust their trimpots to Vgs less than 3V
Yes, it's rather frustrating and is why I think there's a hidden problem elsewhere - it's actually quite instructive too, and I appreciate your patience as I'm sure 'tamra' is too.
I tend to get the power supply organized first (with a variac, not a 'bulb tester) and full current load soaking before attaching the active amp circuits but this isn't not everyone's method
I tend to get the power supply organized first (with a variac, not a 'bulb tester) and full current load soaking before attaching the active amp circuits but this isn't not everyone's method
This is what I do.
1) Test power supply with bulb tester
2) Test amp circuit with lab power supply with current limiting
3) If both are good go to next step
4) Connect them together and turn on
This takes no more than 10 minutes.
I have never had a single failed component in my entire life doing this.
1) Test power supply with bulb tester
2) Test amp circuit with lab power supply with current limiting
3) If both are good go to next step
4) Connect them together and turn on
This takes no more than 10 minutes.
I have never had a single failed component in my entire life doing this.
Excellent advise as always! 🙂
It's implied within Pico's post, but I add one teeny step between 1 and 2 (depending on build sequence) based on reading some other issues and having one of my own saved by the dim bulb tester before I had lab supplies and a variac.
1a) After mounting boards to heatsinks, but before hooking to PSU or lab supply - check for shorts between all output device pins to heatsink. Little holes in the Keratherm (or similar) material seem to pop up unexpectedly at the worst times in people's builds. I've switched over to ceramic pads for newer builds to minimize that failure mode, but this is still a key step for me.
I learn a tremendous amount about the circuits (and how to prevent issues) by reading the troubleshooting segments within the threads. Thanks to all!
Tamra - I hope you get yours working perfectly.
It's implied within Pico's post, but I add one teeny step between 1 and 2 (depending on build sequence) based on reading some other issues and having one of my own saved by the dim bulb tester before I had lab supplies and a variac.
1a) After mounting boards to heatsinks, but before hooking to PSU or lab supply - check for shorts between all output device pins to heatsink. Little holes in the Keratherm (or similar) material seem to pop up unexpectedly at the worst times in people's builds. I've switched over to ceramic pads for newer builds to minimize that failure mode, but this is still a key step for me.
I learn a tremendous amount about the circuits (and how to prevent issues) by reading the troubleshooting segments within the threads. Thanks to all!
Tamra - I hope you get yours working perfectly.
What Meanie asked before about the wattage of the bulb is a good question.
Tamra if you're using a 40W or less bulb this could be making the situation far more problematic than it should be.
Tamra if you're using a 40W or less bulb this could be making the situation far more problematic than it should be.
I am begging you to get the Vgs across the mosfets to less than 3V, and nothing else.
Please do that.
Please do that.
remember, OCD, stop at LEDs, yours
edit: me being taught by few members, hopping to help..... and they tried to make my nose bleed .......
not saying that this is the same case here, but just saying - that taught me that you can't help everyone, even if you're able
no judging, of course, except in case of these swaying at ya
just one caveat in that , I'm bloody bad with memory, stumbled on same ones not once
edit: me being taught by few members, hopping to help..... and they tried to make my nose bleed .......
not saying that this is the same case here, but just saying - that taught me that you can't help everyone, even if you're able
no judging, of course, except in case of these swaying at ya
just one caveat in that , I'm bloody bad with memory, stumbled on same ones not once
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