I need help again.
I have cleaned screw holes and set trimpot
at middle point.
There is no voltage between R2 0.47resister and offset.
I have been checking parts but can not find any fail.
R7.R.8=3.3K. R11.R12=110 IRFP150mpbf
3orange led have set oposit to zenner diode.
I have cleaned screw holes and set trimpot
at middle point.
There is no voltage between R2 0.47resister and offset.
I have been checking parts but can not find any fail.
R7.R.8=3.3K. R11.R12=110 IRFP150mpbf
3orange led have set oposit to zenner diode.
The led will have to be lit during operation.
You may try turning the pot while watching for voltages across 0.47R.
If you have reached both ends of the pot travel and no bias....then something is wrong.
You may try turning the pot while watching for voltages across 0.47R.
If you have reached both ends of the pot travel and no bias....then something is wrong.
I have turned trimpot both ends but nothing happened.
I might start changing parts one by one...
I might start changing parts one by one...
What voltage do you have across gate and source pins?
What voltage do you measure across the 3 x led voltage reference?
What voltage do you measure across the 3 x led voltage reference?
R cahnnel
Bias gate-source 2.5v. Led 4.4v
Offset. Gate-source. 1v. Led 3.7v
L channel
Bias gate-source 2.4v Led 4.2v
Offset gate-source 1.7v Led 3.8v
Bias gate-source 2.5v. Led 4.4v
Offset. Gate-source. 1v. Led 3.7v
L channel
Bias gate-source 2.4v Led 4.2v
Offset gate-source 1.7v Led 3.8v
Your LED string does not have adequate voltage to bias the output stage. 4.4V is not adequate.
What is the resistor value feeding the LEDs?
You may need to change the LEDs.
If you use LTL-4231N you will generate adequate voltage. Or you could add an additional LED (ie 4 LEDs of the same type you already have).
What is the resistor value feeding the LEDs?
You may need to change the LEDs.
If you use LTL-4231N you will generate adequate voltage. Or you could add an additional LED (ie 4 LEDs of the same type you already have).
Last edited:
R7,R8 is 3.3K.
I have plugged without bulb tester...
Then it sparked with sounds. Oh, I surprised and tuned off.
But did not find any fried parts so I plugged with bulb tester again.
Now bulb light on only in a moment then turn off.
LEDs are on and have 5.5V and R2 have 0.1V now.
I suspect my bad solder. Not sure if everything ok but I check it
tomorrow evening its midnight so.
Thank you for helping me picoDumbs and people here.
The BOM didn't call out a specific LED for D1 (or I missed it), so I ordered the Vishay TLHB5400. Will that LED generate adequate voltage?
If you're using an LED in the D1 position just as a light to show there is power
then pretty much anything will work. (Yours seems to be about 3.9V according to
mouser.)
What 2 pico was referring to is his snazzy trick to the use of a series of LEDs as a voltage reference
in place of the Z1 and Z2 zener diodes in the schematics. In that usage, you want
something with certain temperature characteristics.
2pico's original presentation here:
Dumb Biasing Mod, applicable to F6 and other Papa Amps. Possibly My Dumbest Idea Yet
then pretty much anything will work. (Yours seems to be about 3.9V according to
mouser.)
What 2 pico was referring to is his snazzy trick to the use of a series of LEDs as a voltage reference
in place of the Z1 and Z2 zener diodes in the schematics. In that usage, you want
something with certain temperature characteristics.
2pico's original presentation here:
Dumb Biasing Mod, applicable to F6 and other Papa Amps. Possibly My Dumbest Idea Yet
Oh, okay that makes sense now - Thanks for clarifying and providing the link!
Tamra do one more check of every Star 0V connection it's possible you could have a poorly soldered joint somewhere, causing intermittent problems.
I have checked every star ground.
Then measured again.
There are no problem with star ground but there is no voltage at R2 both sides.
Without bulb tester, no voltage at R2 0.47ohm as well...
Then measured again.
There are no problem with star ground but there is no voltage at R2 both sides.
Without bulb tester, no voltage at R2 0.47ohm as well...
What is voltage across leds?
Is the value constantly changing?
I am getting confused, one minute you said it was around 4V, then later it was 5.5V.
Is the value constantly changing?
I am getting confused, one minute you said it was around 4V, then later it was 5.5V.
There was no light on LEDs 4.4v before.
After plugged without bulb tester, Led turns light on then
Now it's 5.5v. But still 0v between R2 0.47ohm.
Psu+ has 24.7v ,-has -25.5v now.
After plugged without bulb tester, Led turns light on then
Now it's 5.5v. But still 0v between R2 0.47ohm.
Psu+ has 24.7v ,-has -25.5v now.
Hi Tamra,
This is just my suggestions....
You may want to go a step back to the original F6 circuit, and try to run it properly first.
Listen to music a few days before jumping back to the "3 led schematics" mod.
At the meantime, to order those proper part numbered Led components, to eliminate any unnecessary guesswork along the way.
It is frustrating to troubleshoot for days without any end to it.
This is just my suggestions....
You may want to go a step back to the original F6 circuit, and try to run it properly first.
Listen to music a few days before jumping back to the "3 led schematics" mod.
At the meantime, to order those proper part numbered Led components, to eliminate any unnecessary guesswork along the way.
It is frustrating to troubleshoot for days without any end to it.
5.5V may not be adequate, you may need more. It will depend on the Vgs threshold of your parts.
Did you adjust pots so that you also measure 5.5V between Gate and Source pins?
Did you adjust pots so that you also measure 5.5V between Gate and Source pins?